A COMPARISON OF INVERTEBRATE BENTHOS POPULATIONS IN FOUR SINK LAKES SIXTEEN YEARS AFTER FERTILIZATION _ Thesis for ”the Degree of M. S. MICHIGAN STATE UNIVERSITY DELL H. S'ILER 1968 \]]]]]]]]]]]W T f: 5;] A, :5 University ABSTRACT A COMPARISON OF INVERTEBRATE BENTHOS POPULATIONS IN FOUR SINK LAKES SIXTEEN YEARS AFTER FERTILIZATION by Dell H. Siler This study was initiated to determine if any of the biological or chemical changes induced by earlier fertil- ization (Ball, 1950; Tanner, 1952 , 1960) were still evi— dent in four small sink-hole lakes in the northern Lower Peninsula of Michigan. Monthly samples of benthic organisms were taken during the summers of 1966 and 1967. Water chemistry data were also collected during the 1967 sampling period. The results indicated that oxygen depletion during the-summer stagnation period definitely occurred in three of the four lakes. Winter oxygen depletion also occurred in the two lakes measured, but to a lesser extent than indicated by earlier investigators (Ball, 1950; Tanner, 1952). The average total alkalinity appeared close to prefertilization levels in the fertilized lakes. The averages for the unfertilized lakes showed only Slight variation when the 1967 results were compared with those of 1948-1950. Bottom sampling indicated that considerable variation existed between the standing crop estimates of the two samplin] The pre Dell H. Siler sampling periods (1966 and 1967) in three of the four lakes. The presence of the blue-green algae, Aphanothece stignina (Spreng), which apparently was not present during earlier studies, was suggested as one possible explanation for this variation. The organism chiefly responsible for the greater standing crop estimate in 1966 was the midge, Chironomus plumosus (L.), which was concentrated in the 20-30 ft. area of the three lakes in 1966. In both sampling periods, 1966 and 1967, the standing crop estimates were higher _ than prefertilization levels with the possible exception of South Twin Lake where this level was not known. An analysis of the depth distribution of bottom fauna indi- cated that South Twin Lake, which received the greatest amount of inorganic fertilizer, had a distribution in 1967 similar to that of l9h8, the first year following fertil— ization. The distribution in the two remaining fertilized lakes most closely resembled that of l9u9, the first year of fertilization. A brief discussion of the taxonomic groups of benthos fauna was also included. A COMPARISON OF INVERTEBRATE BENTHOS POPULATIONS IN FOUR SINK LAKES SIXTEEN YEARS AFTER FERTILIZATION By ‘ 1 Dell Hf Siler A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Entomology 1968 r L! t \3 “'4 {C Q (‘1 tva3 ACKNOWLEDGMENTS I would like to thank my major Professor Dr. Gordon E. Guyer, Chairman of the Department of Entomology, for his invaluable advice on the organization of my research program and in the preparation of this manuscript. I am also grateful for the financial assistance which he pro- vided for me in the form of an assistantship. Special appreciation is extended to Dr. Robert C. Ball for his consultation on numerous aspects of my research and also for providing essential equipment for the collection of limnological data. I would like to further acknowledge Dr. Fredrick Stehr and Dr. Howard Tanner for their aid in reviewing this manuscript. I am indebted to Dr. Gerald COOper of the Depart- ment of Conservation for providing me with summer employment at the Pigeon River Trout Research Station, the cite of my research. Further thanks go to Mr. Howard Gowing and the staff of the Pigeon River Station for their assistance in providing necessary equipment. In conclusion I would like to acknowledge my wife, Lorraine, for her untiring help and understanding during the research and preparation of this manuscript. ii TABLE OF CONTENTS Page LIST OF TABLES . . . . . . . . . . . . . . iv LIST OF FIGURES . . . . . . . . . . . . . v INTRODUCTION . . . . . . . . . . . . . . 1 DESCRIPTION OF AREA . . . . . . . .7 . . . . 7 METHODS AND MATERIALS . . . . . . . . . . . 9 Bottom Sampling . . . . . . . . . . . 9 Chemical and Thermal Analysis of Lakes . . . . 10 LABORATORY PROCEDURE . . . . . . . . . . . . 13 Bottom Fauna . . . . . . . I. . . . . 13 RESULTS AND DISCUSSION . . . . . . .. . . . . 14 Comparison of Physical and Chemical Properties . lu Thermocline . . . . . . . . . . . . 14 Oxygen Depletion . . . . . . . . . . 15 Total Alkalinity . . . . . . . . . 18 Bottom Sampling . . . . . . . . . . . 20 Bottom Fauna Distribution . . . . . . . 54 Species Composition . . . . . . . 57 Predation-. . . . . . . . . . . . . 60 SUMMARY . . . . . . . . . . . . . . . . 6A LITERATURE CITED 0 O O O O O O O O O O O 0 66 iii Table 2. 10. ll. l2. l3. 1“. LIST OF TABLES Rates of fertilizer application . . . Physical and chemical characteristics prior to fertilization . . . . . Average depth in feet of the thermocline mid-points A comparison Invertebrate South Twin Invertebrate North Twin Invertebrate of average total alkalinity . fauna collected by bottom sampling Lake 1948, 1949, 1950 and fauna collected by bottom sampling Lake 19u8, 19u9, 1950 and fauna collected by bottom 1967 1967 sampling West Lost Lake 19u8, 19u9, 1950 and 1967 Invertebrate fauna collected by tottom sampling Section-Four Lake 1948, 1949, 1950 and 1967 Invertebrate South Twin Invertebrate North Twin Invertebrate fauna collected by bottom sampling Lake July-Sept. 1966-1967 fauna collected by bottom sampling Lake July-Sept. 1966-1967 fauna collected by bottomr West Lost Lake July—Sept. 1966-1967 . Invertebrate fauna collected by bottom sampling Section-Four Lake July—Sept. A comparison of calculated average volume of small invertebrates . . . . . . sampling 1966-1967 . A comparison of planting records for the years 19A8, 1949, 196“ and 1965 . iv Page . 15 . 19 . 23 26 . 27 . 28 . 29 54 62 Figure LIST OF FIGURES Page South Twin Lake, composition of bottom fauna by per cent of total volume . . . . . . 30 North Twin Lake, composition of bottom fauna by per cent of total volume . . . . . . 32 West Lost Lake, composition of bottom fauna by per cent of total volume . . . . . . 3A Section-Four Lake, composition of bottom fauna by per cent of total volume . . . . . . 36 South Twin Lake, depth distribution of bottom fauna organisms . . . . . . . . 