Pressure-retaining sampler to study deep-sea microbial activity and diversity of prokaryotes under in situ conditions

Abstract:

Most of the ocean is deep with the majority of its volume (high than 80%) lying under a depth higher than 1000 m and is poorly sampled (lower than 0.01%). It is characterized by high hydrostatic pressure, low temperature, high inorganic nutrients and low organic carbon concentrations. Substrates input is mainly supplied as organic matter (in particulate and/or dissolved forms) by physical and biological processes. Bioavailable dissolved organic carbon (DOC) is mainly consumed in surface water by prokaryotes, while most of DOC in the deep ocean is recalcitrant, more difficult to degrade. To study deep-sea prokaryotes under in situ conditions, we have a ready-to-use pressure-retaining sampler, which can be adapted to use on a CTD-carousel sampler and able to collect, to transfer and to incubate sample under in situ conditions (high hydrostatic pressure and temperature). Firstly, we have shown that maintaining in situ condition is the best way to study the ability of deep-sea microbes to utilize recalcitrant dissolved organic matter. Secondly, we have shown that the composition of the prokaryotic community is influenced by sampling methods.