0 Feeding interactions between native freshwater mussels (Bivalvia: Unionidae) and zebra mussels (Dreissena polymorpha) in the Ohio River Bruce C. Parker1, Matthew A. Pattersoni, and Richard J. Neves2 1 DepartmentofBiology, VirginiaPolytechnic Institute andState University, Blacksburg, Virginia24061, U. S. A. 2 Virginia Cooperative Fish and Wildlife Research Unit, Department ofFisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, U. S. A. Abstract: Theeffectsofzebramussel infestationon thefeedingofnative unionids in the OhioRiverwereevaluatedthrough gutcontentsandavailable food in the watercolumn. In 1996, heavily infestedAmblemaplicata (Say, 1817) and Quadrulapustulosa (I. Lea, 1831) had significantly less (p <0.01) organic matterin theirguts(1.4and0.6mg ash-freedry weight [AFDW],respectively) than lightly infested specimens(4.6and 1.8 mg AFDW,respective- ly),andheavily infestedQ.pustulosahadasignificantly lower(p<0.05)mean algal cell number(1.8x 104) inthegutsthan lightly infestedspecimens(3.9 x 105). However, mean algal cell numbers in the guts ofheavily infested and lightly infestedA.plicata (5.7 x 105 versus 9.1 x 1 s, respectively) were not significantly different(p=0.17). In 1997, significantreductions(p<0.05) in total algal cells andorganic matteringut samplesagain occurred forheavily versus lightly infested individuals ofboth species. In addition, gut contents ofindividual A. plicata from one oftwo sites containedsignificantly less (p< 0.05)organicmatter(0.92versus4.55 mgAFDW)andfeweralgalcells(9.4x 104versus2.3 x lO5)thanthecombinedgutcontentsofall zebramussels(18- 33 mm in length) attached to their shells. Gut analyses also revealed significant diet overlap between native unionids and infesting zebra mussels. Water samplescollected fromjust above the mussel beds in 1997 showed that algal densities and total suspended solids at the heavily infested site (> 360 zebra mussels/m2)werereducedbymorethan50%,whencompared tosamplescollected from thesurface.Thus,competitive interactionsorinterferenceby zebra musselslikelyreducedtheavailabilityofalgal anddetritalfoodresourcesforconsumptionbyunionids. Key words: algae,zebramussels,unionids,OhioRiver,competition Since its introduction into Lake St. Clair, the zebra Mackie, 1994; Nalepa, 1994; Schloesser and Nalepa, mussel, Dreissena polymorpha (Pallas, 1771), has greatly 1994). By attaching to the shells ofunionids, zebra mussels reduced phytoplankton and bacterioplankton levels in the can directly affect unionid survival by interfering with Great Lakes (Wu and Culver, 1991; Maclsaac et a!., 1992; feeding, respiration, balance, burrowing, and locomotion Cotner et al, 1995; Fanslow et al, 1995; Heath et al, (Mackie, 1991; reviewed by Schloesser et al, 1996). Large 1995). Phytoplankton levels in Lake Erie, for example, densities ofzebra mussels, however, also can affect unionid dropped 62-92% (Leach, 1993), and planktonic diatoms survival indirectly by reducing or removing food resources decreased 85% despite sufficient nutrients for growth from the water column (Lewandowski, 1976; Hebert et al., (Holland, 1993). Consequently, Secchi disk transparencies 1991; Mackie, 1991; Haag etal, 1993). A large gill-area to in Lake Erie have increased 85% (Leach, 1993). body-dry-weight ratio, and a large number of gill cirri in Phytoplankton grazing by zebra mussels also can alter the individual zebra mussels, allow for increased filtration effi- composition of the phytoplankton community. In Lake ciency and filtration rate relative to those ofnative unionids Huron, forexample, zebra mussel feeding has shifted domi- (Silverman et al, 1995). Filtration rates of the freshwater nance from diatoms to filamentous green algae (Lowe and mussel, Lampsilis siliquoidea (Barnes, 1823), for example, Pillsbury, 