Modelling microbial diversity in Antarctic soils

Abstract

Microorganisms play a crucial role in supporting biodiversity, maintaining marine and terrestrial ecosystems at the crux of the nutrient cycle. They are the most diverse and abundant of all living creatures, yet little is understood about their distribution or their intimate relationship with the environment. Antarctic ecosystems are among the most simple on Earth; with basic trophic structuring and the absence of many taxonomic groups, they are also isolated geographically with small patchy areas of nutrient inputs. In this instance, Antarctica becomes a pristine laboratory to examine the ecological paradigms already applied to macro-organisms, to determine if common biological laws govern the distribution of biology globally. The decline of biodiversity with increasing latitude is one such observation in the distribution of macro-organisms. In this study, soil microbial community samples were retrieved over a latitude of 56 to 72 °S across the Antarctic Peninsula region. This is a region of special interest due to a rapidly warming climate with mean temperatures increasing at several times the rate of mean global warming. Sites were biologically and environmentally profiled and data used in a variety of multivariate analysis in order to identify spatial trends and infer mechanisms that may be driving Antarctic terrestrial food webs; or where this was not possible, the areas where focus was needed to increase the information profile to allow this. Results indicate a lack of linear latitudinal gradient in microbial diversity, but do show a correlation with environmental heterogeneity; analysis of site diversity identified a gradient between warmer wetter areas, and areas synonymous with cold desert environment at 66⁰S, supported by both phylum composition and indicative soil chemistry. This was confirmed through principal co-ordinates of neighbours’ matrices analysis (PCNM), with distinct regions of community composition being identified when viewed with respect to environmental variables. Considering an overview of diversity with respect to environmental variables provided additional structure to test hypotheses about nutrient webs through structural equation modelling (SEM), and inferred that areas of patchy nutrient input exist and by means of ornithogenic guano additions promote higher C and N availability, increasing microbial abundance and richness.