Microbial community structure in the hadal water is reported to be different from that in the upper abyssal water. However, the mechanism governing the difference has not been fully understood. In this study, we investigate the vertical distributions of humic-like fluorescent dissolved organic matter (FDOM_H), chemoautotrophic production, apparent oxygen utilization (AOU), and N* in the Izu-Ogasawara Trench. In the upper abyssal waters (< 6000 m), FDOM_H has a significantly positive correlation with AOU; FDOM_H deviates from the relationship and increases with depth without involving the increment of AOU in the hadal waters. This suggests that FDOM_H is transferred from the sediments to the hadal waters through pore water, while the FDOM_H is produced in situ in the upper abyssal waters. Chemoautotrophic production and N* increases and decreases with depth in the hadal waters, respectively. This corroborates the effluxes of dissolved substances, including dissolved organic matter and electron donors from sediments, which fuels the heterotrophic/chemoautotrophic microbial communities in the hadal waters. A simple box model analysis reveals that the funnel-like trench topography facilitates the increase in dissolved substances with depth in the hadal waters, which might contribute to the unique microbiological community structure in these waters.

据报道，在深海水域的微生物群落结构与上层深海水域的微生物群落结构不同。然而，控制差异的机制尚未完全了解。在这项研究中，我们调查了伊豆-小笠原海沟中类腐殖质荧光溶解有机物 (FDOM _H )、化学自养产生、表观氧利用 (AOU) 和 N*的垂直分布。在上层深海水域（< 6000 m），FDOM _H与AOU 呈显着正相关；FDOM _H偏离该关系并随深度增加而未涉及深海水域中 AOU 的增加。这表明 FDOM _H通过孔隙水从沉积物转移到深渊水中，而 FDOM_H是在上层深海水域原位生产的。化能自养产生和 N* 分别随着深海水域的深度增加和减少。这证实了溶解物质的流出，包括来自沉积物的溶解有机物质和电子供体，这些物质为海水中的异养/化学自养微生物群落提供燃料。一个简单的盒子模型分析表明，漏斗状的沟渠地形促进了深渊水中溶解物质的增加，这可能有助于这些水域中独特的微生物群落结构。