38 North Twin Lake, depth distribution of bottom fauna organisms . . . . . . . . . . “0 West Lost Lake, depth distribution of bottom fauna organisms . . . . . . . . . . A2 Section-Four Lake, depth distribution of bottom fauna organisms . . . . . . . . AA of As The g which there cultu: namel: INTRODUCTION The cultivation of fish in ponds has been a part of Asian agriculture for nearly 2500 years (Neess, 1949). The growth and develOpment of fish culture in EurOpe, which began in the fourteenth century, was discussed thoroughly by Neess (1949). The goals of American fish culture differ somewhat from those of the Europeans, namely in reference to the use of the fish and the species preferred. The Americans are, generally speaking, con- cerned with the sport fishing value of the fish as opposed to the commercial value stressed by the EurOpeans. As for species, predatory fish are most commonly associated with sport fishing while the fish which lend themselves best to economic production are those feeding closer to the base of the food chain. Fish culture in the United States increased in stature during the 1930's and early 1940's when fish yields were increased markedly through the application of inorganic fertilizer to ponds. These early investigators, as exemplified by Meehean (1934), Swingle and Smith (1939) and Smith and Swingle (1940) determined that fertilizers increased the basic elements of the food chain, and from their abundance higher levels, including fish, benefited. The components of fertilizers used in aquatic situations fall into five basic groups: nitrogen, phosphorus, potassium, calcium and organic matter. Maciolek in 1954 completed an extensive summation of work on pond and lake fertilization. These early studies of pond culture in the United States were centered mainly in the southern states. They were followed by investigations to evaluate the effects of fertilization on lakes, on bodies of water under different climatic conditions, and to determine which elements of fertilizers were the most important. The process of lake fertilization proved much more complex and the results much less predictable than pond fertilization. Maciolek (1954) sites the following characteristics of lakes which differ from ponds as among those partly responsible for the difficulty of lake fertilization; size, depth, thermal stratification, nondrainability and presence of affluents and effluents. In the past 30 years, fertilization studies have been conducted on many lakes of diverse size and form resulting in varying degrees of success; yet there are very few established guide lines along which one may proceed, with assurance, toward the ultimate goal of increased fish production. The fertilization of limited salt water areas has also been attempted with apparent success (Gross 32 al., 1944; Raymont, 1950). were 1“ 10-6-4 liZEr, during heavy ] During were CC Researchers in the field of lake fertilization have witnessed several undesirable effects, including increase in the numbers of undesirable species of fish, extensive blooms of filamentous algae, dense growths of aquatic plants and oxygen depeltion to the extent of "winterkill" of fish and fish food orgnaisms. Attempts to increase the productivity of ponds and unproductive lakes were initiated in Michigan by Dr. R. C. Ball (1949, 1950), Patriarch and Ball (1949) and Ball and Tanner (1951). Two of these studies (Ball, 1950; Ball and Tanner, 1951) involved a shallow, warm water lake and a small cold water trout lake both located in the north central area of Michigan's Lower Peninsula. The lakes were fertilized during the summer of 1946 and 1947 using 10-6-4 (nitrogen, phos0porus, potassium) commercial ferti- lizer. Fertilizer was applied at three week intervals during both summers. The warm water lake supported a heavy bloom of phytOplankton throughout the first summer. During the second summer the shallow areas of the lake were covered with mats of filamentous algae until halfway through the summer when a bloom of phytoplankton again appeared. No plankton bloom of any significance was produced during either summer in the cold water lake despite increased fertilization. However, a tendency toward eutrOphication was shown by a raise in the level of the thermocline, depletion of oxygen in the hypolimnion and the appearance of dense mats of filamentous algae. Both of the fertilized lakes suffered a severe "winterkill" during the winter following the second summer of fertilization. There was no evidence of "winterkill" in either of the control lakes. This made evaluation of fish growth difficult but evidence from fish scales collected during the study seemed to indicate fish growth rate had increased considerably. In 1948, the year following the completion of the above study, Dr. Howard Tanner initiated a fertilization program under the direction of Dr. R. C. Ball to determine if some fraction of the fertilizer applied to South Twin, the cold water lake, could bring about increased fish production without the undesirable effect of severe oxygen depletion. Five sister lakes in close proximity to South Twin were well suited to this purpose due to their simi- larity in origin, size and other morphological character- istics. Prefertilization data were gathered during the _ summer of 1948. During 1949 and 1950, fertilizer similar to that used by Ball (1950) was applied to four of the five lakes with the fifth serving as a control. The lake with the greatest total alkalinity received the largest (dosage of fertilizer with the softer lakes receiving lesser amounts. The amounts applied are shown in Table 1. 'The results were evaluated through temperature and water chemist 1 +- troa. 3 found 1 rate of Or not t produnt: Carried pPeSEnt after th] chemistry analysis, bottom sampling, Secchi disk readings, trout stOmach content study and a creel census program. This study was reported by Tanner (1952, 1960). Tanner found increased productivity roughly correlated with the rate of fertilization. TABLE 1.--Rates of fertilizer application.* Total** Lake Pounds ppm Percent . South Twin 1946 1947 g 2,000 3,000 28.5 100. 5 Section-Four 1949 1950 1,700 1,272 15.0 52.6 West Lost 1949 1950 400 300 3.9 13.7 North Twin 1949 1950 0 O 0 0 *Taken from Tanner, 1952. **For the two summers. The objective of this study was to determine whether or not there were any residual effects of the increased productivity brought about by the fertilization programs carried out by Ball (1950) and Tanner (1952, 1960). The present study was initiated in July of 1966, sixteen years after the last fertilization by Tanner. The literature in the area of lake fertilization is characterized by a general lack of information regarding long term effects of this enrichment process. Tanner (1960) stated, in regard to observations made on South Twin Lake during the three years following fertilization by Ball (1950), ". . . the duration of the increased biological activity and reduction of oxygen may be three years or more." Maciolek (1954) mentioned that “Nutrients are added before or during the growing season and must be renewed at least annually to sustain yields." Garton (1967), in conducting a follow-up study of the liming of an unproductive soft-water bog lake in northern Michigan (Waters, 1956; Waters and Ball, 1957), found after 10 years that hardness alkalinity, conductivity and total phosphorus were still above pre-liming levels. Bottom fauna seemed to have increased greatly and yellow perch (Perca flavescens) appeared to have a faster rate of growth than before liming. ht Ian—aw 23; "E DESCRIPTION OF AREA The four lakes involved in this study (South Twin, North Twin, West Lost and Section—Four) are located in a special section of the Pigeon River State Forest, including part of Otsego and Cheboygan counties, and designated as the Pigeon River Trout Research Area. This area was placed under the administration of the Institute of Fisheries Research in 1949 and through reorganization is presently administered by the Research and Deve10pment