1995), and recent studies show selective rejection were found to be only one-tenth the filtration rate of indi- of the nuisance bluegreen alga Microcystis by zebra mus- vidual zebra mussels (Heath et al, 1995). In laboratory sels, such that Microcystis becomes dominant in the plank- experiments, Baker and Hornbach (1997) reported that ton (H. Vanderploeg, NOAA, pers. comm.) Amblemaplicata (Say, 1817) filtered 74 ml/hr, while the 28 Zebra mussel colonization of the Great Lakes also infesting zebra mussels filtered 130 ml/hr as a group. Thus, has caused dramatic declines in the survival and fitness of relatively small populations of zebra mussels can affect the native freshwater mussel populations (Hebert et al., 1991; feeding ofunionids. Hunter and Bailey, 1992; Haag et al., 1993; Gillis and Zebra mussel populations in the lower Ohio River AmericanMalacological Bulletin,Vol. 14(2)(1998):173-179 173 174 AMER. MALAC. BULL. 14(2) (1998) have achieved densities comparable to those in the Great Whatman GF/F filters, dried (100°C), and ashed (500°C) to Lakes (350,000/m2; A. Miller, USACOE, pers. comm.). determine the ash-free dry weight (AFDW) ofseston. Because ofdocumented impacts to the phytoplankton com- Gut contents of unionids and of zebra mussels munities and native mussel populations ofthe Great Lakes, attached to Amblema plicata were individually removed large populations of zebra mussels in the Ohio River could from each specimen, pooled, then suspended in 3 ml of have similar consequences for native mussel populations. water, and fixed with 50 pi of acid Lugol's solution for Strayer and Smith (1996) found that low zebra mussel analysis. A 50 ul aliquot ofthe gut contents was placed on infestation rates in the Hudson River were associated with a microscope slide. Ocular grids divided the field of view high unionid mortality and hypothesized that reduced food into 59 transects, and algal cells were counted and identi- resources might be the cause. No studies, however, have fied to genus from two transects using an directly confirmed whether zebra mussels affect the feeding Ausjena/Nomarsky microscope at 400X. The variability of ofunionids in a riverine environment where organic materi- this semi-quantitative method (± 20%, a = 0.05) was deter- als are continually supplied from upstream. Thus, the mined using ten counts from the same sample. The remain- objective of this study was to determine whether zebra ing gut contents were collected on pre-ashed Whatman mussels reduce unionid ingestion of phytoplankton and GF/F filters, dried (100°C), and ashed in a muffle furnace organic matter by (1) ingesting similar food resources, and (500°C) overnight to determine AFDW. Mean algal cell (2) reducing food resources at the sediment-water interface. numbers and mean AFDW values in the gut samples of each species were compared by ANOVA. METHODOLOGY RESULTS On 23 July 1996, ten specimens each of the three- ridge, Amblemaplicata, and the pimpleback, Quadrulapus- In 1996, significant differences in total algal cells tulosa (I. Lea, 1831), were collected from a lightly infested and organic matter were observed in guts of lightly and site on the Ohio River near Parkersburg, West Virginia, heavily infested unionids (Table 1). While mean algal cell which had a mean density of 0.3 zebra mussels/m2, and a numbers in guts of lightly and heavily infested Amblema maximum of one zebra mussel/unionid (P. Morrison, plicata (5.7 x 105 versus 9.1 x 105 cells) were not signifi- USFWS, pers. comm.). On 16 August 1996, ten specimens cantly different (p = 0.17), the gut contents oflightly infest- of A. plicata were collected from a heavily infested site edA. plicata had significantly more (p < 0.01) organic mat- nearPaducah, Kentucky, which had 3,600 zebra mussels/m2 