o How available to the biological community are organotins adsorbed 

 on suspended or bottom sediments? 



o Is the tributyltin in planktonic cells or on the surface membrane 

 available to the consumer organisms or is it eliminated? 



o Do pelagic birds feeding on neustonic organisms increase their 

 risk of exposure to TBI? Some species of pelagic birds move into 

 coastal waters seasonally. Does this seasonal migration provide 

 a significant pathway to transport TBT beyond coastal waters? 



o What is the relative bioavailability of butyltin compounds and 

 metabolites from various sources such as spilled liguid paint, 

 paint sanding dust, paint chips and scrapping, compared with 

 leaching directly from the immersed cured paint film? 



5.2.1.4 Bioaccumulation/Biomaqnification 



To date, the only documented path for butyltin loadings in vertebrates 

 other than man is direct absorption from the water. No published studies 

 are available concerning TBT levels in birds such as cyster-catchers or 

 gulls which are known to feed on the type of invertebrates shown to 

 accumulate TBT and its degradation products in their tissues. 



Studies are needed to provide more information on: 



o What are the key organisms in the bioaccumulation of TBT from the 

 water and from the sediment? 



o To what extent is biamagnif ication of TBT observed in the coastal 

 food chain? 



o What are the bioconcentration rates and feeding pathways from the 

 lower trophic level organisms through sea birds and mammals? 



5.2.1.5 Degradation 



Identification of organisms and mechanisms responsible for degradation of 

 organotins and the different metabolic results produced by different 

 metabolic pathways (e.g. , production of methylated butyltins vs. 

 dibutyltins and monobutyltins) are critical. Studies should also focus 

 more on the roles played by phytoplankton and bacteria. 



Studies are needed to provide more information on: 



o How do changes in salinity or temperature affect the biological 

 and chemical degradation rates of TBT in marine or estuarine 

 waters? 



V-5 