Division of the Michigan Conservation Department. There are six lakes, or "pot-holes" as they are commonly called, in the area; South Twin, North Twin, Lost, West Lost, Hemlock and Section-Four. In addition to approximately a five mile stretch of the Pigeon River in the area there are two other sink-holes that contain water but they are so small that they are not managed and thus not normally considered as members of the Pigeon River Lakes. The four lakes under study lie in sandy soil forested largely with Jack pine and aspen typical of the runcth central part of Michigan's Lower Peninsula. No inlets or outlets were present on any of the four lakes. These lakes were regarded by early observers (Eschmeyer, 1938) to be of glacial origin corresponding to the pit lakes of Michigan described by Scott (1921). However, as Tanner (1952) later reported, more recent geological evidence strongly supports the theory that the lakes are limestone sinks. The lakes, with the exception of Hemlock, are very similar in form. They are very nearly circular and range in size from 2.6 to 4.7 acres. They are characterized by having the water surface 30 to 60 feet below the immediate surrounding terrain. They also have in common steep sloping banks, narrow shoal areas, and clear water. Table 2 has been borrowed, in part, from Tanner (1952) to provide more concise information about certain physical and chemical prOperties of the lakes. TABLE 2.--Physical and chemical characteristics prior to fertilization (Tanner, 1952). Surface Maximum Average Total Per areas depth depth alka- cent (acres) (ft.) linity shoa1* South Twin 3.9 34 24 74 15.3 North Twin 4.7 44 28 32 13.0 West Lost 3.7 44 29 138 11.0 Section-Four 2.6 72 51 192 4.0 *Shoal and littoral zone are considered synonymous. MATERIALS AND METHODS The methods and materials used were largely deter- mined by those used by Tanner (1952), since a comparison with his data was the basis on which this study was organized. Certain changes were made when dictated by availability of materials or when the author felt they would improve the accuracy cfi‘ the study. Bottom Sampling Bottom sampling of the four lakes selected (N. Twin, S. Twin, W. Lost and Section-Four) began in July of 1966 and was continued through September. In 1967, sampling began in June and terminated in September. Bottom samples were taken each summer on a monthly basis at a rate of 10 samples per lake. All samples were taken by means of a 6"7x 6" Ekman dredge. A steel sounding cable was used to assure accurate depth measurement of each sample. Samples were brought to the surface and emptied into a plastic bucket. Samples were then taken to the shore and sifted through a wire screen of 30 mesh to concentrate the organisms. The resulting material was placed in a labeled quart jar and removed to the laboratory where it was placed in White enamel pans and examined for organisms. All samples were "picked live" mes; . 10 and the organisms were placed in vials containing a pre- serving solution of six parts water, three parts 95% alcohol, and one part formalin. Sampling was confined to an area reaching from shore to a depth of 30 feet. This area was determined by Tanner (1952) to contain 95% of the benthos fauna in the lakes. Sampling sites were chosen by placing a grid with numbered squares over the map of the lake and drawing corresponding numbers at random. Five of the monthly samples were chosen from the area 0 to 15 feet and five is from the area 16 to 30 feet. Sampling sites were divided into these two groups in order to insure a more uniform sampling of the bottom fauna. The sample sites were located on the lakes by means of a compass and shore markers. All of the lakes contained numerous submerged logs and related debris which prevented the sampling of certain small areas with the Ekman dredge. The composition of the bottom in certain areas of the lakes often made it necessary to take 10-15 samples before the dredge functioned properly. Chemical and Thermal Analysis During the summer of 1967, June 19 to September 11, water chemistry data were collected at approximately 7 to 10 day intervals from 19 June to 11 September. 11 An electrical resistance thermometer was used to obtain a temperature profile of the lakes so that the position of the thermocline could be determined. After the thermocline was located, water samples were taken by means of a Kemmerer sampler at four vertical stations: surface, mid-epilimnion, upper boundary of the thermocline and mid-hypolimnion. The dissolved oxygen content of the samples was determined at all four stations by means of the Basic Winkler Method. One or two additional samples were taken at each sampling in an attempt to determine the level at which the dissolved oxygen content reached 4 ppm. so that a comparison might be made with similar data collected by Tanner (1952). Samples were fixed in the field and removed to the laboratory for titration. An exception to this was made during the last two sampling dates of 1956 when a Hach Chemical Kit was used. The two methods were checked against each other prior to this time to assure uniformity in readings. The methyl orange alkalinity was determined at three vertical stations: surface, upper boundary of the thermo- cline and mid-hypolimnion. Determinations were made using ‘the method outlined in Standard Methods for the Examination <3f water and Wastewater. Although temperature and water chemistry data were ruyt taken by the author during the summer of 1966, monthly Hmqu go pcoo Loo mom A.HEV oESHo>IIm .Lmoezc HmpOp mo pcoo Loo ocm meESZII< .mpmofiom new moofluom:0poz .mLopoozowpe .mpmpoowmm .moHHmcc< .mmUHxHLoo .wEmHo .mHHmcm moozHQCH mpmzpo HH<** .mmonHor zaflsmw mop moosHocH mmoHEocopflnox o.ms ma.s m. mo. o.m mH. :.H Ho. m m.~H mHH N.H m w.m om s.m m < *xmpozpo HH<, m.: mm. o.H mo. m.m no. Q.H Ho. .m m.HH as m.m NH m.© 3H ~.H m a aHmHHmsz m.m mm. s.m mm. o.m mo. m.H Ho. m m.m mm m.w H: m.m NH N.H m a aquwEmnam ... B w.o oz. m.mH mm. m.Hm om. m m. H m.mH mm m.>m mm m.mm m: < mzpooomgo :.H mH. H.0m 3m.H :.mm mm. m.H Ho. m m. H o. m H.m A m. H a mpmaaoche m.mH mo.H :.Hm mo.m m.m: m:.H m.m© on. m m.@s ms: m.mm mmm m.wm am m.mm so a *mmaHEocongo om. sq. m. no. .pm .Um Loo oESHo> mm.m Hm.m mm.m ms. A.HEV wEchmeo mo mESHo> HopOE m.oo :.mm H.mH H.HH .pg .am pmq pwasz mow om: wmm s4a mEmflcmmLo mo Lopezc Hmpoe OH m.mH mH m.OH H.ac .amv mmHoEmm no mood o.m OH 2.H ®.mm zaaEm mmHoEmm wo pcmo mom on om on m: mmHoEwm mo Lopezz ammH ommH msmH . mqu mmame coHpomHHoo . . .AommHumsmH emNHHprmov ammH cam ommH .mamH mama oxmq pmoq pmmg wcflaoEmm Eoupoo mo ompomHHoo mczmm mpmpnophm>cHla.w mqm<8 TABLE 8.--1nvertehrate fauna collected by bottom sampling Section-Four Lake 1948, 1949, 1950 and 1967 (fertilized 1949-1950). 25 Collection dates 1948 1949 1950 1967 Number of samples 32 53 51 40 Per cent of samples empty 28.1 7.6 3.9 0 Area of samples (sq. ft.) 8 13.2 12.8 10 Total number of organisms 63 451 1974 1178 Number per sq. ft. 7.9 34.2 154.5 117.8 Total volume of organisms (m1.) .29 4.86 12.65 4.97 Volume per sq. ft. .04 .37 .99 0 Chironomidae* A 47 74.6 232 51.4 1934 98.0 780 66.2 B .08 26.8 .89 1C.3 9.42 74.5 1.48 29.8 Anisoptera A 3 4.8 9 '2.0 7 .4 13 1.1 B 16 56.4 1.56 32.1 .05 24.1 1.41 28.4 Ephemerida A 3 4.8 65 14.4 11 .6 34 2.9 B 02 5.2 . 