haw 5% g. :2. i L, a}... .1... g .. (Eu... .1 , .3: .H . .unuufi: {in l...’ ~ 0 4 ii; 5.. 3.! SI 33 3:: .2: 31;..‘51 kl»... p51. 339.44‘3: 1. A... I. .I...I.. urn! la... 1“...“ F» F 4 . .. V Eli kw... 1.9.1.135 15:71.). Slauliaa 1'; IVA}? ‘vngu : 7;: ‘ {.34 x A...) .3. {iv v ”V9? ‘ v ., .3454 II sJ‘B‘n :1).§u\:.r .r ii 5 A . 71. .r 5:5»)...3. <.7.-,..1 h. .. ’35:... D. . . 51...»..0'319.’ 1:35; 0.. .2 3.55% .5 I 21?, a .9 51135:.— L 11.: I. 2007 This is to certify that the thesis entitled INVASIVE SPECIES IMPACTS ON ECOSYSTEM STRUCTURE AND FUNCTION presented by ANDREA L. JAEGER has been accepted towards fulfillment of the requirements for the Master of degree in the Department of Fisheries Science and Wildlife We. be Major Professor’s Signature ill/[24700 (a Date MSU is an Affirmative Action/Equal Opportunity Institution UBRARY Michigan State University PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. MAY BE RECALLED with earlier due date if requested. DATE DUE DATE DUE DATE DUE 7 it??? 2&2! 120.9az MA 00 2/05 p:/ClRC/Dale0ue.indd-p.1 INVASIVE SPECIES IMPACTS ON ECOSYSTEM STRUCTURE AND FUNCTION By Andrea L. Jaeger A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Fisheries and Wildlife 2006 ABSTRACT INVASIVE SPECIES IMPACTS ON ECOSYSTEM STRUCTURE AND FUNCTION By Andrea L. J aeger Exotic species invasion is a worldwide threat to the integrity of aquatic ecosystems. To understand ecosystem level response to the introduction of exotic species, I compared food web characteristics of two eutrophic Great Lakes ecosystems - the Bay of Quinte, Lake Ontario, Canada, and Oneida Lake, New York, USA - before and after zebra mussel (Dreissena polymorpha) invasion using ecological network analysis (ENA) and a social network analysis method, cohesion analysis (CA). ENA quantifies ecosystem function through an analysis of food web transfers, while CA assesses ecosystem structure by organizing food web members into subgroups of strongly interacting predators and prey. In Oneida Lake and the Bay of Quinte, zebra mussel invasion increased food web organization and the potential for system development. Additionally, zebra mussel invasion stimulated benthic production in both systems. Effects on food web structure were strongest in the Bay of Quinte where zebra mussel invasion removed subgroup structure entirely. In Oneida Lake, over 33% of taxa changed subgroup association after invasion, with benthically associated subgroups gaining the most members. This analysis suggested that the effects of zebra mussel introduction are similar in ecosystems of comparable trophic status and that future invasions of eutrophic systems could have similar impacts on ecosystem structure and function. Dedicated to the memory of Beryl Timmer iii ACKNOWLEDGEMENTS This research was supported by the Great Lakes Fishery Commission, the NOAA Great Lakes Environmental Research Laboratory, and Michigan State University. I am indebted to the numerous people at these organizations that made this work possible. My major professor, Dr. Doran M. Mason, has been a valuable mentor throughout this research. Despite the distance between his office and mine, he has motivated, guided, and inspired me. My committee members have also contributed greatly to this work. Dr. Kenneth A. Frank offered much assistance with cohesion analysis methods and interpretation; Dr. William W. Taylor was a source of boundless energy and enthusiasm; and Dr. Scott D. Peacor always provided insightful feedback. The graduate work of Dr. Ann E. Krause formed the foundation for much of this research. I highly value her insight in the merging of ecological and social network analysis methods, and the effort she devoted to these analyses. I would also like to thank Dr. Stefano Allesina for his willingness to discuss network analysis, and Drs. Michael L. Jones and James R. Bence for making me a part of their lab. This research was linked with another food web modeling effort to understand the effects of zebra mussel invasion on Oneida Lake and the Bay of Quinte. The Bay of Quinte — Oneida Lake Comparative Modelling Project Workgroup, a group composed of many respected scientists including Dr. E. Scott Millard, P.I. (DFO-GLLFAS), Dr. Edward L. Mills, P.I. (Cornell University), and Dr. Marten Koops (DFO-GLLFAS), provided extensive data and guidance. Additionally, Dr. Mills and the staff at the Cornell iv University Biological Field Station graciously hosted me during June 2004 for Oneida Lake data collection. I would also like to acknowledge the many others who surround and influence my daily life. My (fiber) labmates were an abundant source of intellectual discussion and entertainment. My close friends and colleagues at the Illinois Natural History Survey Lake Michigan Biological Station, my previous employer, have continued to encourage me throughout this research. The instruction of Drs. Stephen B. Hager (Augustana College), C. Kevin Geedey (Augustana College), and Jason Powell (Zion-Benton Township High School) still inspires me even today; these teachers brought learning outside the classroom and into my life. I thank my parents, Douglas and Barbara Jaeger, and brother, Jeffrey Jaeger, for encouraging me to explore all that holds my curiosity. Finally, I thank Scott M. Miehls, my fiance, for unwavering support and companionship. TABLE OF CONTENTS LIST OF TABLES ........................................................................................................... viii LIST OF FIGURES ......................................................................................................... x CHAPTER 1 A Prologue and Context to Understanding Invasive Species Impacts on Ecosystems....l References ........................................................................................................... 6 CHAPTER 2 Invasive Species Impacts on Ecosystem Structure and Function: A comparison of Oneida Lake, USA, Before and After Zebra Mussel Invasion ........................................ 8 Abstract ............................................................................................................... 8 Introduction ......................................................................................................... 9 Methods ............................................................................................................... 1 3 Study Site ................................................................................................... 13 Network Construction ................................................................................ l4 Ecological Network Analysis ..................................................................... 17 Cohesion Analysis ...................................................................................... 19 Results ................................................................................................................. 22 Ecological Network Analysis — Entire Network ........................................ 22 Cohesion Analysis ...................................................................................... 24 Ecological Network Analysis - Grouped Network .................................... 25 Discussion ........................................................................................................... 29 ~ Cohesion Analysis — Structure ................................................................... 30 Ecological Network Analysis — Function .................................................. 32 Acknowledgements ............................................................................................. 38 References ........................................................................................................... 59 CHAPTER 3 Invasive Species Impacts on Ecosystem Structure and Function: A Comparison of the Bay of Quinte, Canada, and Oneida Lake, USA, Before and After Zebra Mussel Invasion ............................................................................................................................ 65 Abstract ............................................................................................................... 65 Introduction ......................................................................................................... 66 Methods ............................................................................................................... 70 Study Site ................................................................................................... 70 Network Construction ................................................................................ 71 Ecological Network Analysis ..................................................................... 71 Cohesion Analysis ...................................................................................... 73 Results ................................................................................................................. 75 Ecological Network Analysis — Entire Network ........................................ 75 Cohesion Analysis ...................................................................................... 76 vi Ecological Network Analysis — Grouped Network .................................... 77 Discussion ........................................................................................................... 78 Cohesion Analysis -— Structure ................................................................... 79 Ecological Network Analysis — Function .................................................. 80 Acknowledgements ............................................................................................. 84 References ........................................................................................................... 96 APPENDICES ................................................................................................................. 101 vii LIST OF TABLES Table 2.1 List of food web taxa. Cisco were present in the pro-zebra mussel time stanza but not the post-zebra mussel time stanza; lake sturgeon, zebra mussels, and Camptocercus harpae were present in the post- zebra mussel time stanza, but not the pre-zebra mussel time stanza ......... 40 Table 2.2 Association between common subgroup membership and the occurrence of ties between predators and prey (adapted from Frank 1995). The odds ratio method maximizes the ratio AD : BC ................... 41 Table 2.3 Ecosystem indices for the full Oneida Lake food web network before and after zebra mussel invasion. The percent difference was calculated as: %Diflerence = Wx100% ...................................... 42 re Table 2.4 Subgroups identified for the pre-zebra mussel invasion time stanza. * Refers to taxa present in the pre-zebra mussel time stanza, but not the post-zebra mussel time stanza .............................................................. 43 Table 2.5 Subgroups identified for the post-zebra mussel invasion time stanza. "‘ Refers to taxa present in the post-zebra mussel time stanza, but not the pre-zebra mussel time stanza. T Refers to taxa that changed subgroup membership after zebra mussel invasion ................................... 44 Table 2.6 Throughput of subgroups before and after zebra mussel invasion. Only six subgroups were identified before zebra mussel invasion ............ 45 Table 2.7 Ecosystem indices for the zebra mussel subgroup before and after zebra mussel invasion. The percent difference was calculated as: %Difference = M x100% ............................................................. 46 Pre Table 3.1 List of food web taxa. Brook silverside, emerald shiners, largemouth bass, round gobies, zebra mussels, and Cercopagis pengoi, were present in the post-zebra mussel time stanza, but not the pre-zebra mussel time stanza ................................................................ 85 Table 3.2 Association between common subgroup membership and the occurrence of ties between predators and prey (adapted from Frank 1996). The odds ratio method maximizes the ratio AD : BC ................... 86 Table 3.3 Ecosystem indices for the full food web (Panel A), subgroup throughput (Panel B), and ecosystem indices for subgroup 1 viii (Panel C). The percent difference was calculated as: %Diflerence = 132% x100% ............................................................. 87 re Table 3.4 Subgroups identified for the pre-zebra mussel invasion time stanza ......... 88 ix Figure 2.1 Figure 2.2 Figure 2.3 Figure 2.4 Figure 2.5 Figure 2.6 Figure 3.1 LIST OF FIGURES Images in this thesis are presented in color Zebra mussel impacts on the Oneida Lake food web, organized by subgroup. The scale is relative: impacts above the zero line are positive impacts of zebra mussels and impacts below the zero line are negative impacts of zebra mussels. Taxa numbers are placed above or below each bar. Taxon 21 was not present after zebra mussel invasion; taxa 75-77 were not used in the subgroup analysis. See Table 2.1 for taxa codes ............................................................................. 47 Panel A: Crystalized sociogram for the pre-zebra mussel time stanza. Units are relative distances based on the inverse of the density of interactions (see Frank 1996). Subgroups 1 through 6 are plotted with the direction of feeding relationships represented by arrows (e.g., subgroup 6 consumes members of subgroup 1, but not vice versa); thickness of arrow indicates weight of feeding relationships. Panel B: Placement of taxa within subgroups. Circles indicate subgroup boundaries and colors represent general trophic groupings of taxa. Subgroup numbers are located to the upper right of all subgroups ............ 49 Crystalized sociogram for the post-zebra mussel time stanza. See Figure 2.2 for description of panels ........................................................... 51 Zebra mussel impacts on subgroup members. The scale is relative: impacts above the zero line are positive impacts of zebra mussels and impacts below the zero line are negative impacts of zebra mussels .......... 53 Lindeman trophic spine for the pre-zebra mussel time stanza. Boxes with Roman numerals represent the integer trophic levels; the number within each trophic box is the percent efficiency of that trophic level at processing material. Arrows between the trophic boxes are flows in the grazer food chain, arrows leaving the top of trophic boxes are exports, arrows entering the top of trophic boxes are imports, and arrows leaving the bottom of trophic boxes are flows to detritus, represented by the detrital box. The ground symbol from electronic circuitry represents flow loss due torespiration. All flows are in gC 111'2 yr.1 ........................................................................................ 55 Lindeman trophic spine for the post-zebra mussel time stanza. See Figure 2.5 for a description of the figure ................................................... 57 Map of the Bay of Quinte (Source: Carolyn Bakelaar, Department of Fisheries and Oceans, Canada) .................................................................. 89 Figure 3.2 Figure 3.3 Figure 3.4 Zebra mussel impacts on the Bay of Quinte food web. The scale is relative: impacts above the zero line are positive impacts of zebra mussels and impacts below the zero line are negative impacts of zebra mussels. Taxa numbers are placed above or below each bar. See Table 3.1 for taxa codes ...................................................................... 90 Panel A: Crystalized sociogram for the pre-zebra mussel time stanza. Units are relative distances based on the inverse of the density of interactions (see Frank 1996). Subgroups 1 through 6 are plotted with the direction of feeding relationships represented by arrows; thickness of arrow indicates weight of feeding relationships. Panel B: Placement of taxa within subgroups. Circles indicate subgroup boundaries and colors represent general trophic groupings of taxa. Subgroup numbers are located to the upper right of all subgroups ........................................... 92 Lindeman trophic spine for the pre-zebra mussel time stanza. Boxes with Roman numerals represent the integer trophic levels; the number within each trophic box is the percent efficiency of that trophic level at processing material. Arrows between the trophic boxes are flows in the grazer food chain, arrows leaving the top of trophic boxes are exports, arrows entering the top of trophic boxes are imports, and arrows leaving the bottom of trophic boxes are flows to detritus, represented by the detrital box. The ground symbol from electronic circuitry represents flow loss due to respiration. All flows are in gC m'z yr'l .................................................................................................. 94 xi CHAPTER 1 A Prologue and Context to Understanding Invasive Species Impacts on Ecosystems Andrea L. J aeger Aquatic ecosystems worldwide are in the midst of large-scale ecological alteration, including exotic species invasion (Mills et al. 1994; Holeck et al. 2004), fisheries collapse (Pauly et al. 1998; Myers 2003), trophic uncoupling from global climate change (Winder and Schindler 2004), and rapid loss of native biodiversity (Dunne et al. 2002). Exotic species invasion, in particular, is one of the most insidious anthropogenic influences on ecosystems (Mills et al. 1994) and is the most significant worldwide threat to native biota (Hall and Mills 2000). The Laurentian Great Lakes of North America have experienced pronounced invasion pressure for centuries. Exotic species introductions have been documented since the early 18005 (Mills et al. 1993) and number over 170 for recognized invaders (Holeck et al. 2004).1 Many more species threaten introduction into the Great Lakes, but have yet to become established. The numerous invasions in the Great Lakes have greatly affected ecosystem integrity (Mills et al. 1994), structure, and function (Vanderploeg et al. 2002), causing substantial economic hardship through damaging highly valued commercial and recreational fisheries and municipal structures (Mills et al. 1994; F acon et a1. 2005). The extent and frequency of these disturbances make management of Great Lakes ecosystems challenging. To address these types of challenges, some researchers (e. g. Christensen et ' In this context, we define exotic species as non-indigenous flora and fauna which have successfully established reproducing populations (Mills et al. 1993). al. 1996; Pauly 2002) advocate an ecosystem management approach. Christensen et a1. (1996) define ecosystem management as “management driven by explicit goals, executed by policies, protocols, and practices, and made adaptable by monitoring and research based on our best understanding of the ecological interactions and processes necessary to sustain ecosystem composition, structure, and function.” Many policy makers and managers have embraced this paradigm shift from historical single-species management to ecosystem management. As of 1994, at least 18 Federal agencies committed to ecosystem management (Congressional Research Service 1994) and that number has surely risen in the past decade. However, understanding ecosystem structure and function — which is fundamental to ecosystem management — is a formidable task due to the complexity of ecosystem processes (Gaedke 1995). If we do not have a clear depiction of ecosystem structure and function, then we have no goal for which to manage. Moreover, ecosystems are dynamic, undergoing both natural and anthropogenic change (e.g., exotic species invasion) that can impact ecosystem processes on a continual basis. To meet the goals of ecosystem management, we first need an understanding of ecosystem structure and function, inclusive of ongoing ecological change. In this research, I used a suite of methods collectively termed network analysis to examine the effects of exotic species invasion on food webs in the Great Lakes basin. Network analysis has wide applicability across disciplines, including ecology, engineering, economics (Ulanowicz 1986), and sociology (Johnson et al. 2001). In the context of ecology, network analysis depicts food webs as networks of exchange and evaluates the efficiency of energy and material flow. On a more comprehensive scale, network analysis examines the development of ecosystems and can be used to study ecosystem change. Network analysis differs from traditional food web analysis by incorporating weighted flows between taxa, as opposed to simply using flow presence or absence data. As such, network analysis allows for a more realistic depiction of food web flow and better understanding of ecosystem processes (Gaedke 1995). Moreover, network analysis offers an objective means to articulate the structure and function of ecosystems. To evaluate structure and function, I used two network analysis methods: ecological network analysis (ENA), which quantified ecosystem function, and a social network analysis method, cohesion analysis (CA), which quantified structure. Food web structure encompasses the components of ecosystems, including food web taxa and the arrangement of interactions between them, whereas function incorporates the flux processes in food webs, such as production, consumption, and respiration (Stevenson et al. 1996). ENA quantifies function through an analysis of the efficiency of flow between predators and prey, trophic levels, and cumulatively across the entire food web (Ulanowicz 1986). The efficiency of flow corresponds to ecosystem development such that highly developed (mature), stable ecosystems sustain greater flow efficiency than lesser developed or perturbed ecosystems (Ulanowicz 1986). CA quantifies structure by organizing the food web into subgroups of strongly interacting predators and prey (Krause et al. 2003). Subgroup structure is theorized to increase the stability of food webs and buffer ecosystems from perturbation (Krause et al. 2003). In this research, I applied ENA and CA methodologies to understand how exotic species invasion (as an ecosystem perturbation) affects the functional and structural attributes of food webs. One of the best studied exotic species in the Great Lakes basin is zebra mussels (Dreissena polymorpha). Zebra mussels are part of a recent wave of invaders from the Ponto-Caspian region of eastern Europe and Russia. Zebra mussels pose a considerable threat to the Great Lakes through engineering ecosystems (V anderploeg et al. 2002) and facilitating the establishment of other Ponto-Caspian species (Ricciardi 2001). Zebra mussel impacts have been far-reaching in the Great Lakes, affecting habitat structure, nutrient dynamics, and all trophic levels (Mills et al. 2003). With this research, I examined the effects of zebra mussel invasion in Oneida Lake, New York, USA, and the Bay of Quinte, Lake Ontario, Canada, two eutrophic ecosystems in the Great Lakes watershed. Both systems are valuable recreationally to their surrounding areas and sustain economically important walleye (Sander vitreus) and yellow perch (Perca flavescens) fisheries which have declined in recent years (Rudstam et al. 2004; Mills et al. 2003). Zebra mussels were discovered in 1991 in Oneida Lake and were established throughout the ecosystem by 1992 (Mayer et al. 2000); zebra mussels colonized the Bay of Quinte in 1993-1994, but were not established until 1995 (Nicholls et al. 2002). The ecology of both systems has been studied since the mid-19005, making Oneida Lake and the Bay of Quinte ideal systems in which to examine ecological change. Finally, to facilitate this research, I collaborated with researchers in the Bay of Quinte — Oneida Lake Comparative Modelling Project Workgroup who built dynamic simulation models to examine the effects of zebra mussel introduction on these systems. Our network analysis of Oneida Lake and the Bay of Quinte was guided by three research objectives: 1) quantify zebra mussel impacts on food web subgroup structure; 2) quantify zebra mussel effects on ecosystem function at the full food web and subgroup level; and 3) compare results between Oneida Lake and the Bay of Quinte, assessing whether ecosystems of comparable trophic status respond similarly to zebra mussel invasion. Chapter 2 addresses objectives 1 and 2 in Oneida Lake; Chapter 3 focuses on objectives 1 and 2 for the Bay of Quinte, and concludes with a comparison between Oneida Lake and the Bay of Quinte, addressing objective 3. With this analysis, I tested the hypothesis that zebra mussel invasion led to the benthification of Oneida Lake and the Bay of Quinte. Mills et al. (2003) define benthification as a shift of importance from pelagic to benthic processes promoting bottom-dwelling organisms and benthic sources of production. These changes not only have implications for how these ecosystems should be managed (e.g., for pelagic versus benthic fisheries), but also the prediction of zebra mussel impacts in other systems. References Christensen, N. L., A. M. Bartuska, J. H. Brown, S. Carpenter, C. D'Antonio, R. Francis, J. F. Franklin, J. A. MacMahon, R. F. Noss, D. J. Parsons, C. H. Peterson, M. G. Turner, and R. G. Woodmansee. 