[Species selection methods in deriving water quality criteria for aquatic life]

The Mann-Whitney U test method was used to analyze the species sensitivity to ammonia toxicity. And based on the analysis, the relationship between species selection method and WQC deriving method was studied by using toxicology, biological taxonomy and sampling-inference theory. Results showed that vertebrate species, especially the Actinopterygii, accounted for the vast majority in the toxicity test species. And the species composition of toxicity test species was inconsistent with the species composition of the ecosystem. Sensitivity to ammonia toxicity among different taxa varied significantly for most species except some species in individual taxa, especially the less sensitive species. The variable coefficient of interspecies decreased with the reduction of biological classification level. To a certain extent, it showed that the species sensitivities in the same taxa to toxicant were more similar than those in different taxa. According to sampling-inference theory, the WQC for aquatic life deriving method belonged to the design-based inference. And taxonomic groups could be used as auxiliary variables to conduct a stratifactory sampling for species selection in WQC deriving which could improve the sampling efficiency and precision.