4 7.0 .08 .6 .14 2.8 Hyallela A l 1.6 33 7.3 14 .7 303 25.7 B 01 1.7 .18 3.7 07 .5 1.52 30.6 C113111431W15 A 1 1. 6 5 1. l .. . .. . .. . . .. B 01 3.1 02 .4 . . . .. Trichoptera A .. 6 1.3 6 .5 B .. ... 02 .4 . . .04 .8 quoptera A 2 3.2 4 .3 B 01 2.7 ... ... . . .04 .8 Clam A 21 4.6 5 2 11 .9 11 . . .7117 15.6: .01 .1 .21 4.2 Snail A 63 14 0 .. .. 1 .1 a .. 3,12 11 5 .. .. .01 .2 Annelida A 3 4.8 8 1.8 3 .2 .23 2.0 P 01 3.4 32 6.6 T .. .07 1.4 All others** A 3 2.8 9 2.0 1 .0 4 .3 B .01 1.7 21 4.3 .01 .1 .05 1.0 *Chironomidae includes the family heleidae. **All others includes Corixidae, A--Numher and per Cent of total number. B--Volume (m1.) and per cent of total volume. Hviracarnia __w___._’ ColeOptera and Tabanidae. 7 l'i 1.4-v 26 TABLE 9.--Invertebrate fauna collected by bottom sampling South Twin Lake July—September 1966 and 1967 (fertilized 1946-1947). . Collection dates 1966 1967 Number of samples 30 30 Per cent of samples empty 0 3.3 Area of samples (sq. ft.) 7.5 7.5 Total number of . organisms 757 720 Number per sq. ft. 100.9 100.1 Total volume of ' . . organisms (ml.) 10.09 4.91 Volume per sq. ft. 1.34 .65 Chironomidae* A 615 81.2 497 69.0 B 3.78 37.5 1.30 26.6 Anisoptera A 2 .3 14 1.9 B .02 .2 1.06 21.6 Clams A 13 1.7 8 1.1 B 5.9 58.4 1.62 33.0 Snails A ... ... l .l B ... ... .01 .2 Chaoborus A 51 6.7 6 .8 B .07 .6 .01 8.8 H allela A 53 7.0 135 1 . ‘X—_____' B .26 2.6 .68 13.7 Ephemerida A 4 .5 29 4.0 B .01 .l .12 2.5 Zygoptera A ... ... 1 .1 B ... ... .02 .4 TrichOptera A 3 .4 3 .4 B' .02 .2 .02 ... Annelida A 16 2.1 23 3.2 B .03 .3 .04 .9 Coleoptera A ... 2 .3 B ... ... .02 .... All others** A ... ... 1 .1 B ... ... .01 .2 *Family Heleidae is included under the heading Chironomidae. **All others includes Notonectidae. A--Number and per cent of total number. B--Volume (ml.) and per cent of total volume. 27 TABLE 10.--Invertebrate fauna collected by bottom sampling North Twin Lake July-September 1966 and 1967. Collection dates 1966 1967 Number of samples 30 30 Per cent of samples 12 5 empty 0 ° Area of samples (sq. ft.) 7.5 7.5 Total number of organisms 1183 312 Number per sq. ft. 157.7 41.3 Total volume of ' organisms (m1.) 11.58 1.94 Volume per sq. ft. 1.54 .26 Chironomidae* A 1048 88.6 252 80.8 B 10.09 87.2 .93 47.9 Ephemerida A 4 .3 17 5.4 B .01 .1 .03 1.5 Anisoptera A 2 .2 8 2.6 B .66 5.7 .86 44.3 Clams A 1 .1 1 .3 B .02 .2 .01 .5 Hyallela A 1 .l 2 .6 B .01 ... .01 .5 Tabanidae A ... ... ... ... B ... ... ... ... Hemiptera A ... ... 8 2.6 B ... ... .04 2.1 All others** A 127 10.7 24 7.7 B .79 6.9 .06 3.1 *Family Heleidae is included under the heading Chir- onomidae. ' **All others includes Chaoborus, Annelida, Coleoptera and Leeches. A--Number and per cent of total number. B--Volume (m1.) and per cent of total volume. .' Mug—34 .- 28 TABLE 11.--Invertebrate fauna collected by bottom sampling West Lost Lake July-September 1966-1967 (fertilized 1949- 1950). Collection dates 1966 1967 Number of samples 30 30 Per cent of samples empty 0 3.3 Area of samples (sq. ft.) 7.5 7.5 Total number of organisms 579 523 Number per sq. ft. 77.2 69.7 Total volume of organisms (m1.) 9.29 7.57 Volume per sq. ft. 1.24 1.01 Chironomidae* A 422 72,9 326 62.3 B 1.74 18.7 .74 9.7 Anis0ptera A 4 .7 1 .2 B .03 .3 .13 1.7 Chaoborus A 2 .3 1 .2 B T ... T .... Ephemerida A 3 .5 17 3.2 B .02 .3 .28 2.7 Hyallela A 6 1.0 13.0 B .03 .3 .34 4.5 All others** A 142 24.5 103 19.7 B 7.37 80.4 6.16 81.3 *Family Heleidae is included under the heading Chironomidae. **All others includes Annelida, Notonectidae, Clams, TrichOptera and Spiders. A--Number and per cent of total number. B--Volume (m1.) and per cent of total volume. 29 TABLE 12. --Invertebrate fauna collected by bottom sampling Section-Four Lake July- September 1966 and 1967 (fertilized 1949-1950) Collection dates 1966 1967 Number of samples 30 30 Per cent of samples 0 0 empty Area of samples (sq. ft.) 7.5 7.5 Total number of organisms 1128? 11453 Number per sq. ft. ' ° Total volume of organisms (m1.) 3°EZ 3'23 Volume per sq. ft. ' ' Chironomidae* A 656 74.0 540 63.0 B 1.05 32.1 1.00 25.8 AniSOptera A 10 1.1 10 1.2 B .62 19.0 1.30 33.3 Ephemerida A 7 .8 27 3.2 B .02 .6 .12 3.0 Hyallela A 183 20.6 248 28.9 B .92 28.1 1. 24 31.8 Chaoborus A ... ... ... ... B ... ... ... ...- TrichOptera A 6 ..7 3 .4 B .06 1.7 .02 .6 Zygoptera A 3 .3 3 .4 B .02 .6 .02 .4 Clam A 3 .3 5 .6 B .38 11.6 .11 2.8 Snail A 1 .1 ... ... B .15 4.6 ... ... Annelida A 15 1.7 17 2.0 B .03 .9 .03 .8 All others** A 2 .2 4 .5 B .02 .8 .05~ 1.3 *Family Heleidae is included under the heading Chironomidae. **All others includes Tabanidae. A--Number and per cent of total number. B--Volume (m1.) and per cent of total volume. 30 it. {it 7.. .oezao> Amoco mo pcmo Loo an wzHHoEwm Eosm mcsmm Eonuoo mo coapflmoosoo .Auzmalmqma pomflfiflpsomv oxmq :HBB npsomll.H omsmfim 31 museso HH< mamaammm muouooowuh mmwwwz «HonoOmws< o. HM Amoco mo pcoo poo mp mafiaosmm Eopm madam Eonuop mo soaprOQEoo .AemNHHHpsmo pogo mxmq case spsozuu.m magmas 33 muoauo HH< o. . I covenanma o.n% .mwwumaonmm 7//////// ZHNSB $sz 97.332 . 7 .memoz «HouQOmHad - A "xxx x xx x , "XXI , 1,.“- I III I- '1‘. ill mu -‘tl "Wflum ’ ////- OH om 0m 00 on ow INHOHHJ 34 .oESHo> Amoco no name poo mp wQHHQEmm Eonm mczmm Eonuon mo COHpHmOQEoo .Aommanmsma emNHHHpsmmv memo smog pmmznn.m magmas ..ml . . I. AVE»... 4...“... Sn ma rOma BBQ. ///////z / .o bawmounmnm 950.655 moron—mug» 53 H Hows >5. Onrmnm SE 36 F. ‘D‘F‘. .ossao> Amoco no name poo an wcflaosmm Eopm «sumo Eonuon mo coapamoosoo .Aommalmzma UoNHHHmemV oxmq psomICOHpommll.: mhswfim IIIIIII: ///////////////////////. Blandostuv . ensnIION apIJamang atattefin U) 111 O F] H O 2 '11 O C an t‘ .'> - P'w‘ t1] 8:9an uv LE 38 Figure 5.--South Twin Lake (Fertilized 1946—1947). Depth distribution of selected bottom fauna organisms during the summers of 1948, 1949, 1949 and 1967. 39 SOUTH TWIN LAKE _ . . u . - m . u u t \\ Rvo,nv7. ‘fi“o \\ s w. w. m. % \\ ...\x J 1.. 1 1 1 ‘\‘\ \\ 00000 ’ “|‘|\ \“ 000.. ““‘ \ “000 1 ss. \\\\s\‘ . \....o..... s?\\ .1... \“ r‘ “‘ \ (’ ISIIRI‘ \ ot‘tfi‘f _ _ _ . _ F . _ . _ h o. 0. 542/720. 0. . 5. 4. q... 9... L 11-15 16-20 21-25 26-30 6-10 DEPTH IN FEET 4O Figure 6.--North Twin Lake (Not fertilized). Depth distribution of selected bottom fauna organisms during the summers of 1948, 1949,‘ 1950 and 1967. 41 2.g_ . .. 1948 l-I- 1949 ..4 1950 ----' ' 1967 000000 1.2... J .— ‘H g. - m \ ° 1.2— ...; E I-- C o o o .. ,\°., \\g 0'21..— A I" “ P \ ’I” \ _. " 35§.'0 ‘8 o‘L ..q.. o . '.\ 2.5 .. 80": ‘.. :‘ 0-5 6-10 ' 11-15 16-20 DEPTH IN FEET LAKE \ ... .O" A ‘4' Qt. «lira-IIIIIu-ufl.::.- ‘ 21-25 26-30 L42 Figure 7.--West Lost Lake (Fertilized 1949-1950). Depth distribution of selected bottom fauna organisms during the summers of 1948, 1949, 1950 and 1967. 43 [o m1. / sq. ft. WEST LOST .LAKEf 1948‘I-I- 1949 7.. 1950 ---- 1967 000000. 0-5 6-10 ' 11-15 16-20 21-25 26-30 DEPTH IN FEET 44 Figure 8.--Section-Four Lake (Fertilized 1949-1950). Depth distribution of selected bottom fauna organisms during the summers of 1948, 1949, 1950 and 1967. ‘- ““IJI 45 SECTION FOUR LAKE 4-2- b 1948 -'-' .. 