Effects of Heavy Metals in a Polluted Aquatic Ecosystem

Abstract

The field of ecotoxicology includes the study of (1) the effects of toxic substances on single species and (2) the consequences for the resulting composition of species assemblages, which we shall call communities. In the study of single species we seek to understand how toxic substances affect the physiological function of individuals, and how toxic substances might affect the demography of the population. In essence, we wish to predict whether or not the species will decline as the result of the influence of the toxic substance. On the community level, minimally, we wish to know how the presence of a toxic substance alters the relative and absolute abundance of the species present. If there were no interactions among the species, this objective would involve merely a bookkeeping process whereby the toxic effects on all of the individual species would be summed up to predict the effect on the assemblage. Given the presence of species interactions such as predation and competition, such additivity may not occur. The effect of a toxic substance might vary among species. Some toxic substances are, for instance, transferred through a food web without harming lower trophic levels, but, owing to peculiarities of physiology, may have substantial effects at higher levels. Mechanisms of detoxification and uptake, furthermore, may profoundly affect such transfer to higher trophic levels, influencing the effect on the overall community.