Primary production: Marine ecosystems

The seas occupy the greater part (70%) of the earth's surface, but their total net primary production is less than that of the land. Depletion of nutrients in the lighted surface waters is responsible for low productivities of most of the open ocean; higher productivities occur in coastal waters and areas of upwelling. A recent estimate of total production for the marine plankon is 50×10 ⁹ metric tons of dry matter per year; the total with benthic production may be 55×10⁹ tons/year. The value for the plankton may be too low; there are persistent problems in measuring productivity with the radiocarbon technique. Because harvestable fish populations are concentrated in a limited area of more productive waters, where they are subject to overharvest and pollution effects, major increase in food production from the seas is not likely.This paper was presented at the symposium, The Primary Production of the Biosphere, given at the Second Congress of the American Institute of Biological Sciences, Miami, Florida, October 24, 1971.