1996. The report of the Ecological Society of America Committee on the scientific basis for ecosystem management. Ecol. Applic. 6: 665-691. Congressional Research Service. 1994. Ecosystem management: Federal agency activities. Congressional Research Service, Library of Congress, Washington, DC, USA. Dunne, J. A., R. J. Williams, and N. D. Martinez. 2002. Network structure and biodiversity loss in food webs: Robustness increases with connectance. Ecol. Lett. 5: 558-567. Facon, B., B. J. Genton, J. Shykoff, P. Jame, A. Estoup, and P. David. 2005. A general coo-evolutionary framework for understanding bioinvasions. TREE. 21: 130-135. Gaedke, U. 1995. A comparison of whole-community and ecosystem approaches (biomass size distributions, food web analysis, network analysis, simulation models) to study the structure, function and regulation of pelagic food webs. J. Plankton Res. 17: 1273-1305. Hall, S. R. and E. L. Mills. 2000. Exotic species in large lakes of the world. Aq. Ecosys. Health Man. 3: 105-135. Holeck, K. T., E. L. Mills, H. J. MacIsaac, M. R. Dochoda, R. I. Colautti, and A. Ricciardi. 2004. Bridging troubled waters: Biological invasions, transoceanic shipping, and the Laurentian Great Lakes. BioScience. 54: 919-929. Johnson, J. C., S. P. Borgatti, J. J. Luczkovich, and M. G. Everett. 2001. Network role analysis in the study of food webs: An application of regular role coloration. J. Soc. Struct. 2: 1-15. Krause, A. E., K. A. Frank, D. M. Mason, R. E. Ulanowicz, and W. W. Taylor. 2003. Compartments revealed in food-web structure. Nature. 426: 282-285. Mayer, C. M., A. J. VanDeValk, J. L. Fomey, L. G. Rudstam, and E. L. Mills. 2000. Response of yellow perch (Percaflavescens) in Oneida Lake, New York, to the establishment of zebra mussels (Dreissena polymorpha). Can. J. Fish. Aquat. Sci. 57: 742-754. Mills, E. L., J. H. Leach, J. T. Carlton, and C. L. Secor. 1993. Exotic species in the Great Lakes: A history of biotic crises and anthropogenic introductions. J. Great Lakes Res. 19: 1-54. Mills, E. L., J. H. Leach, J. T. Carlton, and C. L. Secor. 1994. Exotic species and the integrity of the Great Lakes. BioScience. 44: 666-676. Mills, E. L., J. M. Casselman, R. Derrnott, J. D. F itzsimons, G. Gal, K. T. Holeck, J. A. Hoyle, O. E. Johannsson, B. F. Lantry, J. C. Makarewicz, E. S. Millard, I. F. Munawar, M. Munawar, R. O'Gorman, R. W. Owens, L. G. Rudstam, T. Schaner, and T. J. Stewart. 2003. Lake Ontario: Food web dynamics in a changing ecosystem (1970-2000). Can. J. Fish. Aquat. Sci. 60: 471-490. Myers, R. A. and B. Worm. 2003. Rapid worldwide depletion of predatory fish communities. Nature. 423: 280-283. Nicholls, K. H., L. Heintsch, and E. Carney. 2002. Univariate step-trend and multivariate assessments of the apparent effects of P loading reductions and zebra mussels on the phytoplankton of the Bay of Quinte, Lake Ontario. J. Great Lakes Res. 28: 15- 3 l. Pauly, D., V. Christensen, J. Dalsgaard, R. Froese, F . Torres, Jr. 1998. Fishing down marine food webs. Science. 279: 860-863. Pauly, D., V. Christensen, S. Guenette, T. J. Pitcher, U. R. Sumaila, C. J. Walters, R. Watson and D. Zeller. 2002. Towards sustainability in world fisheries. Nature. 418: 689-695. Ricciardi, A. 2001. Facilitative interactions among aquatic invaders: Is an "invasional meltdown" occurring the Great Lakes? Can. J. Fish. Aquat. Sci. 58: 2513-2525. Rudstam, L. G., A. J. VanDeValk, C. M. Adams, J. T. H. Coleman, J. L. F omey, and M. E. Richmond. 2004. Cormorant predation and the population dynamics of walleye and yellow perch in Oneida Lake. Ecol. Applic. 14: 149—163. Stevenson, R. J ., M. L. Bothwell, and R. L. Lowe. 1996. Algal Ecology: Freshwater Benthic Ecosystems. Academic Press. Winder, M. and D. E. Schindler. 2004. Climate change uncouples trophic interactions in an aquatic ecosystem. Ecology. 85: 2100-2106. Ulanowicz, R. E. 1986. Growth and Development: Ecosystems Phenomenology. Springer Verlag. Vanderploeg, H. A., T. F. Nalepa, D. J. Jude, E. L. Mills, K. T. Holeck, J. R. Liebig, I.A. Grigorovich, and H. Ojaveer. 2002. Dispersal and emerging ecological impacts of Ponto Caspian species in the Laurentian Great Lakes. Can. J. Fish. Aquat. Sci. 59: 1209-1228. CHAPTER TWO Invasive Species Impacts on Ecosystem Structure and Function: A Comparison of Oneida Lake, USA, Before and After Zebra Mussel Invasion Andrea L. J aeger, Doran M. Mason, Ann E. Krause, Kenneth A. Frank, William W. Taylor, and Scott D. Peacor Abstract Exotic species invasion is one of the greatest ecological restructuring forces. To understand impacts of exotic species on ecosystem level properties, we compared Oneida Lake, New York, USA, food web characteristics before and after zebra mussel (Dreissena polymorpha) invasion using ecological network analysis (ENA) and social network analysis (SNA) methods. ENA quantifies ecosystem function through an analysis of food web energy and material transfer. The SNA method we used, cohesion analysis, assesses ecosystem structure by organizing food web members into subgroups of strongly interacting predators and prey. These methods detected direct and indirect effects, changes in trophic flow efficiency, and alterations of food web organization and ecosystem activity resulting from zebra mussel invasion. ENA indicated that zebra mussels altered food web function by shunting energy from pelagic to benthic pathways, increasing dissipative flow loss, and decreasing ecosystem growth. SNA suggested that zebra mussels altered food web structure by reorganizing carbon flow within and between discrete subgroups of predators and prey and also increasing the importance of benthically associated subgroups. Together, these analyses demonstrate that zebra mussels exert strong influence on food webs and promote the benthification of aquatic ecosystems. Introduction Globally, exotic species invasion is one of the greatest restructuring forces to ecosystems (Baxter et al. 2004). Non-native species can impact ecosystems through competition with and predation on native species, and by altering habitats, nutrient cycles, and energy budgets (Mack et a1. 2000). Invasions can occur across all trophic levels with effects propagating throughout entire ecosystems via direct and indirect pathways (Crooks 2002). In recent years, vertebrate and invertebrate species from the Ponto-Caspian region of eastern Europe have exerted pronounced invasion pressure in North America, Europe, and Russia (Drake and Bossenbroek 2004). Among the most recognized Ponto-Caspian invertebrate invaders in North America are two species of mussels, the zebra (Dreissena polymorpha) and quagga (D. bugensis) mussels. These invaders exhibit wide environmental tolerances and high phenotypic variability (Reid and Orlova 2002) which make them adaptable to many different ecosystems and thus helps facilitate their invasion into non-native food webs. Dreissenid mussels pose a considerable threat to aquatic environments by altering food web structure and function (Jones et al. 1994; Vanderploeg et al. 2002). Zebra mussels increase water clarity through filtration (Idrisi et al. 2001) and shunt energy from pelagic to benthic pathways (Rutherford et al. 1999; Mayer et a1. 2002). Additionally, dreissenid mussels can affect zooplankton production and abundance through decreasing pelagic primary production and changing nutrient cycling in lakes (Mellina et al. 1995; Johannsson et al. 2000) and rivers (Strayer et al. 1999; Thorp and Casper 2003). Also, dreissenid mussels may facilitate macroinvertebrates, such as amphipod and isopod species, in the Laurentian Great Lakes through pseudofeces deposition which can be used as a food resource (Beekey et al. 2004). Yet, the abundance of some macroinvertebrate species, such as Diporeia spp., has precipitously declined in correlation with the invasion and expansion of dreissenids (Nalepa et al. 2000). Dreissenid invasions may also affect fish communities, although the causal linkages are difficult to establish in some systems. Dreissenids may affect fish recruitment and production through modification or degradation of spawning habitat (Stewart et al. 1999; Marsden and Chotkowski 2001). Additionally, some Great Lakes fishes, such as lake Whitefish (Coregonus clupeaformis), exhibit decreased body condition and growth potentially due to a diet shift away from high-energy prey, such as Diporeia, to the lower-energy dreissenid mussels (Pothoven et al. 2001). Dreissenid impacts on yellow perch (Percaflavescens) vary by life stage and ecosystem. For example in Lake Michigan, zebra mussels may have adversely affected larval yellow perch by decreasing zooplankton food resources (Dettrners et al. 2003). Conversely in some inland lakes, zebra mussels have not noticeably affected young yellow perch growth, biomass, or production (Mayer et al. 2000, Idrisi et al. 2001) and may indirectly benefit adult yellow perch and lake sturgeon (Acipenserfulvescens) through enhanced benthic invertebrate production (Rutherford et al. 1999; Jackson et al. 2002). Centrarchid fish can also benefit indirectly by zebra mussel facilitation of macrophyte production which serves as habitat (Strayer et al. 2004). 10 The uncertainty within systems and confounding results of dreissenid impacts between systems highlight the complexities associated with understanding ecosystem level response to invaders. Integrated and quantitative approaches, such as network analyses, offer innovative methods to disentangle the complexities of ecosystems. For network analysis, food webs are depicted as networks of exchange by quantifying (i.e., weighting) feeding interactions and energy flow (Bondavalli et al. 2000). The ability to quantify trophic interactions can contribute significantly to food web analysis (Gaedke 1995; Zorach and Ulanowicz 2003; Krause et al. 2003). Much of the early work conducted on food webs used unweighted flows, frequently over-simplifying or misrepresenting flux processes: the role of minor contributors was exaggerated while the role of major contributors was diminished. By quantifying flows, researchers tease apart these unequal contributions to provide a clearer depiction of food web energy and material transfer, and allow a better understanding of how interactions are transmitted through ecosystems. Moreover, network analyses are applicable at the whole-system level. By quantifying interactions throughout the entire ecosystem, insight into processes not evident at small-scale resolutions may be gained (Heymans et al. 2002). Bailey et al. (1999) suggested that small-scale impacts may aggregate synergistically and these overall impacts may only be visible when viewed at the ecosystem level. As such, network analysis has proven useful for examining the effects of fisheries harvest (Pauly et al. 1998), fisheries stocking (Fayram et al. In press), and nutrient loading (Bondavalli et al. In press) on ecosystems, while having implications for managing carbon emissions (Bondavalli et al. 2000) and habitat for endangered species (Heymans ct al. 2002). By 11 taking into account entire ecosystems, the use of network analysis in these studies allowed an understanding — distinct from, but complementary to, single-species, species- pair or similar studies — of how changes percolated through entire food webs, including indirect pathways. Moreover, network analysis can give insight into causality between events, not just correlation. The causality aspect makes network analysis a valuable tool for clarifying the effects of ecosystem perturbation, including exotic species invasion. In light of the equivocal effects of dreissenid invasion described above, we seek to elucidate dreissenid impacts at the ecosystem scale using network analysis. Numerous data exist describing the qualitative effects of dreissenid mussels, especially zebra mussels; however, less literature quantifies these effects at the ecosystem scale, specifically with regard to ecosystem structure and function. Ecosystem structure encompasses the components of a food web, whereas ecosystem function refers to the processes that occur within food webs (Stevenson et al. 1996). Structural characteristics include measurements of system state, such as biomass and taxonomic composition; whereas, functional characteristics deal with rates of change in a system state, including measurements of productivity and respiration (Stevenson et al. 1996). Mills et al. (2003) documented changes in Lake Ontario structure and function after zebra mussel invasion and coined the term “benthification” to encompass these changes. Benthification refers to a shift of importance from pelagic processes to benthic processes, entailing a change in energy flow “favoring colonization of bottom-dwelling organisms, promoting fish communities that make efficient use of the benthic habitat, and enhancing growth rate cycles of benthic algae and submersed aquatic vegetation”. Using Mills ct al. (2003) attributes of ecosystem benthification, we examined ecosystem properties of a eutrophic 12 lake, Oneida Lake, New York, USA, to determine if benthification occurred as a result of zebra mussel invasion. The primary objective of this paper was to quantify zebra mussel impacts on ecosystem structure and function in Oneida Lake, specifically by addressing the following questions: 1. Structure: Do zebra mussels alter the membership of food webs and food web subgroups (defined as clusters of strongly interacting predators and prey)? 2. Function: Does the magnitude of carbon flow within food webs and food web subgroups change as a result of zebra mussel invasion? Using food web network analysis, we hypothesized that zebra mussels led to the benthification of Oneida Lake with concomitant changes in ecosystem structure and function that promoted benthic communities. Methods Study Site Oneida Lake is a shallow, eutrophic, 207 km2 lake on the Ontario Lake Plain in central New York with a mean depth of 6.8 m and maximum depth of 16.8 m (Jackson et al. 2002; Rudstam et al. 2004). The lake freezes in winter and mixes continuously during summer except for brief periods of thermal stratification during calm weather (Hansen and Hairston 1998). Oneida Lake supports a valuable warrnwater recreational fishery for walleye (Sander vitreus) and yellow perch, in addition to multiple other species (V anDeValk et al. 2002). Zebra mussels were discovered in 1991 and were established throughout the ecosystem by 1992 (Mayer et al. 2000). Because of the long-terrn history 13 of limnological and fishery research on Oneida Lake (e.g., Mills et al. 1978; Mills and Fomey 1988), data exist throughout the various stages of invasion - from pre- introduction, to invasion, through establishment, and finally reorganization and accommodation of the ecosystem — to examine the effects of zebra mussel invasion. Network Construction We constructed weighted food web networks before and after zebra mussel invasion and analyzed the networks using ecological network analysis (ENA) (U lanowicz 1986) and a social network analysis (SNA) method, cohesion analysis (CA) (Frank 1995; Krause et al. 2003). We defined the years 1986 to 1991 as the pre-zebra mussel invasion time stanza and the years 1992 to 2002 as the post-zebra mussel invasion time stanza. To construct the networks, we first identified the taxa in the ecosystem (including full-year resident taxa as well as transient taxa), and then quantified material exchange (flows) between taxa and with the environment (we adjusted flows for transient taxa based on duration in the ecosystem). For taxa identification, we attempted to be as thorough as possible and included all species from Oneida Lake for which data were available. Taxonomic resolution affects the study of food webs and lumping organisms into aggregate groups may decrease the ability to detect differences in strengths of connections between functionally different organisms (Abarca-Arenas and Ulanowicz 2002; Krause et al. 2003; Pinnegar et al. 2005). Therefore, wherever possible, we used species level data to avoid information loss and in some cases, e.g., walleye, yellow perch, and seven other fish taxa, species data was sub-divided by life stage. However, in some cases, data limitations forced aggregation of taxa (e.g., age-0 panfish). In some of these situations, we aggregated by “trophospecies”, a collection of species in a food web 14 that share similar predators and prey (Yodzis and Winemiller 1999). This aggregation method is a fundamental unit of study in food web and ecosystem research (Yodzis and Winemiller 1999) and is widely used in food web analysis (e.g., Teal 1962; Moloney and Field 1991; Bondavalli et al. 2000). Where high resolution trophic information was not available (such as for benthic invertebrate and phytoplankton species), clustering adhered closely to taxonomic distinctions as opposed to trophic relationships. Finally, data on the microbial food web was not available for Oneida Lake and was not included in our networks. The complete list of the seventy-seven species and aggregate groups for the pre- and post-zebra mussel invasion networks are listed in Table 2.1. After identifying the food web components, we created the network connection topography, i.e., food web exchanges. Exchanges occur both within the food web through predator-prey interactions and between the food web and surrounding environment through migration, primary production, respiration, and harvest (Bondavalli et al. 2000). We used carbon as our network currency for biomass (gC m'z) and exchange between taxa (gC m"2 yr'l). To estimate carbon exchanges, we obtained data on biomass, production-, consumption-, and respiration-to-biomass ratios, diet proportions, migrations, and harvest for all taxa from the primary literature, field studies, and expert researchers on Oneida Lake (including the Bay of Quinte - Oneida Lake Comparative Modelling Workgroup). These parameters along with their sources are listed in Appendix 2.1. Exchanges either flow into a taxa as a carbon input (e. g., consumption and immigration), or flow out of the taxa as a carbon output (e.g., production, respiration, harvest, and emigration). To calculate production, consumption, and respiration for taxa, we multiplied the production-, consumption-, and respiration-to- 15 biomass ratios by the taxa biomass. To quantify feeding relationships between predatory taxa and prey, we apportioned the predator’s consumption among its prey items by multiplying the predator consumption estimate and predator diet vector (a list of predator diet items proportioned by weight). This calculation yielded a vector of carbon exchanges (gC rn'2 yr'l) between the predator and its prey. Aligning the exchange vectors for every predator in the system creates what is called the exchange matrix. The exchange matrix quantifies all feeding relationships within the network and is the foundation of our network analysis calculations. Our ENA required networks to be mass-balanced, i.e., a condition where the amount of medium entering any taxa equals the amount leaving (Allesina and Bondavalli 2003). We assessed the flow balance of our networks by comparing inputs and outputs for all taxa. If a flow imbalance existed, we rectified the discrepancy by either assigning a flow to detritus (if inputs exceeded outputs) or changing one or more model inputs. The detrital-balancing approach is partially drawn from mass-balance methods employed in the software EcoPath (Christensen and Pauly 1992) and was our means to assign flow to detritus in lieu of field estimates. When changing a model input to obtain mass- balance, we used factors such as ecological plausibility (i.e., the similarity of the Oneida Lake parameter to other systems of similar trophic status) and confidence in accuracy of parameter estimates as guides to determine which parameter to change. Finally, to resolve any remaining imbalances, we used the DATBAL routine incorporated in the EcoNetwrk software (http://www.glerl.noaa.gov/EcoNetwrk/). These routines resulted in balanced food web networks with as few changes to the original model inputs as possible. 16 Appendix 2.2 presents the balanced exchange matrices for the pre- and post-zebra mussel invasion networks. Ecological Network Analysis After we constructed the networks, we performed the ENA and CA routines to quantify Oneida Lake function (via ENA) and structure (via CA) before and after zebra mussel invasion. ENA is a method that evaluates the efficiency of energy and material flow (e. g., transfers, assimilations, and dissipations) in ecosystems (U lanowicz 1986). We used three types of ecological network analyses (U lanowicz 1986): 1) input / output analysis, 2) trophic level analysis, and 3) the calculation of ecosystem indices. To perform the analyses, we used the software package EcoNetwrk, a Windows-based version of the NETWRK software (U lanowicz & Kay 1991). We provide a brief description of ENA methods below; for greater detail see Ulanowicz (1986) and Ulanowicz (1997). Input / output analysis (Harmon 1973; Patten et al. 1976) details the direct and indirect linkages between any two taxa in a network, quantifying the requisite carbon needs of any one taxon supplied by any other taxon (Bondavalli et al. 2000). The analysis includes a routine called IMPACTS that quantifies the relative effect of one taxon on another by tracing direct and indirect predatory interactions (Heymans and Baird 2000). Trophic analysis reinterprets the web of predator-prey transfers in terms of the linear trophic chain concept of Lindeman (Lindeman 1942). Using input / output techniques, the trophic analysis apportions the activities of omnivores among a series of 17 hypothetical integer trophic levels to create the Lindeman spine, which can be used to evaluate the efficiency of carbon flow in the system (Heymans and Baird 2000). Ecosystem indices quantify abstract system level properties such as growth and development, and provide insight into both the vulnerability and resilience of an ecosystem to perturbation (Ulanowicz 1997). These indices are: total system throughput (TST), average mutual information (AMI), ascendency (A), overhead (0), and development capacity (C). The activity level of the ecosystem is quantified via TST which is simply the sum of all the carbon flows (gC rn'2 yr'l) in the system. TST relates to the size of an ecosystem gauged similarly to how economic activity is measured (i.e., as the flow of some currency) and can be used to quantify ecosystem growth. AMI is an information theoretic index (Shannon 1948; McEliece 1977) that quantifies the organization of a network based on pathway flow constraints. Ascendency quantifies the growth and development of an ecosystem (Ulanowicz 1986) as well as the network’s performance in processing medium. Ascendency is calculated by scaling the AMI with TST: A = TST x AMI . As such, ascendency encompasses both the size (via TST scaling) and organization (via AMI) of an ecosystem. Overhead quantifies the system’s inefficiencies at processing material and energy (Heymans et al. 2002) as well as the degree of freedom that the system has to reconfigure itself in the face of perturbation (Heymans and Baird 2000). There are four main contributors to ecosystem overhead: imports (i.e., immigrations) to and exports (i.e., emigrations and fisheries harvest) from the ecosystem, dissipative flow loss due to respiration, and redundant food web flows (i.e., multiple paths over which energy flows between taxa). Overhead is calculated by scaling the system’s conditional entropy (Ulanowicz 1986), a measure of the 18 disorganization in a network, by TST: 0 = T ST x Conditional Entropy. Development capacity represents the theoretical upper bound on system organization and growth. Capacity subsumes both ascendency and overhead, such that: C = A + 0. Cohesion Analysis Cohesion analysis identifies subgroups in food webs based on the strength of interactions (i.e., predator-prey relationships) within subgroups (Krause et al. 2003), where the maximization of an odds ratio is used as a criterion to assign subgroup membershipz. CA uses an iterative algorithm that reassigns taxa to subgroups to maximize the odds that interactions occur within subgroups, versus between subgroups. The algorithm uses interaction weight to preferentially assign predators and prey with strong interactions to common subgroups. This algorithm is a robust method for assigning subgroups because it: 1) is an objective technique to assign subgroups; 2) does not require pre-specification of the number of subgroups; 3) identifies discrete (i.e., non- overlapping) subgroups; and 4) tests the statistical significance of the results (Frank 1995; Frank 1996; Krause et al. 2003). To determine the optimized subgroups, the algorithm sums the weight of realized interactions (i.e., predator-prey exchanges) within a subgroup and evaluates that sum against realized interactions that occur between subgroups, in addition to unrealized interactions (i.e., taxa combinations that do not interact) within and between subgroups. Table 2.2 describes this process. The intent is to determine the network structure that maximizes realized interactions within subgroups and unrealized interactions between subgroups while minimizing realized interactions between subgroups and unrealized interactions within subgroups. 