Can saltwater toxicity be predicted from freshwater data?

The regulation of substances discharged to estuarine and coastal environmen ts relies upon data derived from ecotoxicity tests. Most such data are gene rated for freshwater rather than saltwater species. If freshwater toxicity data are related to saltwater toxic effects in a systematic and predictable way, the former can be used to predict the latter. This would have economi c advantages due to a reduction in toxicity testing of saltwater species. I f toxicity data are plotted as species sensitivity distributions, four theo retical relationships between freshwater and saltwater can be envisaged. Ex amples show that each one of these relationships is supported by empirical data. These examples show that although there is considerable potential for freshwater to saltwater prediction, species parity and representativeness need to be examined for each chemical substance to avoid bias. (C) 2001 Els evier Science Ltd. All rights reserved.