Metal Speciation and Cyanolbacterial Ecology in the Sargasso Sea

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ABSTRACT OCE-9618729 / OCE-9701681 Chemical oceanographers and marine microbiologists have known for some time now that trace metals in seawater affect ocean phytoplankton and bacteria differently depending upon the concentrations actual chemical forms, or species, in which the trace metal is present. Similarly, it is also known that such organisms are capable of secreting complexating agents that change trace metal speciation, making them more or less assimilable and more or less toxic. It is known that the very low concentrations at which trace metals are present in surface waters of the central ocean gyres may limit biological production, as has been demonstrated recently for iron. In this project, investigators from the Woods Hole Oceanographic Institution and the Massachusetts Institute of Technology will study these phenomena as a two-way street: water column trace metals affecting oceanic microbial communities and oceanic microbial communities affecting the water column trace metal chemistry. The studies will involve field (Sargasso Sea) and laboratory studies with two species of cyanobacteria and their biogeochemical relationship with cobalt, iron, and copper in the water column. The primary emphasis will be on cobalt because of its importance as a micronutrient and because so little is know about its chemical speciation in the oceanic environment.