Soil microalgal communities on an antarctic active volcano (Deception Island, South Shetlands)

Contemporary eruptive episodes and present volcanic activity at Deception Island have created a mosaic of different environmental conditions. In this study, the microalgal communities inhabiting 18 sites differing in geology, degree of disturbance and physico-chemical features (texture, water, organic matter and nutrient contents) were characterized in terms of composition, species richness and biomass. One hundred and forty taxa were recorded, with richest communities associated with stable sites and some of the poorest ones in locations affected by recent eruptions. In accordance, a canonical correspondence analysis ordinated species and sites along the first axis according to the percentage of coarse particles, and degree of disturbance (eigenvalues 0.79 and 0.65, P = 0.04). Results of a cluster analysis grouped firstly those algal taxa with high fidelity to one set of environmental conditions, while "ubiquitous" ones had the lowest similarity values. These taxa, mainly filamentous Cyanobacteria and diatoms, are the only colonizers of harsher or recently formed environments.