Benthic mats in Antarctica: biophysical coupling of sea-bed hypoxia and sediment communities

Transient white and grey mats were observed in depressions and enclosed basins in marine sediment in the Windmill Islands, East Antarctica. These patches have not been described in the Antarctic marine environment previously although a similar phenomenon has been described in the Arctic. Our aim was to describe the sediment geochemical and biological properties inside the patches and to determine their similarity to each other. We compared the benthic infaunal communities and the chemical properties of the sediment in the white patches to nearby sediment without white mats. We observed differences in sediment pH, Eh and elemental concentrations inside and outside patches. The benthic infaunal communities inside the patches were significantly different, lower in abundance and diversity, compared to outside the patches. The structure of the microbial communities within the mats was described by constructing clone libraries from four different patches. These clone libraries were dominated by bacteria from the bacteroidetes phylum. Clones closely related to sulphur-oxidising bacteria from the gammaproteobacteria and/or the epsilonproteobacteria were present in all libraries. This is the first detailed description of these patches in the Antarctic and demonstrates the link between physico-chemical factors and microbial and infaunal community structure. It appears that this phenomenon may be driven by the formation and persistence of sea-ice, and as both the spatial extent of sea-ice and its persistence in polar regions are likely to change under predicted climate change scenarios, we suggest this is a previously undocumented mechanism for climate change to impact polar ecosystems.