Hadal trenches represent the deepest part of the ocean and are dynamic depocenters with intensified prokaryotic activity. Here, we explored the distribution and drivers of prokaryotic and viral abundance from the ocean surface and 40 cm into sediments in two hadal trench regions with contrasting surface productivity. In the water column, prokaryotic and viral abundance decreased with water depth before reaching a rather stable level at ~ 4000 m depth at both trench systems, while virus to prokaryote ratios were increasing with depth, presumably reflecting the declining availability of organic material. Prokaryotic and viral abundances in sediments were lower at the adjacent abyssal sites than at the hadal sites and declined exponentially with sediment depth, closely tracking the attenuation of total organic carbon (TOC) content. In contrast, hadal sediment exhibited erratic depth profiles of prokaryotes and viruses with many subsurface peaks. The prokaryotic abundance correlated well to extensive fluctuations in TOC content at centimeter scale, which were likely caused by recurring mass wasting events. Yet while prokaryotic and viral abundances cross correlated well in the abyssal sediments, there was no clear correlation in the hadal sites. The results suggested that dynamic depositional conditions and higher substrate availability result in a high spatial heterogeneity in viral and prokaryotic abundances in hadal sediments in comparison to more stable abyssal settings. We argue that these conditions enhance the relatively importance of viruses for prokaryotic mortality and carbon recycling in hadal settings.

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克马德克和阿塔卡马海沟地区原核生物和病毒丰度的空间变异性

哈达尔海沟代表了海洋的最深处，是原核生物活动增强的动态沉积中心。在这里，我们探索了海洋表面和 40 厘米处沉积物中原核和病毒丰度的分布和驱动因素，这些丰度在两个海沟区域具有对比的表面生产力。在水体中，原核生物和病毒丰度随水深而降低，然后在两个海沟系统的约 4000 m 深度达到相当稳定的水平，而病毒与原核生物的比率随深度增加，可能反映了有机物质的可用性下降。邻近深海位点沉积物中的原核和病毒丰度低于深海位点，并且随着沉积物深度呈指数下降，密切跟踪总有机碳 (TOC) 含量的衰减。相比之下，哈达尔沉积物表现出原核生物和病毒的不规则深度剖面，具有许多地下峰。原核丰度与厘米级 TOC 含量的广泛波动密切相关，这可能是由反复发生的质量浪费事件引起的。然而，虽然深海沉积物中的原核和病毒丰度相互关联，但在深海地点没有明显的相关性。结果表明，与更稳定的深海环境相比，动态沉积条件和更高的底物可用性导致了深海沉积物中病毒和原核生物丰度的高度空间异质性。我们认为，这些条件增强了病毒对原核生物死亡率和原核环境中碳循环的相对重要性。