ter (4.6 mg AFDW) than heavily infested specimens (1.4 (A. Miller, USACOE, pers. comm.). Specimens ofQ. pustu- mg AFDW). Heavily infested Quadrula pustulosa showed losa were difficult to find at this site, so on 21 August 1996, significantly lower (p < 0.05) organic matter and mean ten specimens were collected from another heavily infested algal cell number (0.6 mg AFDW and 1.8 x 104 cells, site near Maysville, Kentucky, which had 360 zebra mus- respectively) than lightly infested specimens (1.8 mg sels/m2 and a maximum of 92 zebra mussels/unionid (P. AFDW and 3.9 x 105 cells, respectively). Morrison, USFWS, pers. comm.). In the field, mussel bod- In 1997, significant reductions in organic matter ies were removed from shells, weighed, preserved in 95% content and total algal cells also were observed in guts of ethanol, and transported tothe laboratory foranalysis. heavily infested unionids (Table 2). Organic matter content In 1997, ten specimens each of A. plicata and Q. and total algal cells were significantly lower (p < 0.05) in pustulosa were collected from a highly infested (370 zebra the guts of heavily infested Amblema plicata (0.9 mg mussels/m2) and a lightly infested (< 1 zebra mussel/m2) site on the Ohio River for gmutmcontent analysis. In addition, Table 1. Meanalgal cell numberandash-freedry weight (AFDW; ±SD) all zebra mussels, 18-33 in length, attached to the in guts ofAmblemaplicara and Quadrulapustulosa heavily infested (H) shells of A. plicata were removed and preserved in 95% andlightly infested(L)withzebramussels, July-August 1996. mm ethanol for gut content analysis. Zebra mussels 18-33 in length were chosen, because it is difficult to remove the Species N AlgalCell Number AFDW(mg) etnitoinresitgeu,twactoentresntasmpolfessmwailtlheralignadeivwieduraelsc.olAltecteeadchfrcoomlletch-e A.plicata (L) 1 1 9.1 x 105±6.0x 105 4.6±0.9 the surface and overlying the mussel bed, fixed with acid A. plicata (H) 10 5.7x 105±4.9x 105 1.4±0.7 Lugol's solution (Saraceni and Ruggiu, 1969), and placed in settling chambers to compare the density and relative Q. pustulosa (L) 10 3.9x 105±2.8x 105 1.8± 1.0 abundance of algal genera using inverted microscopes. Q.pustulosa (H) 10 1.8x 104±9.2x 1Q3 0.6±0.3 Aliquots of 100 ml were then filtered through pre-ashed PARKER ETAL:. FEEDING INTERACTIONS 175 Table 2. Mean algal cell numberandash-free dry weight (AFDW; ±SD) matter (4.55 mg versus 0.92 mg, respectively) and twice as in guts ofDreissena polymorpha and ofAmblema plicata and Quadrula many algal cells (2.3 x 10s cells versus 9.4 x 104 cells, pustulosaheavily infested(H) and lightly infested(L) with zebramussels, respectively) than the specimen ofA. plicata to which they July-August 1997. were attached (Table 3). In addition, the dominant algal Species N AlgalCell Number AFDW(mg) genera - Chlorella, Cyclotella, Mougeotia, Melosira, and Scenedesmus - and range of cell sizes (4-70 um) in zebra A.plicata (L) 10 5.5 x 106±2.4x 106 5.1 ± 1.7 mussel guts were nearly identical to those in infestedA. pli- cata (Table 4). Relative abundances of algal genera within A. plicata (H) 10 9.4x 104±7.6x 104 0.9±0.8 zebra mussel guts were similar to relative abundances in Q. pustulosa (L) 10 1.9x 106± 1.3 x 106 2.0± 1.2 water samples collected from the riverbottom (Table 5). Q.pustulosa (H) 9 6.9x 104±7.3x 104 0.3±0.2 D.polymorpha 9 2.3 x 105±1.3x 10? 