Most of the ocean is deep with the majority of its volume (> 80%) lying under a depth greater than 1000 m. Deep-ocean 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. Deep-sea prokaryotes are known to be adapted to degrade complex substrates. In this study, we investigate the utilization of HMW-DOC on the short temporal scale (10–15 days) by deep-sea prokaryotes maintained at in situ high-pressure conditions. Deep-sea prokaryotic natural assemblages were collected in the Mediterranean Sea in two contrasting hydrological conditions (water column stratification and deep-water formation period conditions). The experimental results were coupled with a cell-quota model, in order to quantify the kinetics of HMW-DOC degradation and its impact on the prokaryotic assemblages under these two contrasting hydrological conditions. The results show that under stratified water conditions autochthonous deep prokaryotic assemblages are able to degrade up to 46.6% of DOC on the timescales of the incubation, when maintained under in situ sampling high-pressure conditions. By contrast, during deep-water convection period condition, DOC is weakly degraded on the timescales of the incubation under in situ high-pressure conditions. This study shows that the remineralization rates of DOC are controlled by the prokaryotic communities, which are further driven by the hydrological conditions of the water column.

大多数海洋深处，其大部分体积（> 80％）位于大于1000 m的深度下。深海底物输入主要通过物理和生物过程以有机物（颗粒和/或溶解形式）形式提供。生物可利用的溶解有机碳（DOC）主要被原核生物消耗在地表水中，而深海中的大多数DOC是顽固的。已知深海原核生物适于降解复杂的底物。在这项研究中，我们调查了原位维持的深海原核生物在短时间范围（10-15天）内对HMW-DOC的利用高压条件。在两个截然不同的水文条件（水柱分层和深水形成期条件）下，地中海收集了深海原核自然组合。实验结果与细胞配额模型耦合，以量化在这两种相反的水文条件下HMW-DOC降解的动力学及其对原核生物组合的影响。结果表明，在分层水条件下，当在原位采样高压条件下进行维持时，在培养的时间尺度上，原生的深原核生物组合能够降解高达46.6％的DOC。相比之下，在深水对流期条件下，DOC在温育条件下的时间尺度上微弱降解。原位高压条件。这项研究表明，DOC的再矿化率是受原核生物群落控制的，而原核生物群落则进一步受到水柱水文条件的驱动。