a? éké . J. m”. ,5: o o v aka-J .i a- $56 2&3 .. "(wfiufimuwr Maui. — hawk. I I Vt. . . 010. v N) . ‘01.» o . . g ...,. .3 5 Afr-:rkanAfiHWImWJHDv am!» 3...... .1: 4‘ cl‘ ‘A _ _ 2W . . .. . Raouocu « ~ . 3.?o1m nu ‘ . u".9..v‘¢a H. I! "H‘lw WW5: vr' l'l"'"Y‘! . g» - . V 'yvvrx'" . ¢ .olunurlrw-nwvnm' an. ‘ ’ ‘ 9.. ‘ l 1 ' r ’ ‘ I o . . Inn" ~. “gm: unuqumv . ‘ A I -L...z..t!,.. ...‘.$H~..!l... nt..L;L1...$..$..- .31.... ; .:. - .. ‘"4.12mié.q...wa.,,wr;....§;.v . A. - ....u. . .3-.. V; .. I- - v. . I . . . p i“ . é. L M! in (are University I This is to certify that the thesis entitled "A Limnological-Biological Investigation of Spring Lake, Michigan" presented by Robert W. Bentz, Jr. has been accepted towards fulfillment of the requirements for M.S. degree in Fisheries & Wildlife , A . - 5 ”L";- flfi/afi/Z Major proéssor Date 9/2/77 0-7 639 A LIMNOLOGICAL-BIOLOGICAL INVESTIGATION OF SPRING LAKE, MICHIGAN By Robert N. Bentz Jr. 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 T977 a 3;“), l 1" ’33-" (‘7'. (t f‘ 3 i i” _ '._.' I‘ f" ' :»»i bid ’ ABSTRACT A LIMNOLOGICAL-BIOLOGICAL INVESTIGATION OF SPRING LAKE, MICHIGAN By Robert N. Bentz Jr. This study provides background information on the physical, chemical, and biological parameters of Spring Lake, Michigan, gath- ered from March to October, 1976. Spring Lake has a surface area of 172,572 square meters with amaximum depth of 9.75 meters. Thermal stratification was observed at the two deep-water stations from June through October. A clinograde oxygen curve appeared after thermal stratification was established. Chemical characteristics were: total alkalinity, 152-196 mg/l; pH, 7.3-8.4; total hardness, l60-200 mc/l; Kjeldahl nitrogen, 0:47-0.55 mg/l; total phosphorus, 0.026-0.042 mg/l; calcium, 33.0- 50.0 mg/l; and chlorides, 4.0-5.5 mg/l. Seasonal distribution of phytoplankton was characteristic of medium hardwater lakes in the temperate region. Zooplankton papula- tions were limited to nine genera. 0f the aquatic insects, mayflies were most numerous in shallow water while chironomids were most abundant in deep water. Distribution and abundance of aquatic macro- phytes were influenced by wave action and sediment characteristics. Bluegills exhibited a slower growth rate and lower coefficient of condition than the state average. ACKNOWLEDGMENTS I wish to express my appreciation to the property owners of Spring Lake for funding this research. I would like to acknowledge Michigan State University, Department of Fisheries and Wildlife for the use of their facilities and equipment. I would like to thank my major professor Dr. E. w. Roelofs for his support and many helpful suggestions in carrying out this research and in writing this thesis. I also wish to thank graduate committee members Dr. C. D. McNabb Jr. and Dr. C. Humphrys for their assistance. I thank fellow graduate student Bob Ceru for helping to col- lect these data. Finally, I thank my dearest friend and wife Mary, who has always stood by me. ii TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES INTRODUCTION DESCRIPTION OF STUDY AREA . PHYSICAL AND CHEMICAL PARAMETERS Morphology Transparency . Temperature and Dissolved Oxygen Alkalinity, pH, and Hardness Nitrogen and Phosphorus Calcium . . . . Chlorides . BIOLOGICAL PARAMETERS I. II. III. IV. V. SUMMARY . Phytoplankton Zooplankton Aquatic Insects . Aquatic Macrophytes Fish . . . LITERATURE CITED APPENDIX Page iv vi Table A1. A2. A3. A4. LIST OF TABLES Areas and volumes of water at various levels in Spring Lake . . . . . Morphometric features of Spring Lake List of phytoplankton collected in Spring Lake from April through September, 1976. Genera are listed in order of decreasing abundance within each phylum or subphylum . . . . . . . . . . . Seasonal distribution of zooplankton genera in Spring Lake from April through September, 1976. Vertical and horizontal values listed are percentages of total sample based on four and two tows respectively . Number of aquatic insects collected in two Eckman Dredge samples on October 9, 1976, along a transect form shore to Station 5 on Spring Lake List of aquatic macrophytes and macroalga in Spring Lake, September, 1976 . . . . . . . Number, ages, mean weights, mean calculated total lengths, mean total lengths at capture, mean growth increments, and mean coefficient of condition factors of bluegills from Spring Lake, Michigan Sampling schedule by date (month/day) for various chemical and biological parameters on Spring Lake from April through October, 1976 . . Summary of pH values of Spring Lake measures at all sampling stations from April through October, 1976 Summary of total alkalinity concentrations (mg/l CaCO3) of Spring Lake measured at all sampling stat1ons from April through October, 1976 Summary of total hardness concentrations (mg/l CaCO3) of Spring Lake measured at all sampling stations from April through October, 1976 . . . . iv Page 30 37 38 4O 45 60 61 62 63 Table Page A5. Summary of Total Kjehdahl nitrogen (mg/1N) of Spring Lake measured at all sampling stations from April through October, 1976 . . . . . . . . . . . 64 A6. Summary of total phosphorus concentrations (mg/1P) of Spring Lake measured at all sampling stations from April through October, 1976 . . . . . . . 65 A7. Summary of calcium concentrations (mg/l Ca) of Spring Lake measured at all sampling stations from April through October, 1976 . . . . . . . . . . . 66 A8. Mean calculated total length at each annulus for 25 largemouth bass from Spring Lake, Michigan . . . . 67 A9. Mean calculated total length at each annulus for 29 black crappie from Spring Lake, Michigan . . . . 68 A10. Mean calculated total length at each annulus for 24 rockbass from Spring Lake, Michigan . . . . . . 69 A11. Mean calculated total length at each annulus for 18 yellow perch from Spring Lake, Michigan . . . . . 70 A12. Mean calculated total ength at each annulus for 11 northern pike from Spring Lake, Michigan . . . . 71 Figure 10. 11. 12. LIST OF FIGURES Locations of sampling stations, gill nets, zooplank- ton tows, and invertebrate transect on Spring Lake, Michigan . . . . . . Hydrographic map of West Lake, Montcalm County, Michigan . . Average Secchi disk transparency values for Spring Lake, Michigan . . . . Temperature (C; solid line) and dissolved oxygen (mg/1; broken line) profiles at Station 5, Spring Lake from April through October, 1976 . . . . Depth- pH curves for Station 5, Spring Lake, Michi- gan . . . Depth- -total alkalinity curves for Station 5, Spring Lake, Michigan . . . . Depth-hardness curves for Station 5, Spring Lake, Michigan . . . . . . . . . Depth- -tota1 Kjeldalh nitrogen curves for Station 5, Spring Lake, Michigan . . . Depth- -total phosphorus curves for Station 5, Spring Lake, Michigan Depth-calcium curves for Station 5, Spring Lake, Michigan . . . . . . . . Distribution of the major groups of phytoplankton and the dominant genera in Spring Lake based on monthly numerical averages of samples collected from April to September, 1976 . . . . Chlorophyll a concentrations at Station 5, Spring Lake from May through September, 1975 vi Page 10 12 16 18 19 21 23 26 31 34 Figure 13. 