4.6±3.6 DISCUSSION Reduced food resources at the sediment-water inter- AFDW and 9.4 x 104 cells, respectively) than lightly infest- face can cause decreased growth rates in bivalves despite ed specimens (5.1 mg AFDW and 5.5 x 106 cells, respec- adequate food resources at the water surface (Frechette and tively). Significant reductions in both organic matter con- Bourget, 1985). This phenomenon could be particularly tent and total algal cells also were observed for heavily important for unionids in the lower Ohio River because infested (0.3 mg AFDW and 6.9 x 104 cells, respectively) zebra mussels occur in large densities at the sediment-water versus lightly infested (2.0 mg AFDW and 1.9 x 106 cells, interface and often attach directly to the shells of unionids. respectively) Quadrulapustulosa. In fact, water samples collected from just above the mussel AFDW Examination ofunionid guts in 1996 and 1997 indi- beds in 1997 showed that algal densities and at the cated thatAmblemaplicata and Quadrula pustulosa readily heavily infested site (> 360 zebra mussels/m2) were ingested a significant amount of detritus (ca. 90%) along reduced by more than 50% when compared to samples col- with algal cells between 4 and 80 um in length. Diatoms lected from the surface. Thus, it appears that zebra mussel (Bacillariophyta) and green algae (Chlorophyta) dominated densities in heavily infested sections ofthe Ohio Rivercon- gut samples, and the dominant algal genera in 1996 tribute to reduced food resources at the sediment-water (Chlorella, Cyclotella, Navicula, Melosira, and interface. Scenedesmus; Table 3) and 1997 {Chlorella, Cyclotella, Regardless ofreductions in total algal cell densities, Mougeotia, Melosira, and Scenedesmus; Table 4) were sim- the effects of zebra mussel infestation on unionid ingestion ilar. Usually, the relative abundance of algal genera within can be reduced if zebra mussels and unionids selectively unionid guts was very similar to relative abundances of feed on different food types. Currently, studies on selective algae in water samples collected from the river bottom feeding in bivalves appear to be inconclusive. Some authors (Table 5). Interestingly, the pennate diatom Synedra domi- have concluded that bivalves select food particles of high nated water samples at the lightly infested site (43%), but quality (Allen, 1914; Loosanoffand Engel, 1947; Shumway few if any of these > 100 um-long cells were found in the et al., 1985), while others have concluded that feeding is AFDW unionid guts. In 1997, algal cell densities and seston non-selective (Churchill and Lewis, 1924; Gale and Lowe, at the water surface (8.37 x 104 cells/ml and 9.0 mg/1, 1971; Bayne etal, 1976). Thus, selective feeding could be respectively) and above the mussel bed (8.42 x 104 cells/ml species dependent. Zebra mussels have been reported to and 9.0 mg/1, respectively) were nearly identical at the ingest a wide range of food particles between 0.7 and 450 AFDW lightly infested site (Table 5). Seston (5.0 mg/1) and urn (Mikheyev, 1967; Jorgensen et al., 1984). However, algal cell densities (2.2 x 104 cells/ml) overlying the mussel Sprung and Rose (1988) indicated that retention efficiency bed at the heavily infested site, however, were greatly in zebramussels is maximized for food particles between 5- reduced compared to samples taken from the surface (7.2 35 pm; Ten Winkle and Davids (1982) also concluded from mg/1 and 8.3 x 104cells/ml, respectively). gut content analysis that zebra mussels select particles In 1997, individual Amblema plicata collected from between 15-50 pm. In our study, zebra mussel gut samples the heavily infested site were infested with > 100 zebra contained food particles between 4-70 pm in maximum mussels/unionid, averaging 50 zebra mussels between 18 dimension. In comparison, Miura and Yamashiro (1990) mm and 33 in length. Gut contents of zebra mussels con- indicated that the unionid Anodonta calipygos (Kobelt, tained large amounts of detritus. Pooled samples of zebra 1879) ingests food particles between 0.5 and 100 pm. Like mussel guts contained five times more (p < 0.05) organic for the zebra mussel, maximum retention efficiencies were 176 