2 Our use of the term “subgroup” is analogous to the Pimm and Lawton (1980) definition of food web “compartment”. We use the term “subgroup” to avoid confusion between Pimm and Lawton (1980) and Ulanowicz(1986) uses of the term “compartment”. 19 Using the software Kliquefinder (Frank 1995), we identified subgroups within the Oneida Lake food web networks before and after zebra mussel invasion and compared the grouped webs to reveal changes in food web structure. Although our ENA required balanced networks, our CA did not. Therefore, in order to avoid introducing uncertainty to the CA models from ENA balancing procedures, we used the unbalanced networks for CA of both time stanzas. Furthermore, because we derive detrital diet as a result of balancing procedures, we could not include detrital groups in our CA. For the pre-zebra mussel invasion network, carbon flows ranged from 8.26x10'lo to 8.25 gC rn'2 yr'l, a difference of 10 orders of magnitude; for the post-invasion -ll - network, carbon flows ranged from 7.48x10 to 18.38 gC rn'2 yr'l, a difference of 12 orders of magnitude. Kliquefinder accepts flow weights only within 5 orders of magnitude; therefore, we needed to adjust the range of network data. Appendix 2.3 describes, in detail, the method we used. We tested three adjustments of data ranges, and compared the adjustments based on statistical tests of subgroup membership. The three adjustments involved: 1) changing the range of data by one order of magnitude between the schemes; 2) assigning the maximum flow weight to flows above the range of Kliquefinder; and 3) assigning the minimum flow weight to non-zero flows below the range of Kliquefinder. Adjustment one set the highest flows one order of magnitude above the upper range of Kliquefinder, and adj ustrnents two and three set the highest flows two and three orders of magnitude above the upper range for Kliquefinder, respectively. Subgroup membership was similar for all adjustments (p g 0.001 for all comparisons); we chose adjustment two because it assigned maximum and minimum values to the fewest flows overall. 20 Kliquefinder incorporates a Monte Carlo-like routine to test the odds ratio of a subgrouped network against a distribution of odds ratios from randomly generated re- combinations of data (Frank 1996). Using this method, we tested the statistical significance of our subgroups against 1,000 randomized versions of our networks. Additionally, using the Quadratic Assignment Procedure (QAP) method (Hubert 1987) for significance testing, we statistically compared subgroup membership between the pre- and post-zebra mussel invasion time stanzas. We summarized results of the CA as “crystallized sociograms” through multidimensional scaling (Frank 1996) in SAS System for Windows. With this scaling method, proximity of subgroups corresponds to: 1) the strength of predator-prey relationships spanning the subgroups (i.e., closely spaced subgroups have relatively stronger interactions connecting them than subgroups farther apart); 2) connections to similar subgroups; and 3) the subgroup’s importance to overall food web structure (i.e., centrally located subgroups are more important to food web structure than peripherally located subgroups). Also, taxa location within a subgroup boundary indicates: 1) the strength of interactions between taxa; and 2) the importance of taxa to the subgroup (i.e., taxa in the center of subgroups relate more strongly to the subgroup, while taxa near subgroup boundaries only experience peripheral relationships to the subgroup). After we identified cohesive subgroups, we performed ENA on the largest subgroup before and after zebra mussel invasion to evaluate functional linkages. We maintained the same mass-balance in the subgroup analysis as the full food webs by treating all flows to and from taxa outside the subgroup as imports and exports to subgroup taxa. Because detrital groups were not assigned to subgroups, detritus could 21 not be explicitly incorporated into the subgroup ENA. Inclusion of the microbial food web could serve as a surrogate for detritus flow; however, as stated above, microbial data was not available for Oneida Lake. Nevertheless, flow to detritus was implicitly included in the subgroup ENA by treating detrital flow as an export from the subgroup. This procedure had two ramifications: 1) we could address detrital flow, albeit indirectly, in the subgroups; and 2) we maintained the same mass-balance used in the full food web ENA. If, as hypothesized, zebra mussels led to the benthification of Oneida Lake, we expected to see increased importance of benthic pathways within this subgroup. Results Ecological Network Analysis — Entire Network Input / output analysis Zebra mussels had more negative impacts across all taxa than neutral or positive impacts (Figure 2.1). In general, zebra mussels positively influenced benthic fish such as ictalurids, carp, and lake sturgeon, while negatively affecting pelagic fish, including walleye, yellow perch (pelagic for some life stages), white perch, alewife, and shiners. Some fish, such as gizzard shad and centrarchid species, showed mixed impacts based on life stage (e.g., juvenile gizzard shad were negatively affected while adult gizzard shad were positively affected). Most likely this is due to ontogenetic diet shifts between the juvenile and adult life stages (Werner and Gilliam 1984), although some fish that undergo diet shifts, e.g., yellow perch, did not show a similar pattern. Benthic invertebrates exhibited mixed impacts, with amphipods and isopods benefiting from zebra mussel interaction, while zebra mussels had a large negative influence on themselves due to 22 heavy grazing on their food sources. Zebra mussels also negatively influenced zooplankton and phytoplankton. Zebra mussels had little, if any, effect on some fishes (e.g., smallmouth bass and white bass), invertebrates (e.g., oligochaetes and snails), and periphyton, epiphyton, and macrophytes. Finally, zebra mussel influence on detritus was mixed: pelagic detritus and DOC were negatively affected, most likely through direct consumption by zebra mussels, while sedimented detritus was positively affected likely due to deposition of pseudofeces. The positive effect on sedimented detritus may explain why impacts on benthic invertebrates were mixed. Amphipods and isopods rely more heavily on sedimented detritus and less heavily on plankton resources than do other benthic invertebrates such as chironomids and clams. Lindeman trophic analysis We were unable to create the Lindeman trophic spine for the full Oneida Lake food web networks due to computational limitations in the EcoNetwrk software resulting from the complexity of our networks. Although we could not analyze efficiency of flow between trophic levels, we can diagnose the efficiency of flow summed across the entire food web. Flow loss due to respiration in the full food web was 1015.6 gC m'2 yr'l before zebra mussel invasion and 777.9 gC rn'2 yr'1 after zebra mussel invasion, a 23% decrease. Total production (i.e., feeding exchanges between taxa plus the usable exports from the system) in the full food web was 624.1 gC m'2 yr'l before zebra mussel invasion and 589.1 gC m'2 yr.1 after zebra mussel invasion, 3 5% decrease. Ecosystem indices TST decreased from 2653.8 to 2143.6 gC m'2 yr'l, approximately a 20% loss in ecosystem activity (Table 2.3). Additionally, the development capacity decreased from 23 13316.7 to 11037.2 gC-bits m'2 yr'1 after zebra mussel invasion. Likewise, ascendency dropped after invasion, from 3350.9 to 2926.3 gC-bits rn'2 yr'l constituting a 13% decrease, as did total overhead, from 9965.9 to 8110.9 gC-bits rn'2 yr'l representing a 19% decrease. However, these results were partially driven by changes in TST (i.e., system growth), which scales capacity, ascendency, and overhead. To remove the effects of TST scaling on capacity, we divided capacity by TST. Unsealed capacity increased from 5.0 to 5.1 bits, representing a 2% increase in the potential for system development. To remove the effect of TST scaling on ascendency and overhead, and look solely at the amount of organized and disorganized ecosystem function, we divided both indices by the development capacity. This calculation removed the TST scaling through division and yielded the proportion that ascendency and overhead comprised of capacity (expressed as a percent of capacity in Table 2.3), termed “relative ascendency” and “relative overhead”, respectively. Ascendency constituted 25.2% of capacity before zebra mussel invasion and 26.5% of capacity after invasion. Overhead represented 74.8% of capacity before zebra mussel invasion and 73.5% after. These results indicate that the Oneida Lake food web is predominantly comprised of disorganized flow, but became slightly more organized after zebra mussel invasion. Considering the ecosystem processes that contribute to system overhead (imports, exports, dissipations, and flow redundancies), the relative overhead indices decreased after zebra mussel invasion between 1% and 22% except for flow redundancies, which increased almost 7%. Cohesion Analysis We identified six significant subgroups for the pre-zebra mussel invasion network (p S. 0.001; odds ratio = 15.4) and seven significant subgroups for the post-invasion 24 network (p 5 0.001; odds ratio = 14.7). Tables 2.4 and 2.5 present the subgroup membership for the pre- and post-invasion networks, respectively. Both networks contained three subgroups of predator-prey interactions: 1) a planktivorous food web (including planktivorous fish, zooplankton, and phytoplankton), 2) benthically associated predators and prey, and 3) planktivores and zooplankton prey. Additionally, both networks contained three mostly fish subgroups: l) panfish, 2) piscivores, and 3) piscivores and invertivores. Finally, the seventh subgroup in the post-invasion network contained mainly low biomass taxa from multiple trophic levels. We loosely named subgroups based on ecological descriptions that represent the majority of taxa within each subgroup. The names are meant as a tool to facilitate discussion of analyses; however, not all taxa fit the subgroup name. Subgroup membership was similar between the two time stanzas (Z-score = 20.60, p 5 0.001) despite a large number of changes to subgroup membership. Of the seventy taxa present for both time stanzas, twenty-three (33% of all taxa) changed subgroup membership after invasion: seventeen fish, five zooplankton, and one benthic invertebrate. Zebra mussels invaded the planktivorous food web subgroup (subgroup 1), the largest subgroup (based on number of taxa) in both time stanzas. Subgroup shifts relevant to Oneida Lake fisheries management include subadult (age 1-3 years) walleye, which moved to the subgroup (subgroup 6) with cormorants (Phalacrocorax auritus) after invasion and adult walleye (age 4 years and older), which shifted to the subgroup containing zebra mussels. Juvenile (age-0) yellow perch also transferred to the subgroup containing zebra mussels while subadult (age 1-2 years) yellow perch shifted to the benthically associated subgroup (subgroup 2). 25 Figures 2.2 and 2.3 summarize the cohesion analysis in crystallized sociograrns. Before zebra mussel invasion, the planktivorous food web, benthically associated, and piscivore (subgroup 5) subgroups strongly interacted and played central roles within the food web (Panel A). The remaining subgroups had more peripheral roles. After invasion, the subgroups were more closely related except for the subgroup containing low biomass taxa (subgroup 7). The taxa within the planktivorous food web and benthically associated subgroups strongly interact whereas the taxa in the remaining subgroups are not as cohesive (Panel B). Phytoplankton and zooplankton play central roles within the planktivorous food web subgroup, while benthic invertebrates occupy central positions within the benthically associated subgroup. Ecological Network Analysis — Grouped Network Below, we analyze the functional characteristics of the subgroup that zebra mussels invaded, the planktivorous food web subgroup (hereafter also referred to as the zebra mussel subgroup), which is the largest subgroup before and after invasion in terms of number of taxa and TST (Table 2.6). Input / output analysis When we deciphered the direct and indirect effects of zebra mussels on their subgroup (via the IMPACTS analysis), we found that zebra mussels negatively affected all their subgroup members (Figure 2.4). Our full food web analysis also indicated that zebra mussels negatively affected these taxa (Figure 2.1); however, the magnitudes of the effects differed slightly in the subgroup analysis. The largest difference involved zebra mussel influence upon themselves. The IMPACTS value changed from -0.33 in the full food web (Figure 2.1) to -0.11 in the subgroup, representing a 67% change. Potentially 26 we see a lessened effect of zebra mussels upon themselves at the subgroup level because detrital groups, including pelagic detritus and DOC, were not included in the analysis. Zebra mussels prey heavily on detrital groups, negatively affecting themselves via depletion of their food supply. Although we cannot directly conduct an IMPACTS analysis of zebra mussels on the other six subgroups (to conduct the analysis, zebra mussels would need to be present in the subgroup network) we can indirectly detect zebra mussel influence in those subgroups by considering impacts on individual taxa from our full food web analysis (Figure 2.1). Unlike the (wholly negative) zebra mussel influence on taxa in their subgroup, zebra mussel effects on taxa in other subgroups were mixed with no consistent pattern between subgroups. The majority of negative effects were confined to the zebra mussel subgroup while some subgroups, including subgroups 2, 4, 5, and 6, exhibited net positive effects of zebra mussels Lindeman trophic analysis The Lindeman trophic analysis identified six trophic levels in the zebra mussel subgroup before invasion and nine trophic levels after invasion (Figures 2.5 and 2.6). Before invasion, age-0 gizzard shad were the top predator in the subgroup and fed up to the sixth trophic level; after invasion and with the addition of multiple fish to this subgroup, adult walleye were the top predator and fed at the ninth trophic level. Zebra mussels fed at the second trophic level; consequential to their invasion, trophic flow efficiency fell almost 10% at trophic level II as respirative losses more than tripled and flow loss to detritus almost doubled. Flow efficiencies at trophic levels IV and higher increased subsequent to invasion. 27 Total respiration and production decreased in the zebra mussel subgroup after invasion. Flow loss due to respiration was 424.1 gC rn'2 yr'l before invasion and 396.2 gC m'2 yr'1 after invasion (6% decrease), while production was 484.7 gC m.2 yr'l before invasion and 401.0 gC rn'2 yr'1 after invasion (17% decrease). Subgroup production constituted 78% of the full food web production before invasion, but only 68% after invasion. Furthermore, subgroup respiration contributed 42% to the full food web before invasion, and 51% after invasion. Ecosystem indices Similar to the analysis of the full food web, TST and development capacity fell after zebra mussel invasion. Before invasion, TST and capacity were 1705.2 gC m'2 yr-1 and 7574.4 gC-bits rn'2 yr°l, respectively; after invasion, throughput and capacity declined to 1415.8 gC rn'2 yr'l (a 17% decrease) and 6651.5 gC-bits m°2 yr'1 (3 12% decrease), respectively. Unsealed capacity increased after invasion, from 4.4 to 4.7 bits, a 7% increase. Unlike the full food web ecosystem analysis, relative ascendency decreased over 3% while relative overhead increased by 1% in the subgroup after invasion. Relative overhead on imports and exports decreased by 4% and 28%, respectively, while relative flow redundancies increased by 54% after invasion. These results parallel the full food web analysis, although the increase in relative flow redundancies was substantially greater for the subgroup than the full food web (7% increase). However, unlike the full food web, relative dissipative overhead increased by 4% in the subgroup after invasion. Finally, the subgroup constituted 64% of the full food web TST and 57% of capacity before invasion, and 66% of TST and 60% of capacity 28 after invasion. Essentially, subgroup size and potential for development increased after zebra mussel invasion relative to the full food web, making this subgroup a more important part of the food web. Discussion Zebra mussels exerted a far-reaching influence on the Oneida Lake food web, altering the membership of food web subgroups (question 1) and changing the magnitude of carbon flows within the full food web and subgroups (question 2). Our analyses support the hypothesis that zebra mussels lead to the benthification of their invaded ecosystems by shunting energy from pelagic to benthic pathways and promoting benthically associated species. Our research constitutes the first test of this hypothesis using ecosystem level measures. Furthermore, this research is the first application of CA, a social network analysis, in conjunction with ENA. Recent unions of methods from ecology and sociology (e.g., Krause et al. 2003; Zhao and Frank 2003) reveal there is value found in the convergence of these disciplines, especially when applied to food webs. While SNA largely focuses on structural analyses (Mayhew 1980), ENA is a functional analysis (U lanowicz 1986). However, Johnson et al. (2001) affirm that ENA and SNA are markedly similar mathematically and conceptually. The merging of these two methods to understand the integration of ecosystem structure and fimction seems a natural extension. Our application of ENA in combination with CA offers a novel analytical technique for understanding zebra mussel impacts on ecosystem processes. We begin our discussion below with CA, and then place the structural findings within the 29 context of the full food web and subgroup ENA, emphasizing the contribution to our knowledge of ecosystems. Cohesion Analysis - Structure Almost one-third of all taxa changed subgroups after invasion. Although the difference in subgroup membership between the pre- and post-zebra mussel time stanzas was not statistically significant (despite 33% of all taxa shifting subgroups), we believe these shifts are ecologically significant based on the restructuring of the paths of carbon flow within subgroups. The zebra mussel subgroup underwent the greatest change, increasing membership from twenty-four to twenty-nine taxa, including the addition of zebra mussels as well as multiple fish and zooplankton. These shifts broadened the once pelagic-based subgroup by increasing food chain length and creating important links via benthic pathways. Although this subgroup underwent the greatest change after invasion, the benthically associated subgroup also increased membership by one fish group, while all other subgroups lost members. These subgroup shifts suggest that benthic pathways gained importance as a result of zebra mussel invasion. According to food web stability theory, a taxon that is not directly affected by a disturbance event, such as exotic species invasion, can still be affected via the transfer of effects over strong interactions (McCann et al. 2005). Within subgroups, the strong interactions among members can transfer the effect of a disturbance throughout the subgroup even if not all members are directly affected by the event. Conversely, taxa in other subgroups will be either weakly impacted or not impacted as the effects must be transferred through the weak interactions between groups. Thus taxa within the subgroup invaded by zebra mussels are especially vulnerable to effects of this exotic species, 30 whereas taxa in other subgroups may be more sheltered from effects. Life stages of walleye and yellow perch comprised a large proportion of the subgroup shifts after zebra mussel invasion. Common subgroup membership offers structural underpinnings for zebra mussel influence on juvenile yellow perch growth rate (Mayer et al. 2000) and adult walleye abundance (Rutherford et al. 1999). Additionally, due to the tight coupling of walleye and yellow perch populations in Oneida Lake (Rose et al. 1999), within- subgroup influence of zebra mussels on these species can cascade to their corresponding life stages in other subgroups, despite the buffering that subgroup structure may offer. After invasion, subadult walleye moved to the subgroup containing piscivore and invertivore taxa (subgroup 6), including cormorants. Common subgroup membership gives structural support for Oneida Lake diet studies that suggest cormorants exert strong predatory pressure on subadult walleye (F omey 1993; VanDeValk et al. 2002; Rudstam et al. 2004). Since subadult walleye composed one-quarter of cormorant diet by weight (Appendix 2.2) and cormorant biomass more than quadrupled from the 19808 to the 19908 (Appendix 2.1), we feel it is likely that cormorants, rather than zebra mussels, influenced the shift of subadult walleye. However, despite strong cormorant predation pressure on all life stages of yellow perch and walleye (totaling over two-thirds of cormorant diet, Appendix 2.2), most life stages were found in benthic pathways after invasion, despite the influence of an important pelagic predator. Structural analyses also lend insight into the fundamental ecological structure of Oneida Lake. In both time stanzas, one large subgroup dominated food web structure while multiple smaller subgroups played less significant roles. This result differs from CA findings on the Chesapeake Bay by Krause et al. (2003) who identified two 31 subgroups (one benthic, the other pelagic) co-dorninating food web structure. Perhaps structure differs between the systems because Oneida Lake is a shallow, well-mixed ecosystem with only brief periods of thermal stratification, while the Chesapeake Bay maintains thermal stratification from late spring to early fall (Bidle and Fletcher 1995), creating distinct structure between the thermal regions. These findings potentially suggest that food web structure is, at least in part, related to physical system structure. Similar to the Chesapeake Bay analysis, bivalve taxa (zebra mussels in Oneida Lake; clams and oysters in the Chesapeake Bay) shared subgroup membership with their pelagic prey. The majority of carbon flow in the zebra mussel subgroup originated in phytoplankton and was immediately routed through zebra mussels, making these mussels the main flow nexus in the system linking pelagic and benthic pathways. Our study suggests that this coupling of pelagic and benthic structure is a central influence of zebra mussels in Oneida Lake. Ecological Network Analysis - Function Aquatic ecosystems worldwide are in the midst of large-scale ecological alteration. To address ecosystem level change, we need quantifiable, objective criteria at the whole-system level (Westra et al. 2000), especially with the contemporary emphasis on ecosystem management (Christensen et a1. 