1949 7.. 1950 III-- 1967 900000 341- | I " | ‘. .‘ :3 "' ‘. /\ a: _ ,V \ 2 w. x 42.11.. | \ E “ ‘ I‘~ | ‘ ’ ~ ~~ ' | \ ,’ \ | \ , \ l ’ \ 5' | \ 5 | . | ‘ 1 \ .. O. ‘ " “ -. | g , . o 8 1ng_ 13% ‘u-II""'"‘§K ‘8 ... \ 9‘ o \ . 1% ‘§\ ‘k _ ......“ ‘\‘ _ o...........9"‘..ooooooooooc av". \s L1.."'—'—‘ 1 .~'.-'SL-.-.L:.fl___. 0-5 6-10 ' 11-15 16-20 21-25 26-30 DEPTH IN FEET 46 1967. Figures 1, 2, 3, and 4 show in the form of a histo- gram the relative importance by per cent of total volume of the various bottom fauna groups for each of the years 1948, 1949, 1950 and 1967. Figures 5, 6, 7, and 8 show the depth distribution of bottom fauna in volume per sq. foot for the years 1948, 1949, 1950 and 1967. The first lake presented in each series is South Twin Lake (Table 5), which, as mentioned earlier, was fertilized‘ by Ball (1950) at a rate concluded to be excessive. Unfor- tunately no estimate was made of the standing crop of South Twin before it was fertilized and thus caution should be exercised in drawing any conclusions from the resulting data. However, if it is assumed that the prefertilization level of the standing crOp was approximately equal to those of the neighboring lakes it would then follow that the present level of standing crop is considerably higher than before fertilization. The clams and snails showed a great decrease from the extremely high level in 1948-1950 to that exhibited in 1967. This is probably due to their feeding habits being linked to the abundance of plankton algae and aquatic plants during the fertilization period and imme- diately after. The relatively high level of abundance maintained by the midges in 1967 compared favorably with levels immediately following fertilization. Table 9 indi- cates that the 1966 sampling yielded an even larger number and volume of midges equaling nearly twice that of the 47 four month sampling period of 1967. One possible eXplan- ation for this large population might be found in the presence of the blue-green alga Aphanothece stignina (Spreng) which occurs in the form of gelatinous balls ranging in size from less than 5 cm. to over 1% cm. in diameter. The "algae balls" were extremely abundant in the deeper areas of South Twin. Their presence was not noted by either Ball (1950) or Tanner (1952). It is very unlikely that their presence could have been overlooked due to their conspicuous nature. It is possible that this alga was to some extent a result of the earlier fertilization programs. Prescott (1962) in describing this species of algae states- " . . . often forming almost continuous gelatinous expanses in the bottoms of favorable eutrophic habitats." This species of algae also occurs in West Lost Lake and the control lake North Twin, however, it was not nearly as extensive in North Twin as in the other two lakes. It was not found in Section-Four but it may exist below the 30 ft. depth to which bottom samples were taken. It is possible that this alga provided the chironomids with browse. This was substantiated somewhat by the occurrence of large numbers of midge cases and often large plumosus- type midges among the alga colonies. A comparison of the 1966 results with those of 1967 in South Twin as presented in Table 9, shows some inter— esting differences. The volume per sq. ft. of organisms 48 in 1966 is more than twice that of 1967. Some of this difference can be attributed to the few extra large clams collected in 1966. A substantial part was due to a larger population of chironomids in 1966 which, upon examination of the localities of individual samples, resulted more specifically from a greater population of the large Chironomus plumosus (L.) midges at a depth of 20 to 30 feet. Why this population was not present or was not detected in 1967 is not known. This area between the 20 and 30 ft. depths roughly corresponds to the expanse of '31: the blue-green alga Aphanothece stagnina mentioned earlier. In 1966, the composition of each bottom sample was noted after it had been passed through the 30 mesh wire. The shallowest occurrence of this alga in South Twin during that summer was 23 ft. The composition of the bottom samples was not noted during the summer of 1967 so it is not known how extensive the alga was, only that it did occur in the same three lakes. A change in the abundance or distribution of the algae could be responsible for the vastly different midge population either because of its food value or possibly as a result of toxic by-products. According to Dr. G. W. Prescott (personal communication) this particular species has never been evaluated to deter- Inine if it possesses any such toxic by-products. It is known that other blue-greens, largely the filamentous forms, do excrete toxic by-products sometimes harmful to ‘1 ‘. I' '. v-v—u 49 aquatic life (Prescott, 1948; Ingram and Prescott, 1952). Also, in South Twin the specimens of Anis0ptera showed a considerable increase in 1967 (Table 9). One explanation might be the rise in the water level of 8-10 inches which occurred in all the lakes in 1967. This new water level submerged a small area around the edge of the lake con- taining thick grasses which seemeed to provide increased cover and feeding area for the dragonflies. This might have brought about increased survival. Relatively large numbers of dragonfly naiads and crayfish were observed in this area of the lake. The volume of Anis0ptera increased 1 in all lakes in 1967 but due to the relatively low numbers collected it was possible that the difference was due merely to chance. North Twin Lake (Table 6) served as the control lake in the studies conducted by Ball (1950) and Tanner (1952). However, it too was fertilized to a small extent by Eschmeyer (1938) who suspended "several hundred pounds" of fertilizer from a raft in the center of the lake in 1934. He then attributed increased growth and survival of brook trout and perch to the fertilization but admitted that the relationship was not proven. Although these "several hundred pounds" probably did not approach the magnitude of the fertilization applied to the other lakes by Ball (1950) or Tanner (1960), it is possible that they could have had some eutrophying effects. The volume of organisms per sq. 50 ft. from Table 6 is about the same in 1967 as during Tanner's study. Again the midge seems to be much more abundant in 1967 than earlier. The percent of empty samples from North Twin was noticeably less in 1967, possibly because of the increased midge population. In North Twin Lake between 1966 and 1967, there was a more pronounced difference in the midge populations than “7 in South Twin. The 1966 samples contained 10 times the volume of midges as did the 1967. The same pattern was followed in North Twin as in South Twin. The midges respon- sible for most of the increase are the large Chironomus plumosus and the population was centered in the same locality at depths of 20-30 ft. The shallowest recorded occurrence of Aphanothece stagnina in 1966 in North Twin was 29 ft. The area covered by the alga in the three lakes was very erratic and Spotty. There are several other possible eXplanations for this fluctuation in midge