Aquatic primary production in the Antarctic

A review is presented of studies, including recent work by members of the British Antarctic Survey, on the primary productivity of plankton, ice-flora and benthos in both marine and freshwater habitats in the Antarctic. Those members of the flora so far studied have low compensation points enabling slow growth in low light intensities but otherwise show no apparent adaptation to temperatures around freezing point. Certain sea areas, mostly inshore, have dense standing crops with daily and annual productivities as high as those of productive areas elsewhere in the oceans but in the open Southern Ocean productivity seems generally low even although nutrient concentrations are high, probably because of excessive turbulence carrying plankton out of the photic zone. There is as yet insufficient data to show whether, as a whole, the photosynthetic efficiency of the Southern Ocean is greater or less than that of other sea areas. Antarctic algae liberate extracellular products of photosynthesis but there is no definite evidence that these are reassimilated to support growth when light intensities are low and it may be that this material, carried by currents, supports heterotrophic production in other parts of the ocean. Comparison of data for adjacent marine and freshwater systems shows that their rates of primary production are much the same but the marine phytoplankton shows characteristics of shade-adapted cells consistent with the greater turbulence to which it is exposed.

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