Assessment of the health of aquatic ecosystems exposed to low-level environmental contamination

This project was undertaken as an integrated field-laboratory program designed to determine the impacts of copper and zinc contamination on white sucker (Catostomus commersoni) populations in several lakes in the Manitouwadge district of Northern Ontario. White suckers were collected from lakes with elevated levels of both copper (13-15 ug l;Examination of the reproductive performance did not detect differences in suckers from contaminated sites. However, larvae hatched from eggs collected at contaminated sites exhibited differences in size, developmental rate, survival and growth, relative to controls. Larvae from contaminated eggs showed increased resistance and tolerance to waterborne copper during the period of endogenous nutrition. This study provides evidence for a maternal yolk factor associated with increased resistance and tolerance of larvae to copper. Incubation of eggs in streams flowing out of the tailings area resulted in a decreased egg size and tolerance to copper.;In addition to the field validation, a framework was developed as a simple, cost-effective, rapid mechanism for assessment of toxicant impact on aquatic environments. The framework is known as Population Indicators of Sublethal Contaminant Effects on Suckers (PISCES), and separates response patterns based on population characteristics. The application of PISCES to this study, and to several published data sets, showed that white sucker populations responded to environmental stressors in a predictable fashion. Limitations of PISCES and requirements for the further development of a model for field validation and environmental health assessment are discussed.;After the age of sexual maturation, contaminated fish were significantly smaller and shorter, and female suckers failed to exhibit significant increases in either length or weight with age. The fish from contaminated lakes also exhibited decreases in egg size and fecundity, and exhibited an increased incidence of spawning failure. Alterations in sucker growth, lipid reserves and fecundity appear to be related to nutritional deficiencies as a result of the chronic effects of elevated sediment metals on the food base of the suckers.