population . . . for example, dissolved oxygen levels. The dissolved oxygen levels in the lake were determined at about 10 day inter- vals during the summer of 1967. During the summer of 1966, monthly oxygen determinations were made by the staff of the Pigeon River Trout Research Station. When the two were compared, there did not seem to be any noteworthy difference in the level of depletion of dissolved oxygen in either of the Twin Lakes. Hilsenhoff (1967), in his discussion of the ecology and population dynamics of Chrionomus plumosus in lake 'Winnebago, found that the ". . . g. plumosus population 51 fluctuated greatly, both yearly and seasonally, and often differed markedly from one area of the lake to another." He also states that "some of the most important, yet least studied, factors influencing Q. plumosus populations in Lake Winnebago are the diseases and parasites." It may be that one or more of these factors contributed to the fluctuating midge population in West Lost and the Twin Lakes. West Lost Lake (Table 7) received the least amount of fertilization under the Tanner study. When the results of the 1967 bottom sampling were compared with those of Tanner, the volume of organisms per sq. foot is nearly twice the level reached in 1950, the second summer of fertilization. An examination of the volumes contributed by the individual groups of organisms in 1967 (Figure 3) shows that the clams are responsible for about 80 per cent of the total volume where as in Tanner's study they were not present in benthos samples. The 1966 results (Table 11) show an even larger volume contributed by the clams under the "all others" category. The amphipod, Hyallela, also increased considerably in numbers in 1967 as compared to the 1948, 1949 and 1950. However, this increase was not supported by the 1966 samples. The number and volume of Inidges was much larger in the 1967 samples than in 1948 (prefertilization). This increased chironomid volume was surpassed in the results of the 1966 sampling. The clams 52 and chironomids, due to their feeding habits, Would logically be expected to increase in numbers if the lake had moved toward a eutrophic condition. It also would seem that Chaoborus would be likely to reflect any increase in the primary production due to their plankton feeding habits (Pennak, 1953). Just the opposite occurred; Chaoborus, which was formerly abundant in the lakes, was barely detected in 1966 and 1967. Section-Four, the lake fertilized at the highest rate by Tanner, displays a substantially greater standing crop in 1966 and 1967 than in either the prefertilization year or in the first year of fertilization (Tables 8 and 12). The two groups which were largely responsible for this increase were the chironomids and the amphipod, Hyallela. Section-Four showed less variation for the 1966-1967 comparison than any of the other three lakes. The volume per sq. ft. of organisms was slightly higher in 1967 but the number and volume of chironomids was again greater for 1966. Although the blue-green alga mentioned earlier was not detected in Sectionafknu‘the green alga.Dichotomosiphon was found in a bottom sample at a depth of 22 ft. Although crayfish were important members of the benthic community in all the lakes they are not included in the above tables. It was felt that their numbers were not sufficiently great to allow an accurate estimate of laawl- 53 the pOpulation by the sampling program employed. Also it seems likely that they might be able to avoid the dredge as it is lowered to the bottom. Crayfish were originally included in the data taken by Tanner (1952). Although very few crayfish were taken during any of the sampling periods of this study, when they did occur their relatively large volume often tended to mask trends exhibited by the smaller organisms. Patriarche and Ball (1949) excluded crayfish from the results of their bottom fauna sampling for basically the same reasons. A study of the population dynamics and the produc- tivity of the crayfish population in West Lost Lake, one of the lakes in this study, has been conducted by Dr. W. T. Momot (1965, 1967). In order to obtain a more accurate estimate of the volumes of the smaller organisms, it was necessary to accumulate considerable numbers of each group so that an average volume of the organisms for each of the groups could be calculated. This method was also used by Tanner (1952). The organisms, size groups, numbers and volume are presented in Table 13 along with the results obtained by Tanner. Two additional groups, annelid and Chaoborus, were calculated in addition to the groups used by Tanner (1952). Tanner's method of volume determination was followed as closely as possible for all groups listed. 'The resulting volumes are quite close to those calculated ....- 4 Mia—...; 54 TABLE l3.--A comparison of calculated average volumes of small invertebrates. Volume Number of Volume Number of Millimeters (m1.) organisms (m1.) organisms Tanner Siler Midges O - 4 .0005 200 .0006 200 5 - 6 .0014 150 .0012 150 7 - 8 .0032 200 .0033 200 9 - 10 .0046 200 .0048 200 11 - 12 .0070 100 .0063 100 13 - 14 .0120 50 .0112 40 15 - 16 .0178 45 .0168 35 Hyallela .0053 250 .0050 250 Annelid .0019 200 Caenis .0050 140 .0030 80 Chaoborus .0013 100 by Tanner except for the larger size groups. One possible reason for the author's volumes being lower for these groups is that the larger groups contained a high per- centage of Heleidae (Ceratopogonidae) larvae which appeared to have a lower condition factor than the chironomid midges. Bottom Fauna Distribution The vertical distribution and type of bottom fauna in lakes has been used by past investigators to categorize the productive capacities of lakes (Deevey, 1941; Eggleton, 1931). Tanner (1952) mentioned that the pattern "i.“A. ' 3 ’ 1. . . . WW4": I. 55 of bottom fauna distribution changed in certain of his fertilized lakes after fertilization from a pattern con- sidered to be characteristic of unproductive oligotrophic lakes to that commonly exhibited by more productive eutrOphic lakes. The comparisons shown in Figures 5, 6, 7 and 8 repre- sent the bottom fauna populations including the crayfish but excluding the mollusks. These adjustments were made to conform with the manner of tabulation used by Tanner (1952) who excluded the mollusks to get a more accurate view of important trout food organisms.