14. Page Mean calculated total length for bluegills in Spring Lake (dached line). Mean total length at capture for bluegills in Spring Lake (dot and dash line) and Michigan state average (solid line) . . . 46 Length-weight relationship for 163 bluegills from Spring Lake, Michigan . . . . . 48 vii INTRODUCTION Within the past decade a large number of lake surveys and water quality investigations have been conducted across the United States. The vast majority of these investigations have dealt with eutrophication or pollution problems occurring in lakes and streams with a resulting lack of good "background" water quality determina- tions (Edmondson, 1970). In many instances, we do not know what the lake conditions were before they became objectionable. This gap in our understanding makes it difficult to evaluate long-term water quality trends as they occur. The purpose of this study is an attempt to provide such back- ground information from one of the many small lakes located through- out Michigan. Physical, chemical, and biological parameters of Spring Lake, Montcalm County, were monitored extensively over a seven- month period from the vernal mixing period through summer stratifi- cation to the onset of fall overturn. The major objectives of this study are: 1. to provide a morphological description of Spring Lake; 2. to evaluate important chemical parameters of Spring Lake and record temporal and spatial deviations; 3. to describe the relative abundance, distribution, and diversity of aquatic macrophytes, plankton, inverte- brates, and fish in Spring Lake. This study was initiated on March 24, 1976, and terminated October 24, 1976. DESCRIPTION OF STUDY AREA Spring Lake is located in the drainage basin of the Flat River (TllN, R8N, Sec. 22, Pine Township, Montcalm County). The Lake has a surface area of 172,572 square meters, and a mean and maximum depth of 2.19 meters and 9.75 meters respectively. The lake is fed by springs which emerge from the lake bottom. There are no inlets, and only one small outlet which connects Spring Lake with West Lake. Thirty-five summer cottages have been established around the lake- shore. Six sampling stations within the lake were determined and permanently marked withanchored buoys (Figure l). Stations 1, 2, 3, and 4 were situated in near-shore areas ranging in depth from .91 to 4.57 meters. Stations 1 and 4 had steeply sloped, predominantly marl bottoms with limited aquatic macrophyte colonization. The mud bot- toms at Stations 2 and 3 were flat with an abundance of macrophytes. Stations 5 and 6 had depths of 8.0 and 9.14 meters respectively, and were located in the deepest portions of the central lake basin. No aquatic macrophytes were found at these stations. Approximately 80% of the shoreline area consists of Rifle and Tawas peats (U. S. Department of Agriculture, 1960). These poorly drained organic soils are composed of woody and fibrous plant remains. The watertable is near the surface and the spongy soil is moderately I] .._.<:)._. it Q) ED @ ,’ I, .. _ a] ~~~~~ / G) J/ ./ ED ;:://,A 11 g] (:) Major Sampling Stations [3 Chloride Sampling Stations Experimental Gill Nets -------- Horizontal 200plankton Tows —- ----- Benthic Invertebrate Transect Figure l.--Locations of sampling stations, gill nets, zooplankton tows, and invertebrate transect on Spring Lake, Michigan. acidic. Vegetation includes tamarack, red maple, and oak. Cleared areas support a dense growth of sedges and grasses. The remainder of the lake's shoreline area is composed of Montcalm and McBride loamy sands. These well drained soils support a mixed hardwood and conifer forest with oak and maple dominating. PHYSICAL AND CHEMICAL PARAMETERS I. Morphology A shoreline map of Spring Lake was constructed on March 24, 1977, using the plane-table survey method (Welsh, 1948). Nineteen stations around the lakeshore were selected to determine the shore configuration. Shoreline details were drawn in by walking around the lake. Hydrographic contours were determined with a Ray Jefferson Model 6010 Depth Finder and Precision Optical Range Finder. Measurements of the lake map were made with a Dietzen Com- pensating Polar Planimeter and Dietzen Model 1718 Map Measurer. Methods used in calculating the areas, volumes, and various morpho- metric parameters are those given by Welsh (1975) and Cole (1975). The areas and volumes within each contour stratum are shown in Figure 2 and are listed in Table 1. Other morphological para- meters are listed in Table 2. Extensive shallows along the north and northwestern shores result in nearly 50% of the total lake surface area to be 3.05 meters (10 feet) deep or less which is equivalent to 60% of the total lake volume. Hard, compacted sediments with a high marl content and little vegetation characterized the shallow areas along the wave swept eastern shoreline. Shallow areas along the protected western shore had soft, organic sediments that supported large numbers of macrophytes. SPRI N G L AKE / MWTCALM COUNTY. PINE TOWNSHIP T.” N. R.8W. SEC. 22 SURVEYED- MARCH. 1976 g ,. .. QR SCALIII'EU LAKE AREA- 42.62 ACRES ‘1: / Figure 2.—-Hydrographic map of Spring Lake, Montcalm County, Michigan TABLE 1.--Areas and volumes of water at various levels in Spring Lake. Depth Areas Sgepth Volumes Feet ' ra um (Meters) Square Percentage Feet Cubic Percentage Meters of Total (Meters) Meters of Total Surface 172,572 100 0-32 378,329 100 5 62,032 36 0-5 171,988 45 (1.52) (0-1.52) 10 17,411 10 5-10 57,148 15 (3.05) (1.52-3.05) 15 21,906 13 10-15 29,937 8 (4.57) (3.05-4.57) 20 21,865 13 15-20 33,391 9 (6.10) (4.57-6.10) 25 23.120 13 20-25 34,316 9 (7.62) (6.10-7.62) 30 19,274 11 25-30 32,306 9 (9.14) (7.62-9.14) 32 6,964 4 30-32) 19,243 5 (9.75) (9.14-9.75) TABLE 2.--Morphometric features of Spring Lake. Item Value Volume 378329 m3 Surface Area 172572 m2 Maximum Depth 9.75 m Mean Depth 2.19 m Maximum Length 565 m Maximum Width 557 m Average Width 305 m Total Shorelength 1945 m Shore Development 1.32 Water Exchange Rate 108 days Discharge from the outlet channel was measured once in September, 1976, using the Embody float method (Kevern, 1973). The discharge from Spring Lake into West Lake was 0.04 cubic meters per second. Rawson (1955) has stated that there is a definite correlation between mean depth and the standing crops of plankton, bottom fauna, and the sustained production of fish. Shallow lakes exhibit a higher carrying capacity than deep lakes. With a mean depth of only 2.19 meters, Spring Lake has the potential to be highly productive, based on its morphological characteristics. Hooper (1955) studied the influence of alkalinity on lake basin shape in eight southern Michigan lakes. When the alkalinity exceeded 105 mg/l the marl precipitation and sedimentation rates increased greatly, forming sharp drop-offs into deep water. This type of marl bench formation is found frequently in Spring Lake which has alkalinity values ranging from 150 to 180 mg/l. Perhaps the chemical mechanisms described by Hooper led to these formations. II. Transparency Water transparency was measured with a 20-cm Secchi disk approximately every two weeks at all sampling stations from April 10 to October 24, 1976. Exact sampling dates are listed in the Appen- dix, Table A1. The data are shown in Figure 3. Average Secchi disk values for Spring Lake ranged from 2.07 to 3.78 meters during the sampling period. No significant differ- ences in transparency were noted between any of the sampling stations. Early spring and late fall transparency values were higher than mid- summer values although phytoplankton concentration (as measured by chlorophyll g) which usually lowers transparency, (Hutchinson, 1957) decreased throughout the sampling period. These low summer values may have been due to the frequent high winds. Heavy wave action can stir up and distribute decomposition products and debris from shallow areas throughout the water mass (Tressler and Domogalla, 1931). Another possible explanation for low tranSparency values may be the presence of suspended solids. Hooper and Ball (1964) found low Secchi Disk Depth (m) Time (months) Figure 3.