ANTARCTIC RESEARCH SERIES, VOL. 70, PP. 155-172, 1996
Pelagic and sea ice microbial communities
The base of the pelagic food web is made up of a diversity of forms including bacteria and autotrophic and heterotrophic nano-
and microplanktonic organisms. In antarctic waters the importance of many of the microbial forms has been underestimated because
of the prevailing dogma that this region is characterized by a short, simple food web, and the technical limitations of recognizing
and quantifying many of the small delicate forms. This chapter focuses on the composition of the base of the food web and,
in particular, the abundance and distribution of heterotrophic flagellates and ciliates. In polar waters, microbial assemblages
inhabit sea ice and the water column; both of these communities are considered in this chapter. Data are scarce from the Western
Peninsula region, so information from the Scotia and Weddell Seas has been incorporated to provide a fuller description of
Microbial assemblages are made up of a number of species. Many of these, particularly species of heterotrophic flagellates and ciliates, are poorly known, and studies have generally identified these organisms at higher taxonomic (or functional) groups. Studies of the water column have shown that the heterotrophic nano- and microplankton are a significant fraction of the particulate biomass. Estimates of grazing suggest they should be important consumers in the antarctic food web. There are too few observations to evaluate seasonality, but present observations suggest that the heterotrophic nano- and microplankton develop following autotrophic blooms and may reach maximum biomass in the summer.
Organisms occupy a variety of microhabitats in the sea ice, but there is presently little data on the importance and contribution of the ice biota to the ecology of the antarctic pelagic system. Similar to the water column, ice assemblages are comprised of a diversity and abundance of both autotrophs and heterotrophs. Many of the same species occur in both ice and water, supporting the hypothesis that ice-associated forms provide a seed population for water column populations.
Citation: Garrison, D. L., and