Derivation of water quality objectives for hazardous substances to protect aquatic ecosystems: Single-species test approach

Two methodological approaches used to derive quality objectives to protect aquatic communities based on single-species tests will be described. Water quality objectives to protect aquatic life may be derived on the basis of ecotoxicological tests considering toxicity to bacteria, algae, (small) crustaceans, and fish. This spectrum of species comprises representatives of four trophic levels of water biocoenosis. The lowest no observed effect concentration value of the most sensitive specie is reduced by a safety factor (more appropriate: uncertainty factor) to extrapolate a “safe level” for the aquatic ecosystem. An alternative approach is the use of statistical extrapolation methods based on species sensitivity distributions to calculate maxium permissible concentrations. The approach using uncertainty factors will be compared with the approach using species sensitivity distribution to extrapolate safe levels. © 1994 by John Wiley & Sons, Inc..