This research will test the hypothesis that phytoplankton growth in the central equatorial Pacific is limited by a deficiency of iron that results from the very low input of iron-rich atmospheric dust in this area far removed from terrestrial dust sources. It is estimated that the phytoplankton only have 10-20% of the iron they need to fully utilize the nitrate and phosphate upwelling to the surface; hence the potential productivity of a billion tons of C per year is far from being realized. Dissolved and particulate iron in the water column will be measured in which effects on chlorophyll synthesis and nitrate will uptake will be observed with and without added iron. This effort will also provide support to the overall U.S. JGOFS Equatorial Pacific Study by providing clean water and containers to others testing alternative hypotheses. Samples will be collected for measurements of dissolved organic C and N using high temperature catalytic oxidation techniques.
