Comparison of Temperate and Tropical Freshwater Species' Acute Sensitivities to Chemicals: An Update.

Toxicity data for tropical species are often lacking for deriving water quality guidelines (WQGs) and for conducting ecological risk assessment (ERA). To protect and safeguard valuable natural resources and important biodiversity in tropical freshwater ecosystems, a sound framework should be established to assess and manage the ecological risk of an ever-increasing number of chemicals that occur in the tropics. The present study aims to provide a more up-to-date comparison of the species sensitivity distributions (SSDs) between temperate and tropical freshwater species, by incorporating more acute toxicity data which have been documented. Results showed that temperate freshwater species are generally more sensitive to arsenic, chromium, lead, mercury, carbaryl, chlorpyrifos, DDT, lindane and malathion than their tropical counterparts, while tropical species tend to be more sensitive to unionised ammonia, manganese, chlordane and phenol. No sensitivity differences were found between temperate and tropical freshwater species to copper and pentachlorophenol. A general decline in sensitivity trend to chemicals was revealed by comparing taxon-specific SSDs, from crustaceans to molluscs, worms, fishes and insects. On the basis of calculated 10% hazardous concentrations (HC10) ratios from pairwise temperate and tropical SSDs, the temperate-to-tropic safe extrapolation factor was verified and refined as five for tropical countries or regions when deriving their WQGs or conducting ERA from temperate information. This article is protected by copyright. All rights reserved.