Energy Reserves of Three Zoop Ankton Species from Two Lakes with Different Meta Concentrations

Energy Reserves of Three Zoop ankton Species from Two Lakes with Different Meta Concentrations

Michael T. Arts and W. Gary Sprules Dep~ftrnenbof Zoologv, Erlndaie College, Un~r/ersityof Toronto, Mi,>r>~auga,Ont. C5b IC6

Arts, tM. T., and W. G. Sprules. 1987. Energy reserves of three zooplankton species from two lakes with different metal concentrations. Can. 1. Fish. Aquat. Sci. 44: 458-466. Dry weight and lipid content sf three zooplankton species in two lakes differing in concentrations of copper, nic keB, and aluminum were assayed for tiyo consecutive summers. Epischura 1,acustris ;and Wolopediurn gibberurn had lower lipid levels and were generally lighter in the lake with elevated metals. 'The lipid droplet in eggs of H. gibberurn was 21 % smaller in the lake with elevated metal [evels. Total body burdens sf copper in W. gibberurn were twice as high in the lake with elevated metals. There was ~CPdifference in dry weight and levels of energy reserves of Didpeomu minutus between the lakes. Lower lipid content and decreased weight of E. lacustris and W. gibberuns fraamr Round Lake could wot be explained by lowered food availability, since both the edible portion of phytoplankton biomass and abundance of small Bosmirsa were similar in the two lakes. Since there were ns differences in food levels for E. lacujtrij and H. gibberurn in the two lakes, eve attributed lower energy reserves in these species to effects of heavy metal contamination.

Pendant deux 6tes consecutifs, on a d6termine le poids sec et la teneur en lipides de trois espPces de mooplanston pekeplant deux lacs & diffkrentes concentrations de cuivre, de nickel et d'alurniniurn. Dans Be lac A concentration @leveede metaux, Epischura lacustris et Molopedium gibberurn avaient des teneurs en lipides moins @leveeset leur psids etait en general plus faible. Bans les oeufs de H. gibberurn, les gouttelettes lipidiques Gtaient 21 % plus petites dans le cas du lac 2 concentration klevge de metaux. Les charges corporel[es totales de cuivre chez H. gibbeaunl 6taient deux fois plus elevkes dans ce dernier lac. Aucune difference relative au poids sec ou aux niveaux de reserves energetiques chez Biaptornus rnirautus n'a 6te relevee d'un lac ii J'autre. Une plus faible disponibilite de nourriture n'a pu expliquer la faible teneur en lipides et le poids inf6rieur de E. lacuseris et de H. gibberurn du lac Round car la partie comestible de la biornasse phytoplanctonique et I'abondance de petites Bosmir~a6taient semblables dans Bes deux lacs. Conime il n'existe aucune diiikrence' quant 2 la quantite de nourriture disponible pour E. Ic2custri_iet PI. gibberurn d'un lac B I'autre, on attribue les faibles r6serves her- getiques chez ces espPces aux effets de la contamination par des rn6taux Isurds.

Received November 6 5, 7 986 Accepted October 22, 1986 ( J85 70 )

