Applications of compound-specific mass spectrometry to investigate microbial dynamics in Antarctic soils

ABSTRACT Applications of compound-specific mass spectrometry to investigate microbial dynamics in Antarctic soils?Claire A Horrocks1, Jennifer A.J. Dungait1, Filipa Cox2, Kevin K. Newsham3, Roland Bol4, Clare H. Robinson21 Sustainable Soils and Grassland Systems Department, Rothamsted Research-North Wyke, Okehampton, Devon EX20 2SB, UK2 School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Oxford Road, Manchester, M13 9PL, UK3 British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge, CB3 0ET, UK4 Institute of Bio- and Geosciences, Forschungszentrum Jülich, Jülich, GermanyThe activity of soil microorganisms that mineralize soil organic matter (SOM) are difficult to quantify because of the cryptic nature of soils. Measuring biological responses to changing temperature in soils is absolutely key to predicting feedbacks to climate change. The rates of warming in the terrestrial Maritime Antarctic over the past 50-100 years are some of the fastest rates recorded. In this project we sampled soils from islands on a 3000 km latitudinal transect from the sub-Antarctic (Brown non-permafrost soil of Bird Island), low Maritime Antarctic (Brown soil of Signy Island) and high Maritime Antarctic (frozen organic soil of Léonie Island) to investigate the impact of climate change on SOM dynamics. Bulk natural abundance 13C/15N stable isotope analysis was used to investigate the differences in SOM dynamics between the islands. This revealed differences in values between islands and different degrees stratification of soil horizons with depth suggesting increased freeze/thaw cycles on Signy Island. Geochemical biomarkers of bacteria and fungi (phospholipid fatty acids, PLFA; ergosterol and amino sugars) were extracted from depth increments down the soil profile to estimate the changes in microbial abundance and community composition. Fungal activity was greater at lower latitudes. Compound-specific stable 13C isotope analysis of wax lipids (long chain n-alkanes) extracted from plants, guano and soils explored whether there were changes in organic input to the soils, and these were compared with PLFAs 13C values to distinguish any differences in source between islands and within soil profiles.We conclude that there were differences between the microbial activity on the islands along the transect, and that this is probably due to the effect of climate change on freeze/thaw cycles in soils and the nature of organic matter inputs