AMER. MALAC. BULL. 14(2) (1998) Table 3. Percent relative abundances (SD) ofalgae in guts oflightly (L) andheavily (H) infested Amblemaplicata and Quadrulapustulosa collected from the Ohio River, July-August 1996. (+, presence [<2%]; absence). , Algae A.plicata A.plicata Q.pustulosa Q.pustulosa (L) (H) (L) (H) Chlorophyta Ankistrodesmus - - + - Chlamydomonas + - + - Chlorclla 15.3(8.7) 15.0(11.2) 42.3(18.8) 63.0(29.4) Chlorococcum + + + - Closterium - - + - Coelastrum - - + - Cosmarium - + - KJUfllMrft _|_ Mougeotia + + + _ Oedogonium - + - - Oocystis + - - _ Pcdiaslrum - + - _ Scencdcsmus 6.2(5.9) 5.2(4.7) 6.6(5.8) _ Schroedcria + - - _ Selenastrum - - + _ Spirogyra + - - - Staurastrum + - - Bacillariophyta Achnanthcs + - • - Cocconeis + - + - Coscinodiscus + + + - Cyclotclla 11.8(2.7) 45.1 (1 1.1) 7.0(3.8) 31.9(30.8) Cymbella + + + - Diatoma + - + - Fragilaria - - + - Goutphonema + Melosira 5.7(4.0) 16.0(11.0) 8.8(8.2) 2.8(6.4) Navicula 26.5(7.4) 2.2(0.6) 10.6(6.2) Nitzschia - - + - Pinnularia + + + - Pleurosigma - - + - Stcphanodiscus Surirella + _ _ _ Synedra + + + - Tabcllaria + - - - Cyanoprokaryota Chroococcus T Merismopedia + Oscillatoria + + Spirulina + Other Chronudina + Dinobryon + Pcridinium + + Chroomonas + found for intermediate-sized particles (5-30 urn). resources ofsimilarsize. Maximum filtration rates for the unionid Elliptio com- Relative abundances of algal genera ingested by planata (Lightfoot, 1786) also were found for particles zebra mussels and the two unionid species were very simi- between 4 and 5 urn (Paterson, 1984). In ourstudy, unionid lar to those in water samples collected immediately above gut analyses indicate that unionids ingest food particles the mussel bed, giving no evidence of selective feeding. between 4 and 80 urn in maximum dimension. Thus, zebra The only exception was the pennate diatom Synedra which mussels and unionids in the Ohio River ingest food was not readily ingested by unionids or zebra mussels, PARKER ETAL.: FEEDING INTERACTIONS 177 Table4. Percentrelativeabundances (SD)ofalgae in gutsofDrcisscnapolymorpha and lightly (L)andheavily (H) infestedAmblemaplicataandQuadrulapustttlosacollectedfrom theOhioRiver,July-August 1997. (+, presence [< 2%];-,absence). Algae A.plicata A.plicata Q.pustulosa Q.pustulosa D.polymorpha (D (H) (L) (H) f1Vi1r\rr\nhvt^ rAifnt/lvriilclit/f/u\usitoivfmnu11Ac li,f/jt/i/wtihijwy/u/t~/)iJf?i7t//>f#ii/c7iat Chlorella 1.7(1.4) 13.8(10.1) 9.6(8.8) 30.8(24.7) 37.5(16.8) Chlorococcum + + + + + Cosmarium — + Crucigenia — — + — — Gonium - - + — Mougeotia 40.6(7.5) 5.1 (7.0) 21.2(1 1.7) 5.3(9.3) 14.2(12.2) Oedogonium + — - — Pandorina + — + - - Pediasirum + + + + + Scenedesmus 9.5(3.6) 5.7(2.0) 8.2(5.9) 10.9(9.6) 13.9(10.7) Trebouxia + - — - - Bacillariophyta Coscinodiscus - - + - - Cocconeis — — + — Cyclotella 21.3(1 1.9) 38.5(18.6) 25.9(6.9) 16.2(12.7) 5.4(4.5) Diatoma + + ~ — Goniphottcnia + Melosira 13.7(9.2) 25.9(16.7) 17.6(9.4) 28.5 (18.3) 13.7(10.4) Navicula + + + + Siephanodiscus + + Synedra + Tabellaria + + Cyanoprokaryota Aphanocapsa + Chroococcus + + Oscillatoria + Other Pcridinium + probably because of its cell length of> 100 urn. In unionid mussel, unionid mortality thus far at various sites in the gut samples, Mougeotia, Cyclotella, and Melosira did lower Ohio River has been estimated at 20-40% (P. appear in slightly greater abundance than in water samples. Morrison, USFWS, pers. comm.). Interference with unionid Regardless of selective feeding, unionid and zebra mussel feeding by zebra mussels, however, also could have long gut contents contained a nearly identical assemblage of term consequences for the overall fitness ofnative mussels. dominant algal genera. Thus, by ingesting food particles of Recent studies have shown that native unionids from the similar