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ZOOPLANKTON POPULATION DYNAMICS IN EXPERIMENTALLY TOXIFIED POND ECOSYSTEMS
Citation:
Sierszen, M., H. Boston, AND M. Horn. ZOOPLANKTON POPULATION DYNAMICS IN EXPERIMENTALLY TOXIFIED POND ECOSYSTEMS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-92/079.
Description:
The response of aquatic systems to toxic contaminants cannot easily be predicted from laboratory bioassays. In ecosystems, contamination can occur in the concert of natural system processes and could have more or less dramatic effects, depending upon conditions such as system stability or trophic status (McCarthy & Bartell 1988). Furthermore, toxic chemicals can modify trophic interactions or seasonal succession such that ecosystem responses cannot easily be predicted from direct effects alone. o evaluate ecosystem response to and recovery from toxic contamination, we added phenolic compounds to a series of experimental ponds. Toxicants were added repeatedly ina temporally staggered sequence to evaluate the influence of seasonal factors and previous exposure history on the responses to toxicant stress. We hypothesized that seasonal changes in ecosystem structure, e.g. shifts in the relative importance of "to-down" and "bottom-up" controls on energy flow (Bartell et al. 1988), would influence the system-level responses to the toxicant. Information from these experiments is being incorporated into models that predict ecological risk and system-level behavior under toxicant stress. Here we focus on the responses of zooplankton populations to toxicants and factors which may affect the apparent severity of toxic effects.