Melting glacier impacts community structure of B acteria, A rchaea and F ungi in a C hilean P atagonia fjord

Jorge Montt glacier, located in the Patagonian Ice Fields, has undergone an unprecedented retreat during the past century. To study the impact of the meltwater discharge on the microbial community of the downstream fjord, we targeted Bacteria, Archaea and Fungi communities during austral autumn and winter. Our results showed a singular microbial community present in cold and low salinity surface waters during autumn, when a thicker meltwater layer was observed. Meltwater bacterial sequences were related to Cyanobacteria, Proteobacteria, Actinobacteria and Bacteriodetes previously identified in freshwater and cold ecosystems, suggesting the occurrence of microorganisms adapted to live in the extreme conditions of meltwater. For Fungi, representative sequences related to terrestrial and airborne fungal taxa indicated transport of allochthonous Fungi by the meltwater discharge. In contrast, bottom fjord waters from autumn and winter showed representative Operational Taxonomic Units (OTUs) related to sequences of marine microorganisms, which is consistent with current models of fjord circulation. We conclude that meltwater can significantly modify the structure of microbial communities and support the development of a major fraction of microorganisms in surface waters of Patagonian fjords.