Studies are needed to provide information on: 



o What portion of TBT introduced into the environment from 

 antifouling paint remains in solution in the water, in the 

 surf ace microlayer and in the sediment? 



o To what extent does TBT move with movement of bottom and 

 suspended sediments, either by dredge spoil disposal or storm 

 induced resuspension of sediments? 



o What is the role of physical parameters on the distribution and 

 concentration of TBT, including winds, waves, tidal cycles and 

 turbidity maximums? 



o Is there a biological component to TBT transport, is it being 

 distributed as tissue burden or absorbed on external surfaces of 

 planktonic or nektonic organisms? 



o What are the effects of seasonal variations in temperature and 

 salinity on leaching rates of TBT in antifouling paints? 



o How rapidly does TBT and its degradation products accumulate or 

 degrade in water, aerobic or anaerobic sediments from a seasonal 

 perspective? 



o Can the behavior of TBT in different localities be described with 

 similar partitioning coefficients? 



5.2.1.3 Bioavailability 



Current research has focused on the filter feedi n g molluscs and the 

 carnivorous gastropods. The deposit feeding molluscs and the 

 polychaete/oligochaete worms are important components in the diet of many 

 fish. These worms are feeding on material that has the strongest affinity 

 for butyltins. These deposit feeders may be a significant pathway to the 

 transfer of butyltin from the sediment into the food chain. An additional 

 component in the consideration of bioavailability is the role played by 

 the bacteria in sequestering, concentrating and metabolizing TBT. 

 Bacteria are a food source for deposit feeding organisms. What is their 

 role in the transfer of TBT from the water or from the sediment into the 

 food chain? 



Studies are needed to provide more information on: 



o What are the roles of bacterial and other microorganisms in the 

 availability of TBT to marine organisms? 



o How available to the biota is tributyltin in the surface 

 microlayer or the water column? 



V-4 



