Polymetallic nodules increase habitat heterogeneity in some abyssal benthic ecosystems by providing hard substrate. Besides their important role in structuring ecosystems, polymetallic nodules have high grades of valuable minerals and are a target of likely future exploitation, particularly in the Pacific Clarion-Clipperton Zone (CCZ). Mining activities will remove hard substrate and sediment and cause sediment plumes potentially affecting faunal communities over large areas. Long-lived megafaunal assemblages may be particularly vulnerable but data are lacking on the density, biodiversity and community structure in many areas of the CCZ. This study aims to provide megabenthic community baseline data from two physically similar areas (B6S02 and B4S03) located in the contract area of Global Sea Mineral Resources N.V. (GSR). Seafloor images, obtained by an autonomous underwater vehicle are used to characterise the large areas required for robust evaluation of sparse megafauna. Higher altitude images cover a larger area for the same effort but have reduced resolution compared to images obtained closer to the seafloor, leading to difficulties in detecting and identifying individuals. Our comparison of images obtained at different altitudes shows that images taken above 8m altitude underestimate the megafauna density by almost 50%, so images <8m were used for further analysis. We also used multiobserver agreement analysis to improve the megafaunal annotation consistency, and the quality and robustness of the data in this study. The two GSR areas were significantly different in nodule coverage and megafauna composition and a general positive relationship between nodule coverage and megafauna abundance was observed. Differences in the megafaunal composition were primarily caused by differences in echinoderms (asteroids, echinoids, ophiuroids and holothuroids), representing almost 70% of the megafauna.

多金属结核通过提供坚硬的基质，在一些深海底栖生态系统中增加了栖息地的异质性。除了在构造生态系统中的重要作用之外，多金属结核还具有高品位的有价值的矿物质，并且是未来可能开采的目标，特别是在太平洋克拉里昂-克利珀顿区（CCZ）。采矿活动将清除坚硬的底物和沉积物，并造成沉积物羽流，从而可能影响大面积的动物群落。长寿命的大型动物群落可能特别脆弱，但缺乏CCZ许多地区的密度，生物多样性和群落结构数据。这项研究旨在提供位于全球海洋矿产资源NV（GSR）合同地区的两个物理相似区域（B6S02和B4S03）的大型底栖动物群落基线数据。海底图片，由自动水下航行器获得的数据用于表征对稀疏巨型动物进行鲁棒评估所需的大面积。较高的高度图像以相同的努力覆盖了较大的区域，但与距离海底较近的图像相比，分辨率降低了，从而导致难以检测和识别个人。我们对在不同高度获得的图像的比较表明，在海拔8m以上拍摄的图像低估了大型动物的密度，几乎降低了50％，因此使用<8m的图像进行进一步分析。在本研究中，我们还使用了多观察者一致性分析来改善大型动物注释的一致性，以及数据的质量和鲁棒性。这两个GSR区域的结核覆盖度和大型动物组成明显不同，并且观察到结核覆盖度与大型动物丰富度之间存在大致正相关关系。巨型动物组成的差异主要是由棘皮动物（小行星，棘突类动物，蛇类和类类动物）的差异引起的，占到了大型动物的近70％。