Pressure-induced leakage of dissolved organic matter (DOM) from different diatom species@en

Four diatom strains obtained from different culture collections were grown to stationary phase in L1 medium plus silicate (Guillard & Hargraves 1993) at 15°C under a light/dark regime of 14/10 h. For experimentation, the diatom strains were incubated at either atmospheric pressure (0.1 MPa = control treatment) or at gradually increasing hydrostatic pressure (0.1-100 MPa = pressure treatment) throughout 21 days in darkness and at 3°C. The pressure treatment simulated the sinking of particle-associated diatoms from the ocean surface down into a hadal trench of 10 km depth. Pressure-induced leakage of dissolved organic matter (DOM) was followed throughout the incubations. Both ambient concentrations and intracellular concentrations of different DOM components were measured: Dissolved organic carbon (DOC), total dissolved nitrogen (TDN), protein-like and humic-like DOM fluorescence, total proteins, total polysaccharides, laminarin, and dimethylsulfoniopropionate (DMSP). The cell abundance of the different diatom strains was followed throughout the incubations.本研究从不同培养保藏中心获取4株硅藻，将其置于添加硅酸盐的L1培养基（Guillard & Hargraves 1993）中培养至静止期，培养条件为15℃、14小时光照/10小时黑暗的光暗周期。实验阶段，将上述硅藻菌株分别置于常压（0.1 MPa，作为对照处理）或逐步升高的静水压（0.1~100 MPa，作为加压处理）条件下培养，全程保持黑暗、温度控制为3℃，培养周期为21天。该加压处理模拟了附着于颗粒的硅藻从海洋表层沉降至10千米级深渊海沟的全过程。培养期间全程追踪静水压诱导的溶解有机质（dissolved organic matter, DOM）渗漏过程。本次实验测定了多种溶解有机质组分的环境浓度与胞内浓度，涵盖溶解有机碳（dissolved organic carbon, DOC）、总溶解氮（total dissolved nitrogen, TDN）、类蛋白与类腐殖质DOM荧光信号、总蛋白质、总多糖、褐藻淀粉（laminarin）以及二甲基巯基丙酸内盐（dimethylsulfoniopropionate, DMSP）。培养期间同步追踪各硅藻菌株的细胞丰度变化。