size and type, zebra mussels in the Ohio River can heavily infested Ohio River have significantly reduced compete directly with native unionids for food resources. glycogen levels relative to unionids from lightly infested However, competition can only be confirmed if the food areas (Patterson et al, 1997). Glycogen is an important items measured to assess diet overlap constitute a signifi- energy reserve for animals, especially bivalves (de Zwann cant portion of the total diet of one of the potential com- and Zandee, 1972; Barber and Blake, 1981; Bayne and petitors (Buss and Jackson, 1981). Unfortunately, there are Newell, 1983; Haag etah, 1993), and significant reductions no studies on the dietary or nutritional requirements of can lead to chronic mortality or declines in reproductive freshwatermussels. success. Gonad development in marine bivalves, for exam- Significant reductions in the mean AFDW and ple, has been shown to continue despite reduced energy total algal cell numberfrom gut samples ofheavily infested reserves (Gabbott and Bayne, 1973; Bayne, 1975), but sub- versus lightly infested native freshwater mussels indicate sequent growth rates and energy reserves ofthe developing that interference competition for food resources is occur- larvae decreased (Bayne, 1972; Helm etal., 1973; Bayne et ring in the lower Ohio River. Since the arrival of the zebra ah, 1975). Thus, by reducing food resources and interfering 1 . 178 AMER. MALAC. BULL. 14(2) (1998) Table5.Percentrelativeabundancesofalgaeatthesurfaceandjustabove zebramussel (Dreissenapolymorpha) infestation on two unionid themusselbedintheheavily(H)andlightlyinfested(L)OhioRiver,July- mussels, Actinonaias ligamcnlina and Amblema plicata. August 1997.(+,presence [<2%];-,absence). CanadianJournalofFisheriesandAquaticSciences54:512-519. Barber, B.J.andN. B. Blake. 1981. Energystorageandutilizationinrela- Algae Surface Bottom Surface Bottom tion togametogenesisinArgopectenirridiansconcentricus(Say). (L) (L) (H) (H) Journal ofExperimental Marine Biology and Ecology 52:121- 134. Chlorophyta Bayne, B. L. 1972. Someeffectsofstress in theadulton thelarval devel- Ankistrodesmus + opmentofMytilusedulis.Nature237:459. Chlamydomonas 6 5 16 1 Bayne, B. L. 1975. Reproduction inbivalve mollusksunderstress.In: The Chlorella 10 8 25 23 Chlorococcum + 2 + 7 Physiological Ecology ofEstuarine Organisms, J. Vemberg, ed. Gonium + _ _ pp. 259-277. UniversityofSouthCarolinaPress,Columbia,South Mougeotia 8 2 6 5 Carolina. Oedogonium + + _ + Bayne, B. L. and R. C. Newell. 1983. Physiological energeticsofmarine Pediastrum + + _ + molluscs.In: TheMollusca, Vol. 4, Physiology, Part I, A. S. M. Scenedesmus 12 16 13 12 Saleuddin and K. W. Wilbur, eds. pp. 407-515. Academic Press, Staurastrum NewYork. Bayne, B. L., P. A.Gabbott, andJ. Widdows. 1975.Someeffectsofstress Bacilariophyta in the adult on the eggs and larvae ofMytilus edulis. Journal of Coscinodiscus _ + + + theMarineBiologicalAssociationoftheUnitedKingdom55:675- Cyclotella 4 5 3 13 689. Diatoma + + + Bayne, B. L., R. J. Thompson, and J. Widdows. 1976. Physiology I. In: Melosira + 2 4 5 MarineMussels, Their EcologyandPhysiology, B. L. Bayne,ed. Navicula + + pp. 121-206.CambridgeUniversity Press,Cambridge. Sicphanodiscus + + + Buss, L. W. and J. B. C. Jackson. 1981. Planktonic food availability and Synedra 12 43 1 1 10 suspension-feeder abundance: evidence of in situ depletion. Journal ofExperimental Marine Biology and Ecology 49:151- Cyanoprokaryota 161. Chroococcus 2 + 7 Merismopedia 8 7 Churchill, E. P. and S. I. Lewis. 1924. Food and feeding in freshwater Oscillatoria + 6 3 3 mussels.Bulletinofthe UnitedStatesBureauofFisheries39:439- 471. Other Cotner, J. B., W. S. Gardner, J. R. Johnson, R. H. Sada, J. F. Cavaletto, Mallomonas and R. T. Heath. 