1218 / 2024-09-19 20:57:53

Distribution of megabenthic communities on deep-water seamounts with cobalt-rich crusts in the Magellan Seamount Chain in the northwestern Pacific Ocean

megabenthic communities,deep-water seamounts,species distribution models,vulnerable marine ecosystems

The Magellan Seamount Chain is located in the northwest Pacific Ocean, characterized by ancient oceanic crust and oligotrophic conditions. It is situated at the junction of the Eurasian Plate, the Philippine Sea-Pacific Plate, and the Indo-Australian Plate. The surface of the seamounts in this region has been confirmed to host abundant cobalt-rich ferromanganese crust resources, with high concentrations of metals such as Co, Mn, Cu, Ni, rare earth elements (REE), and platinum group elements (PGE), presenting potential for commercial exploitation. To date, a series of mineral exploration activities have been conducted on Caiwei and Weijia seamounts, and large-scale mineral development is expected. However, the environmental impact of mining activities on the deep-sea ecosystem remains uncertain and requires further investigation.

The seamounts are home to a variety of megabenthic communities, primarily composed of corals and sponges, which are highly vulnerable to human activities such as deep-sea mining and bottom trawling. The limited understanding of the distribution and community structure of benthic megafauna on deep-water seamounts (deeper than 800 meters) hinders the advancement of conservation and management efforts. In this study, video data and corresponding environmental datasets were obtained from 27 survey transects using Human Occupied Vehicle (HOV) and Remotely Operated Vehicles (ROVs) on Caiwei and Weijia seamounts. The distribution of 32 morphospecies of benthic megafauna was predicted, and five megabenthic communities were identified through cluster analysis. Model results indicate that bottom current velocity and direction, bathymetric position index, and backscatter intensity have a significant influence on the distribution of most benthic megafauna. Community composition analysis showed that two communities, located on the seamount ridge and on the northwestern seamounts, had more vulnerable species. The five communities exhibited similar distribution patterns across the two seamounts, suggesting a high level of connectivity between the two seamounts. The distribution of communities revealed the spatial characteristics of vulnerability of deep-water seamounts at the community level, which could provide a direct basis for marine spatial planning of deep-sea ecosystems.