Iron in the sea and in marine plankton

Abstract

The amount of Fe in true solution in sea water is less than 2 mg/m3; most of it is present in par-ticulate form, the amount of which varies considerably. Diatoms require several times as much Fe as P, but the Fe requirements of zooplankton are smaller. The plankton catches were richest in Fe at time of spring diatom outburst (2.3 mg/m3) and the amount fell to 0.5 mg/m3 in summer when animals dominated. Excess Fe derived from plants was excreted by animals and became available for a second growth cycle.