1996). ENA is a valuable tool for deciphering impacts of perturbations at the ecosystem level because it offers a quantitative depiction of food web functioning, inclusive of all food web taxa (barring data limitations). Ulanowicz (1996) makes predictions for ecosystem level response to perturbation by drawing from Odum’s (1969) theory on ecosystem development. Ulanowicz suggested that perturbed ecosystems will have less efficient trophic chains, 32 decreased system throughput, and decreased food web organization. Our analysis supports Ulanowicz (1996) and affirms research question 2: zebra mussels considerably alter the magnitude of carbon flow within ecosystems. Our IMPACTS analysis suggested that zebra mussels have an overwhelmingly negative effect on food web taxa, especially subgroup members. This analysis is a rigorous way to determine perturbation effects since all food web paths, both direct and indirect, are incorporated in the analysis. Indirect paths are especially important as they may overwhelm direct interactions and even yield an opposite effect than a direct exchange (Patten 1984). In our analysis, the majority of large effects were contained in the zebra mussel subgroup, validating the assumption that subgroup members exert a stronger influence over one another than non-subgroup members. The few positively affected taxa tended to be benthically associated, yet some taxa with benthic life stages, like yellow perch, exhibited wholly negative impacts. However, when interpreting results of the IMPACTS analysis, it is important to bear in mind that we only conducted the analysis using the post-zebra mussel invasion network; changes in species interactions mediated by zebra mussels may have occurred between the time periods. For example, if zebra mussel invasion alleviated deleterious feeding pressure of certain predators on prey present in the pre-invasion time stanza, we might see zebra mussel facilitation of some taxa upon doing a before and after comparison using other measures besides IMPACTS. As an example, to refine the IMPACTS analysis, we can consider the throughput of subadult yellow perch, juvenile yellow perch, and juvenile walleyes before and after invasion. Although the IMPACTS analysis indicated that zebra mussels negatively influenced these life stages, their throughput increased after invasion, perhaps 33 due to changes elsewhere in the food web mediated by zebra mussels. Therefore, to fully understand zebra mussel influence on the Oneida Lake food web, the IMPACTS analysis must be used in conjunction with other functional analyses. The zebra mussel subgroup is the most important subgroup in Oneida Lake. This subgroup not only dominated food web structure, but also dominated function by sequestering carbon flow. After invasion, we found that the trophic chain increased by three levels and the subgroup garnered more carbon throughput relative to the firll food web. Additionally, the development capacity of the subgroup increased compared to the full food web. These results suggest that this subgroup not only increased in functional size, but also became a more complex and integrated part of the food web after invasion. However, despite gaining functional importance, the subgroup contributed proportionally more to food web flow loss after invasion. Respirative flow losses increased (9%) while production decreased (almost 10%) relative to the full food web. Thus, not only do we see evidence of an energy shunt to benthic pathways after zebra mussel invasion, but also indication of energy flow loss to dissipative paths and decreased food web efficiency. The Lindeman trophic analysis allows further inspection of flow efficiency at each trophic level within the zebra mussel subgroup. After invasion, flow efficiency for trophic level I increased almost 17%, efficiency at trophic level II decreased almost 10%, and the efficiency of the remaining trophic levels marginally changed. The driver of increased efficiency at the first trophic level was probably the decrease in phytoplankton biomass following invasion. With less phytoplankton available for consumption, a greater proportion of biomass passed into the grazing food chain, with less biomass lost to detrital pathways. The efficiency decrease at the second trophic level was potentially 34 due to the high respirative loss of zebra mussels relative to production (Appendix 2.2). In light of the subgroup results, we can conjecture trophic efficiency in the firll food web even though we could not create the Lindeman trophic spine. After invasion, phytoplankton biomass and throughput decreased, potentially increasing flow efficiency at trophic level I, as occurred in the subgroup. Although pelagic primary producers exhibited decreased activity after invasion, other sources of primary production, such as macrophytes and detritus (considered a primary source of carbon in ENA), gained functional importance. Before invasion, macrophytes produced 8.0 gC m'2 yr'l, compared to 9.0 gC m'2 yr'1 after invasion, a 13% increase. Detrital groups combined produced 11.6 gC rn'2 yr'I before invasion and 65.1 gC m'2 yr'1 after invasion. Despite a small absolute increase in carbon flow, this change represented an over 460% increase in detrital use, illustrating the importance of alternate sources of carbon, especially benthic, after zebra mussel invasion. Considering the entire food web, Ulanowicz (1996) predicted that that ecosystem organization, as measured by ascendency, will decrease after a perturbation while ecosystem disorganization, measured by overhead, will increase. To understand why system overhead should increase, it is helpful to consider the components of overhead: dissipative flow loss due to respiration, flow redundancies, imports to, and exports from the system. Although these processes can be disadvantageous during benign conditions, overhead can be advantageous if the system is perturbed in a novel fashion. Bondavalli et al. (2000) described overhead as a “strength in reserve of degrees of freedom which the system can call upon to adapt to a new threat.” In general, overhead increases after perturbation due to reorganization of flow structure while the ecosystem adapts. For 35 instance, as an exotic species becomes established in a system, the ecosystem may Shift from a stable state to a flux system, with concomitant flow reorganization, interruption of carbon cycling, and even loss of native species. Considering this flow of events common to exotic species introduction, we were surprised to observe the full food web relative overhead value decrease after zebra mussel invasion. Perhaps the food web exhibited increased organization due to the considerable flow asymmetry present after invasion. Zebra mussels conduct 10% of food web flow, potentially increasing organization by focusing flow (and increasing AMI). However, Ulanowicz’s (1996) perturbation theory held for the analysis of the zebra mussel subgroup, which should contain the most pronounced influence of zebra mussels in the food web (according to food web stability theory). Relative ascendency decreased, while relative overhead increased in the subgroup, suggesting that the subgroup underwent reorganization of carbon flow as it accommodated zebra mussel presence (as predicted by Ulanowicz’s theory). This finding presents compelling evidence for investigating food web function at multiple structural levels. Despite differences in organization between the subgroup and full food web, we found that (unsealed) deve10pment capacity increased at both levels after invasion. The rise in capacity indicates that zebra mussels added a layer of complexity to food web function. Complexity imparts multiple benefits to ecosystems, including more diversity of interconnections which allow alternate routes for taxa to obtain energy in the face of ecological change (Pérez-Espafia and Arreguin- Sénchez 1999). Consequently, despite eliciting several negative effects on Oneida Lake, including decreased food web efficiency and production, zebra mussel invasion conveyed some benefits to the ecosystem. 36 A limitation of ENA is variability in carbon flow estimates is not incorporated into the analysis. As a result, we cannot discern statistical significance in food web change with ENA. One of the main assumptions of ENA is that ecosystems are in a condition of mass-balance. After constructing a food web network, taxa rarely meet this assumption, as was the case in this analysis. Balancing introduces a degree of uncertainty into the analyses, thus careful choice of methods is imperative. We acknowledge that our balancing routines may have affected our results; however, we were careful to choose balancing methods that yielded ecologically plausible networks. The other critical assumption of this research was that any differences observed in food web structure and function between time stanzas were due to zebra mussel invasion. Although Oneida Lakes has been buffered from most exotic species introductions that plague the Great Lakes (e.g., the spiny (Bythotrephes longimanus) and fish-hook (Cercopagis pengoi) water fleas, the round goby (Neogobius melanostomus), and quagga mussels), zebra mussel invasion is not the only ecological change in recent years. For example, cormorant biomass increased independent of zebra mussel invasion and a lake sturgeon stocking program began in 1995. Although these events may have caused food web alteration, we believe that zebra mussel invasion far outweighed other ecological changes that occurred during our time stanzas. Not only did zebra mussels garner over 10% of total system flow, they also constituted over two-thirds of Oneida Lake’s living biomass (gC m'z). These numbers alone suggest that zebra mussel introduction is undoubtedly one the most significant changes to Oneida Lake’s ecology in recent years. Given the limitations of ENA, but considering the overwhelming presence of zebra mussels in Oneida Lake, we are confident in the robustness of our results and conclusions. 37 Moreover, our research corroborates other work conducted on Oneida Lake as well as supports research on the effects of zebra mussel invasion in other systems. In conclusion, this research supports the work of Mills et al. (2003) who hypothesized that zebra mussels lead to the benthification and reorganization of their invaded ecosystems. Our research presents the first test of this hypothesis using network analysis methods. Network analyses are valuable techniques for illuminating exotic species impacts at the whole-system level while at the same time allowing for inspection of impacts at the level of species or even life stage. We advocate the use of high resolution data for all food web taxa, including microbial pathways (Allesina et al. 2005), to gain a holistic understanding of ecosystem structure and function. As these data were not all available for Oneida Lake, we acknowledge that our aggregation scheme and choice of taxa may have affected results. However, our food web networks, with over seventy taxa and life stages for each time stanza, represent one of the most in-depth treatises of ENA food webs to date. Furthermore, the confluence of network analyses from multiple disciplines allowed us to look at ecosystem structure and function item a new perspective. We suggest network analysis methods be applied to other ecosystems that have experienced exotic species invasion to determine if the results presented here are unique to Oneida Lake, or ubiquitous across invaded ecosystems. Acknowledgements We thank Stefano Allesina, Tyler Wagner, and Andrew Fayram for helpful comments, the Bay of Quinte — Oneida Lake Comparative Modelling Project Workgroup, Edward Mills and the staff at the Cornell University Biological Field Station for data 38 contributions and guidance, Anne Clites, Timothy Hunter, and Marten Koops for their computational and programming assistance, and Cathy Darnell for her aid on graphics. This work was supported by a grant from the Great Lakes Fishery Commission. 39 Table 2.1. List of food web taxa. Cisco were present in the pro-zebra mussel time stanza but not the post-zebra mussel time stanza; lake sturgeon, zebra mussels, and Camptocercus harpae were present in the post-zebra mussel time stanza, but not the pre- zebra mussel time stanza. No. Common Name Taxonomic Classification No. Common Name Taxonomic Classification 1 Cormorants Phalacrocorax auritus 40 lsopods Isopoda 2 Walleye Age 4+ Sander vitreus 41 Lecches Hirudinea 3 Walleye Age 1-3 Sander vitreus 42 Oligochaetes Oligochaeta 4 Walleye Age-0 Sander vitreus 43 Snails Gastropoda 5 Yellow Perch Age 3+ Perca flavescens 44 Zebra Mussels Dreissena polymorpha 6 Yellow Perch Age 1-2 Percaflavescens 45 Alona species Alana species 7 Yellow Perch Age-0 Percaflavescens 46 Bosmina longirostris Bosmina longirostris 8 White Perch Age 1+ Morone americana 47 C amptocercus harpae Camptocercus harpae 9 White Perch Age-0 Morone americana 48 Ceriodaphnia quadrangula Ceriodaphnia quadrangula 10 Black Crappie Age 1+ Pomoxis nigromaculatus 49 Chydorus sphaericus Chydorus sphaericus ll Bluegill Age 1+ Lepomis macrochirus 50 Daphnia galeata mendotae Daphnia galeata mendotae 12 Pumpkinsecd Age 1+ Lepomis gibbosus 51 Daphnia pulicaria Daphnia pulicaria 13 Rock Bass Age 1+ Ambloplites rupestris 52 Daphnia retrocurva Daphnia retrocurva 14 Panfish Age-0 Centrarchidae 53 Diaphanosoma species Diaphanosoma species 15 Gizzard Shad Age 1+ Dorosoma cepedianum 54 Eubosmina coregoni Eubosmina coregoni l6 Gizzard Shad Age-0 Dorosoma cepedianum 55 Sida crystallina Sida crystallina 17 Alewife Alosa pseudoharengus 56 Leptodora kindtii Leptodora kindtii 18 Brown Bullhead Ameiurus nebulosus 57 Acanthocyclops vernalis Acanthocyclops vernalis l9 Burbot Lota Iota 58 Diacyclops thomasi Diacyclops thomasi 20 Channel Catfish Ictalurus punctatus 59 Ergasilus species Ergasilus species 21 Cisco C oregonus artedii 60 Mesocyclops edax Mesocyclops edax 22 Common Carp Cyprinus carpio carpio 61 Epischura lacustris Epischura lacustris 23 Darters Etheostoma species 62 Leptodiaptomus minutus Leptodiaptomus minutus 24 Emerald Shiners Notropis athernoides 63 Skistodiaptomus Skistodiaptomus 25 Freshwater Drum Aplodinotus grunniens oregonensis oregonensis 26 Golden Shiners Notemigonus crysoleucas 64 Nauplii Copepoda 27 Lake Sturgeon Acipenserfulvescens 65 Rotifers Rotatoria 28 Log Perch Percina caprodes 66 Blue-green Algae Cyanophyceae 29 Mottled Sculpin Cottus bairdii 67 Diatoms Bacillariophyceae 30 Northern Pike Esox Iucr'us 68 Euglena Euglenophyceae 31 Red Horse Sucker Moxisoma species 69 Flagellates Cryptophyceae & 32 Smallmouth Bass Micropterus dolomieu Dinophyceae 33 Trout Perch Percopsis omiscomaycus 70 Golden Algae Chrysophyceae 34 White Bass Morone chrysops 71 Green Algae Chlorophyceae 35 White Sucker Catostomus 72 Epiphytes Epiphytes commersonii 73 Macrophytes Macrophytcs 36 Amphipods Amphipoda 74 Periphytes Periphytes 37 Chironomids Chironomidae 75 Pelagic Detritus Pelagic Detritus 38 Clams Sphaeriidae 76 Sedimented Detritus Sedimented Detritus 39 Insects Arthropoda 77 DOC DOC 40 Table 2.2. Association between common subgroup membership and the occurrence of ties between predators and prey (adapted from Frank 1995). The odds ratio method maximizes the ratio AD : BC. Different Subgroup Membership Same Tie Occurring No Yes Possible relations between A B predators and prey in different subgroups Possible relations between C D predators and prey in the same subgroup Unrealrz ed Realized Total possible relations Interactions Interactions 41 Table 2.3. Ecosystem indices for the full Oneida Lake food web network before and after zebra mussel invasion. The percent difference was calculated as: P t - P %Difference = _o_s__r£ x100% . Pre Pre-Zebra Mussels Post-Zebra Mussels % Difference Index Value Value Total system throughput (gC rn'2 yr'l) 2553-3 2143-6 -19.2 Development capacity (gC-bits rn'2 yr'l) 13315-7 1 1037-2 -17.1 Ascendency (gC-bits rn'2 yr'l) 33509 29263 -12.7 Total overhead (gC-bits m'2 yr") 9965.9 8110.9 -18.6 Overhead on imports (gC-bits m'2 yr'l) 2598-4 1373-0 -27.9 Overhead on exports (gC-bits m'2 yr'l) 0-4 0-3 -35.0 Dissipative overhead (gC-bits rn'2 yr'l) 3936-3 3203-3 -18.6 Redundancy (gC-bits 111-2 yr'l) 3430-3 3034-3 -1 1.6 Unsealed capacity (bits) 5.0 5.1 2.0 Ascendency / capacity (%) 25.2 26.5 5.4 Total overhead / capacity (%) 74.8 73.5 -1.8 Overhead on imports / capacity (%) 19.5 17.0 -13.0 Overhead on exports / capacity (%) 0.0 0.0 -21.6 Dissipative overhead / capacity (%) 29.6 29.0 -1 .8 Redundancy / capacity (%) 25.8 27.5 6.7 42 Table 2.4. Subgroups identified for the pre-zebra mussel invasion time stanza. * Refers to taxa present in the pre-zebra mussel time stanza, but not the post-zebra mussel time stanza. Subgroup l: Planktivorous No. Food Web No. Subgroup 2 Con't No. Subgroup 4 Con't 16 Gizzard Shad Age-0 8 White Perch Age 1+ 12 Pumpkinseed Age 1+ 37 Chironomids 20 Channel Catfish 13 Rock Bass Age 1+ 42 Oligochaetes 22 Common Carp 23 Darters 46 Bosmina Iongirostris 25 Freshwater Drum 28 Log Perch 48 Ceriodaphnia quadrangula 35 White Sucker 29 Mottled Sculpin 49 Chydorus sphaericus 36 Amphipods 59 Ergasilus species 50 Daphnia galeata mendotae 39 Insects 51 Daphnia pulicaria 40 lsopods No. Subgroup 5: Piscivores 52 Daphnia retrocurva 41 Leeches . 2 Walleye Age 4+ 53 Diaphanosoma species 43 Snails 3 Walleye Age 1-3 54 Eubosmina coregoni 56 Leptodora kindtii 4 Walleye Age-0 58 Diacyclops thomasi 72 Epiphytes 6 Yellow Perch Age 1-2 60 Mesocyclops edax 73 Macrophytes 7 Yellow Perch Age-0 61 Epischura lacustris 74 Periphytes 9 White Perch Age-0 62 Leptodiaptomus minutus 19 Burbot 63 Skistodiaptomus oregonensis Subgroup 3: Planktivores 30 Northern Pike 64 Nauplii No. & Zooplankton 32 Smallmouth Bass 65 Rotifers 17 Alewife 34 White Bass 66 Blue-green Algae 21 *Cisco 67 Diatoms 26 Golden Shiners Subgroup 6: Piscivores & 68 Euglena 33 Trout Perch No. Invertivores 69 Flagellates 45 Alana species 1 Cormorants 70 Golden Algae 55 Sida crystallina 14 Panfish Age-0 71 Green Algae 57 Acanthocyclops vernalis 15 Gizzard Shad Age 1+ 18 Brown Bullhead Subgroup 2: Benthically No. Subgroup 4: Panfish 24 Emerald Shiners No. Associated 10 Black Crappie Age 1+ 31 Red Horse Sucker 5 Yellow Perch Age 3+ 11 Bluegill Age 1+ 38 Clams 43 Table 2.5. Subgroups identified for the post-zebra mussel invasion time stanza. * Refers to taxa present in the post-zebra mussel time stanza, but not the pre-zebra mussel time stanza. I Refers to taxa that changed subgroup membership after zebra mussel invasion. Subgroup l: Planktivorous Subgroup 2: Benthically No. Food Web No. Associated No. Subgroup4 Con't 2 lWalleye Age 4+ 5 Yellow Perch Age 3+ 19 tBurbot 7 tYellow Perch Age-0 6 lYellow Perch Age 1-2 34 *White Bass 9 lWhite Perch Age-0 8 White Perch Age 1+ 59 Ergasilus species 16 Gizzard Shad Age-0 20 Channel Catfish 24 tEmerald Shiners 22 Common Carp No. Subgroup 5: Piscivores 37 Chironomids 25 Freshwater Drum 4 Walleye Age-0 42 Oligochaetes 32 lSmallmouth Bass 23 TDar'ters 44 *Zebra Mussels 35 White Sucker 29 tMottled Sculpin 46 Bosmina longirostris 36 Amphipods 30 Northern Pike 49 Chydorus sphaericus 39 Insects 33 tTrout Perch 50 Daphnia galeata mendotae 40 lsopods 51 Daphnia pulicarr'a 41 Leeches Subgroup 6: Piscivores & 53 Diaphanosoma species 43 Snails No. Invertivores 54 Eubosmina coregoni 72 Epiphytes 1 Cormorants 56 fLeptodora kindtii 73 Macrophytes 3 lWalleye Age 1-3 57 tAcanthocyclops vernalis 74 Periphytes 10 lBlack Crappie Age 1+ 58 60 61 62 63 64 65 66 67 68 69 70 71 Diacyclops thomasi Mesocyclops edax Epischura lacustris Leptodiaptomus minutus Skistodiaptomus oregonensis Nauplii Rotifers Blue-green Algae Diatoms Euglena Flagellates Golden Algae Green Algae Subgroup 3: Planktivores , & Zooplankton No. lPanfish Age-0 Golden Shiners lLog Perch tClams Alana species Subgroup 4: Panfish 15 18 31 Gizzard Shad Age 1+ Brown Bullhead Red Horse Sucker Subgroup 7: Miscellaneous . Low Biomass 11 12 13 lBluegill Age 1+ Pumpkinseed Age 1+ Rock Bass Age 1+ 44 17 27 47 48 52 55 tAlewife ‘Lake Sturgeon *Camptocercus harpae lCeriodaphnia quadrangula lDaphnia retrocurva tSida crystallina Table 2.6. Throughput of subgroups before and after zebra mussel invasion. Only six subgroups were identified before zebra mussel invasion. Pre-Zebra Mussels Post-Zebra Mussels Throughput Throughput Subgroup (gC m'2 yr'l) (gC 111-2 YI’J) 1 1705.2 1415.8 2 462.9 452.1 3 0.1 0.0 4 0.1 0.2 5 3.9 0.2 6 0.2 0.5 7 Not Present 0.3 45 Table 2.7. Ecosystem indices for the zebra mussel subgroup before and after zebra mussel invasion. The percent difference was calculated as: %Drflerence = M x100% . Pre Pre-Zebra Mussels Post-Zebra Mussels % Difference Index Value Value Value Total system throughput (gC m'2 yr'l) ”052 ”153 -l7.0 Development capacity (gC-bits rn'2 yr'l) 7574-4 5651-5 -12.2 Ascendency (gC-bits m'2 yr'l) 1347-3 1557-0 -15.2 Total overhead (gC-bits m.2 yr'l) 5726.7 5084.5 -11.2 Overhead on imports (gC-bits m"2 yr'l) 1836-3 1552-4 -15.5 Overhead on exports (gC-bits m.2 yrq) 1410-4 390-8 -36.8 Dissipative overhead (gC-bits m'2 er) 1523-1 1492-5 -8.3 Redundancy (gC-bits m.2 yr'l) 351-9 “43-3 34.8 Unscaled capacity (bits) 4.4 4.7 6.8 Ascendency / capacity (%) 24.4 23.6 -3.4 Total overhead / capacity (%) 75.6 76.4 1.1 Overhead on imports / capacity (%) 24.2 23.3 -3.7 Overhead on exports / capacity (%) 18.6 13.4 -28.1 Dissipative overhead / capacity (%) 21.5 22.4 4.4 Redundancy / capacity (%) 1 1.2 17.3 53.6 46 Figure 2.1. Zebra mussel impacts on the Oneida Lake food web, organized by subgroup. The scale is relative: impacts above the zero line are positive impacts of zebra mussels and impacts below the zero line are negative impacts of zebra mussels. Taxa numbers are placed above or below each bar. Taxon 21 was not present after zebra mussel invasion; taxa 75-77 were not used in the subgroup analysis. See Table 2.1 for taxa codes. 47 @5835 02 g o 9:835 w v anewnsm m N uncuwnnm fl @3835 1012de 3 03mm 48 Figure 2.2. Panel A: Crystalized sociogram for the pre-zebra mussel time stanza. Units are relative distances based on the inverse of the density of interactions (see Frank 1996). Subgroups 1 through 6 are plotted with the direction of feeding relationships represented by arrows (e. g., subgroup 6 consumes members of subgroup 1, but not vice versa); thickness of arrow indicates weight of feeding relationships. Panel B: Placement of taxa within subgroups. Circles indicate subgroup boundaries and colors represent general trophic groupings of taxa. Subgroup numbers are located to the upper right of all subgroups. 49 _ 53585 8. 8. a c 355 635m I 835393.. B gins—nooN E 835882: canon B .3..