Elimination rate constants of 36 PCBs in zebra musse Dreissena polymorpha and exposure dynamics in the Lake St. Clair - Lake Erie corridor Heather Morrison, Tamara Yankovich, Rodica Lazar, and G. Douglas Haffner Abstract: The elimination kinetics of 36 PCB congeners, ranging in log octanol-water partition coefficients (log KO,) from 5.60 to 7.50, were determined in zebra mussels (Dreissena pokj~rnorpha) with shell lengths from 1.0 to 1.5 cm. Elimination rate constants, based on lipid- normalized data, ranged from 0.172 to 0.042 day-' and exhibited a significant negative regression with log KO,. Time to 95% steady state ranged from 17.5 to '31.0 days and was used to determine the period over which mussels integrated exposure concentrations. Bioavailable PCB congener concentrations, calculated with a steady-state model, were determined from mussels collected offshore of Middle Sister Island in western Lake Erie. ChemicaI concentrations in water, estimated using mussels, were within an order of magnitude of direct measurements for congeners with log KO, < 6.6. The rapid elimination kinetics of zebra mussels suggests that these organisms can closely track temporal fluctuations in ambient chemical concentrations, and therefore have the potential to regulate contaminant cycling in aquatic ecosystems. RCsumC : La cinCtique de 1'6limination de 36 songCnkres de BBC, dont les coefficients logarithmiques de partage octanol-eau (log Kw) varient B 19intCrieur d'une plage de 5,60 B '3,58, a CtC dCtermimCe pour des rnoules zCbrCes (Dreisserea pokymsrpha) dont la coquille mesure entre 1 ,0 et 1'5 cm. Les constantes des taux d'Climination, Ctablies B partir de donn6es norrnalisies pour Ies lipides, variaient entre 0,172 et 8,042 jour-'. I1 existe une forte rkgression nkgative entre ces mesures et les valeurs du log KO,. Le temps Ccoulk avant l'atteinte d'une valeur h l'kquilibre de 95% est compris entre 17,5 et 71,O jours. Ces valeurs wous ont permis de dkterminer Be temps que mettent les moules pour stabiliser la concentration dans leurs tissus des congknkres de BPC auxquels elks sont exposCes. Les concentrations bioassimitables de ces produits, calculCes au moyen d'un msdkle B l'kquilibre, ont CtC dCtermin6es B partir des tissus de moules prClev6es au large de l'ile Middle Sister, dans le bassin ouest du lac 6riC. Les concentrations dans l'eau, estimkes B partir de la concentration dans les modes, se situaient B un ordre de grandeur des concentrations mesurkes directement de congknkres h log KO, 6 6,6. L'Climination rapide observee chez les moules zCbrCes wous apprend que ces esrgakaisrnes peuvent suivre arks rapidement les fluctuations dans le temps des concentrations de prsduits chimiques dans leur milieu arnbiant; elles prksentent donc le potentiel de rCguler les cycles de contaminants dans les Ccosyst&mes aquatiques. [Traduit par la RCdaction] Received January 23, 1995. Accepted July 7, 1995. J 12729 He Morrison, W. Lazar, and G.D. ~affner.' Great Lakes Institute for Environmental Research, Department of Biological Sciences, University of Windsor, Windsor, ON N9B 3P4, Canada. Te Yankovich. Watershed Ecosystems Graduate Program, Trent University, Peterborough, ON K91 7B8, Canada. Author to whom all correspondence should be addressed. By virtue of their vast numbers and prodigicpaas filtering capacity (MacIsaac et al. 1992), zebra mussels (Breissena polymorpha Pallas) have the potential to influence con- taminant cycling in heavily infested water bodies. Before we can assess ecosystem-level effects of mussels, it is nec- essary to understand how individuals cycle contaminants. The rate at which an organism cycles a particular contami- nant is governed by the kinetics sf the chemical between an organism and its environment. Biological properties such Can. J. Fish. Aquat. Sci. 52: 2574-2582 (1895). Printed in Canada / ImprianC au Canada Can. J. Fish. Aquat. Sci. Downloaded from www.nrcresearchpress.com by Texas A&M University on 06/06/13 For personal use only.