This project will test several hypotheses regarding the control of oceanic primary productivity (primarily phytoplankton productivity) by varying the amounts of dissolved trace metals needed for growth (Fe, Mn and Zn) and also those which may be toxic and are often also present (Cu and Co). In nature the extent to which these metals are complexed by naturally occurring organic compounds may control their availability to the phytoplankton. This research will investigate several areas of the ocean which are underutilizing the dissolved nutrients nitrate and phosphate, perhaps because of lack of needed trace metals or excess of toxic trace metals. The experiments to be done will involve: 1) determining the concentrations of dissolved trace metals versus depth at several stations, and 2) at each station varying the amounts and availabilities of the trace metals Fe, Mn, Zn, Cu and Co in living phytoplankton cultures. The results of the second set of experiments will be compared with phytoplankton growth experiments wherein no additional metals have been added in order to quantify the magnitude of varying availabilities of the trace metals.
