A Review Of Guideline Development For Suspended Solids And Salinity In Tropical Rivers Of Queensland, Australia

Australasian Society for Ecotoxicology
Publication Type:
Journal Article
Australasian Journal of Ecotoxicology, 2008, 14 (2&3), pp. 129 - 142
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Suspended solids and salinity are among the highest priority contaminants for the management of freshwater biodiversity and ecosystems in tropical Australia. Although they are natural constituents of aquatic ecosystems, when elevated above background concentrations they can have negative impacts. The Australian tropics experience intense seasonal rainfall patterns with distinct dry winters and wet summers, with tropical rivers often experiencing large episodic flow events in the wet season and low or no flows in the dry season. Both suspended solids and salinity represent a complex mixture of constituents that are influenced by a range of factors including catchment land use, geology, hydrology and geomorphology. Accurate and reliable water quality guidelines are an essential tool for their management. Given the highly variable nature of tropical rivers and of the stressors themselves, defining trigger values for them in tropical Australia presents a considerable challenge. This paper describes how salinity and sediment sources, mechanisms of transport and the characteristics of their constituents interrelate to influence their patterns of exposure and potential impact. The application of existing approaches to guideline development, including departure from reference condition and toxicological approaches are reviewed in light of the requirements for tropical rivers with recommendations given on the most appropriate techniques to develop guidelines at present. Although concentrations of suspended solids and salinity are highly variable within tropical rivers, their constituents tend to follow patterns that when modelled allow the identification of spatial grouping of relatively homogeneous sediment and salinity zones. These zones provide a basis for better defining regional reference ranges, which can inform the design of toxicity tests to determine the potential effects of suspended solids and salinity in a way that is representative of those zones.
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