riacylglycerols predominate as an energy reserve in vivo synthesis of triacylglycerols, in organisms from bacteria freshwater zoopiankton (Golaiden and Hsrniy 1980; to man, have shown that this enzyme can contain up to 98 Fagkas et al. 898 1; Gcserlden and Henry 1984). These sulfiydryl groups (Burton et a!. 1968, rats and pigeons). Hsu energy resenes play a critical role during periods of et al. (1965) demonstrated that the enzyme was susceptible to starvation (Lee and Barnes 19'75) and affect competitive ability heavy metal inactivation, since chelating agents such as EDTA among neonates (Gosslden and Henry 1984). Zooplankton sue- stimulated activity in the presence of heavy metals as much as cum$ quickly to starvation (Threlkeld 1976); thus, any inter- 200% over controls without EDTA. Thus, uptake sf heavy ference in the accumulation or synthesis sf these energy re- metals capable of inactivating the kitty acid synthetase complex serves could have important ecological consequences. occurs directly in the intestinal tissue. the major site of tri- Triacylglycerol synthesis may represent a target site for met- acylglycerol synthesis. The dry weight of some species, for al cations. Metal ions often exert their toxic effect on aquatic example Dlsphnisi Bairagna, is reduced in solutions of copper or organisms by binding to enzymes and forming transition-metal nickel (Biesinger and Christensen 1972) and nickel alone (Hall complexes, with complex stability largely determining the tox- 19801, and since triacylglycerols can contribute significantly to icity of the metal ion (Shaw 1961). Effects of metal poisoning the total dry weight (up to 25% in Hkalopediurn gibberurn). it on enzyme systems have been documented for sea urchin em- seems likely that some of this weight loss could be explained bryos (Tirnourian and Watchmaker 19729, crayfish (Hub- by fat loss. Alternatively, reduction in filtration rates in zoo- schman L967), and fishes (Crandall and Goodnight 1963; plankton exposed to metals (Flickinger et al. 1982) could result McKim et al. 1970; Jackirn et al. 1970; Jackirn 1973: Bryan in reduced food gathering ability and thus lower lipid levels. 1976). Triacylglycersl synthesis occurs primarily in the cells of Numerous estimates of lethal metal concentrations have been the intestinal wall (Gsulden and Henry 1984), an important site made using organisms such as Dsag~huia!(Bieseazger and Chris- of uptake for metals such as nickel (Hall 1980). Studies on the tensen 1972; Baudouin and Scoppa 1974; Winner and Fan-ell ubiiqtriitous fatty acid synthetase complex responsible for the in 1976; Shcherban 1977) and trout (Brown and Dalton 1970;

