CU SPECIATION AND CYANOBACTERIAL DISTRIBUTION IN HARBORS SUBJECT TO ANTHROPOGENIC CU INPUTS

Cu speciation was studied in four harbors on the south coast of Cape G od, Massachusetts, that are exposed to varying degrees of Cu contamina tion from anthropogenic sources. Copper in waters outside the harbors was complexed by similar to 10 nM of very strong chelators, twofold hi gher than ambient Cu concentrations. In Eel Pond (Woods Hole) and Falm outh Inner Harbor, total dissolved Cu concentrations were 7-10-fold hi gher. However, because the strong chelators were saturated in these tw o harbors, the free Cu increased by 1,000-fold, from, similar to 10(-1 3) M to similar to 10(-10) M. There was no evidence for any enhanced b iological production of chelators in response to the elevated Cu conce ntrations. However, cell densities of cyanobacteria, which have been p roposed as a source of strong Cu chelators in seawater, decline drasti cally in the high Cu harbors. These trends are consistent with culture studies showing that Synechococcus sp., the predominant cyanophyte in these waters, shows a dramatic decrease in growth rates above a free Cu2+ level of 10(-11) M. In Great Pond and Waquoit Bay, which showed n o significant Cu contamination or saturation of strong ligands, cyanob acterial cell densities showed little or no decrease. Results suggest that significant anthropogenic inputs of Cu may overwhelm processes oc curring in seawater that lead Cu and strong chelator concentrations to approach comparable levels.