Arctic Station Dirigibile Italia

Microbial life in the extreme Arctic terrestrial environment (MILEXA)

Call year: 2015 Status: active IADC_id: 36

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Biological Soil Crusts (BSC), microbial communities living on rock surfaces (lithobiota), and cyanobacterial communities of springs and seepages were selected for this study to describe their diversity, evaluate geographic variations and peculiarities, establish a comparison between patterns of development in High- and Low-Arctic environments, and compare them with corresponding counterparts living in mesic temperate climates or in hot and cold deserts. These communities depend from alternating seasonal cycles of water availability, along with other peculiar constrains. Prolonged periods of dryness limit the vegetative activity of BSC and lithobiota to a part of the Arctic summer, while UV irradiation challenges their survival; under the long lasting summer sun, temperature can substantially increase due to the low albedo of these communities which form thin, dark pigmented aggregates, spread on large surfaces, while in winter they are exposed to extreme low temperature and blasting winds without any protection. Also cyanobacterial mats of melt water seepages experience cyclic water availability which conditions their structure and biodiversity, in contrast to spring mat communities which live continuously underwater but are subjected to seasonal cycles of freezing and thawing. A special case is represented by phototrophic communities of homoeothermic springs in which winter dark ecophysiological conditions alternate with summer photosynthesis. We investigate the macro and micro structure and the related hydrodynamic properties of BSC, and their community composition in the initial stages of development; we also look into the process of soil formation and development in relationship to the presence of BSC. We want to understand the role of BSC in reducing erosion, stabilizing the substrate and increasing its nutrient content, thus favouring the establishment of a more complex and resilient vegetation. Our team identify and characterize the dominating members of fungal and cyanobacterial populations which colonise exposed rock surfaces in different microclimatic conditions in the Arctic, with the aim to understand the biodiversity of those communities, living in some of the harshest and most challenging habitats of the terrestrial ecosystems, recalling extraterrestrial conditions. And finally, we identify community members of mats in seepages and spring and characterize their photosynthetic behaviour, with the aim to understand the dependence of their photosynthetic behaviour in response to alternating seasonal conditions of sun light and temperature. Through INTERACT support, our pan-Arctic survey has already included Arctic Station, Disko in West Greenland, Zackenberg in North-East Greenland and Tarfala in high alpine Northern Sweden. During the field work, we mostly collect samples and stabilize them for further manipulation in our home laboratories. There, we apply molecular techniques for the identification of the community members, and isolate strains in pure culture to better characterize them. We determine the soil structure and the hydrological properties of the BSC that are mediated by the presence of a matrix of complex exopolysaccharides released by microorganisms. Photosynthetic activity measurements are either performed in the laboratories of the visited stations and at home on preserved samples and isolated strains. We hope to understand better how water dynamics influence the development of microbial communities in extreme habitats impacted by climate change. Since strong effects of climate change on water balance are not only restricted to the Arctic, we aim to supply valuable information to foresee habitat evolution under conditions where water is a main constrain, not only in the Arctic but also in mesic temperate climates or in hot and cold deserts.

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Microbial life in the extreme Arctic terrestrial environment (MILEXA)