458 Can. 9. Fish. Ayuut. Sc-i., Vd.44, 1987 McKim and Benoit 197 1; Dmmmond et al. 1973). While these nizer. Centrifugation at 4588 x g for 15 min removed heavy studies outlined conditions associated uith short-term survival, carapace components. Triacylglycerols were separated by thin- chronic effects of toxins have rarely been assessed (however, layer chromatography on silica gel plates (kieselgel 606. E. see Winner and Fanell 1976; Borgmann et al. 1980). especially Merck Co.). The solvent system used was 90: 10: 1 6v/v) pe- under field conditions (Yan and Stms 1980). troleum ether - diethyl ether - glacial acetic acid (Malins and We measured triacylglycerol energy reserves (storage fats) Mangold 1960). Triacylglycerols were detected with iodine in three zooplankton species, Episcshlrr6~luc-srstv-is Forbes, and quantified calorimetrically (Pye Unisarn SP6) using a sul- Diaptcrmlrs minutus Lilljeborg. and Holspediscrn gibberams furic acid - dichromate reagent (Arn~enta1964). Trjipalmitin Zaddach. common to a metal-contanainated and an uncon- standard was used for calibration. taminated Iake in central Ontario. These species occur in 65, The availability of food naturally affects energy reserves in 43, and 6292, respectively. sf 666 lakes in norfheastem North organisms. Therefore, for both lakes. in 1982, we estimated America (Carter et al. 1980). Because of its wide geographical density of Bosmina lorzgir-sstris (8. F. hjuller), a small clado- range (Carter et al. 1980) and presence in acid and metal- ceran that is the major component sf the diet of E. 1ac.lrsrri.s stressed lakes (Spmles 1975: Yan and Strus 1980B, Dominutus (Wong 198 1 ). Roughly every 2 wk, two metered-hauls using appears to be a tolerant species. Based on geographical distri- the Wisconsin-style townet from bottom to surface over the bution, we predict that if chronic exposure to elevated metal center of the deepest basin were combined and preserved visith concentration affects triacylglycerols. then E. bacustris and H. 5% formalin. A microcon~puter-based measuring device gibbsr~nawould have Bower levels of triacylglycerols in the (Spmles et al. 1981) coupled to a dissecting microscope was metal-contaminated lake whereas B. ~nis~utaaswould show little used to determine densities of B. Iongirostv-is. or no difference between the lakes. Egg and fat droplet diameters of H. gibbpsraun were measured using a dissecting microscope (Wild-Leitz, M5) with an ocular Methods micrometer. As a rough index of algal food available to the herbivorous Two lakes were chosen for comparative purposes: Blue D. sninutus and H. gibb~rurra,the biolgaass of edible algae Chalk Lake in the Muskoka district of south-central Ontario, (<30 pm) was determined in both lakes. Samples were taken which has metal levels at or below the limits of detection of with a weighted Tygon tube 66 m x 1 cm) over the deepest standard atomic absorption methods. and Round Lake, 1-4 krn basin in the lake at approximately 2-wk intervals in 1981 southwest of Sudbury, Ontario, with substantially higher levels (May-August). Ten such integrated hauls were combined in a of copper, nickel, and aluminum. plastic bucket. A 100-mL aliquot was removed for phyto- Zooplankton for lipid analyses were obtained at roughly plankton analyses and preserved with Lugol's acidified iodine 2-wk intervals, from May to October in 1981 and May to solution. Five millilitres from this bottle was settled overnight August in 1982, by unmetered vertical townet hauls from bot- onto a microscope slide that had been pretreated with a gel to tom to surface at the center of the deepest basin. The large enhance adhesion of settled algae (Knoechel and Kalff 1976). zooplankters E. Bacustv-is and H. gibbsruraa were collected with Slides were desiccated over silica gel for 24 h. A drop of 10% a tapered net, length I .5 m with a 1-rn' opening, and 1 mm glycerol in water was added after which slides were preserved mesh (Nero 1982). This net was used to advantage for E. by sealing the edges of the coverslip with nailpolish. Counting lacaastris, since this species can avoid smaller nets and rarely was done by transects on a binocular. inverted, conapound achieves densities in excess of 1.5 animals/&. A Wisconsin- microscope (Leitz b'etzlar, Diavert). Phytoplankton were di- style townet with 30- and 45-cm hoops and 153-pm mesh was vided into four groups - unicells. colonies <30 pm in di- used to collect the smaller, more abundant B. rnirzaibus. Since ameter, colonies >30 pm in diameter. and filaments <30 pm zooplankton with broken appendages leak significant quantities - and placed in 1.4-pm size intervals based on cell size of storage fat (pers. obs.), both nets were equipped with deep (longest dimension). Biovolul-nes derived from simple geo- Plexiglas buckets (20 x 7.5 cm) having two small windows (7 metric models were converted to biomass using a specific x 4 cm of 153-pm mesh) to minimize mechanical damage. gravity of unity. In this way, biomass estimates (wet weight) Zooplankton were anaesthesized with carbonated water were made for each size class within a group. Summation of within 4 h of collection and adults of the three species separated these weights for unicells, colonies. and filaments less than under a dissecting microscope. Cladocerans and copepods were 30 p.m was used as an index of edible algal food available. Identified using Brandlova et al. (1972) and Smith and pH was measured at 2-m intervals from bottom to surface Fernando ( 1978), respectively. The calanoid E. lucustris was over the center of the deepest basin every 2 wk from May to separated by sex. Only living, intact animals were selected for August in both 1981 and 1982. In 1981, pH was measured with subsequent analyses, i.e. those that continued twitching under a Hydrolab water monitoring system (Surveyor model 5) anaesthetic or that had beating hearis. Bead animals, or those whereas in 1982, a portable field meter was used (Corning with broken appendages, were not used. model 3D). After separation, zooplankton were quickly frozen in plastic Water from the consolidated Tygon tube samples was stored scintillation vials dipped into a propanol dry-ice bath. The in acid-washed 1-6, Nalgene bottles for metal analyses. A samples were then freeze-dried and stored at -30°C under 100-mL aliquot from these Nalgene bottles was acidified by nitrogen. Prior to lipid extraction, animals were counted and adding 0.5 m& of nitric acid (BBH-Aristar grade). The aliquot weighed on an electrobalanee (Cahn-4401). Between 0.40 and was then evaporated to 5 mL in a 95°C oven. Copper, nickel, 0.70 mg of E. /acustris, 6). f 6 and 0.22 mg of D.mksautus, and and a%uminunawere measured by inductively coupled plasma 8.58 and 1.30 mg of H. gibberuppa tissue (dry weight) were atomic emission on a Jobin Yvon-48 spectrophotometer (MOE needed to obtain sufficient lipid for reliable measurement. 198 1 ). Detection limits were 1, 2, and 3 pg/& for copper, Total fat was extracted by homogenizing samples with 2: 1 nickel, and aluminum, respectively. (v/v) chloroform-methand in a hand-held glass homoge- All three zooplankton species were segregated in an attempt

