Laroche Olivier, Kersten Oliver, Smith Craig R, Goetze Erica
Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii at Mānoa, Honolulu, HI, USA.
Centre for Ecological and Evolutionary Synthesis, University of Oslo, Oslo, Norway.
Mol Ecol. 2020 Dec;29(23):4588-4604. doi: 10.1111/mec.15484. Epub 2020 Jun 14.
The deep seafloor serves as a reservoir of biodiversity in the global ocean, with >80% of invertebrates at abyssal depths still undescribed. These diverse and remote deep-sea communities are critically under-sampled and increasingly threatened by anthropogenic impacts, including future polymetallic nodule mining. Using a multigene environmental DNA (eDNA) metabarcoding approach, we characterized metazoan communities sampled from sediments, polymetallic nodules and seawater in the western Clarion Clipperton Zone (CCZ) to test the hypotheses that deep seamounts (a) are species richness hotspots in the abyss, (b) have structurally distinct communities in comparison to other deep-sea habitats, and (c) that seafloor particulate organic carbon (POC) flux and polymetallic nodule density are positively correlated with metazoan diversity. eDNA metabarcoding was effective at characterizing distinct biotas known to occur in association with different abyssal substrate types (e.g., nodule- and sediment-specific fauna), with distinct community composition and few taxa shared across substrates. Seamount faunas had higher overall taxonomic richness, and different community composition and biogeography than adjacent abyssal plains, with seamount communities displaying less connectivity between regions than comparable assemblages on the abyssal plains. Across an estimated gradient of low to moderate POC flux, we find lowest taxon richness at the lowest POC flux, as well as an effect of nodule size on community composition. Our results suggest that while abyssal seamounts are important reservoirs of metazoan diversity in the CCZ, given limited taxonomic overlap between seamount and plains fauna, conservation of seamount assemblages will be insufficient to protect biodiversity and ecosystem function in regions targeted for mining.
深海海底是全球海洋生物多样性的一个储存库，深渊深度处80%以上的无脊椎动物仍未被描述。这些多样且偏远的深海群落采样严重不足，并且日益受到包括未来多金属结核开采在内的人为影响的威胁。我们采用多基因环境DNA（eDNA）宏条形码方法，对从克拉里昂-克利珀顿区（CCZ）西部的沉积物、多金属结核和海水中采集的后生动物群落进行了特征分析，以检验以下假设：（a）深海海山是深渊中物种丰富度的热点地区；（b）与其他深海栖息地相比，海山具有结构上不同的群落；（c）海底颗粒有机碳（POC）通量和多金属结核密度与后生动物多样性呈正相关。eDNA宏条形码在表征已知与不同深渊底物类型相关的独特生物群（例如，结核和沉积物特有的动物群）方面很有效，不同底物的群落组成不同，共享的分类单元很少。海山动物群的总体分类丰富度更高，与相邻的深海平原相比，群落组成和生物地理学也不同，海山群落区域间的连通性低于深海平原上类似的组合。在估计的低到中等POC通量梯度上，我们发现在最低POC通量下分类单元丰富度最低，以及结核大小对群落组成有影响。我们的结果表明，虽然深海海山是CCZ后生动物多样性的重要储存库，但鉴于海山和平原动物群之间的分类重叠有限，保护海山组合不足以保护目标采矿区域的生物多样性和生态系统功能。
