9617675 Fisher The biogeochemical cycling of many trace elements in ocean surface waters is strongly influenced by biological process. Despite this fact, relatively little is known about what controls the fate of elements once they are incorporated into biomass. For example, metals can be assimilated into the food web, or regenerated to the dissolved phase or exported on sinking particles. Given our lack of understanding in this area, it is difficult at present to predict the fate and relative importance of different pathways in metal cycling throughout the wide range of oceanic settings. The principal investigators propose here to advance our understanding of trace metal cycling by quantifying for the first time the effects of subcellular partitioning and metal stoichiometires on metal biogeochemistry in natural systems. There are two main approaches, consisting of laboratory and field work. The lab studies use controlled measurements and labeled metal radionuclides to examine carbon:metal ratios and the partitioning and the fate of metals incorporated into biomass. A novel dual labeling technique allows the principle investigators to separate between intercellular and cell surface pools of metals. In the field, natural assemblages of phytoplankton will be examined for the cellular partitioning of the various metals, and ship board incubation experiments will be conducted to examine the rates of metal turnover. The results of this study will significantly increase our understanding of the role of biological processes in chemical cycling and transport in the oceans.