--Average Secchi disk transparency values for Spring Lake, Michigan. 11 transparency values in marl lakes was due to large amounts of sus- pended marl. III. Temperature and Dissolved Oxygen ' Water temperature was measured monthly from April 10 to October 23, 1977 (Appendix Table A1) at one-meter intervals from surface to bottom at all six sampling stations using a portable Y.S.I. telethermometer with a thermistor. Dissolved oxygen profiles at one-meter intervals from surface to bottom were conducted simultaneously with temperature profiles at all stations (Appendix Table A1). Dissolved oxygen was measured in the field titrimetrically, using the azide modification of the Wink- ler iodemetric method (A.P.H.A., 1970), on samples collected with a one-liter Kemmerer bottle. Samples were allowed to overflow for 10 seconds before reagents were added, so that any bubbles which might have formed would be removed. Spring Lake was dimictic, with complete mixing periods in mid-March and late October of 1975. Thermal stratification occurred between early June and late October (Figure 4). Only the deep-water Stations 5 and 6 became thermally stratified during the sampling period. Littoral Stations 1, 2, 3, and 4 exhibited uniform tempera- ture profiles from surface to bottom. There were no observed hori- zontal variations in temperature between the deep-water and littoral stations. Surface temperature varied from 10°C to 25°C during the sampling period. The upper four meters of water, or epilimnion, were 12 ll 10 O O {N/ 1) {‘C) 0.0. lecap. 1.) 10 0 ("Cl (awn 0.0. Tm. " .— .— .———----—.- F‘ '\ '— \ J~ A \ o A. q .— : \ " N U i, 8‘ ‘ 4 - \ , _ A E o a _ -\1 / 1 .— o a ‘ :3 0 - \ 1 - ' ‘ ' 1 I ‘5 c J \ .. a. ‘ q 9 ____---_.._.__--_._./ , .L. :7 :4: ‘4' .. .».I 3 9a, u -— . -. v < ” E‘ c I” am " 12min; «ll-(l a _' fl \ 4‘ '- ‘ A 1 \ . -v ( fl 5 1 _, . \ a \ L _ ‘-________‘~ —. g 7‘? (a \ ’——"’ “‘~ \ .- > | \ \ a v: 1 \ I \ \ _. _ \ \ . \ ,9... . ‘ ‘ I .: f 4 » 9 C T. ‘ 9‘ —- L'. C, .: g .2 o I _ I .: I . I E '* 'x'q ': ‘ i :; _'_ .. .3 .1 . a C 'j '- .' P 'r J 1' " 57‘! “UGO-w iii-‘91 '— ‘ o N 2". 1 (V _—-_—___——--‘ ~ ‘- t. “ 1 ~~ ~~ “~. ~‘ “ ~‘ 4‘ \ ~37 \ .1 J -- I ‘ \ \ a .x ‘ (J < r- l.. , ' “. s q ‘ _ I“; , . g: i. I: . L 1 E O I. , .5 v- Q 3 v. ' / ' v ! " .T' .751" “-1 C a ._ — .‘c a -« a V —V a I . a 5 'v 0 _ N n q .5 yo >~ m Ow (ham) «mag 13 .oump .Lonouoo smaotcu Pweq< Eocw mxmo acream .m cowpmum pm mopweoea Amcwp coxocn m_\mev cwmxxo uw>_ommwo ocm Amcvfi nwFOm ”00v mcaomtmaemhul.e mtzmva 4 L .s nu b . m . _ x \ . \\ _ \\ _ \\ . \\ _ \\ _ \\ — \\ _ a . . . _ . . - _ _ . . . _ .. _ . . ‘ u. m m « .. . .u _ .... ~ . . . _ 1 . _ . . . . . _ . n . . it. .o 0 I11 _ . — _ x. 'U' _ _ 3 i 92— I _ u C i .91: . _ _ . . _ > . r N a n. c m _ _ a . ._ _ a. Z 0.. a 4 A . . 2 S o o a o m n q _ .c . . c n q . ,. _ r a 7. A .1 I, I, . L a... CA 1 x C 3-2... He .4 1.5.. . r, 5.; . a a Z .. 93:1... \ \ L \\ \\\ \ \ \ \\ \\ \\ \ \ \\\ \\\ o I n. .r. m u.‘ 4.1 H J . .. I a - 1.. . _ v m . _ _ _ .. :35 5d .1! u . :23: .93 Ill Au. Job.» I — — — — AU.” 95» VIII . a F o 2 m o a - r _ . at» 3 r 2 I I. 1 2 2 n a c p o 3; at... . n a . a 2...... Pa 2 : 3 . I s o a v n ~ . a :3. .o a 14 homothermal for most of the summer. The temperature dropped sharply from four meters to six meters, the metalimnion, and the change was accentuated as the season progressed. At five meters the temperature varied from 9.7°C in early April to 22.3°C in late September. The temperature in the hypolimnion, near the bottom at eight meters, increased gradually from 8.8°C in April to 12.7°C in October. Hutch- inson (1957) attributes this increase in hypolimnetic temperatures to a downward turbulent conduction of heat from warmer upper waters and to heating by chemically produced density currents. Stratification of the vertical distribution of dissolved oxygen occurred at the two deep-water stations while uniform dis- tributions were observed at the four littoral stations throughout the sampling period. No horizontal variations in oxygen concentra- tions were noted between the deep-water and littoral stations. The dissolved oxygen distribution at the deep-water stations stratified by June 5, and established a clinograde curve with a meta- limnetic maximum of 11.0 mg/l at six meters (Figure 4). Metalimnetic maxima are nearly always the result of oxygen produced by algal popu- lations that are concentrated in this zone of high density water which retards the algal sinking rate (Wetzel, 1975). This maximum increased to 12.3 mg/l in July and then gradually decreased until a typical clinograde curve developed in September. The clinograde curve disappeared in October due to the autumn turnover and complete mixing of the lake water. 15 A maximum oxygen concentration of 10.1 mg/l occurred in the bottom water during the spring turnover in April. Depletion of oxy- gen in the hypolimnion began immediately after the lake stratified thermally. Dissolved oxygen concentrations within one-meter of the bottom dropped below 1.0 mg/l during a three month period from July through September. With the breakdown of thermal stratification and resultant mixing of the entire water column in late October, oxygen concentrations near the bottom increased to 10.0 mg/l. IV. Alkalinity, pH,pand Hardness Values for alkalinity, pH, and hardness were determined in the field three times during the study period (Appendix Table A1). Samples were collected with a one-liter Kemmerer bottle. Water samples were taken just below the surface at all six sampling sta- tions, with additional samples taken at the mid-depth and bottom levels of the two deep-water stations. Water entering the lake from one of the lake bottom springs was also sampled once during the study. A Beckman portable pH meter was used to determine the pH. Total alkalinity (phenolphthalein alkalinity plus Bromcresol green alkalinity) was analyzed by the acid titration method (APHA, 1970). The EDTA titration method (Kevern, 1973) was employed to calculate hardness. Spring Lake was consistantly alkaline, with pH values ranging from 7.3 to 8.4 during the study period (Figure 5; Appendix Table A2). Horizontal variations in pH between the different stations were small. 16 pH 7.2 7.3 7.4 7.5 7.6 7.7 7.8 0 1 1 l I l 1 April 10 14 ——————JmeW --d--- September 14 2« 3 . Depth (m) & 5 « ”I I I I 6 ~ ’I I I "4’ ”/’ 71 I’ ’ ’ / ’ I ’ / I / 8i I ./ Figure 5.