Cell size and other phenotypic traits of prokaryotic cells in pelagic areas of the Ross Sea (Antarctica)

We test the suitability of microbial parameters to assess environmental pressures, and investigate the abundance and phenotypic traits of prokaryotic cells in an Antarctic area. During two oceanographic cruises, carried out in 2001 and 2005, seawater samples were collected in two mooring stations of the Ross Sea. As ancillary parameters, determinations of lipopolysaccharides, chlorophyll a , and/or fractionated adenosine- tri -phosphate were done. Furthermore, in the 2005 survey, six more stations were sampled. Results show that prokaryotic cells—in terms of abundance, shape, and size—change in relation with environmental changes. Prokaryotic abundance was high, where a strong condition of eutrophication was detected. Sizes of cells showed the prevalence of very small forms (>0.1 μm 3 ), but larger morphotypes were observed in high trophic conditions (till 0.4 μm 3 ). In Antarctic marine systems, such prokaryotic parameters can be used to evaluate environment status.