Nutrients limiting the production of phytoplankton in the Sargasso sea, with special reference to iron

The effects of enriching surface water samples from the Sargasso Sea upon the rate of C¹⁴ assimilation was investigated. The addition of nitrate, phosphate and vitamins, added separately or in combination, had no stimulatory effect, while addition of a trace metal mixture increased C¹⁴ uptake by several-fold. The effective component of the trace metal mix found to be iron, which alone enhanced C¹⁴ uptake for 24 hours but which required the addition of nitrogen and phosphorus to produce a comparable effect of over a three-day period.