Can. J. Fish. Aqwr. Sci., Fol. 44, I987

fig DRY WEIGHTIANIMAL JJg DRY WEBGHT/ANIMAL Fss. 1. Triacylglycerol (TAG) levels and dry weights for E. Iacusbris. (a) males and (b) females during a 2-yr period from Blue Chalk Lake (open squares) and Round Lake (solid squares). Model [I regressions are shown.

TABLE3. Regression equations (mode I) and analyses of covxiasace for fat versus weight data presented in Fig. 1, 3, and 5. *Indicates significant differences.

Ho: equal Blue Chalk Wound slopes Slope Intercept Slope Intercept F prob > F

Male Epischerm 0.16 -1.26 -0.01 1.05 13.01 0.000" Female Episckurw 0.13 -0.78 -0.04 2.68 25.62 0.0001* Hslopedium 0.01 -0.41 0.03 -0.90 41.52 O.CBWI* Biaptomus 0.65 -0.87 0.76 - 1.40 4.22 0.0414*

FIG. 2. Seasonal pattern sf energy reserves for (a) males and (b) females from Blue Chalk (stippled) and Round (hatched) lakes pooled for two summers. The solid lines are boundaries representing the minimum and maximum TAG levels recorded on each date.

the pattern of lipid allmation for Round Lake H. gibberurn is coated with a ""surface" growth resembling a fungus. By con- page of a normal continuum, rei'lecting genetic differences be- trast, Blue Chalk H. gibberkam persisted until October and tween the two populations. It is, however, difficult to conceive ultimately attained levels of storage fats five times greater and of a "natural9' selective force that would result in a population body weights three times greater (Fig. 3 and 4) than maximum composed entirely of individuals with low fat content. Never- values recorded for H.gibberurn from Round Lake. The greater theless, potential for growth during development, and perhaps weights attained by Blue Chalk H. gibberurn are csnsistent ultimate size, must surely be affected by lipid stores present with findings that B. magna was lighter after laboratory ex- during initial, critical periods of development. There remains a posure to acute concentrations of nickel (Hall 1980) and possibility, then, that this reduction in energy per egg is related chronic levels of copper or nickel CBlesinger and Christensen to metal-induced stress and could account for absence sf H. 1972). gibberurn neonates in June -Jul y in Round Lake. In 1982, Blue Chalk H. gibberkam reproduced partheno- In both years, H. gibberurn from Round Lake persisted only genitally until October, at whish point opaque resting eggs until midJuly and had amassed on the lakes' windward side. were produced. 'P1-aroughout summer. females were found Individuals were observed to move only feebly and many were carrying eggs with at least three, and occasionaIly all five,

&'an. I, Fish. Aquat, Sci., hi.44, 1987' 46 1 TABLE4. Selected reproductive parameters (se in parentheses) of female Holopediunl gibberurn caving stage one eggs."

96 females Mean no. Mean female Egg diaan. Meran fat Bate with eggs eggs/fernale length (mm)\pm) diam. (pm)

20 May 1982. 9.8 9.2 1.4 192.3 83.9 Blue Chalk (0.9) (0.02) (1.5) (0.9) 19 May 1982, 2.5 3.9 0.8 166.5 77.7 Round (0.3) (0.01) (1.4) (1. 1) "Mean number of eggs/fernale and mean female length are significantly different between Iakes (p< 0.05, t-test modified for unequal variances, Sokal and Rohlf, 1981), as are mean fat volumes and egg size (p < 0.001, t-test); rm = 50 in each case. 'Segment defined by a point just above the eye, to the most posterior tip of the carapace (refered to as the core body length). These measurements for egg-carrying females only.

