Following EEC directives on organotin-based antifoulants, hopes that the TBT problem may now be eradicated have not been entirely fulfilled: though levels of TBT in water have declined in many areas, steady state is approaching in some locations, occasionally exceeding water quality standards by more than two orders of magnitude. There are also concerns over the build-up and fate of TBT in sediments. Determinations of the present state of TBT contamination, trends in persistence and bioavailability and the assessment of risk for benthic organisms, in different climatic conditions (northern temperate to Mediterranean), form the core of this proposal.
The focus will be on infaunal clams Ruditapes. decussata, Scrobicularia plana, bottom- dwelling fish e.g. Platichthys flesus, Mullus barbatus and neogastropods, Nucella lapillus, Nassarius reticulatus. TBT biovailability, metabolism and persistence in various components of sediment-based ecosystems will be quantified, accompanied by measurements of clam populations whose distributions are thought to have been influenced by TBT (confirmation of relative sensitivities of different life-stages to organotin will be sought). Comparisons will be made between areas where small boats are predominant (where existing legislation should be most effective) and those which are influenced by larger ships (still entitled to use TBT/TPT-based paints). Mesocosm studies will determine pathways of bioaccumulation, and how sediment conditions (physico-chemistry; granulometry; geological origin) influence partitioning, release, bioavailability and persistence.
Molecular effects - on the mixed function oxidase (MFO) system, membrane damage, oxyradical generation, lipid peroxidation, mutagenicity and detoxification - will be determined with a view to development of novel markers of organotin exposure.
The masculinizing effect of TBT on female gastropods is currently the most well-documented but the mechanisms underlying this response ('imposex') are poorly understood: experiments will test whether the gastropod MFO system is disturbed by TBT. Observations on imposex in British and Irish populations will be used to assess the effectiveness of legislation. Studies will be extended to important aquaculture centres in S. Europe as a means of predicting deleterious trends associated with the region's development.
Funding SchemeCSC - Cost-sharing contracts