Alternate carbon pathways at lower trophic levels in the Antarctic food web.

Abstract

Over 50% of total chlorophyll found in waters surrounding Antarctica is contained in the pico- and nanoplankton (<20mu m) size-fraction. approx 30% of the total nanoplankton biomass consists of heterotrophic flagellates. The total phytoplankton standing stock is low, averaging <0.6mu g Chl 1-1 in the East Wind Drift area. Higher concentrations are found in the shallow portions of the Weddell Sea and over the Scotia Ridge. A measurable loss of chlorophyll and cells in the nanoplankton size category apparently results from feeding by heterotrophic microplankton. Ciliate populations in Antarctic environments can attain high cell densities, which suggests they may be an important food reserve for animals requiring microplankton sized food particles. This new information requires that we revise the classical concept of the Antarctic 'diatom-krill' food chain to one which incorporates the feeding by krill (Euphausiacea) on many large-volumed particles (protozoans as well as diatoms), with protozoans acting as a link which couples pico- and nanoplankton production to higher trophic levels.-from Authors