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Because of severe abiotic limitations, Antarctic soils represent simplified systems, where microorganisms are the principal drivers of nutrient cycling. This relative simplicity makes these ecosystems particularly vulnerable to perturbations, like global warming, and the Antarctic Peninsula is among the most rapidly warming regions on the planet. However, the consequences of the ongoing warming of Antarctica on microorganisms and the processes they mediate are unknown. Here, using 16S rRNA gene pyrosequencing and qPCR, we report highly consistent responses in microbial communities across disparate sub-Antarctic and Antarctic environments in response to 3 years of experimental field warming (+0.5 to 2 °C). Specifically, we found significant increases in the abundance of fungi and bacteria and in the Alphaproteobacteria-to-Acidobacteria ratio, which could result in an increase in soil respiration. Furthermore, shifts toward generalist bacterial communities following warming weakened the linkage between the bacterial taxonomic and functional richness. GeoChip microarray analyses also revealed significant warming effects on functional communities, specifically in the N-cycling microorganisms. Our results demonstrate that soil microorganisms across a range of sub-Antarctic and Antarctic environments can respond consistently and rapidly to increasing temperatures. [ABSTRACT FROM AUTHOR]

The unusually harsh environmental conditions of terrestrial Antarctic habitats result in ecosystems with simplified trophic structures, where microbial processes are especially dominant as drivers of soil-borne nutrient cycling. We examined soil-borne Antarctic communities (bacteria, fungi and nematodes) at five locations along a southern latitudinal gradient from the Falkland Islands (51°S) to the base of the Antarctic Peninsula (72°S), and compared principally vegetated vs. fell-field locations at three of these sites. Results of molecular (denaturing gradient gel electrophoresis, real-time PCR), biochemical (ergosterol, phospholipid fatty acids) and traditional microbiological (temperature- and medium-related CFU) analyses were related to key soil and environmental properties. Microbial abundance generally showed a significant positive relationship with vegetation and vegetation-associated soil factors (e.g. water content, organic C, total N). Microbial community structure was mainly related to latitude or location and latitude-dependent factors (e.g. mean temperature, NO3, pH). Furthermore, strong interactions between vegetation cover and location were observed, with the effects of vegetation cover being most pronounced in more extreme sites. These results provide insight into the main drivers of microbial community size and structure across a range of terrestrial Antarctic and sub-Antarctic habitats, potentially serving as a useful baseline to study the impact of predicted global warming on these unique and pristine ecosystems. [ABSTRACT FROM AUTHOR]

Biodiversity is threatened by climate change and other human activities [ 1 ], but to assess impacts, we also need to identify the current distribution of species on Earth. Predicting abundance and richness patterns is difficult in many regions and especially so on the remote Antarctic continent, due to periods of snow cover, which limit remote sensing, and the small size of the biota present. As the Earth's coldest continent, temperature and water availability have received particular attention in understanding patterns of Antarctic biodiversity [ 2 ], whereas nitrogen availability has received less attention [ 3 ]. Nitrogen input by birds is a major nutrient source in many regions on Earth [ 4–7 ], and input from penguins and seals is associated with increased plant growth [ 8–10 ] and soil respiration [ 11–13 ] at some Antarctic locations. However, the consequences of increased nitrogen concentrations in Antarctic mosses and lichens for their associated food web has hardly been addressed [ 14, 15 ], despite the fact that nutrient status of primary producers affects the abundance and diversity of higher trophic levels [ 16, 17 ]. We show that nitrogen input and δ15N signatures from marine vertebrates are associated with terrestrial biodiversity hotspots well beyond (>1,000 m) their immediate colony borders along the Antarctic Peninsula. Invertebrate abundance and richness was two to eight times higher under penguin and elephant seal influence. The nitrogen footprint area was correlated with the vertebrate population size. These findings improve our ability to predict biogeographical patterns of Antarctic terrestrial biodiversity through knowledge of the location and size of penguin and elephant seal concentrations. • Antarctic penguins and elephant seals transfer nitrogen from the sea to land • Antarctic vegetation is nitrogen enriched well beyond the colony borders • Terrestrial biodiversity is higher within the nitrogen enrichment footprint • Biodiversity hotspots can be predicted from penguin and elephant seal presence Bokhorst et al. show that the location and size of Antarctic terrestrial biodiversity hotspots can be predicted from the presence of penguin colonies and elephant seal aggregations. Increased abundance and richness of terrestrial invertebrates is linked to the marine-derived nitrogen through δ15N, which extends well beyond the colony borders. [ABSTRACT FROM AUTHOR]