Functioning of deep-sea nano- and microfauna food webs fostered by sedimentation of organic matter

虽然深海构成了生物圈的大部分，但人们对其底栖微生物食物网的结构和功能知之甚少。对于底栖动物中最小的真核生物——原生生物（异养纳米鞭毛虫、裸变形虫和小纤毛虫）来说尤其如此。这与微生物对全球深海碳通量的潜在重要性形成了对比。第一阶段的研究成果主要有：1)发现深海沉积物中原生生物具有极高的多样性，需要进一步了解它们的功能；2)多样性在小尺度和大尺度上都具有特异性；(3) percolcoans、自助纲和placidid鞭毛虫具有特定的分布模式；4)深海群落与上深海区存在显著差异，表明它们具有隔离性；5)大有机颗粒的沉积改变了原生生物群落结构，尽管过程相对缓慢。这里提出了一个更新的建议，以阐明一个特定的方面，即大型有机颗粒（例如沉到海底的马尾藻褐藻）在深海食物网中的作用。我们假设，大型植物下沉作为生物泵的潜在重要组成部分，在深海中构建群落。我们假设马尾藻聚集体在前往深海的途中被微生物定植。此外，我们推测深海纳米和微型底栖生物可能会提高营养贫乏的褐藻的食物质量（例如通过PUFA富集），从而为深海后生底栖动物提供合适的食物来源。我们假设底栖巨型动物和大型动物被马尾藻聚集物的存在所吸引。为了解决这些研究问题，我们打算使用专用的小型ROV系统和随后的沉积褐藻分子分析来研究定植；我们打算进行长期的实验室实验，在第一阶段分离深海原生生物和相关细菌的培养，并在普通花园实验中添加到褐藻中；我们将对现有的高分辨率AUV海底照片进行重新分析，这些照片以5000 m深度的马尾藻强烈下沉事件为特征，以研究微生物定植的大型植物对底栖大型和巨型动物的潜在吸引力。

Although the deep sea makes up most of the biosphere, little is known about the structure and function of its benthic microbial food webs. This is especially true for the smallest eukaryote fraction of the benthos, the protists (heterotrophic nanoflagellates, naked amoebae, and small ciliates). This contrasts with the potential importance that microorganisms may have on global carbon fluxes in the deep sea. Among the results obtained in the first phase were the following results, most of which are new to science and have been published in international journals: 1) We found an extremely high diversity of protists in deep-sea sediments, indicating the need to understand their function; 2) Diversity is specific at small and large spatial scales; 3) Specific distribution patterns were exemplified for percolocoans, cafeteriaceans, and placidid flagellates; 4) Deep-sea communities differ significantly from upper bathyal regions, indicating their isolation; 5) Sedimentation of large organic particles alters protist community structure, albeit in a relatively slow process. A renewal proposal is made here to shed light on a particular aspect, namely the role of sinking of large organic particles (exemplified by Sargassum brown algae sunk to the seafloor) on the deep-sea food web. We hypothesize that macrophyte sinking acts as a potentially important part of the biological pump, structuring communities in the deep sea. We hypothesize that Sargassum aggregates are colonized by microorganisms while still en route to the deep sea. Furthermore, we hypothesize that the deep-sea nano- and microbenthos may enhance the food quality of nutrient-poor brown algae (e.g., through PUFA enrichment), which may then provide a suitable food source for the deep-sea metazoobenthos. And we hypothesize that benthic megafauna and macrofauna are attracted to the presence of sedimented Sargassum aggregates. To address these research questions, we intend to use a dedicated small ROV system and subsequent molecular analyses of sedimented brown algae to study colonization; we intend to conduct long-term laboratory experiments with cultures of deep-sea protists and associated bacteria isolated in the first phase and added to the brown algae in common garden experiments; and we will undertake a re-analysis of existing high-resolution AUV seafloor photos of regions characterized by strong Sargassum sinking events at 5000 m depth to study the potential attraction of microbial-colonized macrophytes to benthic large macro- and megafauna.