The Speciation of Bioactive Metals in Oxygen Minimum Zones

Woods Hole Oceanographic Institution, Woods Hole MA

Investigators

Abstract

ABSTRACT OCE-0327226 A investigator from Woods Hole Oceanographic Institute proposes to investigate and characterize the speciation of bioactive metals (Cu, Co, Fe and Zn) in oxygen minimum zones (OMZ) in the Eastern Tropical Pacific near Mazatlan and the Costa Rica Dome, as well as the Arabian Sea. The PI will characterize the redox state, degree of organic complexation and the role of reduced sulfur ligands within the OMZ and in the overlying surface waters. Speciation data obtained during this study will be used to test the following seven hypotheses: (1) Cu is strongly complexed by organic ligands in the OMZ thereby limiting its bioavailability; (2) a large fraction of Cu is present as Cu(I) complexes with organic and inorganic sulfur ligands; (3) Fe(II) is important in the OMZ except when Fe(III) is stabilized with organic ligands; (4) the subsurface particle maxima which is predominantly a bacterial biomass is a source of Fe and Cu chelators and plays a role in the preferential removal of Fe relative to Mn; (5) Cu speciation influences the activity of denitrifiers; (6) Prochlorococcus populations in OMZ regimes may produce extracellular chelators to detoxify Cu creating an antagonistic relationship with denitrifiers; and (7) metal chemistry within the OMZ contributes to the unique metal regime in the Costa Rica Dome, which contributes to the characteristic bloom of the cyanobacterium Synechococcus. To obtain the speciation data the PI will use a combination of electrochemical, inductively coupled plasma-mass spectrometry, chemiluminescence and liquid chromatographic/electrospray mass spectrometric methods. The broader impacts of this project is its contribution to India and Chile, two developing countries, whose economies are tied to regions with strong oxygen minima and who are dramatically affected by fluctuations in the climatic regimes over these ocean basins.