58 100 150 20 8 FIG. 4. Seasonal pattern of energy reserves for I%. gibberurn from Blue pg DRY WEBGHT/ANIMAL Chalk (stippled) and Round (hatched) lakes pooled for two surn~ners. The solid lines are bcrundaries representing the minimum and max- FIG.3. Log TAG kvels and dry weights far H. gibberem obtained imumTAG levels on each date. over a 2-yr period from Blue Chalk Lake (open circles, 23 hidden observations) and Round Eake (solid circles, - 10 Ridden observations). Model II regressions are shown. developmental stages represented (Threkeld 1979). Round Eake females, by contrast, produced only one parthenogenic summer generation. followed immediately by production of overwintering eggs in June. The skannrner generation attempt was deemed a failure for three reasons: (1) no females were found in May or June carrying eggs later than stage two; (2) no new neonates were seen entering the population in May-July; and (3) production of resting eggs in June was followed by a sharp population decline to complete disappearance by mid- July. Thus, as apposed to Blue Chalk animals, this population did not persist into the fall to utilize the renewed algal growth stimulated by fall turnover. FIG. 5. TAG Ievels and dry weights for D.rninueus obtained over a M. 2-yr period from Blue Chalk Lake (open triangles) and Wound Lake Copper levels in tissues of gibberurn from Round Lake (solid triangles). Model 11 regressions are shown. were roughly two times greater than those for H. gibberurn from Blue Chalk Lake (Table 5). Round Lake H. gibberurn had concentratians of copper that were B -5-3 times greater than H. gibberkern from Round Lake favor the hypothesis that ob- those found in zooplankton of the Sudbury drainage system, sewed differences in lipid accumulation are due to metal stress. undoubtedly reflecting higher levels of copper in waters of The manner of population deterioration and the small size of H. Round Lake (Table 5). Although H. gibberurn from Round gibberam from Round Lake is reminescent of suggestions of Lake experience elevated total body burdens of copper, it does CrandalB and Godnight ( 1963) and Bryan (1976) that severe not always follow that there is a positive comelation between inanition produced by metabolic lesions can cause an inhibition body burden and toxic effect of copper (Brown 1977; Dixon of normal growth. and Sprague 198 1; Winner 1985). The observed reproductive impairment (absence of late developmental stages), reduced lipid volume in eggs, the manner Contrary to findings for E. Hwcu,~lrisand H. gibberurn, of population decline, and elevated copper levels in tissues of D. minutus showed no consistent effects of lake of origin on

Can. J. Fish. Ayuat. Sci., Vol. 44, 1987 T.~BLE5. Copper levels in the water (p,g/L) and the tissues of zooplankton (pgig dry weight) taken from various locations. All zooplankton analyzed are mixtures of all species present except for Blue Chalk and Round lakes, which were H. gihbrrurn only.

Concn. in Consn. in Location water (kg/L)" animals (pg/g) Source Ontario Wanapitei River 32.5 Hutchinson et al. 1976 Hartley Bay 36.0 Western Outlet 24.0 Main Outlet 22.0 East Outlet 16.0 French River 12.0 Pickerel River 15.0 Blue Chalk Lake 21.6 This study (1982) Round Lake 57.6 This study ( 1982) 48.2

30 - 661 Gachter and Gcigcr 1979 "The Sudbury drainage system (Ontario) and Bluc Chalk and Round lakes are average summer values. hEsfirnated from Fig. 1.

TABLE6. Mcan sephalothorax length and mean number of eggs/fernale (SE in parentheses) for D.rnital.ms from Blue Chalk Lakc and Round Lake in 1982. Sample size was 20 in all cases cxccpt for Round (2 June) when it was 8.

