Trace Element Nutrients

Abstract

In addition to regulation by major nutrients (nitrogen, phosphorus, and silicon), the productivity and species composition of marine phytoplankton communities are affected by a number of trace element nutrients (iron, zinc, cobalt, manganese, copper, cadmium, and selenium). Of these, iron has the dominant influence on carbon fixation rates and algal species diversity. It is also thought to play an important role in controlling dinitrogen fixation rates, and thus may exert an important influence on oceanic inventories of biologically fixed nitrogen. Because of these effects, iron is thought to play a key role in controlling carbon and nitrogen cycles in the ocean, including the biological transfer of carbon to the deep sea, the so-called biological CO2 pump. This pump regulates atmospheric CO2 concentrations and CO2-linked global warming. Other micronutrient metals (zinc, cobalt, copper, and manganese) have a lesser effect on productivity; but because of large differences in metal requirements among algal species, they may exert an important influence on the species composition of algal communities. The interactions between trace metals and ocean plankton are reciprocal: not only do the metals affect the plankton, but the plankton regulate the distributions, chemical speciation, and cycling of these metals through cellular uptake and regeneration processes, vertical flux of biogenic particles, cellular release of organic chelators, and mediation of redox reactions.