Cold seeps occur globally in areas where gases escape from the seafloor, occasionally resulting in the formation of topographic depressions (pockmarks), characterised by unique physicochemical conditions such as anoxic and sulphuric sediments. Free-living marine nematodes tend to dominate the meiofaunal component in such environments, often occurring at extremely high densities and low richness; the mechanisms defining community assembly in areas of fluid seepage, however, have received little attention. Here we focus on a low-activity pockmark at 789 m in the Mozambique Channel (MC). We assessed the diversity, co-occurrence patterns and phylogenetic community structure of nematodes at this bathyal site to that of a nearby reference area as well as abyssal sediments using metabarcoding. In addition, we compared our molecularly-derived diversity estimates to replicate samples identified morphologically. Overall, nematode Amplicon Sequence Variants (ASVs) and generic richness were similar between Pockmark and Abyssal sediments, but lower compared to the Reference area. Although more than half the genera were shared, over 80% of ASVs were unique within each area and even within each replicate core. Even though both methodologies differentiated the Pockmark from the Reference and Abyssal sites, there was little overlap between the molecularly and morphologically identified taxa, highlighting the deficit of reference sequences for deep-sea nematodes in public databases. Phylogenetic community structure at higher taxonomic levels was clustered and did not differ between the three areas yet analysis within three shared and dominant genera (Acantholaimus, Desmoscolex, Halalaimus), revealed randomness with respect to phylogeny as well as co-occurrence which was exclusive to the Pockmark area. These patterns point to the influence of neutral dynamics at this locality resulting from the stochastic sampling of early colonizing taxa, the successional stage at sampling and/or the functional redundancy within the investigated genera.

冷渗漏在全球范围内发生，这些区域的气体从海底逸出，偶尔会导致地形凹陷（麻点）的形成，其特征是独特的物理化学条件，例如缺氧和含硫沉积物。在这种环境中，自由生活的海洋线虫往往是主要的动植物成分，通常以极高的密度和低的丰度发生。然而，在流体渗流区域定义社区聚集的机制很少受到关注。在这里，我们重点关注莫桑比克海峡（MC）789 m处的低活动麻点。我们使用metabarcoding评估了该海底站点到附近参考区域的线虫的多样性，共生模式和系统发育群落结构，以及深海沉积物。此外，我们将分子衍生的多样性估计值进行了比较，以复制从形态上识别出的样本。总体而言，Pockmark和深渊沉积物的线虫扩增子序列变异体（ASV）和一般丰富度相似，但低于参考区域。尽管共有超过一半的属，但在每个区域甚至每个复制核心中，超过80％的ASV是唯一的。即使这两种方法都将“麻子标记”与“参考”和“深渊”站点区分开，但在分子和形态学上识别的分类单元之间几乎没有重叠，这突显了公共数据库中深海线虫参考序列的不足。在较高分类学水平上的系统发育群落结构是聚类的，并且在三个区域之间没有差异，但在三个共有和显性属中进行了分析（Acantholaimus，Desmoscolex，Halalimus），揭示了系统发育和共生方面的随机性，这是Pockmark区域所独有的。这些模式指出了由早期定殖类群的随机采样，采样的连续阶段和/或所研究属内的功能冗余所导致的该位置中性动力学的影响。