Date Mean Mean no. Lake ( 1982) length (rnm)" eyys/femaIe Blue I I May Chalk 20 May 28 May 3 June FIG. 6. Seasonal pattern of energy reserves for D. rnirrufmrs from Blue Round 2 June Chalk (stippled) and Round (hatched) Iakes poled for two summers. 16 June The solid lines are boundaries representing the w~imurnand maximum 1 July TAG levels recorded on each date. 15 July 4 August triacylglycerol content (Fig. 5 and 6). Analyses of covariance "Length refers to egg-bearing females only. on the regressions demonstrated that the differences between the slopes were significant. although not nearly as pronounced as for the former two species (Table 3). naked green algae, cryptomonads, nannoflagellates, and cer- The patterns observed foe E. kasustra's and H. gibberurn were tain diatoms, whereas large unicellular algae, colonHaH forms, or forms possessing a gelatinous sheath remain unaffected not seen for D. mkn~t~sfrom Round Lake. Rather, the two regression lines broadly overlap and intersect near their mid- when grazing pressure is artifically increased (Porter 1979). points (Fig. 51, suggesting that the slight difference in slope is Several authors have stressed the irnpofiance of nannoplankton as a food source for grazers (Nadin-Hurley and Duncan 1976; more the result of normal between-lake variation in lipid stor- 88 age ability and different sampling times than consistent differ- Gliwicz 1977; hIeGauley and Kalff I I ) and specifically ences between D.minutus' ability to accumulate storage lipids those species less than 30 Frn (Geller and Muller I98 1; Ross in the two lakes. There was no suggestion of gross perturbation and Munawar 198 1 ; Gates et al. 1983; Chow-Fraser 1985). pm) of the reproductive pattern of D.mistsatus in Round Lake, since Biomass sf small "edible9' phytoplankton (<30 was egg-carrying females were present throughout the season carry- monitored every 2 wk in I981 (Fig. 7). Based on a single sample per date, the two lakes do not show large differences in ing clutches roughly equal in size ts late May - early June clutches in Blue Chalk Lake (Table 6). Although gravid the seasonal pattern of edible algal biomass. This suggests that females appeared later in Round Lake, they persisted longer, food availability alone canot account for the lower levels of lasting 2 mo compared with only 3 wk in Blue Chalk Lake triacylglyceeol found in E. locnasais and Ho%opedisamin Round (Table 6). Lake. This conclusion is tentative, since we have no data on nannoplankton production rates or the nutritional quality of Fsod Densities different species. Mouthpart morphology (Friedman 1977; G. M. Wong, Insti- Biomass of available food influences the accurnulatlon of tute sf Ocean Sciences, Sydney, B .C., pers. comna.) and guts energy stores. Grazers readily consume small algae such as containing both algae and zooplankton indicate that E. lacnastris

