PARENT SESSION
4H Ecological risk assessment for the marine environment
9:00 AM to 7:00 PM, Wednesday, 09 May 2001

(W/EH093) Can freshwater toxicity data be used to predict effects to saltwater organisms?

Whitehouse, Paul ¹, Sorokin, Neal ¹, Cole, Stephanie ¹, Sorokin, Neal¹, Rodgers, Howard¹, Morritt, David², Crane, Mark², Leung, Kenneth², Wheeler, James², Karman, Chris³, ^{1 2 3}

ABSTRACT- A key step in chemical risk assessment is the estimation of a PNEC(predicted no effect concentration), usually involving extrapolation from a dataset comprising ecotoxicity data for a number of species. This poses a problem for marine risk asesment because sufficient data to estimate a PNEC are often unavailable. One option is for saltwater PNECs to rely on extrapolations based on freshwater toxicity data. This 'surrogate' approach assumes that freshwater species respond similarly and that distributions of freshwater and saltwater species sensitivities are indistinguishable. Currently these assumptions remain untested and this is the subject of the research described here. Using published data for compounds for which there are data for both freshwater and saltwater species, species sensitivity distributions (SSDs) have been constructed based upon on log-logistic responses. Key parameters of the SSD (e.g. HC5, slope)have been compared using ANCOVA to determine whether or not they are significantly different. Several compounds give rise to freshwater and saltwater SSDs which are indistinguishable (e.g. phenol, 3,4-dichloroaniline). In some cases, incongruities between freshwater and saltwater SSDs can be attributed to differences in physico-chemical factors on speciation and bioavailability whilst in others (e.g. malathion), differences in taxonomic composition of the datasets (especially in the sensitive 'tail' of the SSD)are responsible. Generic guidance about the validity of a 'surrogate' approach to estimating saltwater PNECs is limited by the availability of saltwater toxicity data for many compounds. It is also important to consider the possible influence of taxa for which there are no freshwater analogues (e.g. Ctenophora, Echinodermata, Cephalopoda). Consequently, recommendations for further testing to address the influence of taxonomic groups which appear to play an important role in determining the PNEC and also address differences in the taxonomic diversity of saline and freshwater environments are highlighted.

Key words: freshwater, marine, extrapolation, toxicity