Modelling response of single-species populations to microcontaminants as a function of species size with examples for waterfleas (Daphnia magna) and cormorants (Phalacrocorax carbo)

Unlike the variety of eutrophication models that are available to water quality management and research, tools for estimating the effect of microcontaminants on populations have received little attention. To bridge the gap between theoretical analysis and empirical fitting, an analytical model was designed that links traditional ecological variables to common toxicological endpoints. ow generalization of the model for different species, ecological variables were correlated to species size using reported allometric equations. The size-scaling exponent for age variables and bioenergetic rates were approximately of the same magnitude but of opposite sign, suggesting that lifetime fecundity is independent of species size. ion of classical population models to include microcontaminant effects indicates that the population growth rate may be reduced at toxicant concentrations from 0.01 to 1.0 times the LC50. Populations that exhibit low life-time fecundity concentrations relative to survival effects produce the greatest reductions in population growth rate. del was applied to laboratory populations of waterfleas (Daphnia magna) and to a field population of cormorants (Phalacrocorax carbo). Predicted rates of increase for waterfleas as a function of contaminant concentration appeared consistent with independent measurements. The model was also used to estimate the Dutch cormorant population density from 1952 to 1990. Model calibration indicated that the observed population trend could be explained largely by exposure to polychlorinated biphenyls although other factors will have contributed too. del is believed to be an improvement over past empirical approaches.