In some regions of the oceans, namely the North and Equatorial Pacific and the Antarctic, the surface waters contain relatively high concentrations of nutrients (e.g., PO4 > 1 µM) yet only a low biomass (chlorophyll < 0.5 µg/L). On the basis of measurements of very low iron concentrations (< 0.1 nM) and observations of increased growth on Fe enrichments, J. Martin and coworkers have proposed that iron limits primary production in these waters (Martin, 1991, this issue). Other authors have proposed alternate hypotheses chiefly on the basis of grazing (Miller et al., 1991, this issue) and light limitation (Mitchell et al., 1991). Here we examine the “iron hypothesis” in light of what we know about the iron physiology of marine phytoplankton and its relation to iron chemistry.

Morel, F.M.M., J.G. Rueter, and N.M. Price. 1991. Iron nutrition of phytoplankton and its possible importance in the ecology of ocean regions with high nutrient and low biomass. Oceanography 4(2):56–61, https://doi.org/10.5670/oceanog.1991.03.

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