The P yramid T rough W etland: environmental and biological diversity in a newly created A ntarctic protected area

The P yramid T rough (Lat 78°S) has recently gained protection under the A ntarctic T reaty system, owing to its wetland values. Here, we describe the microbial diversity of this system, with emphasis on cyanobacteria, and evaluate environment–biota relationships. Geochemistry separates ponds along hydrological gradients receiving recent inflows of dilute meltwater, from a second group that is rarely inundated and where chemistry is dominated by evaporation. Cyanobacteria‐based microbial mats dominated the biota throughout. Mats were characterized by light‐microscopy, pigment analysis, automated ribosomal intergenic spacer analysis and 16S rRNA gene clone libraries. A total of 17 morphotypes and 21 ribotypes were identified, mostly O scillatoriales and several taxa that are usually rare in continental A ntarctica, including C hroococcales and scytomin‐rich C alothrix/ D ichothrix , were abundant. There was a general decline in cyanobacterial diversity with increasing conductivity, but weak support for either differences in community composition between the two groups of ponds or sorting of taxa along the hydrological gradients with the pond groups. This implies a broad environmental tolerance and a prevalence of neutral assembly mechanisms in cyanobacterial communities of A ntarctic wetland ecosystems.