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> JEUDI 25 JANVIER 2018, 13h15 \ 14h00
Microbial and viral communities of Hadal Trenches
par Clemens Schauberger Department of Microbiology and Ecosystem Science, Vienne, Autriche
The hadal zone is reached at 6.5 km water depth and stretches thousands of kilometres along tectonic subduction zones, covering about 2% of the global ocean floor. Due to their remoteness and extreme pressures, they remain one of the most scantly explored marine habitats. Life in these settings are energetically dependent on the supply of organic material from the overlying water column. Nevertheless, hadal sediments were recently recognized as hotspots of deposition and mineralization, relative to surrounding abyssal plains. However, the microbial communities that regulate and catalyse these processes remain virtually unknown. One of the major challenges hindering accurate investigations on such deep-sea communities are artefacts associated with sample recovery. These artefacts are already well documented for biogeochemical parameters, and analogous effects on microbial abundance, community composition and rRNA profiles seem likely but remain unknown. To minimize and investigate these sampling artefacts, we developed autonomous sampling instruments, which are either capable of injecting e.g. isotope tracers via needles into sediment cores, or fixating microbes and viruses of the water column in situ with a syringe system. In addition, we are conducting lab based investigations on the stability of ribosomal RNA to potential changes imposed by sediment recovery and effects of hydrostatic pressure to the abundance of chemically fixed microbial cells. In situ fixations for microbial cell counts in combination with in situ incubations should be an important step towards artefact free studies on deep sea samples and ultimately enable us to explore and characterize the uniqueness in both structure and function of microbial communities across hadal trenches in low, intermediate, and high productivity regions of the ocean.
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