- The mollusks were found to have only a very slight effect on the pattern of distribution for the 1967 samples. The 1966 results were not included in these comparisons because it was felt that the smaller number of samples left certain depth areas with too few samples as a result of the random method of selection. Also, with the exclusion of June from the 1966 sampling, the same span of time could not be compared. In 1948, South Twin (Figure 5) which had been fer- tilized by Ball (1950) the two previous summers, exhibited a pattern of distribution similar to some of the "mesotrOphic Chironomus" and "Chironomous" lakes mentioned by Deevey (1949). These lakes were characterized by having a maximum pOpulation in the sublittoral or profundal zones. This pattern of distribution which was not evident in any of the other lakes before fertilization was concluded by Tanner 56 (1952) to be a result of the earlier fertilization. The sublittoral peak, characteristic of this pattern, was believed caused by increased survival of "Chironomus type" midges in the area due to the profuse shower of expended plankton organisms from above (Tanner, 1952). Chironomus- type midges were found to be the chief component in this area of the lake in 1948 (Tanner, 1952). In the two years 77 following, 1949 and 1950, although the standing crop remained high the sublittoral peak was no longer evident. The 1967 sampling (Figure 5) showed a pattern very similar to that of 1948 except that the sublittoral peak was 6; located in a slightly shallower area. North Twin, the unfertilized lake (Figure 6), showed very little difference in the vertical distribution of bottom fauna in the four years under consideration. The 1967 sampling indicated a slightly higher standing crop in the 20—30 ft. area of the lake. The contrasting results of the 1966 sampling (Table 10) present the possibility that a large amount of variation may exist from year to year within the lake. If this were the case, it would be difficult to make any generalizations as to the level of the standing crop on the basis of only two years of sampling. West Lost Lake (Figure 7), fertilized in 1949 and 1950, was noted by Tanner (1952) as having a pattern of distribution in the second summer of fertilization similar 57 to that of South Twin in 1948 and to Deevey's (1941) more productive lakes. As mentioned earlier, West Lost Lake showed a large increase in the standing crOp during 1966 and 1967 over the earlier sampling by Tanner (Tables 7 and 11). This was found to be due largely to the high populations of clams (Figure 3). However, when the clams were excluded the pattern of distribution was quite similar to that of 1949, the first year of fertilization (Figure 7). The fourth lake, Section-Four, displayed the same sort of distribution in 1950, the second year of fertili- zation, as South Twin in 1948 and West Lost in 1950. The 1967 depth distribution curve (Figure 8) resembles the 1949 curve more closely than either of the other two years. This type of pOpulation was said by Deevey (1941) to be characteristic of lakes where the total quantity of bottom fauna was low. However, it appears considerably higher than the prefertilization, 1948, curve (Figure 8). Species Composition A detailed analysis of the species composition of the various taxonomic groupings was not attempted since this procedure was not followed by earlier investigators (Ball, 1950; Tanner, 1952) and, therefore, a comparison would not be possible. A brief analysis, however, is presented. 58 The most prominent group on all lakes in numbers was the family Chironomidae. As mentioned earlier, the family Heleidae was included under this heading. Specimens of this family were widely distributed in all lakes but never important volumetrically. Mature midge larvae of the species Chironomus plumosus (L.) were identified from all four lakes but were not common in Section-Four Lake. A large majority of the remaining midges were probably earlier instars of this species. This species was believed also to be predominant during Tanner's study (Tanner, 1952). The AniSOpterns were important volumetrically due to their relatively large size but were never very numerous. The family Gomphidae, genus Gomphus, was the most common genus found in all four lakes and the only anisoptern taken from Section-Four Lake. Members of the families Libellulidae and Aeschnidae were also present. Among the latter, the genera Anax and Boyeria were pre- dominant. Zngpterns were rarely found in the bottom samples. Those present were members of the family Coenagrionidae. Among the EphemerOptera, the genus Caenis (Family Caenidae) was common and found in all four of the lakes, but due to its minute size they were never important con- tributors to the total biomass. Stenonema, a member of the family Heptageniidae, was also encountered in all of 59 the lakes but was much less numerous. A similar status of these two genera was noted by Tanner (1952). A few members of the family Baetidae and one of the family Ephemeridae were found in Section—Four Lake. The amphipod, Hyallela, was also common to all four of the lakes and was especially abundant in Section—Four Lake (Table 8). The phantom midge larvae Chaoborus (family Culicidae), although found in all of the lakes was seldom encountered in the bottom samples. Chaoborus larvae are predatory on small crustaceans and make pronounced daily vertical migrations in the lakes where they are found (Pennak, 1953). Because of this behavior, the larvae are nearly pelagic and thus their occurrence in bottom samples could not be taken as a true index of their abundance. Representatives of the order TrichOptera were found in each of the lakes, the most common family being Molan- nidae, genus Molanna. Tanner (1952) stated that the Limnophilidae were the most numerous of the Trichoptera, however, this statement takes into consideration the two lakes, Hemlock and Lost, not included in the present study. 'The limnophilids were second in abundance in 1966 and 1967. 'Tanner found the genus Molanna only in North and South 'Twin Lakes. Phryganeidae was the third and least abundant of the caddis larvae present. The micro-caddis, family :Hydroptilidae, which were mentioned by Tanner as occurring 6O occasionally in the algae mats of South Twin Lake were no longer present, obviously due to the lack of such algae. The only clams present belonged to the genus Musculium. Snails were very uncommon in all of the lakes. According to Table 5, the snails appear to have progressively declined in South Twin following the early fertilization by Ball (1950). Although they appeared in Section-Four during the .3 first summer (1949) of fertilization (Table 8), they were u unexplainably absent from the 1950 sampling. Small oligochaetes were present throughout the gl four lakes in moderate numbers. The crayfish, Orconectes virilis, as mentioned earlier, were important members of the benthos fauna but were not included in the results of this study. Predation One other factor that must be taken into consider- ation in making this comparison is the possible differen- tial effects of fish predation upon the benthos organisms. Species composition and abundance of fish are the factors which could cause a difference in the level of predation. Hayne and Ball (1956) concluded from their study of a group of Michigan fish hatching ponds that in the absence of fish the standing crop is relatively high and production is low while with fish present the standing crop decreases and production increases. These results decrease the 61 validity of a productivity comparison on the basis of standing crop when two different fish populations are in- volved. Table 14 gives a comparison of the number of fish stocked in 1948 during Tanner's study and those planted in the same lakes prior to the 1966-1967 sampling. The inter- pretation of these data is complicated by the fact that the 1948 planting occurred in the fall of that year after the