Evaluating effects of contaminants on fish health at multiple levels of biological organization: Extrapolating from lower to higher levels

Effects of environmental stressors such as contaminants on the health of aquatic ecosystems usually involve a series of biological responses ranging from the biomolecular/biochemical to the population and community levels. To establish relationships and to determine the feasibility of extrapolating between higher and lower levels of biological organization, spatial patterns in fish responses to contaminant loading were investigated in a stream receiving point-source discharges of various contaminants near its headwaters. Relationships among fish responses at four major levels of biological organization (biochemical/physiological, individual, population, and community levels) were evaluated relative to patterns in contaminant loading along the spatial gradient of the stream. Both individual and integrated response analysis demonstrated that bioindicators at several levels of biological organization displayed similar downstream patterns in their response to contaminant loading within the stream. Some of the bioindicator responses at lower levels of organization appear to be useful for the ecological risk assessment process because of their sensitivity and apparent relationships to higher levels. By identifying and establishing relationships between levels of biological organization we should be better able to understand the mechanisms of stress responses in ecological systems that could ultimately result in improved predictive capability of ecological risk assessment and also allow for more informed decisions regarding remedial actions.