river flood events. Organism responses are poorly understood, as each of the numerous inshore species has its own tolerance limit at every life stage, and interactions between the organisms add to the complexity. Though considerable knowledge has been gained from singlespecies exposure experiments in the laboratory, it is difficult to extrapolate from such laboratory studies to field settings and ecosystem responses. Taxonomically detailed field survey data of major assemblages along environmental gradients should therefore provide valuable information about ecosystem responses to changing water quality.