1995. Effectsofzebramussels (Dreissenapoly- morpha) on bacterioplankton: evidence for both size-selective consumption and growth stimulation. Journal ofGreat Lakes Research21(4):517-528. with normal feeding, zebra mussels could have their great- de Zwann, A. and D. I. Zandee. 1972. Body distribution and seasonal est effect on the long-term persistence of unionid beds in changesin theglycogen content of the common sea mussel the lower Ohio River through reduction in reproductive Mytilus edulis. Comparative Biochemistry and Physiology success and recruitment. 43A:53-58. Fanslow, D. L.,T. F. Nalepa,andG. A. Lang. 1995. Filtration ratesofthe zebra mussel (Dreissena polymorpha) on natural seslon from Saginaw Bay, Lake Huron. Journal ofGreat Lakes Research 21(4):489-500. ACKNOWLEDGMENTS Frechette, M. andE. Bourget. 1985. FoodlimitedgrowthofMytilusedulis L. in relation to the benthic boundary layer. CanadianJournalof We thank Patty Morrison, Mitch Ellis, and others at the Ohio FisheriesandAquaticSciences42:1166-1170. RiverIslands National WildlifeRefuge, as well asDr. Andrew Millerand Gabbott, P. A. and B. L. Bayne. 1973. Biochemicaleffectsoftemperature the United States Army CorpsofEngineers forhelp incollecting mussels and nutritive stress on Mytilus edulis. Journal ofthe Marine from the Ohio River. Thanks also go toCatherine Gatenby and the many BiologicalAssociationoftheUnitedKingdom53:269-286. volunteers who assisted with collection and processing ofmussels in the Gale,W. F. and R. L. Lowe. 1971. Phytoplankton ingestionbythe finger- field. Additionally, we thank Ashleigh Funk, Lana Shurts, and Doug nail clam, Sphaerium transversum (Say), in pool 19, Mississippi Smithforlaboratoryassistance.ThisstudywasfundedbyQuickResponse River.Ecology52(3):507-513. FundsoftheBiological ResourcesDivision,U.S.GeologicalSurvey. Gillis, P. L. and G. L. Mackie. 1994. Impact of the zebra mussel, Dreissenapolymorpha,on populationsofUnionidae(Bivalvia) in LakeSt.Clair.CanadianJournalofZoology72:1260-1271 Haag, W. R., D. L. Berg, D. W. Garton, and J. L. Farris. 1993. Reduced survival and fitness in native bivalves in response to fouling by LITERATURE CITED the introduced zebra mussel (Dreissenapolymorpha) in western Lake Erie. CanadianJournal ofFisheries andAquatic Sciences Allen, W. R. 1914. The food and feeding habits offreshwater mussels. 50:13-19. Baker, SB.ioMl.ogaicnadlDB.ullJ.etHinor2n7b:a1c2h7.-14179.97. Acute physiological effects of Heath, RH.wTa.,ngG.. L1.99F5ah.neEncstoiseyls,tWe.m-lS.evGealrdneefrf,ecJt.sF.ofCazveablertatom,uasnsdelSs. . PARKERETAL:. FEEDING INTERACTIONS 179 (Dreissena polymorpha): an enclosure experiment in Saginaw Nalepa, T. F. 1994. Decline ofnative unionid bivalves in Lake St. Clair Bay, Lake Huron. Journal ofGreat Lakes Research 21(4):501- after infestation by the zebra mussel, Dreissena polymorpha. 516. Canadian Journal ofFisheries and Aquatic Sciences 51:2227- Hebert, P. D., C. C. Wilson, M. H. Murdoch, and R. Lazar. 1991. 2233. Demography and ecological impacts of the invading mollusc Paterson, C. G. 1984. A technique fordetermining apparent selective fil- Dreissenapolymorpha.CanadianJournalofZoology69:405-409. tration in the fresh-waterbivalve Flliptiocomplanala (Lightfoot). Helm, M. M., D. L. Holland, and R. R. Stephenson. 1973. The effect of TheVeliger27(2):238-241 supplementary algal feeding of a hatchery breeding stock of Patterson, M. A., B. C. Parker, and R. J. Neves. 1997. Effects ofquaran- Ostrea edulis on larval vigour. Journal ofthe Marine Biological tinetimeson glycogen levels of native freshwater mussels Associationofthe UnitedKingdom53:673-684. (Bivalvia: Unionidae) previously infested with zebra mussels. Holland,R. E. 1993.Changesin planktonicdiatomsandwatertransparen- AmericanMalacologicalBulletin 14(l):75-79. cy in Hatchery Bay, BassIslandarea,westernLakeErie,sincethe Saraceni, C. and D. Ruggiu. 