Climate warming impact on alpin lake´s bacterioplankton

If present trends on mean air temperature continue, climate change will strongly impact the ecology, biology, and chemistry of aquatic ecosystems. Particularly, high-mountain lakes in the Alps have been found to be extremely sensitive to climatic warming. In the short-term, higher mean air temperatures will affect the integral of incident solar ultraviolet (UV) radiation received by those lakes because of the earlier disappearance of the ice/snow cover. In a longer time scale, it might lead to changes in the origin (i.e., quality) of the organic substances fueling the microbial food web due to better conditions for development of terrestrial vegetation in the catchment. Up to now, knowledge on the consequences of these potential changes for the functioning and structure of lake`s microbial compartments is scarce or not available. Thus, in this project we aim to assess the response of the bacterial assemblage of a high-mountain lake to UV radiation concomitantly to changes in the quality of organic substances. Changes in the bacterial community composition and activity will be assessed considering both factors separately and together, as the quality of dissolved organic substances influences the water transparency to UV radiation. We will focus on heterotrophic bacteria because due to their short generation times they respond faster than other biological compartments to environmental changes. Research will be conducted both in the field (mesocosms) and in the laboratory using a combination of methods to estimate the abundance, biomass, activity, and composition of bacterioplankton as tracked by the (CARD)-FISH method. Results obtained in this project will fundamentally contribute to understand the potential impact of climate change on bacterioplankton and thus on the biogeochemical cycling of carbon in alpine lakes.