Can. J. Fish. Aquut. Sci., Vol. 44, 1987 MAY JUNE JULY AUGUST

MONTH FIG. 7. Biomass of edible algae (<30 ~m)in BBue Chalk (open circles) and Round (solid circles) lakes in 1981. is omnivorous. In laboratory feeding experiments, E. bacus~ris clearly denaonstrates a nutritional requirement for invertebrate zooplankton prey (Main 1962) and, in particular, for the clado- ceran B. 10ngircastris (Wong 1981 ) , selecting this species over other cladocerans such as Ca-ip-kodaphlaka QWong 1981) and Dqhrzin amB9s'graa (Kerfoot 1977). The small "feeding basketq' formed by mouthparts of E. lactasrris means that only B. &oragi~-ostris.less than 0.40 mrn can be effectively handled (Keffoot 1977 BVong 1981). The con- tinuous availability of B. bsngirostrks (<0.40 mm) in Round Lake, at densities matching those in Blue Chalk Lake (Fig. 81, is nat surprising, since this zooplankter is encountered fre- quently in acid- and/or metal-stressed lakes (Haines 198 1) and can attain a much greater percentage of total crustacean biomass in acid lakes contaminated with copper and nickel than in fi- B - comparable taw metal, circumneutral lakes (Plan and Strus MAY JUNE JU LY AUGUST 1980). Thus, food ?imitation, in this case B . lo~agirostrts,does FIG.8. Seasonal density of B. Iortgs'rostrds in Blue Chalk (open cir- not explain the reduced triacylglycerol levels found in E. lacus- cles) and Round (solid circles) Bakes in 1982. fris from Wound Lake when compared with conspecifics from Blue Chalk Lake. valuable comments on earlier drafts of the manuscript. 6. M. Csurtin, P. A. Horgen, W. W. Nero, and B. I. Roots provided logistic support. Implications We extend our gratitude to the people of the Whitefish Lake Indian Interference in the accumulation of triacylglycersls would Reserve who kindly gave us permission to study Wound Lake. C. W. clearly affect the ability of zooplankton to endure periods of Ramcharan lent freely of his cornputor expertise. We are especially food shortage. Loss of certain sensitive species of zooplankton grateful to W. Norwcwad and AI. Pasitschniak-Arts for their fireless field assistance. This study was suppofled by operating grants to due to heavy metal contamination may result in alterations in W. G. Spmles from the Natural Sciences and Engineering Research the paths of energy flow through trophic levels. The loss of H. Council of Canada and the Canadian National Sportman's Fund and gibberusn and/or E. /acus&ris,when comgbined with possible by a Natural Sciences and Engineering Research Council CentenniaE losses of sensitive Dapbmraia spp., represents a reduction in the Scholarship to M. T. Arts. food base for planktivorous fish. This reduction in forage may further aggravate effects of metals in fish, since animals in por References physiological condition succumb to lower levels of metals than "healthy" individuals (Bryan 1976). &~MENT.~,J. %. 1964. A rapid chemical method for quantification sf lipids separated by thin-layer chromatography. 6. Lipid Wes. 5: 270-272. ARTHUR,T. W.. AND E. N. LEONARD.1970. Eff~Bsof COppr Ow GuM~~~~P-us Acknowledgments psmaedolineeus, Physa integra and Campelornu decisurn in soft wafer- J. Fish. Res. Board Can. 27: 1277- 1283. We are most grateful to 8. L. Baker, U. Borgmann, N. C. Collins, BALI~UBN,M. F., AND P. SCOPPA.1974. Acute toxicity sf various metals to H. H. Harvey, T. C. Hutchinson, and A. B. Zimmerrnan for their freshwater zooplankton. Bull. Environ. Contam. Toxicol. 12: 745-75 1.

464 Can. 9. Fish. Aqmaot. Sci., Val. 44, 1987 BEAMISH,W. 5.. G. A. MCFARL~NE.J. C. VANLOON, AND 1. LICMWA.1975. Ont. 894 p. An examination of the possible effects of Sudbury nickel mining and Hsu, R. Y., 6. WASSON,AND J. W. PORT~R.1965. The purification and snaelting operations on fishes and water chemistry of lakes within the properties of the fatty acid syathetase of pigeon Fiver. J. Biol. Chem. 240: Whitefish Lake Indian Reserve. Can. Dep. Emviron. Fish. Mar. Serv. 3736- 3746. Tech. Rep. 549: 52 p. HUBSCHRI~ZN.5. H. 1967. Effects of copper on the crayfish 0rc.cbnecres rusra'csrs. BIES~GER,#. E., AND G. M. CHRISTENSEN.1942. Effects of various metals on Cmstaceana 12: 141 - 150. survival. growth, reproduction and rnetabolism of Daplmiu nrugrmha. J. ~IJTC~~~NSON,T. C., A. FEDOR~NKO,J. FITCIIKO, A. KUJA,J. $14~LOON, AND Fish. Rcs. Board Can. 29: 169 1 - 1700. J. Lnc~w~.1976. Movement and compartmentation of nickel and copper BIRGE,W. %., AND J. A. BLACK.l98O. 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Can. J. Fish. Aqlrad. Sci., bl. 44, 1987 WINNER,R. W. 1985. Bioaccumulation and toxicity sf copper as affected by WONG,C. K. 1981. Predatory feeding behaviour sf Epischuacl lucusfais (Go- interactions between humic acid and water hardness. Water Res. 19: pepoda, Calanoida) and prey defense. Can. J. Fish. Aquat. Sci. 38: 449-455. 275 - 279. W~NNER,R. W., AND M. P. FARRELL.1976. Acute and chronic toxicity of YAN,N. B., AND R. Smus. 1980. Crustacean zooplankton communities of copper to four species of Daphnin. J. Fish. Res. Board Can. 33: acidic, metal-contaminated lakes near Sudbury, Ontario. Can. J. Fish. 1685-1691. Aquat. Sci. 37: 2282-2293.

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