Meeting Abstract

S7.11  Tuesday, Jan. 5  Community Dynamics in a Polar Ecosystem: Benthic Recovery From Organic Enrichment in the Antarctic KIM, Stacy*; THURBER, Andrew; HAMMERSTROM, Kamille; Moss Landing Marine Labs; Scripps Institution of Oceanography; Moss Landing Marine Labs skim@mlml.calstate.edu

Antarctic nearshore marine ecosystems are oligotrophic; primary productivity is light limited by the ice overhead as well as the long dark period in the annual cycle. Local productivity depends not only on latitude but also on advection from areas to the north. In this food-poor system, sewage from research bases is a rich source of organic material and can also bury existing communities. An experiment to test benthic community recovery from these two disturbances was conducted in McMurdo Sound. The eastern sound generally experiences an annual pulse of production, but the west side becomes ice-free only every decade or so. Organic enrichment reduced both species richness and abundance at all sites, with abundance increasing over 2 years. Burial did not affect richness but slightly reduced abundance in the first year. Scavenger exclusion had no effect on community recovery. As in more temperate ecosystems, community recovery initiated rapidly, however, richness remained low after two years though overall abundance was recovering. Extremely oligotrophic sites were most highly impacted, possibly because of the lack of a local larval source. Nevertheless, on the scale of these experiments (patch size tens of cm2) there is a suite of r-selected infaunal species that is capable of taking advantage of intense organic input such as might come from natural vertebrate sources (e.g. Weddell seal feces). Large and continuous organic input (tens of m2 from the sewage outfall) resulted in the development of an anaerobic microbial mat that effectively excluded multicellular eukaryotic species. Recovery of outfall-impacted communities is facilitated by disturbance to the microbial mat that allows infaunal colonization.