— U m 35¢ 8588.80 M < .28“— can- com- com. On. 0 2 "06mm 3 on. can own 3 2:5 50 Figure 2.3. Crystalized sociogram for the post-zebra mussel time stanza. See Figure 2.2 for description of panels. 51 _ casein on _ 8 _ an c on. 8 _ . an _ . 8n. an- SN. 8.. a o Z [1018“;le 1.06.6 ._ @§ 3. SN 35: 25.3 I 53338.3.— D coins—QSN j o2 mafia—85>:— uEEom E E D < ESE md ousmmm m ESm 258500 a 8m 52 Figure 2.4. Zebra mussel impacts on subgroup members. The scale is relative: impacts above the zero line are positive impacts of zebra mussels and impacts below the zero line are negative impacts of zebra mussels. 53 _ asewnsm 1012de em 2&5 54 Figure 2.5. Lindeman trophic spine for the pre-zebra mussel time stanza. Boxes with Roman numerals represent the integer trophic levels; the number within each trophic box is the percent efficiency of that trophic level at processing material. Arrows between the trophic boxes are flows in the grazer food chain, arrows leaving the top of trophic boxes are exports, arrows entering the tOp of trophic boxes are imports, and arrows leaving the bottom of trophic boxes are flows to detritus, represented by the detrital box. The ground symbol from electronic circuitry represents flow loss due to respiration. All flows are in gC rn'2 yr". 55 v.o :8.» ) tr > W H v 3.58 \r 723.. sex? 86 3d and 2: ems 2.2 3.2 8.3 $22 8.3m 4. A. 4. 4. 4| 4. :86 :52 38a $3.» $8.4m $8.: _> . > ll. 2 T... E . = A . _ I H 2:. a «H N: A, 4% E: H [F 8 3 a «H 8 3... H 4% sex: vex: 92x3 ”-256... maxi So no}: «no 22: as 8.2: 3o nm 2:3 56 Figure 2.6. Lindeman trophic spine for the post-zebra mussel time stanza. See Figure 2.5 for a description of the figure. 57 ) or 4 >1 v .238 23 72564 2:. “.2562. rod Q.2522 v25: 62x? 26% 1.. I... -.I P .m 35. o . I—l a . I—' o . l-I o . I—l BSA—0.5 >25 22 $2 $3 :8; Toioef on 255.4 _ E> moss; => 255a . 3 mid flf h- v. m- 2-2%. a 2-2.8 m MW.2582 MW.253 m.25: 62x? 2:. w 23. m > r .1 i 3.3 i go 25 23 3o 3; 8.2 :2 8.42 3:: 2:8 320D . - u o n .22.. w. 4.. 5.. .H. .4. 028: oh 2.23 .33 so: 2%.: 2.8.: A ., > A >_ E = A . _ :6 82 8.2 22.2 8.2.3 85 :3 2:. a... 25 o; 3% a: 8.43 as 3. 23mm 58 References Abarca-Arenas, L. G. and R. E. Ulanowicz. 2002. The effects of taxonomic aggregation on network analysis. Ecol. Model. 149: 285-296. Allesina, S. and C. Bondavalli. 2003. Steady state of ecosystem flow networks: A comparison between balancing procedures. Ecol. Model. 154: 221-229. Allesina, S., C. Bondavalli, and U. M. Scharler. 2005. The consequences of the aggregation of detritus pools in ecological networks. Ecol. Model. 189: 221-232. Bailey, R. C., L. Grapentine, T. J. Stewart, T. Schaner, M. E. Chase, J. S. Mitchell, and R. A. Coulas. 1999. Dreissenidae in Lake Ontario: Impact assessment at the whole lake and Bay of Quinte spatial scales. J. Great Lakes Res. 25: 482-491. Baxter, C. V., K. D. Fausch, M. Murakami, and P. L. Chapman. 2004. Fish invasion restructures stream and forest food webs by interrupting reciprocal prey subsidies. Ecologi. 85: 2656-2663. Beekey, M. A., D. J. McCabe, and J. E. Marsden. 2004. Zebra mussel colonization of soft sediments facilitates invertebrate communities. Fresh. Biol. 49: 535-545. Bidle, K. D. and M. Fletcher. 1995. Comparison of free-living and particle-associated bacterial communities in the Chesapeake Bay by stable low-molecular—weight RNA analysis. Appl. Environ. Microbiol. 61: 944-952. Bondavalli, C., A. Bodini, G. Rossetti, and S. Allesina. In press. Detecting stress at the whole ecosystem level. The case of a mountain lake: Lake Santo (Italy). Ecosystems. Bondavalli, C., R. E. Ulanowicz, and A. Bodini. 2000. Insights into the processing of carbon in the South Florida Cypress Wetlands: A whole-ecosystem approach using network analysis. J. Biogeo. 27: 697-710. Christensen, N. L., A. M. Bartuska, J. H. Brown, S. Carpenter, C. D'Antonio, R. Francis, J. F. Franklin, J. A. MacMahon, R. F. Noss, D. J. Parsons, C. H. Peterson, M. G. Turner, and R. G. Woodmansee. 1996. The report of the Ecological Society of America Committee on the scientific basis for ecosystem management. Ecol. Applic. 6: 665-691. Christensen, V. and D. Pauly. 1992. ECOPATH II — a sofiware or balancing steady-state ecosystem models and calculating network characteristics. Ecol. Model. 61: 169- 185. Crooks, J. A. 2002. Characterizing ecosystem-level consequences of biological invasions: The role of ecosystem engineers. OIKOS. 97: 153-166. 59 Dettmers, J. M., M. J. Raffenberg, and A. K. Weis. 2003. Exploring zooplankton changes in southern Lake Michigan: Implications for yellow perch recruitment. J. Great Lake Res. 29: 355-364. Drake, J. M. and J. M. Bossenbroek. 2004. The potential distribution of zebra mussels in the United States. BioScience. 54: 931-941. Fayram, A. H., Hansen, M. J ., and T. J. Ehlinger. In press. Characterizing changes in maturity of lakes resulting from supplementation of walleye populations. Ecol Model. F inn, J. T. 1976. Measures of ecosystem structure and function derived from analysis of flows. J. Theor. Biol. 56: 363-380. Fomey, J. L. September 1993. Some observations on cormorant-fish interactions in Oneida Lake. American Fisheries Society — New York Chapter Newsletter. 8-13. Frank, K. A. 1995. Identifying cohesive subgroups. Soc. Networks. 17: 27-56. Frank, K. A. 1996. Mapping interactions within and between cohesive subgroups. Soc. Networks. 18: 93-119. Gaedke, U. 1995. A comparison of whole-community and ecosystem approaches (biomass size distributions, food web analysis, network analysis, simulation models) to study the structure, function and regulation of pelagic food webs. J. Plankton Res. 17: 1273-1305. Harmon, B. 1973. The structure of ecosystems. J. Theor. Biol. 41: 535-546. Hansen, A.-M. and N. G. Hairston Jr. 1998. Food limitation in a wild cyclopoid copepod population: Direct and indirect life history responses. Oecologia. 115: 320-330. Heymans, J. J. and D. Baird. 2000. Network analysis of the northern Benguela ecosystem by means of NETWRK and ECOPATH. Ecol. Model. 131: 197-119. Heymans, J. J ., R. E. Ulanowicz, and C. Bondavalli. 2002. Network analysis of the South Florida Everglades grarninoid marshes and comparison with nearby cypress ecosystems. Ecol. Model. 149: 5-23. Hubert, L. 1987. Assignment Methods in Combinatorial Data Analysis. Marcel Dekker. Idrisi, N., E. L. Mills, L. G. Rudstam, and D. J. Stewart. 2001. Impact of zebra mussels (Dreissena polymorpha) on the pelagic lower trophic levels of Oneida Lake, New York. Can. J. Fish. Aquat. Sci. 58: 1430-1441. Jackson, J. R., A. J. VanDeValk, T. E. Brooking, O. A. vanKeeken, and L. G. Rudstam. 60 2002. Growth and feeding dynamics of lake sturgeon, Acipenserfitlvescens, in Oneida Lake, New York: Results from the first five years of a restoration program. J. Appl. Ichthyol. 18: 439-443. Johannsson, O. E., R. Derrnott, D. M. Graham, J. A. Dahl, E. S. Millard, D. D. Myles, and J. LeBlanc. 2000. Benthic and pelagic secondary production in Lake Erie after the invasion of Dreissena spp. with implications for fish production. J. Great Lake Res. 26: 31-54. Johnson, J. C., S. P. Borgatti, J. J. Luczkovich, and M. G. Everett. 2001. Network role analysis in the study of food webs: An application of regular role coloration. J. Soc. Struct. 2: 1-15. Jones, C. G., J. H. Lawton, and M. Shachak. 1994. Organisms as ecosystem engineers. OIKOS. 69: 373-386. Krause, A. E., K. A. Frank, D. M. Mason, R. E. Ulanowicz, and W. W. Taylor. 2003. Compartments revealed in food-web structure. Nature. 426: 282-285. Lindeman, R. L. 1942. The trophic-dynamic aspect of ecology. Ecology. 23: 399-418. Mack, R. N., D. Simberloff, W. M. Lonsdale, H. Evans, M. Clout, and F. A. Bazzaz. 2000. Biotic invasions: Causes, epidemiology, global consequences, and control. Ecol. Applic. 10: 689-710. Marsden, J. E. and M. A. Chotkowski. 2001. Lake trout spawning on artificial reefs and the effect of zebra mussels: Fatal attraction? J. Great Lakes Res. 27: 33-43. Mayer, C. M., A. J. VanDeValk, J. L. Fomey, L. G. Rudstam, and E. L. Mills. 2000. Response of yellow perch (Percaflavescens) in Oneida Lake, New York, to the establishment of zebra mussels (Dreissena polymorpha). Can. J. Fish. Aquat. Sci. 57: 742-754. Mayer, C. M., R. A. Keats, L. G. Rudstam, and E. L. Mills. 2002. Scale-dependent effects of zebra mussels on benthic invertebrates in a large eutrophic lake. J. N. Am. Benthol. Soc. 21: 616-633. Mayhew, B. 1980. Structuralism vs. individualism, Part 1: Shadow boxing in the dark. Social Forces. 59: 335-375. McCann, K., J. Rasmussen, J. Umbanhowar, and M. Humphries. 2005. Role of space, time, and variability in food web dynamics. In P. deRuiter, V. Wolters, and J. Moore [eds.], Dynamic Food Webs: Multispecies Assemblages, Ecosystem Development and Environmental Change. Academic Press. McEliece, R. J. 1977. The Theory of Information and Coding. Addison-Wesley. 61 Mellina, E., J. B. Rasmussen, and E. L. Mills. 1995. Impact of zebra mussel (Dreissena polymorpha) on phosphorus cycling and chlorophyll in lakes. Can. J. Fish. Aquat.Sci. 52: 2553-2573. Mills, E. L. and J. L. F omey. 1988. Trophic dynamics and development of freshwater pelagic food webs, p. 11-30. In S. R. Carpenter [ed.], Complex interactions in lake communities. Springer. Mills, E. L., J. L. Fomey, M. D. Clady, and W.R. Schaffner. 1978. Oneida Lake, p. 367- 451. In J. A. Bloomfield [ed.], Lakes of New York. Academic Press. Mills, E. L., J. M. Casselman, R. Dermott, J. D. Fitzsimons, G. Gal, K. T. Holeck, J. A. Hoyle, O. E. Johannsson, B. F. Lantry, J. C. Makarewicz, E. S. Millard, I. F. Munawar, M. Munawar, R. O'Gorman, R. W. Owens, L. G. Rudstam, T. Schaner, and T. J. Stewart. 2003. Lake Ontario: Food web dynamics in a changing ecosystem (1970-2000). Can. J. Fish. Aquat. Sci. 60: 471-490. Moloney, C. L. and J. G. Field. 1991. The size-based dynamics of plankton food webs. I. A simulation model of carbon and nitrogen flows. J. Plankton Res. 13: 1003- 1038. Nalepa, T. F ., G. A. Lang, and D. L. Fanslow. 2000. Trends in benthic macroinvertebrate populations in southern Lake Michigan. Verh. Internat. Verein. Limnol. 27: 2540- 2545. Odum, E. P. 1969. The strategy of ecosystem development. Science. 164: 262-270. Pauly, D., V. Christensen, J. Dalsgaard, R. Froese, and F. Torres Jr. 1998. Fishing down marine food webs. Science. 279: 860-863. Patten, B. C. 1984. Toward a theory of the quantitative dominance of indirect effects in ecosystems. Verh. Ges. Okol. 13:271-284. Patten, B. C., R. W. Bosserman, J. T. Finn, and W. G. Cale. 1976. Propagation of cause in ecosystems. In B. C. Pannen [ed.], Systems Analysis and Simulation in Ecology, Vol 4. Academic Press. Pérez-Espafia, H. and F. Arreguin-Sanchez. 1999. A measure of ecosystem maturity. Ecol. Model. 199: 79-85. Pimm, S. L. and J. H. Lawton. 1980. Are food webs divided into compartments? .1. Anim. Ecol. 49: 879-898. Pinnegar, J. K., J. L. Blanchard, S. Mackinson, R. D. Scott, and D. E. Duplisea. 2005. Aggregation and removal of weak-links in food-web models: System stability and recovery from disturbance. Ecol. Model. 184: 229-248. 62 Pothoven, S. A., T. F. Nalepa, P. J. Schneeberger, and S. B. Brandt. 2001. Changes in diet and body condition of lake Whitefish in southern Lake Michigan associated with changes in benthos. N Amer. J. Fish. Man. 21: 876-883. Reid, D. F. and M. I. Orlova. 2002. Geological and evolutionary underpinnings for the success of Ponto-Caspian species invasions in the Baltic Sea and North American Great Lakes. Can. J. Fish. Aquat. Sci. 59: 1144-1158. Rose, K. A., E. S. Rutherford, D. S. McDermot, J. L. Fomey, and E. L. Mills. 1999. Individual based model of yellow perch and walleye populations in Oneida Lake. Ecol. Monogr. 69: 127-154. Rudstam, L. G., A. J. VanDeValk, C. M. Adams, J. T. H. Coleman, J. L. Fomey, and M. E. Richmond. 2004. Cormorant predation and the population dynamics of walleye and yellow perch in Oneida Lake. Ecol. Applic. 14: 149-163. Rutherford, B. S., K. A. Rose, E. L. Mills, J. L. Fomey, C. M. Mayer, and L. G. Rudstam. 1999. Individual-based model simulations of a zebra mussel (Dreissena polymorpha) induced energy shunt on walleye (Stizostedion vitreum) and yellow perch (Percaflavescens) populations in Oneida Lake, New York. Can. J. Fish. Aquat. Sci. 56: 2148-2160. Shannon, C. E. 1948. A mathematical theory of communication. Bell System Tech. 27: 379-423. Stevenson, R. J ., M. L. Bothwell, and R. L. Lowe. 1996. Algal Ecology: Freshwater Benthic Ecosystems. Academic Press. Stewart, T. J ., R. E. Lange, S. D. Orsatti, C. P. Schneider, A. Mathers, and M. E. Daniels. 1999. Fish community objective for Lake Ontario. Great Lakes Fishery Commission Special Publication. 99-1. Strayer, D. L., K. A. Hattala, and A. W. Kahnle. 2004. Effects of an invasive bivalve (Dreissena polymorpha) on fish in the Hudson River estuary. Can. J. Fish. Aquat. Sci. 61: 924-941. Strayer, D. L., N. F. Caraco, J. J. Cole, S. Findlay, and M. L Pace. 1999. Transformation of freshwater ecosystems by bivalves. BioScience. 49:19-27. Teal, J. M. 1962. Energy flow in the salt marsh ecosystem of Georgia. Ecology. 69: 1647- 1676. Thorp, J. H. and A. F. Casper. 2003. Importance of biotic interactions in large rivers: An experiment with planktivorous fish, dreissenid mussels and zooplankton in the St. Lawrence River. River Res. Applic. 19: 265-279. 63 Ulanowicz, R. E. 1986. Growth and Development: Ecosystems Phenomenology. Springer Verlag. Ulanowicz, R. E. 1996. Trophic flow networks as indicators of ecosystem stress. In G. A. Polis and K. O. Winemiller [eds], Food Webs: Integration of Patterns and Dynamics. Chapman and Hall. Ulanowicz, R. E. 1997. Ecology, The Ascendent Perspective. Columbia University Press. Ulanowicz, R. E. and J. J. Kay. 1991. A package for the analysis of ecosystem flow networks. Environ. Soft. 6: 131-142. Vanderploeg, H. A., T. F. Nalepa, D. J. Jude, E. L. Mills, K. T. Holeck, J. R. Liebig, I.A. Grigorovich, and H. Ojaveer. 2002. Dispersal and emerging ecological impacts of Ponto Caspian species in the Laurentian Great Lakes. Can. J. Fish. Aquat. Sci. 59: 1209-1228. VanDeValk, A. J ., C. M. Adams, L. G. Rudstam, J. L. Fomey, T. E. Brooking, M. A. Gerken, B. P. Young, and J. T. Hooper. 2002. Comparison of angler and cormorant harvest of walleye and yellow perch in Oneida Lake, New York. Trans. Am. Fish. Soc. 131: 27-39. Werner, E. E. and J. F. Gilliam. 1984. The ontogenetic niche and species interactions in size structured populations. Annu. Rev. Ecol. Syst. 15: 393-425. Westra, L., P. Miller, J. R. Karr, W. E. Rees, and R. E. Ulanowicz. 2000. Ecological integrity and the aims of the Global Integrity Project, p. 19-41. In Pimentel, D., L. Westra, and R. F. Noss [eds], Ecological Integrity: Integrating Environment, Conservation, and Health. Island Press. Yodzis, P. and K. O. Winemiller. 1999. In search of operational trophospecies in a tropical aquatic food web. Oikos. 87: 327-340. Zhao, Y. and K. A. Frank. 2003. Factors affecting technology uses in schools: An ecological perspective. AERJ. 40: 807-840. Zorach, A. C. and R. E. Ulanowicz. 2003. Quantifying the complexity of flow networks: How many roles are there? Complexity. 8: 68-76. 64 CHAPTER THREE Invasive Species Impacts on Ecosystem Structure and Function: A Comparison of the Bay of Quinte, Canada, and Oneida Lake, USA, Before and After Zebra Mussel Invasion Andrea L. Jaeger, Doran M. Mason, Ann E. Krause, Kenneth A. Frank, William W. Taylor, and Scott D. Peacor Abstract To understand impacts of exotic species on ecosystem level properties, we compared food web characteristics of two eutrophic ecosystems - the Bay of Quinte, Lake Ontario (Canada), and Oneida Lake, New York (USA) - before and after zebra mussel (Dreissena polymorpha) invasion using ecological network analysis (ENA) and a social network analysis method, cohesion analysis (CA). ENA quantifies ecosystem function through an analysis of food web transfers, while CA assesses ecosystem structure by organizing food web members into subgroups of strongly interacting predators and prey. These methods detected direct and indirect impacts, changes in flow efficiency, and alterations of food web organization and ecosystem activity resulting from zebra mussel invasion. In the Bay of Quinte, zebra mussel introduction increased ecosystem grth (9%), stimulated benthic sources of production (e. g., macrophyte and detrital production increased over 1000%), and disrupted subgroup group structure. Previous research on Oneida Lake indicated zebra mussels diminished ecosystem growth (19%), promoted benthic production (e. g., macrophyte and detrital production increased 65 13% and 460%, respectively), and altered subgroup composition (33%). Together, these analyses suggested that zebra mussel influence was similar in ecosystems of comparable trophic status, and that comparative studies may be useful for the prediction of effects in other systems. Introduction Exotic species invasion is a critical driver of worldwide ecological change (Mills et al. 1994). Exotic species have altered ecosystems by disrupting food web dynamics (Chapter 2), biogeochemical cycles (Holeck et al. 2004), modifying habitats (Hall and Mills 2000), and decreasing native biodiversity (Holeck et al. 2004). Invasive species can also cause health risks and affect socio-economic systems by damaging agriculture, commercial and recreational fisheries, and fouling intake and nautical structures (Mills et al. 1994; Facon et al. 2005). Invasions by dreissenid mussels, including zebra (Dreissena polymorpha) and quagga (Dreissena bugensis) mussels, have been pervasive in North America, multiple European nations, and Russia (Drake and Bossenbroek 2004). Dreissenid mussels pose a considerable threat to aquatic environments, causing dramatic direct and indirect effects on food webs (N oonburg et al. 2003). Although dreissenid invasion has led to pronounced changes in aquatic ecosystems, the severity and scope of impacts has varied between ecosystems. In the Great Lakes (V anderploeg et al. 2002) and some inland waters of North America (MacIsaac 1996; Idrisi et al. 2001 ), dreissenid invasion increased water clarity and light penetration, which diverted energy from pelagic to benthic pathways (MacIsaac 1996; Mayer et al. 2002; Mills et al. 2003). However, in shallow and/or turbulent ecosystems, 66 such as the Hudson River, Saginaw Bay (Lake Huron), and western Lake Erie, resuspension of dreissenid pseudofeces via water column mixing resulted in lessened effects on water clarity (Vanderploeg et al. 2002). Dreissenid invasion decreased phytoplankton abundance and/or biomass in most ecosystems, including Saginaw Bay (Nalepa et al. 1999), Green Bay (Lake Michigan) (Padilla et al. 1996), western Lake Erie (Leach 1993), Oneida Lake (New York) (Idrisi et al. 2001), and the Hudson River (Strayer et al. 1999); however, changes in phytoplankton resources did not uniformly affect zooplankton communities in all ecosystems. Zooplankton production and/or density decreased in Lake Erie, particularly the unstratified regions (Johannsson et al. 2000), and the Hudson River (Strayer et al. 1999). However, in Oneida Lake, zebra mussel effects on zooplankton were marginal (Idrisi et al. 2001). Likewise modeling studies on Green Bay (Padilla et al. 1996) and mesocosm experiments on the St. Lawrence River (Thorp and Casper 2003) found similar results. Dreissenid effects on higher trophic levels, including benthic invertebrates and fish, were also mixed. Zebra mussel invasion negatively affected unionid clams in the Great Lakes (Vanderploeg et al. 2002), inland lakes (MacIsaac 1996), and rivers (Strayer et al. 1999). Non-mollusca benthic invertebrates declined in the Hudson River subsequent to invasion (Strayer et a1. 1999), while in Lake Erie (Johannsson et al. 2000) and Saginaw Bay (N alepa et al. 2003), benthic and macroinvertebrate biomass did not decrease. Moreover, dreissenid influence on fish varied by ecosystem. Dreissenid introduction might have indirectly benefited benthic and littoral fish in Oneida Lake (Rutherford et al. 1999; Jackson et al. 2002) and the Hudson River (Strayer et al. 2004); however in Lake Michigan, dreissenids may have negatively affected fish through 67 modification of spawning habitat (Marsden and Chotkowski 2001). F urtherrnore, young fish, which may directly compete with dreissenids for zooplankton food resources, might have been negatively impacted in Lake Michigan (Dettmers et al. 2003), but showed little effect in Oneida Lake (Mayer et al. 2000) resultant from dreissenid invasion. Although these studies indicate dreissenid mussels variably affect aquatic ecosystems, there may be trends in ecosystem response. Comparative analyses could be useful for elucidating these commonalities. For example, the effects of dreissenid invasion may vary with ecosystem morphology, ecosystem size, limiting factors to primary production, predator diets (Strayer et al. 2004), or along a trophic gradient (Padilla et al. 1996). Identifying the similarities in invaded ecosystems would aid in not only predicting which ecosystems might be susceptible to future invasions, but also how those ecosystems might be affected (Drake and Bossenbroek 2004). To decipher dreissenid impacts on ecosystems and draw comparisons between systems, we need a comprehensive understanding of ecosystems, including population and community level effects. Moreover, we need to incorporate the interrelationship between populations and communities, i.e., how change at the population level affects the community, which in turn regulates the population (Gaedke 1995). A major constraint to explicating these processes both within and among ecosystems is the complexity of food web interactions, especially indirect food web effects (Strayer et al. 2004). One tool that is useful for holistically understanding and comparing ecosystems in the face of environmental problems is network analysis (Gaedke 1995). Network analysis examines ecosystems at multiple scales, including at the level of species-pair interaction, trophic level, and whole food web (Heymans et al. 2002) through an analysis 68 of ecosystem structure and function. For network analysis, food webs are depicted as networks of exchange by quantifying feeding interactions and energy flow (Bondavalli et al. 2000). Network analysis has been used to compare ecosystem properties before and after exotic species invasion (Chapter 2), ecosystem dynamics between seasons (Baird and Ulanowicz 1989; Bondavalli et al. 2000), differences in marine upwelling and estuarine systems (Baird et al. 1991; Baird and Ulanowicz 1993), and aquatic ecosystems with and without terrestrial linkages (Heymans et al. 2002). In light of the need to comprehensively understand the effects of dreissenid invasion, we compared zebra mussel impacts within and between two invaded ecosystems using network analysis. The primary objective of this paper was to quantify zebra mussel impacts on ecosystem structure and function, and to compare these characteristics between ecosystems of similar trophic status, specifically by addressing the following questions: 1. Structure: Did zebra mussel invasion alter the membership of food webs and food web subgroups (defined as clusters of strongly interacting predators and prey) in the Bay of Quinte, Lake Ontario (Canada) ecosystem? 2. Function: Did the magnitude of carbon flow within food webs and food web subgroups change as a result of zebra mussel invasion in the Bay of Quinte ecosystem? 