Zinc Biogeochemistry and its Relationship to Cobalt, Phosphate and Phytoplankton Community Structure

Woods Hole Oceanographic Institution, Woods Hole MA

Investigators

Abstract

ABSTRACT OCE-0136835 A trace metal chemist and a molecular biologist from Woods Hole Oceanographic Institution will join forces to determine the speciation and distribution of zinc and cobalt in the marine environment to assess the role these metals play as an essential micronutrient for phytoplankton. The PIs also will determine what the relationship of zinc is to the geochemistry of cobalt and phosphorus and its influence on the composition of phytoplankton assemblages. During cruises to the North Pacific and the Bering Sea, the PIs will measure the speciation of Zn and Co, as well as alkaline phosphatase activity. Deckboard incubation experiments using freshly collected samples and added Zn, Co phosphate and organic P will be used to determine changes in alkaline phosphatase activity via ELF assay. Observed differences in these experiments will be compared with changes in specific growth rates for alkenone producers and the drawdown of nutrients obtained by scientists from the University of Hawaii. Similar measurements will be made during a cruise to the North Atlantic. In the laboratory, culture experiments will be used to ascertain the following: (1) effect of phosphate limitation on the requirements and growth limiting concentrations of Zn and Co and vice versa for cultures of E. huxleyi and Thallassiosira weissflogii by measuring growth rates and alkaline phosphatase activity; (2) whether E. huxleyi can use organically complexed Co; and (3) whether Trichodesmium has an absolute requirement for Co or Zn and the effect of these metals on alkaline phosphatase. From a methodology standpoint, the PIs plan to improve upon current methods available for making Zn speciation measurements, resolve existing discrepancies and lower the limit on free Zn concentrations. They also will develop a new solvent extractions speciation/isotope tracer technique to extend detection limits for Zn and evaluate lability of ambient Zn complexes.