--Depth-pH curves for Station 5, Spring Lake. Michigan. 17 The surface was generally more alkaline than the mid-depth and bottom values although vertical differences at the two deep-water stations never exceeded 0.9 standard units. This observed decrease in pH at the lower depths has been attributed by Wetzel (1975) to respiratory generation of carbon dioxide in the tropholytic zone and sediments. Similar patterns of decreasing pH with increasing depth were reported in studies involving five Michigan lakes by Tucker (1957). The pH of the spring water was 7.5. Total alkalinity as calcium carbonate ranged from 152 to 196 mg/l during the study period (Figure 6; Appendix Table 3A) with slight horizontal variations. Alkalinity values were fairly uniform through- out the water column during the spring mixing period. However, as thermal stratification developed and continued throughout the summer months, a decrease in alkalinity in the epilimnion with a concomitant increase in the hypolimnion was observed. Cole (1975) explains this increase in hypolimnetic alkalinity as the result of photosynthetic activity in the trophogenic zone which causes the precipitation of calcium carbonate. The sinking carbonate is redissolved in the hypolimnion by the carbonic acid formed from hydration of the carbon dioxide of decay. An alkalinity concentration of 180 mg/l was determined for the spring water. Water hardness values ranged from 160 to 210 mg/l during the study period (Figure 7; Appendix Table 4A) and exhibited similar spatial and temporal characteristics to those of alkalinity. A slight decrease in hardness concentrations was observed during the Depth (m) Figure 6.--Depth-total alkalinity curves for Station 5, Spring Lake, Michigan. 18 Total Alkalinity (mg/l CaCO3) 170 180 l 190 i April 10 June 17 September 14 ‘s x s \. ‘5 ‘\ I~§. \ s x x \ \‘ \ ‘s l \ ‘ 19 April 10 ——————— June 17 -----—- September 14 Hardness (mg/1 CaCO3) 150 160 170 180 190 200 210 0 ‘g I 1 l i. I \ I \ I I d \ ' ‘ I ‘ I 2 4 \ | \ \\ I .1 ,. 3 \ 1 55 \I .5 4 “r. :3. \‘§ .8 \. ‘~., 5 j \ - \» «s \. -.. ‘\ 96 6 « ‘~ “~. \. 1~ \. 7~q. \ ~‘ 7 - \ ~~ ‘\ s» \ ~~ ‘\ - - 8 J \ Q Figure 7.--Depth-hardness curves for Station 5, Spring Lake, Michigan. 20 study period. Spring Lake would be classified as a hard water lake (Kevern, 1973) based on an average hardness concentration of 163 mg/l. A hardness value of 200 mg/l was determined for the spring water. V. Nitrogen and Phosphorus Water samples for nitrogen and phosphorus determinations were collected concurrently with water samples for alkalinity, pH, and hardness (Appendix, Table 1A) and were taken to the Water Quality laboratory of the Institute of Water Research for analysis. Total phosphorus and total Kjeldahl nitrogen were determined on the Tech- nician Auto-analyzer with the block digestion technique (U.S.E.P.A., 1974). Total Kjeldahl nitrogen determines organically bound nitrogen and ammonia nitrogen (APHA, 1970). Average nitrogen concentrations decreased during the study period, ranging from 0.55 mg/l in April to 0.47 mg/l in September (Figure 8; Appendix Table A5). These nitrogen values would place Spring Lake into the meso-eutrophic cate- gory of Wetzel's (1975) classification. Nitrogen concentrations in surface samples, which are domi- nated by dissolved organic nitrogen (Birge and Juday, 1922), exhibited little horizontal variation. Average nitrogen concentrations meas- ured at the surface varied from 0.56 mg/l in April to 0.38 mg/l in September. Manny (1972) points out that algae and macrophytes are the major contributors to the dissolved organic nitrogen pool in the trophogenic zone. 21 Total Kjeldahl Nitrogen (mg/l) .3 .4 .5 .5 .7 01—— . + . ‘s \ __.___ April 10 1 . x‘ \ _____ June 17 q, \ §~\ 1---." September 14 2 X‘x‘ \ - 3 \ x 1:: \ ‘~ e. \ ‘Pi. 5 4 \ ‘\ 8 \ o \ \ \ 5 . \ \‘ \ \ \ 6 \ \ ‘ ‘\ 1 \ \ \ \ 7 . \ \ \ \ ‘ \ 8.1 i \\ ‘ Figure 8.--Depth-tota1 Kjeldahl nitrogen curves for Station 5, Spring Lake, Michigan. 22 Nitrogen concentrations near the bottom at the two deep- water stations were similar to surface concentrations during the vernal mixing period. As thermal stratification developed in June and continued through October, a concurrent increase in nitrogen to 0.71 mg/l was observed in the hypolimnion as nitrogen concentrations decreased hithe epilimnion. Ruttner (1963) states that when oxygen concentrations in the hypolimnion decrease to less than 1.0 mg/l, denitrifying bacteria break down the organic nitrogen received from the epilimnion and convert it to ammonia nitrogen. Since the hypo- limnetic oxygen concentrations in Spring Lake were below .5 mg/l for a three-month period, it seems likely that ammonia nitrogen was the dominant component in the bottom samples during this period. The nitrogen concentration in the spring water was 0.17 mg/l. Total phosphorus includes soluble and insoluble; organic and inorganic forms (APHA, 1970). Average total phosphorus concentra- tions in Spring Lake ranged from 0.026 mg/l in April to 0.042 mg/l in June (Figure 9; Appendix Table 6A). These values slightly exceed the total phosphorus average of 0.023 determined by Juday and Birge (1931) for 479 lakes in northeastern Wisconsin, and are much greater than the 0.008 mg/l reported by Hooper and Ball (1964) from a marl lake in northern Michigan. In a study of 13 marl lakes in northern Indiana, Wetzel (1966) reported an average total phosphorus concen- tration of 0.018 mg/l. According to the lake classification table developed by Wetzel (1975), Spring Lake would be categorized as meso-eutrophictesedCNIthe total phosphorus concentrations. 23 Total Phosphorus (mg/l) O .01 .02 .03 .04 .05 .06 0 i L 4 . I I, “ I ‘I 2 - 1“> I .. 1. A Is 55 I ‘N‘ 54- ’ ) a I I 8 I I 5-1 I ” 4' 4' 6 - ’M' II 7 . April 10 8 j _____ June 17 ----I September 14 Figure 9.--Depth-total phosphorus curves for Station 5, Spring Lake, Michigan. 24 Phosphorus concentrations during the spring mixing period exhibited uniform vertical distribution which is characteristic of most lakes (Wetzel, 1975). In June, shortly after thermal stratifi- cation developed, a twofold increase in average phosphorus concen- trations was observed. The cause of this increase in unknown. Totla phosphorus concentration had become stratified by September. Surface concentrations averaged 0.023 mg/l which is identical to surface values determined in April. A marked increase in the quantity of total phosphorus was noted in the deeper waters of the lake where phosphorus values averaged 0.034 mg/l. This increase of phosphorus in the tropholytic zone has been documented in numerous studies (Juday and Birge, 1931; Hutchinson, 1941; Tucker, 1957; Wetzel, 1975). Two processes contribute to the increase. The first process is the constant transfer of phosphorus rich plankton and other organic material from the trophogenic zone (Juday and Birge, 1931; Wetzel, 1975). The second involves the release of phosphorus from the sediments during near anaerobic conditions (Hutchinson, 1941) which were observed in Spring Lake during this period. During periods of severe oxygen depletion, substantial quan- tities of phosphate, ammonia, and iron are released into