3. Comparison: Do systems of comparable trophic status respond similarly, with respect to direction and magnitude of change, to zebra mussel invasion? Using food web network analysis, we hypothesized that the Bay of Quinte would respond similarly to Oneida Lake, New York (USA), a system of comparable ecology and trophic status, subsequent to zebra mussel invasion. Previous network analysis 69 examination (Chapter 2) suggested zebra mussel invasion led to the benthification (Mills et al. 2003) of Oneida Lake, i.e., an energy shunt occurred that promoted benthic sources of production and benthically-associated species. Therefore, we hypothesized that the Bay of Quinte would undergo benthification resultant from zebra mussel invasion, with concomitant changes in ecosystem structure and function that promoted benthic communities. Methods Study Site The Bay of Quinte is a narrow, Z-shaped inlet on the northeastern portion of Lake Ontario (Figure 3.1). The Bay of Quinte has three distinct morphological regions, commonly referred to as the upper bay, middle bay, and lower bay, totaling approximately 80 km in length (Diamond et al. 1994) and 257 km2 surface area (Minns 1995). A strong depth and trophic gradient exists in the Bay of Quinte, ranging from a shallow (mean depth of 3.5 m), eutrophic environment in the upper bay to a deeper (mean depth of 24.4 m), oligotrophic environment in the lower bay (Ridgway et al. 1990; Nicholls et al. 2002), which connects the Bay of Quinte to Lake Ontario. The upper bay is most similar in trophic status and physical characteristics to Oneida Lake (described in Chapter 2); therefore we used only this region in our analysis. The upper bay has a surface area of 134 km2 and stratifies briefly during the summer months (Strus and Hurley 1992). Zebra mussels colonized the bay in 1993-1994, but were not established until 1995 (N icholls et al. 2002). Because of the long-terrn history of limnological 7O research on the Bay of Quinte (e. g., Hurley and Christie 1977) and Oneida Lake (e.g., Mills et al. 1978), ample data exist throughout the invasion history of zebra mussels to study their effects within and between these systems. Network Construction We constructed weighted food web networks for the Bay of Quinte before and after zebra mussel invasion and analyzed the networks using ecological network analysis (ENA) (Ulanowicz 1986) and a social network analysis method, cohesion analysis (CA) (Frank 1995; Krause et al. 2003; Chapter 2). We defined the years 1978 to 1994 as the pre-zebra mussel invasion time stanza and the years 1995 to 2002 as the post-invasion time stanza. We created these networks using the same methodology as for Oneida Lake (Chapter 2) and therefore, do not present details on network construction here. To make the Bay of Quinte analysis comparable to Oneida Lake, we did not include the microbial food web. The complete list of eighty food web species and aggregate groups are presented in Table 3.1. Data used to create network flows (i.e., the exchange matrix) were collected from the primary literature, field studies, and expert researchers on the Bay of Quinte (including the Bay of Quinte - Oneida Lake Comparative Modelling Project Workgroup). These parameters along with their sources are listed in Appendix 3.1. Finally, we mass-balanced our networks such that inputs equaled outputs for all taxa (Heymans and Baird 2000). Appendix 3.2 presents the balanced networks. Ecological Network Analysis After we completed network construction, we analyzed Bay of Quinte ecosystem structure (via CA) and function (via ENA) before and after zebra mussel invasion. We used the software package EcoNetwrk (http://www.glerl.noaa.gov/EcoNetwrk/) to 71 conduct three ENA routines: 1) input / output analysis, 2) trophic level analysis, and 3) the calculation of ecosystem indices. We provide a brief description of ENA methods below; for greater detail see Ulanowicz (1986) and Ulanowicz (1997). Input / output analysis (Harmon 1973; Patten et al. 1976) quantifies the amount of carbon supplied to any one taxon by another taxon over all direct and indirect linkages. The analysis includes a routine called IMPACTS that quantifies the relative effect of one taxon on another via direct and indirect paths (Heymans and Baird 2000). Trophic analysis reinterprets the web of predator-prey transfers in terms of the Lindeman trophic chain concept (Lindeman 1942). Trophic analysis apportions the activities of omnivores among a series of hypothetical integer trophic levels to create the Lindeman spine, which is used to evaluate the efficiency of carbon flow in the system (Heymans and Baird 2000). Ecosystem indices quantify system level properties such as growth and development, and assess the vulnerability and resilience of an ecosystem to perturbation (U lanowicz 1997). These indices are: total system throughput (TST), ascendency (A), overhead (0), and development capacity (C). TST quantifies ecosystem size (and thereby growth) as the sum of all carbon flows (gC m'2 yr'l) in the system. Ascendency quantifies the growth, development, and efficiency of ecosystem function (U lanowicz 1986) and is calculated by sealing the average mutual information (AMI) index (Shannon 1948; McEliece 1977), a measure of network organization, with TST: A = TST x AMI . Overhead quantifies the system’s functional inefficiencies (Heymans et al. 2002) as well as the resiliency of a system to perturbation (Heymans and Baird 2000). There are four primary contributors to overhead: imports (e.g., immigrations) and exports (e. g., 72 emigrations and fisheries harvest), respirative flow loss, and redundant food web flows (i.e., multiple flow paths connecting taxa). Overhead is calculated by scaling the system’s conditional entropy (Ulanowicz 1986), a measure of network disorganization, by TST: 0 = TST x Conditional Entropy. Development capacity is the upper bound on ecosystem grth and development. Capacity subsumes both ascendency and overhead: C=A+0. Cohesion Analysis Cohesion analysis identifies subgroups in food webs based on strengths of feeding relationships (Krause et al. 2003), where the maximization of an odds ratio is used as a criterion to assign subgroup membership3. CA uses an algorithm to iteratively reassign taxa to subgroups to maximize the odds that strong predatory interactions occur within subgroups, versus between subgroups (Frank 1996). The intent of CA is to determine the network structure that maximizes (strong) predator-prey interactions (realized interactions) within subgroups while minimizing predator-prey interactions between subgroups and taxa without connecting flows (unrealized interactions) within subgroups (Table 3.2). Using the software Kliquefinder (Frank 1995), we identified subgroups within the Bay of Quinte food web networks. We tested the statistical significance of our subgroups against 1000 randomly generated re-combinations of our data (Frank 1996) and inspected the structure of significant subgroups. Although our ENA required balanced networks, our CA did not. In order to avoid introducing uncertainty from ENA balancing procedures, we used the unbalanced networks for CA. As a result, we could not include 3 Our use of the term “subgroup” is analogous to the Pimm and Lawton (1980) definition of food web “compartment”. We use the term “subgroup” to avoid confusion between Pimm and Lawton (1980) and Ulanowicz (1986) uses of the term “compartment”. 73 detrital groups in our CA because we derived detrital diet via balancing. Furthermore, our CA required us to adjust the network data to meet the range of Kliquefinder. Kliquefinder accepts flow weights only within 5 orders of magnitude; our networks exceeded this range both before (by 8 orders) and after (by 9 orders) invasion. We encountered this problem in our Oneida Lake analysis and used the same method as presented in Chapter 2 to adjust data. The final adjustment scheme increased values less than 1.0x10'6 gC m'2 yr"l to the minimum Kliquefinder input, and values greater than 1.0 gC m'2 yr'l to the maximum Kliquefinder input both pre- and post-zebra mussel invasion. We summarized results of the CA as “crystallized sociograms” using multidimensional scaling (Frank 1996) in SAS System for Windows. In these diagrams, proximity of subgroups corresponds to: l) the strength of predator-prey relationships spanning the subgroups (i.e., closely-spaced subgroups are connected by relatively stronger interactions than distant subgroups); 2) the similarity of connections to other subgroups; and 3) the subgroup’s importance to overall food web structure (i.e., centrally located subgroups are more important to food web structure than peripherally located subgroups). Similarly, taxa location within a subgroup indicates the strength of connections between taxa and the importance of taxa to the subgroup. After we identified network subgroups, we performed ENA on the largest subgroup to evaluate fiinctional linkages. We maintained the same mass-balance in the subgroup analysis as the full food web by treating all flows to and from non-subgroup taxa as imports and exports to the subgroup. Because detrital groups were not assigned to subgroups, detritus could not be explicitly incorporated into the subgroup ENA. 74 Nevertheless, flow to detritus was implicitly included by treating detrital flow as an export from the subgroup. Results Ecological Network Analysis - Entire Network Input / output analysis Zebra mussel impacts on the Bay of Quinte food web were predominantly negative (Figure 3.2). Cormorants were positively affected, while effects on fish were mixed. Benthic fish (e. g., ictalurids, carp and freshwater drum) and benthically associated fish (e. g., adult panfish) exhibited positive impacts, while pelagic fish (e.g., white perch, alewife and shiners) and some sportfish (e. g., walleye and smallmouth bass) were negatively affected. Round gobies showed the greatest positive impacts throughout the entire food web. Effects on benthic invertebrate taxa were equally positive and negative, with zebra mussels strongly negatively impacting themselves. Effects on zooplankton and phytoplankton taxa were wholly negative and benthic plants were marginally affected. Finally, zebra mussels positively influenced sedimented detritus, while negatively influencing other detrital groups. Lindeman trophic analysis We were unable to conduct the Lindeman trophic analysis on the full food webs due to computational limitations in the EcoNetwrk software resulting from network complexity. However, despite limitations in our trophic analysis, we could nonetheless analyze total food web flow efficiency. Total production (i.e., flow between predators and prey plus the usable exports from the system) was 425.3 gC m"2 yr'l before zebra 75 mussel invasion and 624.3 gC m'2 yr'1 after, a 47% increase. Total flow loss due to respiration was 534.1 gC m'2 yr'l pre-invasion, and 510.9 gC m'2 yr.1 after invasion, a 4% decrease. Ecosystem indices The ecosystem analysis indicated that zebra mussel invasion caused moderate-to- strong changes to ecosystem function (Table 3.3, Panel A). TST (i.e., ecosystem growth) increased 10%, as did development capacity (i.e., ecosystem complexity) by 11%. Concomitantly, ascendency (i.e., organization) increased (47%) while overhead (i.e., disorganization) decreased slightly (1%). In part, changes in capacity, ascendency, and overhead were driven by increases in TST. To remove the efiects of TST scaling on capacity, we simply divided capacity by TST. Unsealed capacity increased from 4.4 to 4.5 bits (2% increase). To remove TST scaling on ascendency and overhead, and look at the proportion of organized flow relative to disorganized flow in the ecosystem, we divided ascendency and overhead by development capacity, yielding “relative ascendency” and “relative overhead”, respectively. Relative ascendency increased from 25% to 33% following zebra mussel invasion, while relative overhead decreased from 75% to 67%. Finally, considering the contributors to relative overhead, overhead on imports, exports, and dissipative overhead decreased between 10 and 28%, while redundancy increased 9%. Cohesion Analysis We identified six subgroups in the pre-invasion network and eight subgroups in the post-invasion network. Even though the odds ratio was greater post-invasion (odds ratio = 14.6) than pre-invasion (odds ratio = 12.7), the pre-invasion subgroups were 76 borderline statistically significant (p < 0.07) and post-invasion subgroups were clearly not statistically significant (p > 0.5) (see Appendix 3.3 for a discussion of these results). Therefore, only results for the pre-invasion network (Table 3.4) are described below. We identified three mixed taxa groups: 1) a planktivorous food web group; 2) benthically associated taxa; and 3) panfish and zooplankton“. The remaining subgroups were largely composed of piscivorous and invertivorous fish taxa. Interactions between (Panel A) and within (Panel B) subgroups were summarized in a crystallized sociogram (Figure 3.3). The planktivorous food web subgroup (subgroup l) was fundamental to Bay of Quinte structure, sharing close interactions with all subgroups. Zooplankton and phytoplankton were central to this subgroup and interactions were closely knit. The remaining subgroups illustrated less dense interactions and more peripheral roles in the food web. Ecological Network Analysis — Grouped Network Since the post-invasion subgroups were non-significant, we could not conduct the input/output analysis at the subgroup level. Below we analyze the functional characteristics of the planktivorous food web subgroup (pre-invasion) with the remaining ENA methods. This subgroup dominated ecosystem structure (in terms of number of taxa) and size (as quantified by TST) (Table 3.3, Panel B). Lindeman trophic analysis The Lindeman trophic analysis identified twelve trophic levels in the planktivorous food web subgroup (Figure 3.4). Adult yellow perch, subadult, and juvenile walleye were the top predators in this subgroup. Flow in the grazer chain decreased substantially as trophic level increased, as did flow to detritus and flow loss ‘ Subgroup names were based on ecological descriptions that represent the majority of taxa in each subgroup, but some taxa may not fit the subgroup name. 77 due to respiration. Efficiency was greatest at trophic level II (21%), similar for trophic levels I and 111 (5-6%), and lowest for all trophic levels IV and above. Total production of the subgroup was 414.7 gC rn'2 yr'1 (97% of full food web) while total respiration was 198.3 gC m'2 yr'1 (37% of full food web). Ecosystem indices Similar to the full food web analysis, the planktivorous food web subgroup was largely composed of disorganized flow (Table 3.3, Panel C). Subgroup throughput amounted to 1192.4 gC m'2 yr'l, constituting 52% of total food web flow. Ascendency represented 32% of development capacity, while overhead composed 68% of capacity. Relative overhead on imports and dissipative flow ranged between 18 and 23%, similar to the full food web. However, relative overhead on exports (21%) was greater in the subgroup; whereas relative overhead on redundant flows (7%) was less in the subgroup. Discussion Exotic species invasion is a pervasive threat to aquatic ecosystems. As the rate of invasions escalates (Holeck et al. 2004), it is essential that researchers understand ecosystem response to invasion in order to successfully forecast and prevent further spread (Drake and Bossenbroek 2004). In this study, we investigated exotic species perturbation on the Bay of Quinte food web. Our analysis indicated that zebra mussels exerted considerable influence in the Bay of Quinte by not only altering ecosystem structure (question 1), but also affecting ecosystem function (question 2). Moreover, our analyses supported the hypothesis that zebra mussels lead to the benthification of their invaded ecosystems. Below we begin our discussion with the CA structural findings, and 78 then place those results within the ENA functional context. Furthermore, we compare (question 3) zebra mussel effects in the Bay of Quinte to previous research on Oneida Lake (Chapter 2). Cohesion Analysis — Structure Structural effects of zebra mussel invasion on the Bay of Quinte were pronounced, as evidenced by a complete disruption of food web subgroup structure. Before invasion, the planktivorous food web subgroup - a primarily pelagic subgroup - dominated structure. The centrality of this subgroup (Figure 3.3) parallels findings on Oneida Lake where we identified a planktivorous subgroup constituting the majority of structure. The prominence of these subgroups makes intuitive sense as both systems were eutrophic and largely comprised of pelagic pathways before invasion. In Oneida Lake, zebra mussels established in the planktivorous subgroup, linking this subgroup to the benthos. However, in the Bay of Quinte, zebra mussel introduction entirely removed subgroup structure. In effect, zebra mussel invasion homogenized the structure of Bay of Quinte food web interactions. Our method of subgroup identification concentrated strong predator-prey interactions within subgroups, leaving only weak interactions between subgroups. According to food web stability theory, strong interactions can propagate the effects of a disturbance event. In this manner, perturbations can greatly affect subgroup members, but may not affect taxa in other subgroups which are connected through weak ties. In a sense, subgroup structure provides a buffering effect against ecosystem perturbation (Krause et al. 2003). In Oneida Lake, we found that the greatest effects of zebra mussel invasion were restricted to taxa within the planktivorous subgroup, corroborating the 79 subgroup buffering effect. Conversely, as described above, zebra mussel invasion overwhelmed subgroup structure in the Bay of Quinte. This result has two implications: 1) the effects of zebra mussel invasion must have been more severe in the Bay of Quinte than Oneida Lake to have overcome the buffering effect of subgroup structure; and 2) zebra mussel influence can be more expansive in the Bay of Quinte without the confines of subgroup structure. Ecological Network Analysis - Function The IMPACTS analysis is a rigorous method to determine perturbation effects over all food web paths, including direct and indirect routes. Indirect paths are especially important as the net indirect effect may overwhelm direct interactions (Patten 1984). Our IMPACTS analysis indicated parallel food web response to zebra mussel invasion in the Bay of 'Quinte and Oneida Lake. The Bay of Quinte analysis suggested that zebra mussels had largely negative effects on food web taxa, yet zebra mussels positively affected some taxa, especially fish. In both the Bay of Quinte and Oneida Lake, benthic fish and panfish garnered positive impacts, although these effects were more pronounced in the Bay of Quinte. Potentially influence was greater in the Bay of Quinte due to the disruption of subgroup structure and the associated loss of subgroup buffering effects resultant from zebra mussel invasion. Walleye, which declined during the 19903 in both systems, showed negative effects for all life stages in both analyses. In Oneida Lake, the decline of walleye may be partially attributable to double-crested cormorant predation (Rudstam et al. 2004); however, cormorant predation pressure on walleye is not as intense in the Bay of Quinte (Hoyle, J. A. pers. comm.; Appendix 3.2). Therefore, declines in walleye abundance may be more ascribable to zebra mussel influence in the 80 Bay of Quinte than Oneida Lake, although commercial and recreational fisheries may also have contributed to declines of walleye in the Bay of Quinte (Appendix 3.2). The strongest positive impact in the Bay of Quinte belonged to round gobies, a recent Ponto- Caspian invader not present in Oneida Lake. Our Bay of Quinte research corroborates a facilitative interaction between zebra mussels and round gobies (Simberloff and Von Holle 1999; Ricciardi 2001), and suggests that Oneida Lake may be susceptible to round goby establishment due its similarity in fish community response to zebra mussel invasion. Considering the lower trophic levels, benthic invertebrate (mixed impacts), zooplankton (all negative impacts), and phytoplankton (all negative impacts) taxa exhibited similar response to invasion in both systems. Changes in trophic flow efficiency were similar in both systems, with the exception of production. Production increased in the Bay of Quinte (47%) afier invasion, and decreased in Oneida Lake (5%). The increase in Bay of Quinte production was largely due to greater primary production in benthic pathways, providing evidence for benthification. Macrophyte production increased from 2.9 to 33.4 gC rn'2 yr.1 (1048% increase), while detrital production increased from 4.5 to 70.2 gC rn'2 yr'] (1462% increase). Oneida Lake macrophyte and detrital production also increased (13% and 460%, respectively) but the growth of benthic production was offset by a decrease in pelagic production. Respiration decreased in both the Bay of Quinte (4%) and Oneida Lake (23%) after invasion. Moreover, trophic chains for the planktivorous food web subgroup were similar in both systems pre-invasion. Although the trophic spine for the Bay of Quinte (12 levels) was longer than Oneida Lake (6 levels), flow efficiency by trophic level decreased with increased trophic level in both systems, and was greatest at 81 trophic level II (21 % - Bay of Quinte; 24% - Oneida Lake). All flows were substantially greater at trophic level 1, indicating the importance of lower trophic levels to these systems. Drawing from Odtun’s (1969) theory of ecosystem development, Ulanowicz (1996) made predictions for ecosystem level response to perturbation. Ulanowicz suggested that perturbed ecosystems would exhibit decreased system throughput and decreased food web organization (i.e., increased overhead) due to an interruption of the ecological processes that Optimize efficient functioning. For example, redundant food web flows, a substantial contributor to overhead, would increase after perturbation as an ecosystem response to maintain food web connectance. Moreover, frequently perturbed systems will adapt to harbor greater overhead values (Ulanowicz 1997). In this sense, overhead is a “strength in reserve of degrees of freedom which the system can call upon to adapt to a new threat” (Bondavalli et al. 2000). Our analysis indicated that zebra mussel invasion perturbed the Bay of Quinte in a different manner than predicted by Ulanowicz (1996). Contrary to theory, total system throughput and ascendency increased after invasion. We attribute the difference in perturbation response to the overwhelming presence of zebra mussels in the Bay of Quinte. Zebra mussels garnered over 15% of TST and comprised 89% of living biomass. Perhaps the food web exhibited increased organization due to this considerable flow asymmetry: focused flow through zebra mussels would increase AMI, which in turn increases ascendency. Ecosystem organization responded similarly in Oneida Lake where zebra mussels also dominated flow (10% of TST) and living biomass (67%). Moreover, both systems were predominantly comprised of disorganized flow (66-75%), 82 potentially indicative of frequent perturbation, such as exotic species invasion (Prout et al. 1990) and changes in nutrient loading (Mills et al. 2003). Finally, zebra mussel invasion increased development capacity in both systems, adding a layer of functional complexity. Complexity benefits ecosystems by promoting flow diversity, which can buffer future ecological change (Pérez-Espafia and Arreguin-Sanchez 1999) in these systems. A limitation of ENA is that variability in carbon flow estimates is not incorporated into the analysis. Therefore, we could not discern statistical significance in our ENA findings. Additionally, one of the primary assumptions of ENA is that the food web is mass-balanced. As aquatic ecosystems are dynamic in space and time, this assumption is rarely met. Balancing introduces a degree of uncertainty into ENA, which makes careful choice of balancing methods and inspection of results for ecological plausibility essential. The final critical assumption of this research was that differences in food web structure and function between the time stanzas were attributable to zebra mussel invasion. Round gobies and Cercopagis pengoi also invaded the Bay of Quinte during our time periods, and cormorant biomass increased substantially. Although these changes may have altered food web structure and fimction, we believe zebra mussel introduction far outweighs all other ecological change during our time periods, as evidenced by the dominance of zebra mussel flow and biomass. Therefore, we are confident in the robustness of our results. In conclusion, zebra mussel invasion exerted a far-reaching influence on the Bay of Quinte ecosystem. Although whole-system analysis is a formidable task due to the complexity of ecosystem structure and function and paucity of long-term data in many 83 systems (Gaedke 1995), the extensive history of data collection by Bay of Quinte researchers and our application of network analysis methods allowed us to decipher zebra mussel impacts at the ecosystem level. Zebra mussel introduction not only caused substantial changes to food web subgroup structure, but also altered food web function by shunting energy from pelagic to benthic pathways. Moreover, zebra mussel effects were similar in Oneida Lake, a system of comparable trophic status. These findings have implications for the prediction of zebra mussel effects in other systems, making network analysis comparisons across invaded ecosystems a valuable endeavor. As exotic species invasion becomes an ever-increasing threat to aquatic ecosystems worldwide, understanding ecosystem dynamics is of paramount importance. Acknowledgements We thank the Bay of Quinte — Oneida Lake Comparative Modelling Project Workgroup for data contributions and guidance, Anne Clites, Timothy Hunter, and Marten Koops for computational and programming assistance, and Cathy Darnell for aid on graphics. This work was supported by a grant from the Great Lakes Fishery Commission. 