Southern Chesapeake Bay - Huggett, 1986 



- Westbrook et al. , 1986 



California Coaxal - Stallard et al., 1987 



San Diego Bay - Seligman et al., 1986 



Navy, Baseline - Valkirs et al., 1986 



- Grovhoug et al., 1986 



Canada, freshwaters - Maguire et al., 1982; 1985; 1986 



- Maguire, 1984; 1987 



- Maguire and Tkacz, 1987 



These early efforts to determine the characteristic concentrations of TBT 

 is selected coastal waters were also steps in methods development. These 

 early studies uncovered several environmental variables which were 

 affecting the measured concentrations of organotin. 



4.6.2 Environmental Variables Affecting Organotin Levels 



Mixing processes in an estuary, bay or river, are a major contributor to 

 variation in the measured levels of TBT in the water column. Much of the 

 mixing is tidal. Marinas and anchorage areas are located insofar as 

 possible to minimize the effects of wind and wind waves on the boats and 

 ships kept there. To provide protection from all points of the compass, 

 the typical marina is constructed with a very narrow entrance relative to 

 the volume of the enclosed body of water. This configuration has the 

 poorest flushing characteristics and the greatest tendency to accumulate 

 materials leaching or spilled from boats. The presence or absence of 

 fresh water inflows and density gradients are also important in 

 determining the mixing processes in any given body of water. 



Sediment type and sediment water interactions also introduce variability 

 to the measured concentrations of organotins in natural waters. Studying 

 the relation of sediment loadings of butyltin and water column 

 concentrations, Grovhoug et al. (1986) concluded that sediments accumulate 

 butyltin to 3 orders of magnitude above the concentrations found in the 

 adjacent water column. Most of the sampling of sediments has been single 

 samples which provide no information on tidal or seasonal variations of 

 TBT uptake or release. A question requiring further study is the effects 

 of butyltin loadings (as paint chips, dissolved or bound to sediment or 

 organic material) in bottom sediments on the benthic community. Goldberg 

 (Scripps Institution of Oceanography) sampled surface waters and sediments 

 in over eighty sites, primarily California coastal marinas and found that 

 "in those marinas where the TBT concentrations were greater than about 100 

 ng/1, there was a conspicuous absence of native organisms, especially 

 molluscs" (Stallard et al., 1986). Goldberg (1986) has also reported that 

 Antioch Marina (Yacht Club) in San Francisco Bay had TBT concentrations 

 over 500 ng/1 and an absence of fauna (such as mussels and tunicates) on 

 the submerged parts of docks and piers. 



IV-43 



