Research Product

Knowledge of the way in which different variables affect interactions among organisms and pollutants in the water column is needed to ensure the most effective protection and management of freshwater ecosystems. These interactions are influenced by changes in environmental variables that can alter the physiological condition of the biota or the physicochemical characteristics of the system.1 Several investigators have reported on the toxicity of chemicals to freshwater organisms in relation to hardness,2-4 pH,2-5 and temperature.2-4,6 Much of the existing toxicity data are from laboratory experiments conducted at optimal and constant conditions (dissolved oxygen, pH, salinity, temperature, etc.). Where factors affecting toxicity have been examined, it has been done with one factor at a time for the most part; a situation which does not occur in the real world. Yet, the role of environmental fluctuations and extremes in confounding biological responses to contaminant exposures must be characterized to facilitate extrapolation from the laboratory to the field. Hence, we will summarize reported effects of hardness, pH, and temperature on the toxicity of contaminants to freshwater organisms, and discuss whether environmental factors affect toxicity or bioavailability and exposure for different kinds of toxic contaminants. For the purposes of this paper, bioavailability is the external availability of a chemical to an aquatic organism,7 and exposure is the concentration of a chemical in an aquatic organism.