Supplementary file 4_Hotspots beyond borders: quantitative assessment of Vulnerable Marine Ecosystems on the Corner Rise seamounts with implications for conservation planning.pdf

The Corner Rise Seamounts (CRS), located in an area beyond national jurisdiction (ABNJ), are recognized biodiversity hotspots protected from bottom-contact fishing by the Northwest Atlantic Fisheries Organization (NAFO). These seamounts are registered as an Other Effective Area-Based Conservation Measure. The Western Central Atlantic Fisheries Commission (WECAFC) has also recommended protection for the southern CRS. While Vulnerable Marine Ecosystem (VME) indicators like corals and sponges are known to occur here, the environmental drivers of their distribution and the status of structure-forming VME habitats remain poorly characterized. We analyzed high-resolution remotely-operated vehicle video from NOAA’s 2021 Okeanos Explorer expedition across eight CRS (940-4,189 m depth). Coral and sponge community composition was assessed using multivariate analysis, and VMEs were identified using internationally recognized spatial criteria. Community structure was primarily driven by depth-related oceanographic gradients, with secondary longitudinal zonation. Assemblages formed three distinct clusters on the seamounts: (1) upper-mid bathyal sites (900-1,900 m) influenced by upper intermediate North Atlantic waters; (2) lower bathyal sites (2,000-2,600 m) associated with Labrador Sea Water; and (3) an abyssal site on Rockaway Seamount (~4,100 m) under Denmark Strait Overflow Water influence. Six habitats down to 2,495 m depth met VME indicator density thresholds for significant concentrations. Our results demonstrate that depth and water mass structure are key drivers of coral and sponge biogeography on the CRS. VME identification provides scientific support for maintaining existing NAFO and WECAFC closures. With NAFO protections due for review in 2027, these findings offer timely evidence to inform conservation and management decisions for CRS and similar ABNJ seamount ecosystems.