Schauberger Clemens, Middelboe Mathias, Larsen Morten, Peoples Logan M, Bartlett Douglas H, Kirpekar Finn, Rowden Ashley A, Wenzhöfer Frank, Thamdrup Bo, Glud Ronnie N
Department of Biology, Nordcee and HADAL University of Southern Denmark Odense Denmark.
Marine Biological Section, Department of Biology University of Copenhagen Helsingør Denmark.
Limnol Oceanogr. 2021 Jun;66(6):2095-2109. doi: 10.1002/lno.11711. Epub 2021 Feb 28.
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.
超深渊海沟是海洋的最深处，是具有强化原核生物活动的动态沉积中心。在此，我们探究了在两个具有不同表层生产力的超深渊海沟区域，从海洋表层至沉积物40厘米深处原核生物和病毒丰度的分布及驱动因素。在水柱中，原核生物和病毒丰度随水深降低，在两个海沟系统约4000米深度处达到相对稳定水平，而病毒与原核生物的比率随深度增加，这可能反映了有机物质可用性的下降。相邻深海站点沉积物中的原核生物和病毒丰度低于超深渊站点，且随沉积物深度呈指数下降，紧密跟踪总有机碳（TOC）含量的衰减。相比之下，超深渊沉积物中原核生物和病毒的深度剖面不稳定，有许多次表层峰值。原核生物丰度与厘米尺度上TOC含量的广泛波动密切相关，这可能是由反复发生的大规模物质流失事件引起的。然而，虽然原核生物和病毒丰度在深海沉积物中具有良好的交叉相关性，但在超深渊站点却没有明显的相关性。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超深渊沉积物中病毒和原核生物丰度具有高度的空间异质性。我们认为，这些条件增强了病毒在超深渊环境中对原核生物死亡率和碳循环作用的相对重要性。