84 Table 3.1. List of food web taxa. Brook silverside, emerald shiners, largemouth bass, round gobies, zebra mussels, and Cercopagis pengoi, were present in the post-zebra mussel time stanza, but not the pre-zebra mussel time stanza. No Common Name Cormorants Walleye Age 4+ Walleye Age 1-3 Walleye Age-0 Yellow Perch Age 1+ Yellow Perch Age-0 White Perch Age 1+ White Perch Age-0 9 Black Crappie 1+ 10 Bluegill Age 1+ 11 Lepomis species Age 1+ 12 Pumpkinseed Age 1+ 13 Rock Bass Age 1+ 14 Sunfish family Age 1+ 15 Panfish Age-0 16 Alewife 17 American Eel 18 Brook Silverside 19 Brown Bullhead 20 Channel Catfish 21 Common Carp 22 Emerald Shiner 23 Freshwater Drum 24 Gizzard Shad 25 Johnny Darter 26 Largemouth Bass 27 Log Perch 28 Longnose Gar 29 Northern Pike 30 Round Goby “qa‘MdKWNu—I 31 Smallmouth Bass 32 Spottail Shiner 33 Trout-perch 34 White Bass 35 White Sucker 36 Amphipods 37 Chironomids 38 Clams 39 Crayfish 40 Insects Taxonomic Classification Phalacrocarax auritus Sander vitreus Sander vitreus Sander vitreus Perca flavescens Perca flavescens Morone americana Morone americana Pomaxis nigramaculatus Lepomis macrachirus Lepomis genus Lepomis gibbosus Amblaplites rupestris Centrarchidae family Centrarchidae family Alosa pseudaharengus Anguilla rostrata Labidesthes sicculus Ameiurus nebulasus lctalurus punctatus C yprinus carpio carpio Notropis athernaides Apladinatus grunniens Dorosoma cepedianum Etheostoma nigrum Micropterus salmaides Percina caprodes Lepisasteus osseus Esax lucius Neogobius melanostomus Micropterus dolomieu Notropis hudsanius Percopsis omiscomaycus Morone chrysops C atastamus commersonii Amphipoda order Chironomidae family Sphaeriidae family Orconectes species Arthropoda phylum No Common Name 41 lsopods 42 Leeches 43 Oligochaetes 44 Snails 45 Zebra Mussels 46 Alana species 47 Basmina langirastris 48 Ceriadaphnia species 49 Chydoridae family 50 Daphnia galeata mendotae 51 Daphnia pulicaria 52 Daphnia retrocurva 53 Eubasmina caregani 54 Sididae family 55 Large-bodied Cladocerans 56 Cercopagis pengoi 57 Leptodora kindtii 58 Acanthacyclaps vernalis 59 Diacyclops thomasi 60 Eucyclaps species 61 Mesocyclops species 62 Trapocyclaps extensus 63 Cyclopoida copepodites 64 Diaptomidae family 65 Temoridae family 66 Calanoida copepodites 67 Harpacticoida 68 Nauplii 69 Rotifers 70 Blue-green Algae 7| Diatoms 72 Flagellates 73 Golden Algae 74 Green Algae 75 Epiphytes 76 Macrophytes 77 Periphytes 78 Pelagic Detritus 79 Sedimented Detritus 80 DOC 85 Taxonomic Classification Isopoda order Hirudinea class Oligochaeta class Gastropoda class Dreissena palymarpha Alana species Basmina langirastris C eriadaphnia species Chydoridae family Daphnia galeata mendotae Daphnia pulicaria Daphnia retrocurva Eubasmina coregani Sididae family Large-bodied Cladocerans C ercapagis pengoi Leptodora kindtii Acanthacyclaps vernalis Diacyclops thomasi Eucyclops species Mesocyclops species Trapacyclaps extensus Cyclopoida copepodites Diaptomidae family Temoridae family Calanoida copepodites Harpacticoida Nauplii Rotifers Cyanophyceae Bacillariophyceae Cryptophyceae & Dinophyceae Chrysophyceae Chlorophyceae Epiphytes Macrophytes Periphytes Pelagic Detritus Sedimented Detritus DOC Table 3.2. Association between common subgroup membership and the occurrence of ties between predators and prey (adapted from Frank 1995). The odds ratio method maximizes the ratio AD : BC. Tie Occurring No Yes Possible relations between Different A B predators and prey in different Subgroup subgroups Membership Possible relations between Same C D predators and prey in the same subgroup Unrealized Realized . . Total ossible relations Interactions Interactions p 86 Table 3.3. Ecosystem indices for the full food web (Panel A), subgroup throughput (Panel B), and ecosystem indices for subgroup 1 (Panel C). The percent difference was calculated as: %Diflerence = Mx100% . re Panel A: Full Food Web Pre-Zebra Mussels Post-Zebra Mussels % Difference Index Value Value Value Total system throughput (gC m'2 yr'l) 2304.2 2505.4 8.7 Development capacity (gC-bits m.2 yr-l) 10160.5 112812 11.0 Ascendency (gC-bits m.2 yr'l) 2541-1 3726.8 46.7 Total overhead (gC-bits m‘2 yr") 7619.3 7554.4 -o.9 Overhead on imports (gC-bits rn'2 yr'l) 2594.2 2591.3 -0.1 Overhead on exports (gC-bits rn'2 yr!) 893.7 711-7 -20.4 Dissipative overhead (gC-bits rn'2 yr'l) 2096-5 1787-7 -14.7 Redundancy (gC-bits m'z yr") 2034.9 2463.7 21.1 Unsealed capacity (bits) 4.4 4.5 2.1 Ascendency / capacity (%) 25.0 33.0 32.1 Total overhead / capacity (%) 75.0 67.0 -10.7 Overhead on imports / capacity (%) 25.5 23.0 -10.0 Overhead on exports / capacity (%) 8.8 6.3 -28.3 Dissipative overhead / capacity (%) 20.6 15.8 -23.2 Redundancy / capacity (%) 20.0 21.8 9.0 Panel B: Subgroup TST Panel C: Subgroup 1 Indices Pre-Zebra Mussels TST (gC m.2 yr'l) Index Value 31113819111? 1 1 192.4 Development capacity (gC-bits m.2 yr'l) 4041.3 SUbSTOUP 2 16.45 Ascendency (gC-bits m.2 yr'l) 1282-1 311138701113 3 0.20 Total overhead (gC-bits m.2 yr'1) 2759.2 SUbgTOUP 4 0.03 Overhead on imports (gC-bits m.2 er) 914.1 Subgroup 5 0.08 Overhead on exports (gC-bits m.2 yr'l) 83 8.8 Subgroup 6 0.06 Dissipative overhead (gC-bits rn'2 er) 727.2 Redundancy (gC-bits m.2 yr!) 2792 Unsealed capacity (bits) 3.4 Ascendency / capacity (%) 31.7 Total overhead / capacity (%) 68.3 Overhead on imports / capacity (%) 22.6 Overhead on exports / capacity (%) 20.8 Dissipative overhead / capacity (%) 18.0 Redundancy / capacity (%) 6.9 87 Table 3.4. Subgroups identified for the pre-zebra mussel invasion time stanza. Subgroup 1: Planktivorous No. Food Web 3 Walleye Age 1-3 4 Walleye Age-0 5 Yellow Perch Age 1+ 7 White Perch Age 1+ 8 White Perch Age-0 16 Alewife 24 Gizzard Shad 36 Amphipods 37 Chironomids 38 Clams 40 Insects 47 Basmina langirastris 48 Ceriodaphnia species 49 Chydoridae family 50 Daphnia galeata mendotae 51 Daphnia pulicaria 52 Daphnia retrocurva 53 Eubasmina caregani 54 Sididae family 57 Leptodora kindtii 58 Acanthocyclaps vernalis 59 Diacyclops thomasi 61 Mesocyclops species 62 Trapacyclops extensus 63 Cyclopoida copepodites 64 Diaptomidae family 66 Calanoida copepodites 68 Nauplii No. Subgroup 1 Can't 69 Rotifers 70 Blue-green Algae 71 Diatoms 72 Flagellates 73 Golden Algae 74 Green Algae 76 Macrophytes 77 Periphytes Subgroup 2: Benthically No. Associated 2 Walleye Age 4+ 17 American Eel 19 Brown Bullhead 21 Common Carp 35 White Sucker 41 lsopods 42 Leeches 43 Oligochaetes 44 Snails 75 Epiphytes Subgroup 3: Panfish & No. Zooplankton 10 Bluegill Age 1+ 11 Lepomis species Age 1+ 14 Sunfish family Age 1+ 46 Alana species 88 No. Subgroup 3 Can't 55 Large-bodied Cladocerans 67 Harpacticoida Subgroup 4: Piscivores & No. Invertivores 1 Cormorants 13 Rock Bass Age 1+ 15 Panfish Age-0 27 Log Perch 31 Smallmouth Bass 32 Spottail Shiner No. Subgroup 5: Piscivores 6 Yellow Perch Age-0 20 Channel Catfish 23 Freshwater Drum 28 Longnose Gar 29 Northern Pike 33 Trout-perch 34 White Bass No. Subgroup 6: Invertivores 9 Black Crappie 1+ 12 Pumpkinseed Age 1+ 25 Johnny Darter 39 Crayfish 60 Eucyclaps species 65 Temoridae family Figure 3.1. Map of the Bay of Quinte (Source: Carolyn Bakelaar, Department of Fisheries and Oceans, Canada). UPPER BAY Deseronto ,1 o Belleville *- . 5; . ' .3, \ Trenton . ' -. . 'I V ’ Y5 ‘ . Big Island Q 9 .a’ In 43' ' ’ w é a Q 0 Q ' \I N O .3; Pieton ’ 0 Lake Ontario 89 Figure 3.2. Zebra mussel impacts on the Bay of Quinte food web. The scale is relative: impacts above the zero line are positive impacts of zebra mussels and impacts below the zero line are negative impacts of zebra mussels. Taxa numbers are placed above or below each bar. See Table 3.1 for taxa codes. 90 06. 1012de he mm 2&2 91 Figure 3.3. Panel A: Crystalized sociogram for the pre-zebra mussel time stanza. Units are relative distances based on the inverse of the density of interactions (see Frank 1996). Subgroups 1 through 6 are plotted with the direction of feeding relationships represented by arrows; thickness of arrow indicates weight of feeding relationships. Panel B: Placement of taxa within subgroups. Circles indicate subgroup boundaries and colors represent general trophic groupings of taxa. Subgroup numbers are located to the upper right of all subgroups. 92 _ comm—8&5 afia 938m I 82382.22 flu :otiuiooN j 33.50235 2555 D in D m _0§nm 95.85.50 fl < ESE ‘3 "P z uorsuourrg In mN .m .2de 93 Figure 3.4. Lindeman trophic spine for the pre-zebra mussel time stanza. Boxes with Roman numerals represent the integer trophic levels; the number within each trophic box is the percent efficiency of that trophic level at processing material. Arrows between the trophic boxes are flows in the grazer food chain, arrows leaving the top of trophic boxes are exports, arrows entering the top of trophic boxes are imports, and arrows leaving the bottom of trophic boxes are flows to detritus, represented by the detrital box. The ground symbol from electronic circuitry represents flow loss due to respiration. All flows are in gC m"2 yr". 94 ) Jr b L 3:28 2.223322an scion-2.2-2.282 h2.53-2.22 92.23.292.236 26% 1.. P 1.. P .m_u>o_ l—I l—I H I._| ciao-D $82. $2.22 $82 $22 sod-.2 2-2.22.” / 53: 22.2. 222 =5 922.82 :> 2.82. 5 22.2.83. ~_-o_xo3~_.c2x2..m -.2x$2 2.282 2.222 2.32 2.5; 252 ) h N, .r v macro ) -2242 -2522” -2532 mg .82 can £2 9i 22$ 8.2: 3222 m m - N .226. 4. .4... 4.. 4. 4. 22322 oh $22 $32 $36 $8: $2... Alli Alll All. 2.2%... 2. > 22. >2 2% :2 8.8 = 822% 2 2 2 #01355 #otnmh-m 2 2 Goths-N ~-o_xam.N amd and and 86 22 Ave-ohm mad 2; 03mm 95 References Baird, D., J. M. Glade, and R. E. Ulanowicz. 1991. The comparative ecology of six marine ecosystems. Philos. Trans. R. Soc. Land. 333: 15-29. Baird, D. and R. E. Ulanowicz. 1989. The seasonal dynamics of the Chesapeake Bay ecosystem. Ecol. Monogr. 59: 329-364. Baird, D. and R. E. Ulanowicz. 1993. Comparative study on the trophic structure, cycling and ecosystem properties of four tidal estuaries. Mar. Ecol. Prog. Ser. 99: 221- 237. Bondavalli, C., R. E. Ulanowicz, and A. Bodini. 2000. Insights into the processing of carbon in the South Florida Cypress Wetlands: A whole-ecosystem approach using network analysis. J. Biogeo. 27: 697-710. Dettmers, J. M., M. J. Raffenberg, and A. K. Weis. 2003. Exploring zooplankton changes in southern Lake Michigan: Implications for yellow perch recruitment. .1. Great Lakes Res. 29: 355-364. Diamond, M. L., D. Mackay, D. J. Poulton, and F. A. Stride. 1994. Development of a mass balance model of the fate of 17 chemicals in the Bay of Quinte. J. Great Lakes Res. 20: 643-666. Drake, J. M. and J. M. Bossenbroek. 2004. The potential distribution of zebra mussels in the United States. BioScience. 54: 931-941. Facon, B., B. J. Genton, J. Shykoff, P. Jame, A. Estoup, and P. David. 2005. A general eco-evolutionary framework for understanding bioinvasions. TREE. 21: 130-135- F rank, K. A. 1995. Identifying cohesive subgroups. Soc. Networks. 17: 27-56. Frank, K. A. 1996. Mapping interactions within and between cohesive subgroups. Soc. Networks. 18: 93-119. Gaedke, U. 1995. A comparison of whole-community and ecosystem approaches (biomass size distributions, food web analysis, network analysis, simulation models) to study the structure, function and regulation of pelagic food webs. J. Plankton Res. 17: 1273-1305. Hall, S. R. and E. L. Mills. 2000. Exotic species in large lakes of the world. Aq. Ecosys. Health Man. 3: 105-135. Hannon, B. 1973. The structure of ecosystems. J. Theor. Biol. 41: 535-546. Heymans, J. J. and D. Baird. 2000. Network analysis of the northern Benguela ecosystem 96 by means of NETWRK and ECOPATH. Ecol. Model. 131: 197-119. Heymans, J. J ., R. E. Ulanowicz, and C. Bondavalli. 2002. Network analysis of the South Florida Everglades graminoid marshes and comparison with nearby cypress ecosystems. Ecol. Model. 149: 5-23. Holeck, K. T., E. L. Mills, H. J. MacIsaac, M. R. Dochoda, R. I. Colautti, and A. Ricciardi. 2004. Bridging troubled waters: Biological invasions, transoceanic shipping, and the Laurentian Great Lakes. BioScience. 54: 919-929. Hurley, D. A. and W. J. Christie. 1977. Depreciation of the warmwater fish community in the Bay of Quinte, Lake Ontario. .1. Fish. Res. Board Can. 34: 1849-1860. Idrisi, N., E. L. Mills, L. G. Rudstam, and D. J. Stewart. 2001. Impact of zebra mussels (Dreissena polymorpha) on the pelagic lower trophic levels of Oneida Lake, New York. Can. J. Fish. Aquat. Sci. 58: 1430-1441. Jackson, J. R., A. J. VanDeValk, T. E. Brooking, O. A. vanKeeken, and L. G. Rudstam. 2002. Growth and feeding dynamics of lake sturgeon, Acipenserfulvescens, in Oneida Lake, New York: Results from the first five years of a restoration program. J. Appl. Ichthyol. 18: 439-443. Johannsson, O. E-, R. Dermott, D. M. Graham, J. A. Dahl, E. S. Millard, D. D. Myles, and J. LeBlanc. 2000. Benthic and pelagic secondary production in Lake Erie after the invasion of Dreissena spp. with implications for fish production. J. Great Lakes Res. 26: 31-54. Krause, A. E., K. A. Frank, D. M. Mason, R. E. Ulanowicz, and W. W. Taylor. 2003. Compartments revealed in food-web structure. Nature. 426: 282-285. Leach, J. H. 1993. Impacts of the zebra mussel (Dreissena polymorpha) on water quality and fish spawning reefs in western Lake Erie. In T. F. Nalepa and D. W. Schloesser [eds.], Zebra Mussels: Biology, Impacts, and Control. Lewis Publishers. Lindeman, R. L. 1942. The trophic-dynamic aspect of ecology. Ecology. 23: 399-418. MacIsaac, H. J. 1996. Potential abiotic and biotic impacts of zebra mussels on the inland waters of North America. Amer. Zool- 36: 287-299. Marsden, J. E. and M. A. Chotkowski. 2001. Lake trout spawning on artificial reefs and the effect of zebra mussels: Fatal attraction? J. Great Lakes Res. 27: 33-43. Mayer, C. M., A. J. VanDeValk, J. L. Fomey, L. G. Rudstam, and E. L. Mills. 2000. Response of yellow perch (Percaflavescens) in Oneida Lake, New York, to the 97 establishment of zebra mussels (Dreissena polymorpha). Can. J. Fish. Aquat. Sci. 57: 742-754. Mayer, C. M., R. A. Keats, L. G. Rudstam, and E. L. Mills. 2002. Scale-dependent effects of zebra mussels on benthic invertebrates in a large eutrophic lake. J. N. Am. Benthol. Soc. 21: 616-633. McEliece, R. J. 1977. The T heory of Information and Coding. Addison-Wesley. Mills, E. L., J. H. leach, J. T. Carlton, and C. L. Secor. 1994. Exotic species and the integrity of the Great Lakes: Lessons from the past. BioScience. 44: 666-676. Mills, E. L., J. L. Fomey, M. D. Clady, and W.R . Schaffner. 1978. Oneida Lake, p. 367- 451. In J. A. Bloomfield [ed.], Lakes of New York. Academic Press. Mills, E. L., J. M. Casselman, R. Dermott, J. D. Fitzsimons, G. Gal, K. T. Holeck, J. A. Hoyle, O. E. Johannsson, B. F. Lantry, J. C. Makarewicz, E. S. Millard, I. F - Munawar, M. Munawar, R. O'Gorman, R. W. Owens, L. G. Rudstam, T. Schaner, and T. J. Stewart. 2003. Lake Ontario: Food web dynamics in a changing ecosystem (1970—2000). Can. J. Fish. Aquat. Sci. 60: 471-490. Minns, C. K. 1995. Approaches to assessing and managing cumulative ecosystem change, with the Bay of Quinte as a case study: An essay. J. Aquat. Ecosyst- Stress Recov. 4: 1-24. Nalepa, T. F ., D. L. Fanslow, M. B. Lansing, and G. A. Lang. 2003. Trends in the benthic macroinvertebrate community of Saginaw Bay, Lake Huron, 1987 to 1996: Responses to phosphorus abatement and the zebra mussel, Dreissena polymorpha- J. Great Lakes Res. 29: 14-33. Nalepa, T. F. G. L. F ahnenstiel, and T. H. Johengen. 1999. Impacts of the zebra mussel (Dreissena polymorpha) on water quality: A case study in Saginaw Bay, Lake Huron. In R. Claudi and J. H. Leach [eds.], Nonindigenous Freshwater Organisms: Vectors, Biology, and Impacts. Lewis Publishers. Nicholls, K. H., L. Heintsch, and E. Carney. 2002. Univariate step-trend and multivariate assessments of the apparent effects of P loading reductions and zebra mussels on the phytoplankton of the Bay of Quinte, Lake Ontario. J. Great Lakes Res. 28: 15- 31. . Noonburg, E. G., B. J. Shuter, and P. A. Abrams. 2003. Indirect effects of zebra mussels (Dreissena polymorpha) on the planktonic food web. Can. J. Aquat. Sci. 60: 1353-1368. Odum, E. P. 1969. The strategy of ecosystem development. Science. 164: 262-270. 98 Padilla, D. K., S. C. Adolph, K. L. Cottingham, and D. W. Schneider. 1996. Predicting the consequences of dreissenid mussels on a pelagic food web. Ecol. Model. 85: 129-144. Patten, B. C. 1984. Toward a theory of the quantitative dominance of indirect effects in ecosystems. Verh. Ges. 0kol. 13: 271-284. Patten, B. C., R. W. Bosserman, J. T. Finn, and W. G. Cale. 1976. Propagation of cause in ecosystems. In B. C. Pannen [ed.], Systems Analysis and Simulation in Ecology, Vol 4. Academic Press. Pérez-Espafia, H. and F. Arreguin-Se’mchez- 1999. A measure of ecosystem maturity. Ecol. Model. 199: 79-85. Pimm, S. L. and J. H. Lawton. 1980. Are food webs divided into compartments? J. Anim- Ecol. 49: 879-898. Prout, M. W., E. L. Mills, and J. L. Fomey. 1990. Diet, growth, and potential competitive interactions between age-O white perch and yellow perch in Oneida Lake, New York. Trans. Am. Fish. Soc. 119: 966-975. Ricciardi, A. 2001. F acilitative interactions among aquatic invaders: Is an "invasional meltdown" occurring the Great Lakes? Can. J. Fish. Aquat. Sci. 58: 2513-2525. Ridgway, M. S., D. A. Hurley, and K. A. Scott. 1990. Effects of winter temperature and predation on the abundance of alewife (Alosa pseudoharengus) in the Bay of Quinte, Lake Ontario. J. Great Lakes Res. 16: 11-20. Rudstam, L. G-, A. J. VanDeValk, C. M. Adams, J. T. H. Coleman, J. L. Fomey, and M- E. Richmond. 2004. Cormorant predation and the population dynamics of walleye and yellow perch in Oneida Lake. Ecol. Applic. 14: 149-163. Rutherford, B. S., K. A. Rose, E. L. Mills, J. L. Fomey, C. M. Mayer, and L. G. Rudstam. 1999. Individual-based model simulations of a zebra mussel (Dreissena polymorpha) induced energy shunt on walleye (Stizostedion vitreum) and yellow perch (Percaflavescens) populations in Oneida Lake, New York. Can. J. Fish. Aquat. Sci. 56: 2148-2160. Shannon, C. E. 1948. A mathematical theory of communication. Bell System Tech. 27: 379-423. Simberloff, D. and B. Von Holle. 1999. Positive interactions of nonindigenous species: invasional meltdown? Biol. Inv. 1: 21-32. Strayer, D. L-, K. A. Hattala, and A. W. Kahnle. 2004. Effects of an invasive bivalve (Dreissena polymorpha) on fish in the Hudson River estuary. Can. J- Aquat. Sci. 99 61 : 924-941. Strayer, D. L., N. F. Caraco, J. J. Cole, S. Findlay, and M. L Pace. 1999. Transformation of freshwater ecosystems by bivalves. BioScience. 49:19-27. Strus, R. H. and D. A. Hurley. 1992. Interactions between alewife (Alosa pseudoharengus), their food, and phytoplankton biomass in the Bay of Quinte, Lake Ontario. .1. Great Lakes Res. 18: 709-723. Thorp, J. H. and A. F. Casper. 2003. Importance of biotic interactions in large rivers: An experiment with planktivorous fish, dreissenid mussels and zooplankton in the St. Lawrence River. River Res. Applic. 19: 265-279. Ulanowicz, R. E. 1986. Growth and Development: Ecosystems Phenomenology. Springer Verlag- Ulanowicz, R. E. 1996. Trophic flow networks as indicators of ecosystem stress. In G. A. Polis and K. O. Winemiller [eds.], Food Webs: Integration of Patterns and Dynamics. Chapman and Hall. Ulanowicz, R. E. 1997. Ecology, The Ascendent Perspective. Columbia University Press. Vanderploeg, H. A., T. F. Nalepa, D. J. Jude, E. L. Mills, K. T. Holeck, J. R. Liebig, I.A. Grigorovich, and H. Ojaveer. 2002. Dispersal and emerging ecological impacts of Ponto Caspian species in the Laurentian Great Lakes. Can. J. Fish. Aquat. Sci. 59: 1209-1228. 100 APPENDICES 101 Appendix 2.1 List of model inputs and data sources for the unbalanced pre- and post-zebra mussel invasion networks. Diet proportions are not included to conserve space, but sources of diet information are listed. N.P. stands for not present. Biomass units are g m’z, wet weight (WW)- Conversions from wet weight to dry weight (DW), and dry weight to carbon, are listed. P/B, C/B, and WE stand for production-to-biomass, consumption-to-biomass, and respiration-to-biomass ratios, respectively, measured as yr'l. Export includes migrations from the ecosystem and fisheries harvest (g m'2 WW). The abbreviation BQ-OL CMP Workgroup refers to the Bay of Quinte — Oneida Lake Comparative Modelling Project Workgroup. The methods for this modeling project, from which much of our data was drawn, are expected to be published in 2006 as a Canadian Technical Report of Fisheries and Aquatic Sciences (Koops, M. A. pers- com.)