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The biogeochemistryof cobalt in theSargasso Sea Mak A. Saito2001 год

The biogeochemistry of cobalt in the Sargasso Sea
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Аннотация: Processes that enable marine phytoplankton to acquire trace metals are fundamental to our understanding of primary productivity and global carbon cycling.This thesis explored the biogeochemistry of cobalt using analytical chemistry and physiological experiments with the dominant phytoplankton species, Prochlorococcus.A high sensitivity method for Co speciation was developed using hanging mercury drop cathodic stripping voltammetry.Dissolved Co at the Bermuda Atlantic Time Series station (BATS) in the Sargasso Sea was bound by strong organic complexes with a conditional stability constant oflogK=16.3l0.9.A depth profile of Co at BATS revealed a nutrient-like profie.Biweekly time series measurements oftotal cobalt near Bermuda from the MITESS sampler were 0-47pM throughout 1999, and averaged 20l10pM in 1999.A transect of total cobalt from BATS to American coastal waters ranged from19-133pM and correlated negatively with salinity (r2=0.93),suggestive of coastal waters as an input source.Prochlorococcus strains MED4-Ax and SS120 showed an absolute requirement for Co, despite replete Zn. 57 Co uptake rates and growth rates were enhanced by additions of filtered low Co cultures, suggesting that a ligand is present that facilitates Co uptake.Bottle incubations from a Synechococcus bloom in the Pacific showed production of 425pM strong cobalt ligand.These and other lines of evidence support the hypothesis that a cobalt ligand, or cobalophore, is involved in cobalt uptake. Co-limited Prochlorococcus cultures exhibited an increase in the fraction of cells in G2relative to other cell cycle stages during exponential growth, and the durations of this stage increased with decreasing cobalt concentrations.This effect was not observed with Fe, N, or P-limited cultures, suggestive of a specific biochemical function of cobalt that would interfere with the late stages of the cell cycle.
Год издания: 2001
Авторы: Mak A. Saito
Ключевые слова: Fish Ecology and Management Studies, Mercury impact and mitigation studies, Water Quality and Pollution Assessment
Другие ссылки: darchive.mblwhoilibrary.org (PDF)
doi.org (HTML)
DSpace@MIT (Massachusetts Institute of Technology) (PDF)
DSpace@MIT (Massachusetts Institute of Technology) (HTML)
Open Access Server of the Woods Hole Scientific Community (Woods Hole Scientific Community) (PDF)
Open Access Server of the Woods Hole Scientific Community (Woods Hole Scientific Community) (HTML)