the water from the sediments (Mortimer, 1971). The phosphorus concentration of the spring water was 0.010 mg/l. VI. Calcium Water samples for calcium determinations were collected con- currently with water samples for alkalinity, pH, and hardness 25 (Appendix Table 1A) and were taken to the Water Quality Laboratory of the Institute of Water Research for analysis. Calcium was determined with a Jarrell Ash Model 800 Atomic Absorption Spectro- photometer. Calcium concentrations ranged from 33.0 to 50.0 mg/l during the study period (Figure 10; Appendix Table 7A). An average concen- tration of 46.2 mg/l was observed uniformly throughout the water column during the spring mixing period. Calcium stratitifcation occurred shortly after thermal stratification developed in June. Epilimnetic values decreased to 42.0 mg/l while hypolimnetic calcium concentrations increased to 50.0 mg/l. This calcium stratification became wore pronounced in September as trophogenic values decreased to 33.0 mg/l while trapholytic values remained at 50.0 mg/l. Otsuki and Wetzel (1974) determined that the epilimnetic decalcification and concomitant increases in the hypolimnion were directly related to rapid increases in the photosynthetic rates of phytoplankton and littoral macrophytes, resulting in the precipitation of calcium car- bonate. A calcium concentration of 46 mg/l was observed in the spring water. Calcium values for Spring Lake were significantly higher than those reported by Hooper (1955) for eight southern Michigan lakes, but were slightly lower than the average calcium concentration in 13 marl lakes in northeastern Indiana (Wetzel, 1966). 26 Calcium (mg/1) 30 40 50 0 -—-1 ‘ a ‘ \. l \\ | 1 4 \‘ 1 . \ l 2 \ 1 ‘1 l 3 . \. I ’e? \‘ | Z 4 . t. L E; ‘5; ‘\ 8 \~ \ \. 5 . is 95 ‘\ April 10 \‘ \ q. ‘\ 6 ~ ————— June 17 \~ \\ ----- September 14 ‘~ \ it \ 7 ‘5 ‘\ \-:L 8 \ Figure 10.--Depth-calcium curves for stations, Spring Lake, Michigan. 27 VII. Chlorides Water samples for chloride determinations were collected monthly from June through September (Appendix, Table 1A) at nine locations (Figure 1) along the lakeshore in shallow water less than one foot deep. Stations 2, 3, 4, 6, 7, 8, and 9 were located in areas with cottages while stations 1 and 5 were in undeveloped areas. The mercuric nitrate titration method (APHA, 1970) was used to determine chloride concentrations. Chloride concentrations in Spring Lake ranged from 4.0 to 5.5 mg/l during the study period. High concentrations can indicate that the lake is receiving sewage wastes from faulty septic tank systems or municipal wastewater (Wetzel, 1975; Cole, 1975). Kevern (1973) states that cholride concentrations over 50 mg/l probably represent some type of human contamnnation. With the low chloride concentrations observed during the study period, it seems likely that Spring Lake receives no appreciable septic tank seepage from the cottages surrounding the lake. BIOLOGICAL PARAMETERS Phytoplankton, zooplankton, aquatic insect, aquatic macro- phyte, and fish communities of Spring Lake were analyzed during the seven-month study period. The following sections deal with the methods used in collection and identification, and the results obtained. 1. Phytoplankton Qualitative phytoplankton samples were taken with a one-liter Kemmerer bottle at all six sampling stations (Figure 1) approximately every two weeks from April through September, 1976 (Appendix, Table A1). Additional samples were collected at a depth of six meters at the two deep-water stations during the observed metalimnetic oxygen maximum. When brought to the surface, a 1% solution of Lugol's kill- ing and preserving liquid was added to 0.5 liter. Samples were taken to the laboratory and allowed to settle. Each sample was reduced to 50 m1 and centrifuges at 1400 R.P.M. for 20 minutes. The condensed algae were then transferred to a slide for identification and counting. Keys of Prescott (1951, 1970) were utilized in iden- tifying the algae to the generic level. Water samples for chlorophyll a_determinations were collected once a week from May through September (Appendix, Table 1A) at Sta- tion 5 between 10 a.m. and l p.m. to estimate quantitative seasonal 28 29 variations. Secchi disk transparency was first determined, after which a continuously-sampling weighted sample bottle was lowered to twice the Secchi disk depth. This procedure ensured a composite sample of the trophogenic water column. Samples were preserved with calcium carbonate to prevent the breakdown of chlorophyll a_into pheophytin, and mailed to the Michigan Department of Natural Resources, Environmental Services, Environmental Support Laboratory in Lansing, Michigan, for analysis. The samples were filtered with an acetone soluble Millipore filter and analyzed according to Stan- dard Methods (APHA, 1970). Numerous studies have reported on the seasonal variation or periodicity of phytoplankton in freshwater lakes (Bozniak and Kennedy, 1968; Klak, 1937; Kraatz, 1941; Hutchinson, 1944, 1967; Lund, 1964, 1965; and F099, 1965). The phytoplankton of Spring Lake exhibited a characteristic seasonal variation which corresponds with many of these reports. A total of 34 genera were identified from the samples. A list of the phytoplankton found, with their relative abundance, is given in Table 3. A phytoplankton study conducted by Raymond (1937) on a marl lake in Michigan with chemical conditions similar to Spring Lake reported many of the genera observed in Spring Lake. Diatoms, with Asterionella spp., Cyclotella spp,, and Fragilaria spp, dominating, comprising 78% of the phytoplankton samples during April (Figure 11). This spring maximum by the Bacillariophyceae has been observed by Klak (1937) in 21 lakes in Minnesota and Kraatz (1941) in lakes of northern Ohio. Diatoms 30 TABLE 3.--List of phytoplankton collected in Spring Lake from April through September, 1976. Genera are listed in order of decreasing abundance within each phylum or subphylum Chloropbyta Cryptophyta Oocystis spp. Cryptomonas spp, Gloeocystis spp, Spondylosiumggpp. Ankistrodesmus spp. Cyanqphyta Microcystis spp. ,Aphanothece spp. Chroococcus spp. Merismopedium spp. Anabaena spp. Scenedesmus spp. Eudorina spp. Pandorina spp. Mgugeotia spp. Pediastrum spp. Spirogyra §pp, Euglenophyta Trachelomonas spp. Zygnema §pp. Pyrrophyta Cosmarium spp. Ceratium gpp. Staurastrum §pp, Gonyaulax spp. Chrysophyta:Chrysophyceae Dinobryon spp. Chrysosphaerella §pp. Synura spp. ChrysophytazBacillarigphyceae Cyclotella spp. Fragilaria spp. Asterionella spp. Navicula spp. Cymbella spp. Diatoma spp. Synedra spp. Tabellaria spp. Gomphonema spp, 31 :1 Q Vi Q to . n . . . o g, . - v— Q Q Q Q Q Q Q U! Q Q. o— - Q Q Q Q Q D. D. n. n. a) a. m m m on 1n n VI Ill 10 m L Q l— 0 In 171 O U U) V, In «I - en M m -- u u 3 3 .- r- O 1— 'r- .c C +3 Q U U U H v— C r- L Q 0 10 .E .2 U U tn 0 O 0.1 a m >. >, H H O 0 >5 +3 w— u o— O L U 0 O U U U 0 L O -- tn .1: O C c O O O r— d) u— c) >, O L as a O 0 L U H U (a L C U .C .E L L Q >~. In >, s. .c w- -- Q n. .c .c - U < D Id. U D I < < 0 U 2 Chlorophyta Chrysophyceae Bacillariophyceae Cryptophy ta Cyanophyta Pyrrophyta Month Figure 11.