Using a non-steady state bioaccumulation model to investigate bioenergetic processes in aquatic food webs.

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Current models of contaminant bioaccumulation assume that steady state kinetics are achieved between an organism at its environment. These models do not, however, explain the variability in chemical body burdens observed among and within species. We have demonstrated that steady state assumptions are invalid for the more hydrophobic organic pollutants, and we predict that many aquatic organisms will not achieve steady state for many chemicals within their life time as a result of the time spent at basal metabolism when essentially there is very little capacity to eliminate chemicals. Non-steady state models are required to explain the large individual differences in contaminant burdens observed within fish populations. We propose to resolve if individual differences in PCB and Hg body burdens are related to differences in chemical uptake or elimination. Furthermore, we will use a non -steady state approach to determine if the observed latitudinal patterns of chemical accumulation in fish are related to the amount of time spent at basal metabolism (overwintering). Development and verification of these novel non- steady state models will provide critical information on the processes the regulate individual variability in natural populations and will also provide an ecological mechanism for the latitudinal gradients observed where arctic populations accumulate higher chemical concentrations than tropical populations even though many of the chemicals of concern remain in use in tropical countries.