Abstract

Aim Seamounts are key components of deep-sea ecosystems. Yet, their biodiversity patterns and conservation needs remain poorly understood, presenting a critical knowledge gap as they face multiple environmental stressors. Here, we aim to characterize benthic community structure across multiple seamounts along the Kyushu Palau Ridge (KPR) and identify conservation priorities. Location Philippine Sea in the Western Pacific. Major taxa studied Deep sea benthos. Methods We surveyed six transects (13.3N to 22.9N; 614 to 5,055 m depth; 165 km in total length) using a towed camera system, yielding 31,342 images and 14,218 identified individuals. Community structure was assessed through species depth range overlap analysis to distinguish nestedness versus turnover patterns. beta diversity was partitioned into local contributions (LCBD) and species contributions (SCBD) to evaluate site level uniqueness and species level influence. Generalized linear mixed models were used to relate LCBD and SCBD to depth, slope, aspect, bathymetric position, and functional traits. Results Community structures varied among slopes and seamounts. Western, steeper slopes were dominated by nestedness, whereas gentler eastern slopes showed mixed patterns of nestedness and gradual turnover. Sessile species largely exhibited nestedness, while mobile taxa showed mixed structures. LCBD declined with depth overall but increased on north facing slopes and sites with higher broad scale bathymetric position. Wide ranging generalist species, particularly among Echinoidea and Holothuroidea, contributed disproportionately to beta diversity. Main conclusions Seamount benthic communities along the KPR are structured by interactions between depth, geomorphology, and species' ecological breadth. The dominance of nestedness on western slopes suggests that protecting shallow, species rich habitats could capture much of the biodiversity therein. In contrast, the mixed structures on eastern slopes indicate the need for a hybrid conservation approach that includes both shallow summits and deeper, compositionally distinct zones. Our findings highlight the importance of slope specific, depth informed strategies to conserve these vulnerable marine ecosystems.