--Distribution of the major groups of phytoplankton and the dominant genera in Spring Lake based on monthly numerical averages of samples collected from April to September, 1976. 32 continued to dominate the phytoplankton community through May and early June, although they comprised only 32% of the total in June as members of the Cyanophyta, Chlorophyta, and Chrysophyceae increased numerically. In mid-June the Chrysophyceae exhibited a large increase in numbers and became the dominant group with 33% of the total. Chrysophaerella spp. and Dinobryon spp. were the predominant genera during this period. The substantial numerical increase of Dinobyron §pp, at this time is atypical. Lund (1965) states from his observa- tions and various other studies that Dinobyron §pp, exhibit a phos- phorus toxicity reaction at concentrations above 0.030 mg/l. Phos- phorus concentrations in Spring Lake were higher during this period (0.046 mg/l) than any other time during the study period. Thus, the observed Dinobryon spp. increases are either a clear exception to the rule or the calculated phosphorus concentrations during this period are erroneous. Blue-green algae (Cyanophyta) became dominant in early July and remained so for the remainder of the study period. Microgystis §pp,, Aphanothece spp., and Chroococcus spp. were the predominant genera. This increase in the blue-green algae coincides with the maximum surface temperature observed during the study period which F099 (1965) cites as a decisive factor in determining the seasonal occurrence of the Cyanophyta. The period of maximum development in the blue-green algae occurred in early August when they composed over 52% of the total sample. This predominance began to decrease shortly 33 thereafter, until the Cyanophyta constituted only 39% of the total in mid-September. The phytoplankton community responsible for the metalimnetic oxygen maximum described earlier had a similar composition to that of the surface waters. Blue-green algae were the dominant group at the six meter level with concentrations nearly identical to those at the surface. Genera of the Chrysophyceae, Cryptophyta, and Chloro- phyta were more numerous in the metalimnetic samples than those at the surface. ChlorOphyll §_has been shown to provide quantitative measure- ments of total organic material in the water (Ryther, 1956; Bachman and Jones, 1974). Raymont (1963) states that 1.0 ug of chlorrophyll g_is approximately equal to 35.0 ug of dry organic matter. Chloro- phyll g_concentrations were used to estimate seasonal variations of the phytoplankton populations in Spring Lake. Chlorophyll g_concentrations based on vertical tows described above, ranged from 0.72 to 4.1 ug/l, or 25.2 to 143.5 ug.l dry organic matter during the study period (Figure 12). Chlorophyll values were high, averaging 2.61 pg/l during the vernal phytoplankton maximum period of May and early June with a steep drop to 0.72 pg/l observed in late June. This decrease in phytoplankton after the spring maximum is characteristic of lakes in the temperate region (Moss, 1972; Wetzel, 1975). Although the chlorophyll g_concentration increased rapidly after the sudden decrease in June, a gradual decline was noted through the summer months of July, August, and 34 5- 4.. Z 1:» 3 1: :2 t: 3- r. .p 1:: m u c: O 0 MI l— 2'1 E a. O 3.. 0 SE 0 1d 0 I l l l M J J A S Month Figure 12.--Chlorophy11 §_concentrations at Station 5, Spring Lake from May through September, 1976. 35 September. This decline in chlorOphyll would indicate a concomitant decline in the phytoplankton populations in Spring Lake. Lund (1965) explains that this decline in phytoplankton populations during the sumner months is characteristic of most lakes except those that are highly eutrOphic. II. Zooplankton Zooplankton p0pu1ations were sampled monthly from April through September, 1976 (Appendix, Table 1A). Vertical samples were collected at Stations 5 and 6 and horizontal samples were obtained in two littoral areas exhibiting an abundance of aquatic macrophytes (Figure 1). Samples were collected in a Wisconsin style plankton net with a mesh size of 80 microns. The zooplankters were preserved with 37% formaldehyde and taken to the laboratory. Identifications were made from the keys in Pennak (1953) and Eddy and Hodson (1961). The entomostracan populations in Spring Lake were confined to seven genera in the order Cladocera and two in the order Copepoda (Table 4). The genera observed are common to many lakes in North America. The number of cladoceran genera in Spring Lake is slightly higher than the average of two to four limnetic cladocerans reported by Pennak (1957) for small to medium-sized lakes of the world. The higher number of cladoceran genera may be due to the fact that lit- toral areas were also sampled. Pennak (1955) states that littoral populations of 200plankton are composed of more species and are less constant that limnetic populations. 36 Table 4 lists the distribution of zooplankton in Spring Lake based on the percentage of the total sample. Sjga_§p, and Bosmina gp, were found predominantly in the littoral area. Quade (1969) reports that aquatic macrophytes can control the distribution of littoral Cladocera. Daphnia §p,, Diaphanosoma pp,, and Simocephalus 5p, were much more abundant in the limnetic samples. The cladoceran populations exhibited one small increase in abundance in mid-June and another larger increase in late August and early September. These increases in abundance correspond with those reported by Pennak (1946) for seven lakes in Colbrado and Hall (1964) for a lake in Michigan, although seasonal abundance of zooplankters is quite variable among different lakes and within lakes during dif- ferent years (Wetzel, 1975). The copepod Diaptomus pp, was observed more frequently than Cyclops pp, in the limnetic samples while the reverse occurred in the littoral areas. Studies by McQueen (1969) have shown that adult Cyclops pp, prey heavily on Diaptomus pp, nauplii. Predation of Diaptomus pp, by large numbers of Cyclops §p, in the littoral zones could have resulted in the low numbers of Diaptomus §p, found in these areas. 111. pAguatic Insects Aquatic insects were sampled at 1.5 meter depth intervals on October 9, 1976, along a trasect from shore to Station 5 (Figure 1). Two samples were collected at each station with an Eckman dredge (6cm x 6cm) and washed in a No. 30 U. S. Standard Sieve with a mesh 37 .mumu mwzu co cmuomF—oo mam; mm_qemm LmHCONWLo; oza .Locuomou venom mew: mgmccopsm goon Lo memnEme weapeEEH+ ~.p~ a.mm m.~L ¢.m~ m.pe a.me m._~ o.Pm ¢.Lm a.mm m.pe - Pepqaez Luce m.~m m.~m e.L~ m.Lp c.Lm a.me m.m~ a.mm ~.m_ e.m a.mm - amm mmo_oxm meuwao_oxo muwoaopoxonevoumaou m.¢~ o.m~ o.mp c.e~ m.N_ a.m a.mm L.N_ “.mp ~.~ m.¢ - umm mzeoummwo mmquouqmwo mowocmLmunenoqoaou - - - - - - - ~.L - - a.o - nmm max0L3oLa omogoo>2u m.m e.~ m.m~ m.m - - - - - - - - .mm mzpmgqoooewm - - - - - - N.m - - ~.o - - Lam mwtmnoficmmom - - - - - - o.L - - - - - «mm mwcnmeoowcou e.m_ m.n n.om m.¢_ o.e - v.5L N.m ~.~ m.~ - - amm ewczmmo mecwcgaeo - m6 - -- -- -- Tm .. ea 92 v.2 .. .mm 2.5.8.. 82:58 3 ~.m N... 2 ma a. -- -- 2. m; -- -- $8.5 m.m m.o o.p o.m «.9 a. m.m p.mp m.m N.m a.m— - amw esomocmcquo oeuwowm memoouQLU > I > I. > z > z , > z > r: 2 #5538 m. 3.52 S .22. t 82. m .9: 2 :aa 13.