LIMITATION OF PRODUCTIVITY BY TRACE-METALS IN THE SEA

Some trace metals such as Fe, Ni, Cu, and Zn are essential for the growth of phytoplankton. The concentrations of these essential trace elements in seawater are so low as to limit their availability to aquatic microbiota. Trace element uptake is ultimately limited by kinetics of reaction with transport ligands or by diffusion to the cell. From what we know of the characteristics of the uptake systems of phytoplankton and their trace metal requirements we can estimate that Fe and Zn may at some times in some places limit phytoplankton productivity, which is in accord with available field data on trace metal enrichments.