Structure and diversity of soil algal communities from Cierva Point (Antarctic Peninsula)

Cyanobacteria and eukaryotic algae, together with bacteria and fungi, ale known to be primary colonizers of mineral soils throughout Antarctica. Their species diversity and soil coverage were studied in 18 soil polygons located at Cierva. Point, Antarctic Peninsula. Undisturbed assemblages were dominated by filamentous Cyanobacteria and cliatoms, whilst almost 40% of the 49 species recorded were observed only after enrichment culture. Nearly all of the isolates from enrichment cultures were Chlorophyta and Tribophyceae. This revealed a higher degree of complexity than reported for similar communities on Signy Island. Water content and concentrations of nutrients were determined at four representative sites, and did not appear to account for the large inter-polygon variation found in species composition and relative frequencies of occurrence. Variables describing community development were not significantly correlated with either area of the polygons or the minimum distance between them. This suggested that these features are not an important short-range barrier to dispersal for those "weed" species dominating the community. Conversely, the relative frequencies of some of the most common species showed significant correlations with species diversity and soil coverage, and it is suggested that biotic interactions could account to a larger extent for community structure than previously reported from Signy Island fellfields.