1969. Techniques for sampling water and establishment of the zebra mussel. Journal ofGreat Lakes phytoplankton. In:A ManualonMethodsforMeasuring Primary Research 19(3):617-624. Production inAquaticEnvironments, R. A. Vollenweider,ed. pp. Hunter, R. D. and J. F. Bailey. 1992. Dreissenapolymorpha (zebra mus- 5-7.BlackwellScientificPublications,Oxford. sel): colonization ofsoft substrata and some effects on unionid Schloesser, D. W. and T. F. Nalepa. 1994. Dramatic decline of unionid bivalves. TheNautilus 106(2):60-67. bivalves in offshore waters ofwestern Lake Erie after infestation Jorgensen, C. B., T. Kiorboe, F. Mohlenberg, and H. U. Riisgard. 1984. by thezebramussel,Dreissenapolymorpha. CanadianJournalof Ciliary and mucus-net filter feeding, with special reference to FisheriesandAquaticSciences51:2234-2242. fluid mechanical characteristics. Marine EcologyProgress Series Schloesser, D. W., T. F. Nalepa, and G. L. Mackie. 1996. Zebra mussel 15:283-292. infestation of unionid bivalves (Unionidae) in North America. Leach, J. H. 1993. Impacts ofthe zebra mussel (Dreissena polymorpha) AmericanZoologist36:300-310. on waterqualityandfish spawningreefs in western LakeErie.In: Shumway, S. E., T. L. Cucci, R. C. Newell, and C. M. Yentsch. 1985. Zebra mussels: Biology, Impacts, and Control, T. F. Nalepa and Particle selection, ingestion, and absorption in filter-feeding D. W. Schloesser, eds. pp. 381-397. Lewis Publishers, Boca bivalves. Journal ofExperimental Marine Biology and Ecology Raton,Florida. 91:77-92. Lewandowski, K. 1976. Unionidae as a substratum for Dreissena poly- Silverman, H., E. C. Achberger, J. W. Lynn, and T. H. Dietz. 1995. morphaPall.PolskieArchiwumHydrobiologic23(3):409-420. Filtration and utilization of laboratory-cultured bacteria by Loosanoff, V. L. andJ. B. Engel. 1947. Effect ofdifferent concentrations Dreissenapolymorpha, Corbiculafluminea,andCarunculinatex- of micro-organisms on feeding ofoysters (O. virginica). United asensis.BiologicalBulletin 189:308-319. StatesFishandWildlifeServiceFisheriesBulletin51:31-57. Sprung, M.andU. Rose. 1988. Influenceoffoodsizeandfoodquantityon Lowe,R. L.andR.W. Pillsbury. 1995. Shiftsinthebenthicalgal commu- the feeding of the mussel Dreissena polymorpha. Oecologia nity structure and function following the appearance ofzebra 77:526-532. mussels (Dreissena polymorpha) in Saginaw Bay, Lake Huron. Strayer, D. L.andL.C. Smith. 1996. Relationshipsbetween zebramussels JournalofGreatLakesResearch21(4):558-566. (Dreissenapolymorpha)and unionidclamsduringearly stages of Maclsaac, H. J., W. G. Sprules, O. E. Johannsson, andJ. H. Leach. 1992. the zebra mussel invasion of the Hudson River. Freshwater Filtering impacts of larval and sessile zebra mussels (Dreissena Biology36(3):771-779. polymorpha)inwestern LakeErie. Oecologia92:30-39. TenWinkle,E. H.andC. Davids. 1982. FoodselectionbyDreissenapoly- Mackie, G. L. 1991. Biology ofthe exotic zebra mussel, Dreissenapoly- morpha Pallas (Mollusca: Bivalvia). FreshwaterBiology 12:553- morpha, in relation to native bivalves and its potential impact in 558. LakeSt.Clair.Hydrobiologia219:251-268. Wu, L. and D. A. Culver. 1991. Zooplankton grazing and phytoplankton Mikheyev,V. P. 1967. [FiltrationnutritionoftheDreissena.](InRussian). abundance: an assessment before and after invasion ofDreissena Trudy vsesoyuzogo Nauchno-issledovatelnogo Inslituta polymorpha.JournalofGreatLakesResearch 17(4):425-436. PrudovogoRybnogoKhoziaisna 15:117-129. [notseen] Miura, T. and T. Yamashiro. 1990. Size selective feeding ofAnodonta Dateofmanuscriptacceptance: 6March 1998 calipygos, a phytoplanktivorous freshwater bivalve, and viability ofegestedalgae.JapaneseJournalofLimnology51(2):73-78.