Life in the Extreme Cold
|Members of the 2003 Antarctic cruise on the Nathaniel B. Palmer (l to r) Becky Gast (WHOI), Julie Rose (USC, red hat), Becky Schaffner (USC, green hat), Matt Travao (USC), Dawn Moran (WHOI), Bob Sanders (Temple), Mark Dennett (WHOI, brown hat), Astrid Schnetzer (USC).|
|from the left the participants are Mark Dennett (WHOI), Dawn Moran (WHOI), Pete Countway (USC), Astrid Schnetzer (USC, back), Steffi Moorthi (USC, front), Bob Sanders (Temple University, back), Julie Rose (U Delaware) and Rebecca Gast (WHOI)|
Mark R. Dennett & Dawn M. Moran Woods Hole Oceanographic Institution
David A. Caron and Julie Rose University of Southern California
The analysis of microbial biodiversity of extreme environments is difficult because traditional methods for examining diversity are often ineffective for assessing species richness within these communities. This problem is not unique to extreme environments, but it is exacerbated in these situations because of the difficulties of recreating and maintaining pertinent environmental features during sample collection and processing. The identification of protistan species in natural assemblages traditionally has entailed direct microscopical analyses (both light and electron microscopy) as well as enrichment and culture techniques for assessing biodiversity. Many small protists (e.g. naked amoebae) are simply not identifiable from preserved specimens. These problems have resulted in profiles of protistan biodiversity that are fragmented, and usually limited to the most abundant species or to those species that are most resilient to culture (i.e. weeds) and/or preservation (e.g. species with skeletal structures).
We are conducting a two-pronged research program in the Ross Sea, Antarctica, focusing on (1) the development and application of molecular biological approaches to assess species diversity of small protists (algae and protozoa <100 micrometers), and (2) the enrichment, isolation and culture of psychrophilic/psychrotolerant species of protozoa for baseline physiological studies under laboratory conditions. Our goal in the molecular aspect of the program is to use culture-independent means to assess biodiversity of protistan assemblages. Protozoa also will be enriched, isolated and cultured at ambient water temperatures to provide clonal cultures of protozoa. These clonal cultures will be characterized with respect to their growth and feeding rates, and growth and remineralization efficiencies over a range of pertinent temperatures. The srDNA of these cultured species also will be sequenced and compared to sequences obtained directly in the biodiversity studies in order to assess their numerical importance in the natural assemblages.