--1,- Am3OL quco~wtoxuz .mzok pmowuco>u>v xpm>wuomamot mzoo 03» one Lao» co women wpgsmm peace we mommucootog age umumwp mmape> Popco~_cog use Feo_ptm> .mump .LmnEmuamm zmsoggu Fwsa< so»; axe; mcwgam cw mgwcmm :ouxcmpaooN Lo couaamtomwo Pecomemm-.a momqe 38 size of 0.595 mm. The residue containing organisms and debris was preserved in a 37% formaldehyde solution and taken to the laboratory. The organisms were removed by careful picking and identified with the aid of Usinger (1956) and Hilsenhoff (l975). The order Ephemeroptera is represented by four families which were found predominantly in shallow water less than 3.0 meters in depth. The sediments of this zone consisted of marl, sand, and organic material which formed a cohesive substrate. A list of aquatic insects collected and their depth distribution is given in Table 5. TABLE 5.--Number of aquatic insects collected in two Eckman Dredge samples on October 9, 1976, along a transect from shore to Station 5 on Spring Lake Depth of Water Order Family Genus 0_3 4-6 7_9 Meters Meters Meters Anisoptera Gomphidae 2 Diptera Ceratopogonidae l Chaoboridae 27 Chironomidae l 21 30l Ephemeroptera Caenidae l Ephemerellidae 4 Ephemeridae Hexagenia 28 2 Heptageniidae l TrichOptera Leptoceridae 9 7 l 39 Caddisflies of the family Leptoceridae were located exclu- sively on the various aquatic macrophytes rooted in the bottom. The number of Leptoceridae declined rapidly below a depth of 6.0 meters. This decline may have been due to the decrease in macrophyte abun- dance which occurred at the 7.5 meter level. The Diptera exhibited a marked increase in numbers with depth. The largest concentrations were recorded at the 7.0 to 9.0 meter level where the sediment ooze was composed of organic particles and decaying leaves. A large percentage of the total Chironomidae population probably excaped capture due to the large mesh size of the seive used. Studies by Jonasson (1955) indicate that mesh sizes above 0.4mm capture only a fraction of the chironomids present during a period from July to November. IV. Aquatic Macrophytes The aquatic macrophyte distribution in Spring Lake was sur- veyed qualitatively in early September, l976. Plants were collected by hand and a weed grapple along numerous transects from shore to deep water around the lake. Identification was conducted in the field with the aid of Fassett (l957). A list of the aquatic macrophytes and macroalgae identified is given in Table 6. The distribution of aquatic plants in Spring Lake at depths up to 3.0 meters was greatly influenced by the degree of exposure and resulting sediment characteristics of the area. Macrophyte zonation due to sediment type in Wisconsin lakes is dis- cussed in detail by Wilson (l935). Hutchinson (l975) states that 40 TABLE 6.--List of aquatic macrophytes and macroalga in Spring Lake, September, l976 Brasenia Schreberi Gmel. ED2I2.§EE: Elodea canadensis Michx. Najas flexilis (Nilld.) Nitella spp. Mymphaea odorata Ait. Polygonum coccineum Muhl. Pontederia cordata L. Potamogeton lucens L. Potamogeton natans L. Potamogeton pgctinatus L. Potamogeton pusillus L. Potamogeton Richardsonii (Benn.) Scirpus americanus Pers. Typha latifolia L. Utricularia spp. 41 sediment characteristics may be the controlling factor in macrophyte distribution. Shallow areas along the western and northwestern shores, which were protected from the prevailing westerly winds, exhibited a soft, highly organic bottom as reported in the morphology section. The greatest concentrations and most diverse populations of macro- phytes were observed in these shallows from shore to a depth of 1.0 meter.. Potamogeton pectinatus, E, lucens, E, natans, Elodea canadensis, Utricularia sp,, Brasenia Schreberi, and Polygonum coccineum were found sparingly with Chara spp, and Najas flexilis dominating. With an increase in depth to 2.0 meters the various species of pondweed observed in the shallow water became much more abundant as the amount of Chara s22, decreased. Najas flexilis remained the predominant species. The four small groups of Nymphaea odorata situated along the western shore were located within the 2.0 to 3.0 meter contour. Potomogetan pusillus and Chara spp, became the dominant submerged macrophytes at these depths as flaja§_decreased in abundance. The eastern shores presented a contrasting type of flora due to constant exposure to the westerly winds and the resulting dense, coarse sediments of intermixed sand and marl. From the shore to a depth of 1.0 meter the bottom was nearly barren. The only macrophyte growing in abundance was the bulrush Scirpus americanus, which was observed in large numbers along most of the shoreline and upon an extensive sandbar, with a few scattered specimens of Chara supp. and 42 Utricularia spp, Rich, et al., (l97l) states that sparse vegetation on shallow marl benches is characteristic of marl lakes in the Great Lakes region. Macrophyte zonation between l.0 and 3.0 meters was similar to that found on the western shore. However, the Potamogeton spp. which were much less abundant and Chara spp, which dominated, were both smaller in stature than their counterparts of the western shore. Najas flexilis was rarely observed on the eastern shore. At depths below 4.0 meters the macroalgae Nitella spp. were the only plants observed. It formed dense, continuous beds over most of the bottom to a depth of 8.0 meters. This complete take-over by Nitella s29, at lower depths was also observed in four medium hardwater lakes in Wisconsin (Wilson, 1935, l94l). Below 8.0 meters the sediments were soft and composed of partially decomposed oak and maple leaves. No macrophytes were found at these depths. V. Fish A total of l63 bluegill sunfish (Lepomis macrochirus) were collected throughout the summer of 1976. Five additional species, Micrgpterus salmoides, Pomoxis nigromaculatus, Amploplites rupestris, Perca Flavescens and Esox lucius were collected in small numbers. Collections were made with two experimental gill nets, 5.5 feet by 200 feet, with four sections of different mesh sizes (l, 2, 3, and 4 inches stretched mesh respectively, as manufactured), a "common sense" minnow seine, and by angling. Each fish was measured to the nearest millimeter for total and standard length. Weight was 43 measured to the nearest gram for fish larger than 20 grams and to the nearest tenth of a gram for fish under 20 grams. The scale method as described by Lagler (1956) and validated by Regier (1962) was employed in assessing age and growth character- istics. Scale samples were collected by removing approximately 10 to 20 scales from the area below the origin of the dorsal fin and just below the lateral line. After drying, 5 to 10 scales from each fish were placed between pieces of cellulose acetate and impressions were made with a roller press as described by Smith (1954). These impressions were then enlarged and examined on a Bausch and Lomb microprojector. From magnified impressions of the scales, positions of the annuli in relation to the scale focus were measured to the nearest millimeter along the scale radius on scale cards. The back- calculated total lengths at each annulus was determined by a homo- graph