prefertilization bottom sampling period. During the summer of 1948, up until the time of poisoning (August 1 and 2), large populations of yellow perch (Perca flavescens) and common suckers (Catostomus commersoni commersoni) were present in North Twin, South Twin, West Lost and Section-Four. Pumpkinseed sunfish (Lepomis gibbosus) were also present in West Lost Lake. As Table 14 shows, many more trout were planted during the 1949-1950 period in North and South Twin than during the 1964-1965 period. Tanner (1952) compared the feeding habits of brook and brown trout from the lakes by means of stomach analysis. It was found that brook trout appeared to feed on bottom fauna organisms to a slightly greater extent than brown trout, while brown trout were observed to feed more on terrestrial insects which alighted on the lake surface. The probability of erroneous results being produced by the stocking of different species and varying numbers is some- what diminished by the bottom sampling results of North Twin Lake. It is evident from Table 6 that these 62 :m owmao>w .amwoa u a m: aaocpmamm osammllmsom oxmpmae an UopGMHQ om m.m usonm .wcaaaomcam n m a=m psonm .amwoansm u Am** moppsap osammllczoam mmaamcapcom magaao>ammllxooamx .mama ca pmoa ammz new case spsom .caze cpsoz ca am ohms mwcaaaowch p309» xooan mo popes: amzvo c<+ m m a moo.m ooo.m mmm msom mzom csonm mmma amma mama am am am a am omm.a omn.a ooa moo.a moo.m csoam xooam xoomm csoam czoam mama mmma amma mama mama oxwa asomlcoapoom mama pmoa ammz am am a mam 0mm mma.a xooam xooam csoam mmma amma mama am am am a am omm.m omm oma mmo.a oma.m czoam xoomm xooam czopm csomm mama .mmma . amma mama +mama mama case apnoz El .mmma mum amma .mama..wama mama case spaom 1' 1'11 mudom map you mvaoooa wsaucqu mo comaamasoo ouam monesz moaooam awow atmNHm monasz *moaomam moo» «1|.aa mgm49 63 fluctuating fish planting levels have not made themselves evident unless of course some other phenomenum is masking their effects. The aforementioned unexplainable high level of standing crop shown by the 1966 bottom samples (Table 10) can hardly be attributed to the fewer fish in 1966 than 1967 since there were no fish planted after 1965, and monthly samples were removed from the lake during 1966 and 1967 by the staff of the Pigeon River Research Station. If there were indeed a substantial suppression of the benthos organisms by the large numbers of fish present during the 1949-1950 period, the standing crOp of these two years would be underestimating the productivity when compared with other years influenced by fewer fish. SUMMARY A comparison of thermocline data from the years 1948,. 1949, 1950 and 1967 seemed to indicate that the thermocline of the fertilized lake, Section-Four, and the unfertilized lake, North Twin, occupied a shallower position in 1967. Oxygen depletion during the summer stagnation period occurred below the 4 ppm. level in South Twin, North Twin and West Lost Lakes. Oxygen depletion under the winter ice and snow cover appeared to be less in the lakes measured (North Twin and South Twin) than shown by Tanner for the 1948-1950 period. The total alkalinity, which was decreased consider- ably by fertilization in West Lost and Section-Four, appeared to have regained.insprefertilization level. A blue-green alga, Aphanothece stignina, character- istic of eutrOphic lakes, was found to occur in the deeper waters of South Twin, North Twin and West Lost Lakes. There was a considerable difference in the estimates of the standing crop between 1966 and 1967 in South Twin, North Twin and West Lost. The 1966 samples showed a higher level in each of these lakes. 64 ., . up.” 65 The bottom sampling results of 1967 indicated the standing crop of benthos organisms was as follows: South Twin was much lower in 1967 than any of the three years following fertilization; North Twin seemed to conform to the 1948-1950 estimates; West Lost was higher than either of the pre- or post-fertilization levels, but this was largely due to the increased number of clams; Section—Four was closest to the results of the first year of fertilization and con- siderably above the prefertilization level. The vertical distribution of bottom fauna in 1967, as indicated by bottom sampling, was as follows: South Twin's pattern of distribution resembled that of 1948, the first year following fertilization, which is a pattern characteristic of some productive lakes; North Twin was similar to the years 1948-1950; the pattern shown by West Lost appeared most like that of 1949, the first year of fertilization; Section-Four was also similar to the first year of fertilization. The standing crop estimates for both of the sampling periods were considerably above the prefertilization levels in West Lost and Section-Four Lakes. The perfertilization level was not known for the third fertilized lake, South Twin. LITERATURE CITED American Public Health Association. 1965. Standard methods for the examination of water and waste- water. 12th ed. New York. 760 p., Ball, R. C., 1948. Relationship between available fish food, feeding habits of fish and total fish produc- tion in a Michigan lake. Mich. State Coll. Exp. Sta. Tech. Bull. 206: 59p. Ball, R. C. 1949. Experimental use of fertilizer in the production of fish food organisms and fish. Mich. State Coll. Ag. Exp. Sta. Tech. Bull. 210: 28p. Ball, R. C. 1950. Fertilization of natural lakes in Michigan. Trans. Amer. Fish. Soc. 78: 145-155. Ball, R. C., and H. Tanner. 1951. The biological effects of fertilizer on a warm-water lake. Mich. State Coll. Ag. Exp. Sta. Tech. Bull. 223: 32p. Barrett, Paul H. 1953. Relationship between alkalinity and absorption and regeneration of added phosphorus in fertilized trout lakes. Trans. Amer. Fish. Soc. 82: 78-90. Deevey, Edward 8., Jr. 1941. The quantity and compo- sition of bottom fauna of thirty-six Connecticut and New York lakes. Ecol. Monogr. 11: 413-455. Eggleton, Frank E. 1931. A limnological study of the profundal bottom fauna of certain fresh water lakes. Ecol. Monogr. 1: 213-332. Eschmeyer, William R. 1938. Experimental management of a group of small Michigan lakes. Trans. Amer. Fish. SOC. 67: 120-129. Garton, Ronald R. 1967. Long-term effects of lime application to some soft—water bog lakes in Northern Michigan. M.S. Thesis. Mich. State Univ. E. Lansing, Mich. 145p. 66 .‘J ‘1. .1 4+1 ‘3‘. 67 Gross, R., F. E. G. Raymont, S. M. Marshall, and H. P. Orr. 1944. A fish farming experiment in a sea loch. Nature. 153: “83-u850 Hayne, D. W., and R. C. Ball. 1956. Benthic productivity as influenced by fish production. Limnol. and Oceanogr. 1: 162-175. Hilsenhoff, William L.’ 1967. Ecology and pOpulation dynamics of Chironomus plumosus (Diptera: Chiron- omidae) in Lake Winnebago, Wisconsin. Annals of the Entomol. Soc. of Amer. 60(6): 1183-1194. Ingram, W. M., and G. W. Prescott. 1952. Illustrations of fresh water algae toxic to animals. Ohio-Tenn. Drainage Basins Office. Div. of Water Pollution Control. Pub. Health Serv. Gin., Ohio. Non-paged. Kusnetzow, S. L. 1939. Determination of the intensity of oxygen absorption in the lake water, caused by bacterial processes. 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