- 102 Appendix 2.1 No. Taxa Parameter Pre Value Post Value Reference(s) 1 Cormorants Biomass ww 1.73x10'4 5.23xm'4 BQ-OL CMP Workgroup ww : ow 3.50x10'l 3.50x10'l Jorgenson 1979 DW : Carbon 4.50x10'l 4.50:.10'l Jorgenscn 1979 P/B 7.62x10'l 6.44x10'l BQ-OL CMP Workgroup C/B 7.19x10l 7.18x10l BQ-OL CMP Workgroup R/B 7.03x10l 7.03x10l BQ-OL CMP Workgroup Diet . - BQ-OL CMP Workgroup 2 Walleye Age 4+ Biomass WW 1.89x10-l 8.24x10-2 BQ-OL CMP Workgroup ww : ow 2.00:.10'l 2.00x10'l Jorgensen 1979 DW : Carbon 4.50x10'l 4.50x10'l Jorgenson 1979 P/B 4.78x10'l 3.2sxio'l BQ-OL CMP Workgroup C/B 3.96 3.83 BQ-OL CMP Workgroup R/B 2.99 2.99 BQ-OL CMP Workgroup Export 1.35x10.2 5.88x10-3 BQ-OL CMP Workgroup Diet . - BQ-OL CMP Workgroup 3 Walleye Age 1-3 Biomass ww 7.351.10'2 2.73x10'2 BQ-OL CMP Workgrouv WW : DW 2.00x10"l 2.00x10-l Jargensen 1979 ow : Carbon 4.50x10'l 4.50x10-l Jargensen 1979 P/B 4.70x10'l 4.70sr10'1 BQ-OL CMP Workgroup 03 3.94 5.54 BQ-OL CMP Workgroup R/B 3.86 3.86 BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 4 Walleye Age-0 Biomass WW 3.49x10-3 3.74x10“3 BQ-OL CMP Workgroup WW : DW 2.00x10.l 2.00x10.l Jargensen 1979 ow : Carbon 4.50x10'l 4.50:.10'l Jorgenson 1979 NB 2.42 2.42 BQ-OL CMP Workgroup 08 7.84 1.46x10l BQ-OL CMP Workgroup R/B 9.89 9.89 BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 5 Yellow Perch Age 3+ Biomass WW 1.50x10.l 7.94x10.2 BQ-OL CMP Workgroup ww : DW 2.00:.10'l 2.00x10'l Jorgensen 1979 DW : Carbon 4.50x10'1 4.50x10'l Jorgenson 1979 P/B 3.99x10'l 5.93x10'l BQ-OL CMP Workgroup 103 Appendix 2.1 (con't) No. Taxa Parameter Pre Value Post Value Reference(s) 5 Yellow Perch Age 3+ C/B 3.8 4.19 BQ-OL CMP Workgroup R/B 3.72 3.72 BQ-OL CMP Workgroup Export 1.74x10'2 9.18x10'3 BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 6 Yellow Perch Age 1-2 Biomass WW 2.26x10-2 3.37x10.2 BQ'OL CMP WOTkSTOUP ww : ow 2.00x10'l 2,002.10“l Jorgenson 1979 DW : Carbon 4.50x10'l 4.50x10'l Jorgensen 1979 WE 3.99x10'l 5.93x10'l BQ-OL CMP Workgroup C/B 3.8 4.19 BQ-OL CMP Workgroup R/B 3.72 3.72 BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 7 Yellow Perch Age-0 Biomass WW 2.02x10-2 3.92x10“2 BQ-OL CMP Workgroup ww : DW 2.00x10'l 2.00m" Jorgenscn 1979 DW : Carbon 4.50x10.l 4.50x10'l Jargensen 1979 P/B 6.14 7.15 BQ-OL CMP Workgroup C/B 1.53x10l 1.94x10l BQ-OL CMP Workgroup R/B 1.68x10l 1.68x10l BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 8 White Perch Age 1+ Biomass WW 7.05x10.2 5.56x10.2 BQ-OL CMP Workgroup ww : ow 2.00x10'l 2.00x10'I Jorgenson 1979 DW : Carbon 4.50x10'l 4.50x10'l Jorgenson 1979 P/B 5.01x10-l 5.86x10'l BQ-OL CMP Workgroup C/B 4 4.18 BQ-OL CMP Workgroup R/B 2.75 2.75 BQ-OL CMP Workgroup Export 1.07x10'4 8.46x10'5 BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 9 White Perch Age-0 Biomass WW 1.82x10.2 1.06x10.2 BQ'OL CMP Workgroup WW : DW 2.00x10.l 2.00x10-l Jorgensen 1979 DW : Carbon 4.50x10.1 4.50x10.l Jorgensen 1979 P/B 4.8 4.8 BQ-OL CMP Workgroup C/B 1.26x10l 1.28x10l BQ-OL CMP Workgroup R/B 7.22 7.22 BQ-OL CMP Workgroup Diet BQ-OL CMP Workgroup 104 Appendix 2.1 (con‘t) No. Taxa Parameter Pre Value Post Value Reference(s) -4 -4 10 Black Crappie Age 1+ Biomass WW 4.70x10 4.70x10 BQ'OL CMP Workgroup -1 - WW : DW 2.00x10 2.00x10 1 Jorgcnsen 1979 -1 -1 DW : Carbon 4.50x10 4.50x10 Jorgensen 1979 -1 -1 P/B 7.08x10 7.08x10 BQ—OL CMP Workgroup C/B 4.42 4.42 BQ—OL CMP Workgroup R/B 2.77 2.77 BQ-OL CMP Workgroup -5 -5 Export 3.24x10 3.24x10 BQ-OL CMP Workgroup Diet - . BQ-OL CMP Workgroup -4 .4 11 Bluegill Age 1+ Biomass ww 3.07x10 3.07x10 BQ-OL CMP Workgroup -l -1 WW : DW 2.00x10 2.00x10 Jorgensen 1979 -1 -1 DW : Carbon 4.50x10 4.50x10 Jorgensen 1979 -1 -1 WE 6.12x10 6.12x10 BQ-OL CMP Workgroup C/B 4.22 4.22 BQ-OL CMP Workgroup R/B 2.77 2.77 BQ-OL CMP Workgroup -5 -5 Export 5.76x10 5.76x10 BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup -3 -3 12 Pumpkinseed Age 1+ Biomass WW 6.33x10 6.47x10 BQ-OL CMP Workgroup -l -1 WW : DW 2.00x10 2.00x10 Jorgensen 1979 -l -1 DW : Carbon 4.50x10 4.50x10 Jorgensen 1979 -l -1 P/B 6.12x10 6.12x10 BQ-OL CMP Workgroup C/B 4.22 4.22 BQ-OL CMP Workgroup R/B 2.77 2.77 BQ-OL CMP Workgroup -4 .4 Export 6.66x10 6.80x10 BQ-OL CMP Workgroup Diet - . BQ-OL CMP Workgroup -3 --3 13 Rock Bass Age 1+ Biomass WW 5.00x10 4.85x10 BQ-OL CMP Workgroup -l -1 WW : DW 2.00x10 2.00x10 Jorgensen 1979 -l -1 DW : Carbon 4.50x10 4.50x10 Jorgensen 1979 -1 -1 P/B 5.15x10 5.15x10 BQ-OL CMP Workgroup C/B 4.03 4.03 BQ-OL CMP Workgroup R/B 2.77 2.77 BQ-OL CMP Workgroup -5 -5 Export 2.60x10 2.52x10 BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup -4 -5 14 Panfish Age-0 Biomass WW 1.68x10 7.24x10 BQ-OL CMP Workgroup 105 Appendix 2.1 (con't) No. Taxa Parameter Pre Value Post Value Reference(s) 14 Panfish Age-0 ww : DW 2.00:.10'l 2.00.110'l Jorgensen 1979 DW : Carbon 4.50x10'l 4.50x10'l Jorgensen 1979 P/B 1.5 1.5 1 BQ-OL CMP Workgroup GB 6 1.19x10 BQ-OL CMP Workgroup R/B 1.10x10l 1.10aml BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 15 Gizzard Shad Age 1+ Biomass WW 7-l8x10.3 7.58x10.3 BQ-OL CMP Workgroup ww : DW 2.00x10-l 2.00:.10'l Jorgensen 1979 DW : Carbon 4.50x10.l 4.50x10.l Jorgensen 1979 WE 1.43 1.43 BQ—OL CMP Workgroup C/B 5.86 5.86 BQ-OL CMP Workgroup R/B 2.59 2.59 BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 16 Gizzard Shad Age-0 Biomass ww 3.54x10'l 8.9sxlo’2 BQ-OL CMP Workgroup WW : DW 2.00x10.l 2.00x10-l Jargensen 1979 DW : Carbon 4.50x10-l 4.50x10-l Jergensen 1979 P/B 1.43 1.43 BQ-OL CMP Workgroup C/B 5.96 5.96 BQ-OL CMP Workgroup R/B 6.93 6.93 BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 17 Alewife Biomass ww 1.04xlo'4 1.87xlo'2 BQ-OL CMP Workgroup ww : DW 2.00x10"l 2.00x10-l Jorgensen 1979 DW : Carbon 4.50x10-l 4.50x10-l Jorgensen 1979 WE 8.65x10'l 8.89x10'l BQ-OL CMP Workgroup C/B 4.68 4.68 BQ-OL CMP Workgroup R/B 1.00x10l 1.00x10l BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 18 Brown Bullhead Biomass ww 1.06x10'2 1.101.10'2 BQ-OL CMP Workgroup ww : DW 2.00x10'l zoos-10'l Jorgensen 1979 DW : Carbon 4.50x10.l 4.50x10.l Jorgensen 1979 P/B 4.24x10'l 3.86x10'l BQ-OL CMP Workgroup OR 3.85 3.77 BQ-OL CMP Workgroup R/B 2.59 2.59 BQ-OL CMP Workgroup 106 Appendix 2.1 (con‘t) No. Taxa Parameter Pre Value Post Value Reference(s) -5 -5 18 Brown Bullhead Export 3.55x10 3.69x10 BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup -3 -3 19 Burbot Biomass WW 6.89x10 6.61x10 BQ-OL CMP Workgroup -l -1 WW : DW 2.00x10 2.00x10 Jargensen 1979 -1 - DW : Carbon 4.50x10 4.50x10 1 Jargensen 1979 -1 -1 WE 2.60x10 2.60x10 BQ-OL CMP Workgroup C/B 3.52 3.52 BQ-OL CMP Workgroup R/B 5.79 5.79 BQ—OL CMP Workgroup -6 -6 Export 7.50x10 7.20x10 BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup -2 -2 20 Channel Catfish Biomass WW 6.11x10 6.16x10 BQ'OL CMP WorkgrouP -1 -1 WW : DW 2.00x10 2.00x10 Jorgensen 1979 -1 -1 DW : Carbon 4.50x10 4.50x10 Jargensen 1979 -1 -1 P/B 2.79x10 2.17x10 BQ-OL CMP Workgroup C/B 3.56 3.43 BQ-OL CMP Workgroup R/B 2.59 2.59 BQ-OL CMP Workgroup -4 -4 Export 2.04x10 2.06x10 BQ-OL CMP Workgroup Diet . BQ-OL CMP Workgroup -4 21 Cisco Biomass WW 9.27x10 N.P- BQ—OL CMP Workgroup -1 -1 WW : DW 2.00x10 2.00x10 Jorgensen 1979 -l -1 DW : Carbon 4.50x10 4.50x10 Jorgensen 1979 WE 1.71 NP. BQ-OL CMP Workgroup C/B 6.42 NP. BQ-OL CMP Workgroup R/B 1.04 NP. BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup -2 -2 22 Common Carp Biomass WW 5.18x10 3.40x10 BQ-OL CMP Workgroup -1 -1 WW : DW 2.00x10 2.00x10 Jorgensen 1979 -l -1 DW : Carbon 4.50x10 4.50x10 Jorgensen 1979 -1 -l P/B 1.56x10 1.60x10 BQ-OL CMP Workgroup C/B 3.33 3.33 BQ-OL CMP Workgroup R/B 2.4 2.4 BQ-OL CMP Workgroup -5 -6 Export 1.10x10 7.20x10 BQ-OL CMP Workgroup Diet BQ-OL CMP Workgroup 107 Appendix 2.1 (con't) No. Taxa Parameter Pre Value Post Value Reference(s) 23 Darters Biomass WW 5.40x10-5 1.35x10.4 BQ-OL CMP Workgroup ww : DW 2.00:.10'l 2.00x10"l Jorgensen 1979 DW : Carbon 4.50x10-l 4.50x10-l Jorgensen 1979 P/B 3.70x10'l 3.70:110'l BQ-OL CMP Workgroup C/B 3.74 3.74 BQ-OL CMP Workgroup R/B 2.59 2.59 BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 24 Emerald Shiners Biomass WW 2.39x10“3 8.60x10-2 BQ-OL CMP Workgroup ww : DW 2.00:.10'l 2.00x10-l Jorgensen 1979 DW : Carbon 4.50x10.l 4.50x10.l Jorgensen 1979 P/B 1.71 1.71 BQ-OL CMP Workgroup C/B 6.42 6.42 BQ-OL CMP Workgroup R/B 5.83 5.83 BQ-OL CMP Workgroup Diet - . BQ-OL CMP Workgroup 25 Freshwater Drum Biomass WW 5.71x10.2 1.03x10-l BQ-OL CMP Workgroup WW : DW 2.00x10.l 2.00x10.l Jorgensen 1979 DW : Carbon 4.50x10-l 4.50x10'l Jergensen 1979 P/B 2.64x10.l 2.50x10-l BQ-OL CMP Workgroup C/B 3.52 3.52 BQ-OL CMP Workgroup R/B 2.57 2.57 BQ—OL CMP Workgroup Export 2.16x10u4 3.91 x10.4 BQ—OL CMP Workgroup Diet . - BQ-OL CMP Workgroup 26 Golden Shiners Biomass WW 1.77x10.3 5.40x10'5 BQ-OL CMP Workgroup WW : DW 2.00x10.l 2.00x10.l Jorgensen 1979 DW : Carbon 4.50x10-l 4.50x10'l Jergensen 1979 P/B 1.71 1.71 BQ-OL CMP Workgroup C/B 6.42 6.42 BQ-OL CMP Workgroup R/B 5.83 5.83 BQ-OL CMP Workgroup Diet . BQ-OL CMP Workgroup 27 Lake Sturgeon Biomass WW N.P. 5.92x10-3 BQ'OL CMP WOTRSTOUP WW : DW 2.00x10.l 2.00x10.l Jorgensen 1979 DW : Carbon 4.50x10.l 4.50x10.l Jorgensen 1979 P/B N.P. 2.00x10-l BQ-OL CMP Workgroup 108 Appendix 2.1 (con't) No. Taxa Parameter Pre Value Post Value Reference(s) 27 Lake Sturgeon C/B NP. 4 BQ-OL CMP Workgroup R/B N.P. 3.3 BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 28 Log Perch Biomass WW 2.70x10-5 6.30x10-5 BQ-OL CMP Workgroup WW : DW 2.00x10.1 2.00x10-1 Jorgensen 1979 DW : Carbon 4.50x10'l 4.50:.10'l Jorgensen 1979 P/B 3.70x10'l 3.70xio" BQ-OL CMP Workgroup C/B 3.74 3.74 BQ-OL CMP Workgroup R/B 2.59 2.59 BQ—OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 29 Mottled Sculpin Biomass WW 9.00x10-b 9.00x10.6 BQ—OL CMP Workgroup ww : DW 2.00x10-l 2.00x10" Jorgensen 1979 DW : Carbon 4.50x10-1 4.50x10'l Jorgensen 1979 P/B 3.70am"l 3.70x10'l BQ-OL CMP Workgroup C/B 3.74 3.74 BQ-OL CMP Workgroup R/B 2.59 2.59 BQ-OL CMP Workgroup Diet . - BQ-OL CMP Workgroup 30 Northern Pike Biomass ww 7.11x10'4 7.11x10'4 BQ-OL CMP Workgrouv WW : DW 2.00x10.l 2.00x10.l Jorgensen 1979 DW : Carbon 4.50:.10'l 4.50:.10'l Jergensen 1979 WE 2.01x10'l 1.98x10'I BQ-OL CMP Workgroup C/B 3.4 3.4 BQ-OL CMP Workgroup R/B 5.79 5.79 BQ-OL CMP Workgroup Export 8.37x10'5 8.37xlo'5 BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 31 Red Horse Sucker Biomass WW 5.29x10.3 6.72x10-3 BQ-OL CMP Workgroup ww : DW 2.00x10-l 2.00x10-l Jorgensen 1979 ow : Carbon 4.50rtlo'l 4.5oxlo‘l Jorgensen 1979 P/B 3.70x10'l 3.70am"l BQ-OL CMP Workgroup C/B 3.74 3.74 BQ-OL CMP Workgroup R/B 2.59 2.59 BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 32 Smallmouth Bass Biomass WW 4.56x10-2 4.87x10.2 BQ-OL CMP Workgroup 109 Appendix 2.1 (con't) No. Taxa Parameter Pre Value Post Value Reference(s) 32 Smallmouth Bass WW : DW 2.00x10.l 2.00x10.l Jargensen 1979 ow : Carbon 4.50x10-l 4.50x10'l Jargensen 1979 P/B 3.90x10'l 3.68x10'1 BQ—OL CMP Workgroup C/B 5.36 5.36 BQ-OL CMP Workgroup R/B 3.92 3.92 BQ-OL CMP Workgroup Export 2.09x10'3 2.23x10'3 BQ—OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 33 Trout-perch Biomass WW 9.26x10.3 1.02x10-2 BQ-OL CMP Workgroup ww ; DW 2.00x10-l 2.00x10-l Jorgensen 1979 DW : Carbon 4.50x10-l 4.50x10"l Jorgensen 1979 WB 1.35 1.46 BQ-OL CMP Workgroup C/B 5.71 5.91 BQ-OL CMP Workgroup R/B 3.19 3.19 BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 34 White Bass Biomass WW 1.06x10-2 1.08x10.2 BQ-OL CMP Workgroup WW : DW 2.00x10.l 2.00x10.l Jorgensen 1979 ow : Carbon 4.50x10"l 4.50x10'l Jergensen 1979 P/B 2.60x10.I 2.60x10.l BQ—OL CMP Workgroup C/B 3.52 3.52 BQ-OL CMP Workgroup R/B 5.79 5.79 BQ-OL CMP Workgroup Export 2.40x10'4 2.45x10'4 BQ—OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 35 White Sucker Biomass WW 4.56x10.2 4.98x10.2 BQ-OL CMP Workgroup WW : DW 2.00x10.l 2.001110-l Jorgensen 1979 DW : Carbon 4.50x10.l 4.50x10.l Jorgensen 1979 WE 3.23x10'l 2.68x10'l BQ—OL CMP Workgroup C/B 3.65 3.54 BQ-OL CMP Workgroup R/B 2.59 2.59 BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 36 Amphipods Biomass WW 5.19x10-2 4.63x10.2 BQ-OL CMP Workgroup WW : DW 1.67x10.l 1.67x10.l Jargensen 1979 DW : Carbon 4.17x10.l 4.17x10.l Jargensen 1979 P/B 5.7 5.7 BQ-OL CMP Workgroup 110 Appendix 2.1 (con't) No. Taxa Parameter Pre Value Post Value Reference(s) 36 Amphipods C/B 3.02x10l 3.02x10l BQ-OL CMP Workgroup R/B 4.26 4.26 Quigley et al. 2002 Diet . . BQ-OL CMP Workgroup 37 Chironomids Biomass ww 5.73x10'2 4.54x1o'2 BQ-OL CMP Workgroup ww : ow 1.67x10'l 1.67x10'l Jorgensen 1979 DW : Carbon 4.62x10.l 4.62x10.l Jorgensen 1979 P/B 1.3lx10l 1.31x10l BQ-OL CMP Workgroup C/B 6.24x10l 6.24x10l BQ-OL CMP Workgroup R/B 4.5 4.5 Johnson and Brinkhur 1971 Diet . - BQ-OL CMP Workgroup Krause 2004 38 Clams Biomass ww 7.19x10'4 4.45x10'4 BQ-OL CMP Workgrouv WW : DW 1.67x10-l 1.67x10.l Jorgensen 1979 -1 -1 DW : Carbon 3.99x10 3.99x10 Jorgensen 1979 P/B 3.8 3.8 BQ-OL CMP Workgroup C/B 2.44x10l 2.44x10l BQ-OL CMP Workgroup R/B 1.03x10l 1.03x10l Johnson and Brinkhur 1971 Diet . . BQ-OL CMP Workgroup Krause 2004 39 insects Biomass ww 6.88x10'3 6.88x10‘3 BQ-OL CMP Workgroun ww : ow 1.67x10'l 1.67xio'l Jorgensen 1979 -l -1 DW : Carbon 4.46x10 4.46x10 Jergensen 1979 P/B 5.35 5.35 BQ-OL CMP Workgroup C/B 3.18x10l 3.18x10l BQ-OL CMP Workgroup R/B 1.33x10l 1.33x10l BQ-OL CMP Workgroup Diet . . BQ-OL CMP Workgroup Krause 2004 40 lsopods Biomass WW 7.25x10-3 1.38x10.2 BQ-OL CMP Workgroup WW : DW 1.67x10-l 1.67x10-l Jorgensen 1979 -l -1 DW : Carbon 3.43x10 3.43x10 Jorgensen 1979 WE 5.7 5.7 BQ-OL CMP Workgroup 1 1 C/B 3.02x10 3.02x10 BQ-OL CMP Workgroup R/B 4.26 4.26 Quigley et a1. 2002 111 Appendix 2.1 (con't) No. Taxa Parameter Pre Value Post Value Reference(s) 40 lsopods Diet . . BQ-OL CMP Workgroup 41 Leeches Biomass ww 3.29x10'3 4.38x111'3 BQ-OL CMP Workgroup ww : ow 1.67x10'l 1.67x10'l Jorgensen 1979 ow : Carbon 4.83x10'l 4.83x10'l Jorgensen 1979 WB 5.35 5.35 BQ-OL CMP Workgroup C/B 3.18x10l 3.18x10l BQ-OL CMP Workgroup R/B 1.33x10l 1.33x10l BQ—OL CMP Workgroup Diet . . BQ-OL CMP Workgroup 42 Oligochaetes Biomass WW 8.98x10-3 1.65x10.2 BQ-OL CMP Workgroup ww : DW 1.67x10'l 1.67x10'l Jorgensen 1979 DW : Carbon 4.02x10.l 4.02x10-l Jargensen 1979 P/B 1.31x10l 1.31x10l BQ-OL CMP Workgroup C/B 6.24x10l 6.24x10l BQ-OL CMP Workgroup R/B 4.5 4.5 Johnson and Brinkhur 1971 Diet . . BQ-OL CMP Workgroup Krause 2004 43 Snails Biomass WW 1.85x10.2 3.10x10-2 BQ-OL CMP Workgroup WW : DW 1.67x10-l 1.67x10.l Jargensen 1979 ow : Carbon 3.99x10'l 3.99x10'l Jorgensen 1979 P/B 3.5 3.5 BQ—OL CMP Workgroup C/B 1.33x10l 1.33x10l BQ-OL CMP Workgroup RIB 1.8 1.8 BQ-OL CMP Workgroup Diet . BQ-OL CMP Workgroup Zebra Mussels Biomass ww N.P. 1.59x10l BQ-OL CMP Workgroup WW : DW 1.67x10.l 1.67x10-l Jorgensen 1979 DW : Carbon 3.99x10.l 3.99x10.l Jargensen 1979 WE NP. 1.35 BQ-OL CMP Workgroup C/B NB 8.6 BQ-OL CMP Workgroup R/B NP. 4.15 Fanslow et al. 2001 Diet . . BQ-OL CMP Workgroup 45 Alona species Biomass WW 1.05x10-4 3.01x10-5 BQ-OL CMP Workgroup WW : DW 1.67x10.l 1.67x10'l Jorgensen 1979 DW : Carbon 4.50x10-l 4.50x10.l Jorgensen 1979 112 Appendix 2.] (con't) No. Taxa Parameter Pre Value Post Value Reference(s) 45 Alana species P/B 3.80x10l 3.80x10l BQ-OL CMP Workgroup C/B 1.53x102 1.53x102 BQ-OL CMP Workgroup R/B 1.86 1.86 Urabe and Watanabe 1989 Diet BQ—OL CMP Workgroup Krause 2004 46 Basmina Biomass WW 2.59x10-2 2.01x10-2 BQ-OL CMP Workgroup langirastris WW : DW 1.67x10-l 1.67x10.l Jorgensen 1979 DW : Carbon 4.50x10.l 4.50x10.l Jorgensen 1979 WE 3.80x10l 3.80x10l BQ-OL CMP Workgroup C/B 1.53x102 1.53x102 BQ-OL CMP Workgroup R/B 1.86 1.86 Urabe and Watanabe 1989 Diet BQ-OL CMP Workgroup Krause 2004 47 Camptocercus Biomass WW N.P. 1.26x10-4 BQ'OL CMP Workgroup harpae WW : DW 1.67x10-l 1.67x10-I Jorgensen 1979 DW : Carbon 4.50x10.l 4.50x10-l Jargensen 1979 P/B N.P. 3.80x10l BQ-OL CMP Workgroup C/B N.P. 1.53xlo2 BQ-OL CMP Workgroup R/B NP. 1.86 Urabe and Watanabe 1989 Diet BQ-OL CMP Workgroup Krause 2004 48 Ceriodaphnia Biomass WW 7.391(10-4 5.32x10.4 BQ-OL CMP Workgroup quadrangula WW : DW 1.67x10.l 1.67x10-l Jorgensen 1979 DW : Carbon 4.50x10'l 4.50x10'l Jorgensen 1979 WE 3.80x10l 3.80x10l BQ-OL CMP Workgroup C/B 1.53x102 1.53x102 BQ-OL CMP Workgroup R/B 1.86 1.86 Urabe and Watanabe 1989 Diet BQ-OL CMP Workgroup Krause 2004 49 Chydorus Biomass WW 1.16x10.2 2.57x10-2 BQ-OL CMP Workgroup sphaericus WW : DW 1.67x10.l 1.67x10-l Jorgensen 1979 DW : Carbon 4.50x10'l 4.50xlo’l Jorgensen 1979 P/B 3.80x10i 3.80x10l BQ-OL CMP Workgroup 113 Appendix 2.] (con't) No. Taxa Parameter Pre Value Post Value Reference(s) 49 Chydorus C/B 1.53x102 1.53x102 BQ-OL CMP Workgroup sphaericus R/B 1.86 1.86 Urabe and Watanabe 1989 Diet BQ-OL CMP Workgroup Krause 2004 50 Daphnia galeata Biomass WW 2.58x10.l 1.88x10-l BQ-OL CMP Workgroup mendotae WW : DW 1.67x10.l 1.67x10"I Jargensen 1979 DW : Carbon 5.07x10.l 5.07x10-1 Jargensen 1979 P/B 3.80x10l 3.80x10l BQ-OL CMP Workgroup C/B 1.53x102 1.53x102 BQ—OL CMP Workgroup R/B 3.13x10l 3.13x10l Urabe and Watanabe1989 Diet BQ-OL CMP Workgroup Krause 2004 51 Daphnia Biomass ww 3.15x1o'l 4.89x10'l BQ-OL CMP Workgroup pulicaria ww : DW 1.67x10-l 1.67x10'l Jargensen 1979 DW : Carbon 5.07x10-l 5.07x10l Jargensen 1979 P/B 3.80x10l 3.80x10l BQ-OL CMP Workgroup C/B 1.53x102 1.53x102 BQ-OL CMP Workgroup R/B 3.13x10l 3.13x10l Urabe and Watanabe 1989 Diet BQ-OL CMP Workgroup Krause 2004 52 Daphnia Biomass WW 7.36x10»3 8.20x10-4 BQ-OL CMP Workgroup retrocurva WW : DW 1.67x10'l 1.67x10'l Jorgensen 1979 DW : Carbon 5.07x10"1 5.07xlo'l Jorgensen 1979 WE 3.80x10l 3.80x10l BQ-OL CMP Workgroup C/B 1.53x102 1.53x102 BQ-OL CMP Workgroup R/B 3.13x10l 3.13x10l Urabe and Watanabe 1989 Diet BQ-OL CMP Workgroup Krause 2004 53 Diaphanosoma Biomass WW 9.11x10-3 9.02x10.3 BQ-OL CMP Workgroup species WW : DW 1.67x10.l 1.6711110.l Jorgensen 1979 ow : Carbon 4.50x10'l 4.50x10'l Jergensen 1979 P/B 3.80x10l 3.80x10l BQ-OL CMP Workgroup C/B 1.53x102 1.53x102 BQ-OL CMP Workgroup 114 Appendix 2.1 (con't) No. Taxa Parameter Pre Value Post Value Reference(s) 53 Diaphanosoma R/B 3-l3x10l 3.13x10l Urabe and Watanabe 1989 sPecies Diet BQ-OL CMP Workgroup Krause 2004 54 Eubosmina Biomass ww 2.09x10'2 3.22xlo'3 BQ-OL CMP Workgroup coregoni WW : DW 1.67x10.l 1.67x10-l Jorgensen 1979 DW : Carbon 4.50x10-l 4.50x10'l Jorgensen 1979 PB 3.80x10I 3.80x10l BQ-OL CMP Workgroup C/B 1.53x102 1.53x102 BQ-OL CMP Workgroup R/B 1.86 1.86 Urabe and Watanabe 1989 Diet BQ-OL CMP Workgroup Krause 2004 55 Sida crystallina Biomass ww 3.27x10'5 7.42x10'5 BQ-OL CMP Workgroup WW : DW 1.67x10-l 1.67x10.l Jorgensen 1979 DW : Carbon 4.50x10-l 4.50x10‘l Jorgensen 1979 WE 3.80x10l 3.80x10l BQ-OL CMP Workgroup C/B 1.53x102 1.53x102 BQ—OL CMP Workgroup R/B 3.13x10l 3.13x10l Urabe and Watanabe 1989 Diet BQ-OL CMP Workgroup Krause 2004 56 Leptodora kindtii Biomass WW 4.7lx10.4 1.57x10-3 BQ-OL CMP Workgroup ww : ow 1.67x10'l 1.67xlo'l Jergensen 1979 DW : Carbon 4.50x10'l 4.50x10'l Jorgensen 1979 P/B 3.10x10l 3.10x10l BQ-OL CMP Workgroup C/B 1.23x102 1.23x102 BQ-OL CMP Workgroup R/B 2.59x‘I 2.59xlo" Hillbricht-llkowska and Karabin 1970 Diet BQ—OL CMP Workgroup Krause 2004 57 Acanthocyclops Biomass WW 1.67x10.5 3.54x10.3 BQ-OL CMP Workgroup vernalis WW : DW 1.67x10-l 1.67x10“l Jorgensen 1979 DW : Carbon 4.36x10.l 4.36x10.l Jargensen 1979 WE 2.00x10l 2.00x10l BQ-OL CMP Workgroup c713 8.20x10l 8.20x10] BQ-OL CMP Workgroup 115 Appendix 2.1 (con‘t) No. Taxa Parameter Pre Value Post Value Reference(s) 57 Acanthocyclops R/B 1.84x10l 1.84x10l Urabe and Watanabe 1989 vernalis Diet BQ-OL CMP Workgroup Krause 2004 58 Diacyclops Biomass ww 1.26x10'l 5.42x10'2 BQ-OL CMP Workgroup thomasi WW : DW 1.67x10-l 1.67x10-l Jorgensen 1979 DW : Carbon 4.36x10'l 4.36x10'l Jorgensen 1979 P/B 2.00x10l 2.00x10l BQ-OL CMP Workgroup C/B 8.20x10l 8.20x10l BQ-OL CMP Workgroup R/B 1.84x10l 1.84x10l Urabe and Watanabe 1989 Diet BQ-OL CMP Workgroup Hansen and Nelson 1998 59 Ergasilus species Biomass ww 2.13x10'4 2.41x10'5 BQ-OL CMP Workgroup ww : DW 1.67x10'l 1.67x10'l Jergensen 1979 DW : Carbon 4.36xlo'l 4.36x10'l Jorgensen 1979 WE 2.00x10l 2.00x10l BQ-OL CMP Workgroup C/B 8.20x10l 8.20x10l BQ-OL CMP Workgroup R/B 1.84x10l 1.84x10l Urabe and Watanabe 1989 Diet BQ—OL CMP Workgroup Hudson and Lesko 2002 60 Mesocyclops edax Biomass WW 5.65x10-2 4.99x10-2 BQ'OL CMP Workgroup ww : DW 1.67x10'l 1.67x10'l Jorgensen 1979 DW : Carbon 4.36x10'l 4.36x10'l Jargensen 1979 WE 2.00x10l 2.00x10l BQ-OL CMP Workgroup C/B 8.20x10l 8.20x10l BQ-OL CMP Workgroup R/B 1.841110l 1.84x10l Urabe and Watanabe 1989 Diet BQ-OL CMP Workgroup Krause 2004 61 Epischura Biomass ww 3.68x10’2 5.25xio'2 BQ-OL CMP Workgroup lacustris WW : DW 1.67x10-l 1.67x10-l Jorgensen 1979 ow : Carbon 4.36xio’l 4.36x10'l Jorgensen 1979 P/B 2.00x10l 2.00x10l BQ-OL CMP Workgroup C/B 8.20x10l 8.20x10l BQ—OL CMP Workgroup R/B 2.96x10l 2.96x10l Banse and Mosher 1980 116 Appendix 2.1 (con't) No. Taxa Parameter Pre Value Post Value Reference(s) 61 Epischura Diet . . BQ—OL CMP Workgroup lacustris Krause 2004 62 Leptodiaptomus Biomass ww 7.34x10'2 6.85x10'2 BQ-OL CMP Workgroup minutus WW : DW 1.67x10.l 1.67x10.l Jorgensen 1979 DW : Carbon 4.36x10'l 4.36x10'l Jargensen 1979 P/B 2.00x10l 2.001110l BQ-OL CMP Workgroup C/B 8.20x10l 8.20x10l BQ'OL CMP Workgroup R/B 2.96x10l 2.96x10l Banse and Mosher 1980 Diet - . BQ-OL CMP Workgroup Krause 2004 63 Skistodiaptomus Biomass WW 1.00x10-l 1.07x10-l BQ—OL CMP Workgroup oregonensis WW : DW 1.67x10.l 1.67x10.l Jorgensen 1979 DW : Carbon 4.36x10.l 4.36x10.l Jorgensen 1979 P/B 2.00x10l 2.00x10l BQ-OL CMP Workgroup C/B 8.20x10l 8.20x10l BQ-OL CMP Workgroup R/B 2.96x10l 2.96x10l Banse and Mosher 1980 Diet . - BQ-OL CMP Workgroup Krause 2004 64 Nauplii Biomass WW 5.46x10.2 4.40x10.2 BQ-OL CMP Workgroup ww : ow 1.67x10'l 1.67x10'l Jorgensen 1979 ow : Carbon 4.50xlo'l 4.50x10'l Jorgensen 1979 WE 2.00x10l 2.00x10l BQ-OL CMP Workgroup C/B 8.20x10l 8.20x10l BQ—OL CMP Workgroup R/B 1.16 1.16 Makarewicz and Likens 1979 Diet . . BQ-OL CMP Workgroup Krause 2004 65 Rotifers Biomass WW 7.20x10.3 7.20x10.3 BQ-OL CMP Workgroup ww : DW 1.67x10'l 1.67x10'l Jorgensen 1979 DW : Carbon 4.50x10-l 4.50x10.l Jorgensen 1979 P/B 5.20x10l 5.20x10l BQ-OL CMP Workgroup C/B 2.08x102 2.08x102 BQ-OL CMP Workgroup R/B 1.16 1.16 Makarewicz and Likens 1979 Diet . . BQ-OL CMP Workgroup 117 Appendix 2.1 (con't) No. Taxa Parameter Pre Value Post Value Reference(s) 65 Rotifers Die‘t Pennak 1978 66 Blue-green Algae Biomass WW 1.38 1.09 BQ—OL CMP Workgroup -1 -1 WW : DW 3.60x10 3.60x10 Jorgensen 1979 -1 -1 DW : Carbon 4.60x10 4.60x10 Jargensen 1979 1 1 P/B 8.70x10 9.00x10 BQ-OL CMP Workgroup C/B None None BQ-OL CMP Workgroup R/B 7.28x10l 7.28x10l Biddanda and Cotner 2002 67 Diatoms Biomass WW 1.77 1.62 BQ-OL CMP Workgroup -1 -1 WW : DW 3.30x10 3.30x10 Jorgensen 1979 -l -1 DW : Carbon 5.17x10 5.17x10 Jargensen 1979 1 1 WE 8.70x10 9.00x10 BQ-OL CMP Workgroup C/B None None BQ-OL CMP Workgroup R/B 7.28x10l 7.28x10l Biddanda and Cotner 2002 -2 -2 68 Euglena Biomass WW 3.48x10 2.25x10 BQ-OL CMP Workgroup -1 -1 WW : DW 4.00x10 4.00x10 Jorgensen 1979 -l -1 DW : Carbon 4.81x10 4.81x10 Jorgcnsen 1979 1 1 P/B 8.70x10 9.00x10 BQ-OL CMP Workgroup C/B None None BQ-OL CMP Workgroup R/B 7.28x10l 7.28x10l Biddanda and Cotner 2002 -l -1 69 Flagellates Biomass WW 8.50x10 5.21x10 BQ-OL CMP Workgroup -l -1 WW : DW 4.00x10 4.00x10 Jorgensen 1979 -1 -1 DW : Carbon 4.50x10 4.50x10 Jorgensen 1979 1 1 P/B 8.70x10 9.00x10 BQ-OL CMP Workgroup C/B None None BQ-OL CMP Workgroup R/B 7.28x101 7.28x10l Biddanda and Cotner 2002 -1 -2 70 Golden Algae Biomass WW 3.27x10 8.77x10 BQ-OL CMP Workgroup -l -1 WW : DW 4.00x10 4.00x10 Jorgensen 1979 -1 -1 DW : Carbon 4.50x10 4.50x10 Jorgensen 1979 l l P/B 8.70x10 9.00x10 BQ-OL CMP Workgroup C/B None None BQ-OL CMP Workgroup R/B 7.28x10l 7.28x10l Biddanda and Cotner 2002 -l -1 71 Green Algae Biomass WW 7.87x10 2.00x10 BQ-OL CMP Workgroup - -1 WW : DW 4.30x10 1 4.30x10 Jorgensen 1979 118 Appendix 2.1 (con't) No. Taxa Parameter Pre Value Post Value Reference(s) 71 Green Algae DW : Carbon 5.05x10-l 5.05x10.l Jorgensen 1979 P/B 8.70x10l 9.001110l BQ-OL CMP Workgroup C/B None None BQ-OL CMP Workgroup RIB 7.28x10l 7.28x10l Biddanda and Cotner 2002 72 Epiphytes Biomass WW 9.56x10-l 9.56x10-l BQ—OL CMP Workgroup WW : DW 1.201(10-l 1.20x10.l Jorgensen 1979 DW : Carbon 4.50x10.l 4.50x10"l Jorgensen 1979 P/B 1.20x102 1.20x102 BQ-OL CMP Workgroup C/B None None BQ—OL CMP Workgroup R/B 1.00x102 9.67x10l Biddanda and Cotner 2002 73 Macrophytes Biomass WW 9.45x10.l 1.1 BQ-OL CMP Workgroup ww : ow 1.20x10'l 1.20xio'l Jorgensen 1979 DW : Carbon 4.50x1o'l 4.50x10"l Jergensen 1979 NB 8.8 8.8 BQ-OL CMP Workgroup C/B None None BQ-OL CMP Workgroup R/B 7.36 7.12 Biddanda and Cotner 2002 74 Periphytes Biomass ww 1.23xlo'l 1.23x10'l BQ-OL CMP Workgroup ww : ow 1.20xlo'l 1.20xio'l iorgensen 1979 DW : Carbon 4.50x10.l 4.501110.l Jorgensen 1979 P/B 2.65x10l 2.65x10l BQ-OL CMP Workgroup 08 None None BQ-OL CMP Workgroup R/B 2.22x10l 2.15x10l Biddanda and Cotner 2002 119 References Banse, K. and S. Mosher. 1980. Adult body mass and annual production/biomass relationships of field populations. Ecol. Monogr. 50: 355-379. Biddanda, B. A. and J. B. Cotner. 2002. Love handles in aquatic ecosystems: The role of dissolved organic carbon drawdown, resuspended sediments, and terrigenious inputs in the carbon balance of Lake Michigan. Ecosystems. 5: 431-445. Fanslow, D. L., T. F. Nalepa, and T. H. Johengen. 2001. Seasonal changes in the respiratory electron transport system (ETS) and respiration of the zebra mussel, Dreissena polymorpha in Saginaw Bay, Lake Huron. Hydrobiologia. 448: 61-70. Hansen, A.-M., and G. H. Nelson Jr. 1998. Food limitation in a wild cyclopoid copepod population: Direct and indirect life history responses. Oecologia. 115: 320-330. Hillbricht-Ilkowska, A. and A. Karabin. 1970. An attempt to estimate consumption, respiration, and production of Leptodora kindtii (Focke) in field and laboratory experiments. Polskie Arch. Hydrobiol. II. 17: 81-86. Hudson, P. L., and Lesko, L. T. 2002. Free-living and parasitic copepods of the Laurentian Great Lakes: Keys and details on individual species. Ann Arbor, MI: Great Lakes Science Center. Published online at