Environmental drivers of abyssal benthic megafaunal biodiversity in the south-central Clarion-Clipperton Zone, Pacific Ocean

The Clarion-Clipperton Zone (CCZ) in the eastern-central Pacific Ocean supports diverse deep-sea megafaunal communities, many of which are associated with polymetallic nodules that provide hard substrates contributing to abyssal habitat heterogeneity. Beyond their ecological importance, nodules are considered a critical mineral resource, making the CCZ a prime target for deep-sea mining. Little is known, however, about the combined effects of variations in nodule cover, geographic distance (inter-sample distance), ocean depth, and nutrient flux on the structuring of benthic communities across the CCZ mining-licensed areas. Understanding the interplay between environmental factors at local scales is critical for developing ecosystem-based conservation strategies before mining activities begin. Here, we used seabed image analyses to investigate spatial variation in megafaunal communities within the Korea Reserved 5 site, approximately 42,000 km2 in the south-central CCZ, to evaluate abiotic drivers determining alpha and beta diversity. We observed significant variations in community density, diversity, and structure that were broadly associated with differences in nodule coverage, with high diversity, though not density, generally associated with high nodule coverage. Nonetheless, the observations of low density alongside high alpha diversity in some areas with high nodule coverage, coupled with substantial within-area dissimilarity in beta diversity, suggest that environmental factors beyond nodule coverage also influence megafaunal communities in this area. Generalized dissimilarity modeling evidenced that multiple environmental drivers shaped beta diversity patterns. Depth was the most influential for the whole megafaunal community, followed by nodule coverage and geographic distance. For Cnidaria, the most abundant group, nutrient flux variation was an additional driver. These environmental factors operated at different ecological scales and jointly shaped the spatial structuring of megafaunal communities within the study site. This knowledge will aid the regulation of mining activities within licensed areas and the development of effective conservation strategies and policies in one of Earth’s last wildernesses.