as described by Carlander and Smith (1944). To estimate the length of a fish at the time of previous annuli formation, a regression must be calculated between the length of the fish and its scale radius. The regression equation repre- senting the body-scale relationship is: TL = a + b (SR) where TL is the total length of the fish in millimeters a is equal to the total length intercept when the scale radius equals 0 b is equal to the close of the regression line 44 SR is the scale radious magnified 22 times and measured in millimeters (Armstrong, 1973). The body-scale relationship was determined from 80 fish. A straight line having the equation: TL =18 +10.8 SR best describes the relationship. The back-calculated total length at each annulus for 163 bluegills is presented in Table 7. Very little incremental growth was observed during the second year while growth rates increased during the third, fourth, and fifth years. A decrease in growth was again noted in the sixth year. A comparison of the growth rates for bluegills in Spring Lake and a state average established by the Research and Development Division of the Michigan Department of Natural Resources is presented in Figure 13. Bluegills in Spring Lake exhibit a very low growth rate during their first two years. Their rate of growth parallels the state average beyond the second year, and is slightly higher beyong the fourth year, but is never able to overcome the deficit created during the initial two years of growth. Growth rates deter- mined for bluegills in Spring Lake were significantly lower than those reported by Carlander (1953) for 21 lakes througout the United States. Age and growth characteristics determined for largemouth bass, black crappie, rockbass, yellow perch, and northern pike are given in Appendix Tables 8A, 9A, 10A, 11A, and 12A respectively. 45 up Fm mm mm up mm pcwEmLucw guzogm cmmz mm~ om_ mop on em Km mapzccm :omm um AEEV cumcm4 Peach cam: mm.m mm_ NNP no _N mm mm mup a.mm m o mm.m mm? mop mm mm mm om_ m._m ea m No.m mop mm mm um mm_ m.o¢ Pm a mm.m mm mm mm cm o.ep mm m mp.m um mm on m.m mm N mm.~ we Fm N.m m P e m e m N F Assv mczpqmu AEmv copupvcou we as spmcmg “save: mpnsmm cw qzocu pcm_o_$mmou mwm< pm Peach cam: cam: gmasaz mm< AEEV cameo; umumpaupmo cum: :mmwguwz .mxm; mcwggm soc» mppwmmzpa mo weapon» copu_ucou mo acmpuwwwmoo cams new .mpcmsmgucw cuzogm came .mcaugmo pm mgumcw— pmpop cums .msumcwp pogop wean—zopmu cams .mpgmwoz come .mmmm .cmaE:z-1.n m4m Lo» Axmu\;p:oev mama xo m_:umcum m:__qum-._< mbmqe 61 TABLE A2.--Summary of pH values of Spring Lake measured at all sampling stations from April through October, 1976 Date Sampling Station April 10, 1976 June 17, 1976 Sept. 14, 1976 Surface 1 7.99 8.30 8.10 2 7.99 8.25 8.10 3 7.95 8.30 8.00 4 8.00 8.38 8.10 5 8.10 8.35 8.20 6 8.00 8.40 8.20 Mid-Depth 5 8.00 8.28 8.00 6 7.99 8.40 8.10 Bottom 5 7.94 7.60 7.30 6 7.90 7.60 7.30 Spring 7.50 62 TABLE A3.--Summary of total alkalinity concentrations (mg/l CaCo of Spring Lake measured at all sampling stations from Spril through October, 1976 3) Date Sampling Station April 10, 1976 June 17, 1976 Sept. 14, 1976 Surface 1 170.0 155.0 154.0 2 169.0 155.0 157.0 3 167.0 157.0 155.0 4 168.0 157.0 152.0 5 168.0 156.0 156.0 6 168.0 156.0 157.0 Mid-Depth 5 167.0 155.0 163.0 6 168.0 155.0 144.0 Bottom 5 168.0 176.0 192.0 6 167.0 180.0 196.0 Spring 180.0 63 TABLE A4.--Summary of total hardness concentrations (mg/1 CaCOR) of Spring Lake measured at all sampling stations from pril through October, 1976 Date April 10, 1976 June 17, 1976 Sept. 14, 1976 Sampling Station Surface 1 190.0 170.0 166.0 2 190.0 170.0 164.0 3 188.0 170.0 164.0 4 186.0 169.0 162.0 5 188.0 170.0 160.0 6 188.0 170.0 163.0 Mid-Depth 5 190.0 170.0 170.0 6 190.0 170.0 170.0 Bottom 5 190.0 190.0 208.0 6 188.0 196.0 210.0 Spring 200.0 64 TABLE A5.--Summary of total Kjeldahl mitrogen (mg/1N) of Spring Lake October, 1976 measured at all sampling stations from April through Date Sampling Station April 10, 1976 June 17, 1976 Sept. 14, 1976 Surface 1 0.88 0.53 0.46 2 0.59 0.46 0.34 3 0.46 0.48 0.36 4 0.44 0.49 0.45 5 0.48 0.44 0.33 6 0.52 0.42 0.36 Mid-Depth 5 0.48 0.52 0.65 6 0.48 0.54 0.37 Bottom 5 0.47 0.67 0.71 6 0.67 0.67 0.68 Spring 0.17 65 TABLE A6.-~Summary of total phosphorus concentrations (mg/1 P) of Spring Lake measured at all sampling stations from April through October, 1976 Date Sampling Station April 10, 1976 June 17, 1976 Sept. 14, 1976 Surface 1 0.006 0.046 0.020 2 0.062 0.056 0.029 3 0.012 0.042 0.021 4 0.017 0.041 0.020 5 0.019 0.047 0.028 6 0.021 0.042 0.022 Mid-Depth 5 0.022 0.042 0.030 6 0.016 0.032 0.032 Bottom 5 0.033 0.032 0.052 6 0.051 0.040 0.020 Spring 0.010 66 TABLE 7A.--Summary of calcium concentrations (mg/1 Ca) of Spring Lake measured at all sampling stations from April through October, 1976 Date Sampling Station April 10, 1976 June 17, 1976 Sept. 14, 1976 Surface 1 46.0 43.0 33.0 2 46.0 42.0 33.0 3 47.0 42.0 33.0 4 46.0 42.0 33.0 5 47.0 42.0 33.0 6 46.0 41.0 33.0 Mid-Depth 5 46.0 42.0 37.0 6 46.0 43.0 34.0 Bottom 5 46.0 50.0 50.0 6 46.0 50.0 49.0 Spring 46.0 67 TABLE A8.--Mean calculated total length at each annulus for 25 large- mouth bass from Spring Lake, Michigan .Mean Calculated Length (mm) Age Number at Ages Coefficient Group in Sample of Condition 1 6 92 2.72 2 6 89 174 2.07 3 5 86 148 222 2.53 4 2 87 149 204 258 2.27 5 3 88 154 203 255 310 2.63 6 2 71 123 182 237 289 335 2.37 7 l 62 104 136 187 270 314 374 2.39 Mean Total Length (mm) at each annulus 86 152 208 243 296 328 374 Mean growth increment 86 66 56 35 53 32 46 68 TABLE A9.-~Mean calculated total length at each annulus for 29 black crappie from Spring Lake, Michigan Mean Calculated Length (mm) Age Number at Ages Coefficient Group in Sample of Condition 1 0 2 0 3 15 54 95 146 2.55 4 12 48 78 130 181 2.62 5 2 53 85 123 165 193 2.75 Mean Total Length (mm) at each annulus 51 87 138 179 193 Mean growth increment 51 36 51 41 14 69 TABLE A10.--Mean calculated total length at each annulus for 24 rockbass from Spring Lake, Michigan Mean Calculated Length (mm) Age Number at Ages Coefficient Group in Sample of Condition l 0 2 O 3 11 41 59 93 4.18 4 7 39 56 83 127 4.14 5 6 40 59 86 122 173 4.1 6 0 7 0 Mean Total Length (mm) at each annulus 40 58 89 124 173 Mean growth increment 40 18 31 35 49 70 TABLE A11.--Mean calculated total Jength at each annulus for 18 yellow perch from Spring Lake, Michigan Mean Calculated Length (mm) Mmb a: Group in Sample 1 2 3 4 5 6 7 1 l 62 1.75 2 6 64 97 1.79 3 4 68 95 137 1.80 4 3 63 86 130 168 1.84 5 2 67 91 119 160 206 1.88 6 0 7 2 73 102 144 189 230 263 294 1.85 Mean Total Length (mm) at each annulus 66 94 133 172 218 263 294 Mean growth increment 66 28 39 39 46 45 31 71 TABLE A12.--Mean calculated total length at each annulus for 11 northern pike from Spring Lake, Michigan Mean Calculated Length (mm) Age Number at Ages Coefficient Group in Sample of Condition 1 2 3 4 5 6 7 8 1 0 2 0 3 2 132 236 328 .61 4 1 105 177 336 424 .73 5 4 137 224 294 418 492 .88 6 2 98 172 263 368 468 516 .81 7 l 126 195 288 361 463 516 542 8 1 152 231 384 487 575 650 690 758 1.1 Mean Total Length (mm) at each annulus 126 210 306 409 493 550 616 758 Mean growth increment 126 84 96 103 84 57 66 142