Published:
January 1, 1994
Originator:
Chesapeake Bay Program

One commitment of the 1988 Chesapeake Bay Basinwide Toxics Reduction Strategy was to give contaminants on the Toxics of Concern List priority in the development of water quality criteria (U.S. EPA. 1991a). Presently the United States Environmental Protection Agency develops water quality criteria for both freshwater and marine systems. Estuarine organisms are supposed to be protected under the marine criteria. There are however, complelling biological and chemical factors that may prevent estuarine biota from being protected under marine criteria and these factors justify the need for specific estuarine criteria. Estuarine organisms, because of their inherent physiological differences from freshwater and marine organisms, may differ substantially in sensitivity to some toxic substances. For example, recent toxicity studies with an estuarine zooplankton and fish showed that salinity ranging from 5 to 25 ppt significantly influenced the toxicity of atrazine (Hall et al., in press). The unique water chemistry of estuarine environments may also be responsible for differences in bioavailability of some toxic substances, thus affecting their toxicities.

Download publication