Along the Benthic to Holoplanktonic Continuum: Seafloor Affinity Increases Distance‐Decay Rates among Abyssal Communities

ABSTRACT Aim Marine species ranges are often large, contributing to relatively high community similarity over space, with decreased ranges expected among taxa that have lower dispersal and/or higher substrate requirements. We tested for a weakening of biogeographic structuring among dispersing abyssal taxa along the benthic to holoplanktonic habitat continuum by comparing geographic ranges and rates of community dissimilarity across the eastern North Pacific seafloor (spanning a total of 3700 km between sites). Location Abyssal Pacific Ocean, within the Clarion‐Clipperton Zone (CCZ). Time Period Present. Major Taxa Studied Benthic, benthopelagic and holoplanktonic invertebrates (18 phyla). Methods We sampled zooplankton in situ via dual pumps attached to a benthic lander and used bulk community metabarcoding (18S V1V2, 18S V7V8, mtCOI) to characterise a diverse suite of taxa and define habitat assemblages. We measured (i) minimum geographic range, (ii) distance‐decay rates and (iii) environmental structuring, with each measure grouped by habitat assemblage to test the effect of seafloor affinity in shaping biogeography. Patterns were also assessed within broad taxonomic groups to evaluate the degree of phylogenetic constraint. Results Distance‐decay rates increased with increasing affinity to the seafloor, and potential environmental drivers differed between benthic and pelagic assemblages. Unexpectedly, range size did not differ significantly by habitat occupancy and instead varied phylogenetically, with taxa that are sessile on polymetallic nodules (e.g., bryozoans, hydroids) having among the smallest observed ranges. Main Conclusions Our results indicate a significant role for habitat occupancy in shaping biogeographic community patterns in the abyss, though community dissimilarity is likely determined by habitat availability rather than by dispersal. In the context of deep‐sea biodiversity conservation planning, we demonstrate that dispersal ranges are insufficient to connect populations inhabiting impacted areas to protected areas for select taxonomic groups, indicative of potentially high extinction risk. We suggest that marine protected areas should capture a broad range of habitats and environmental variability to protect entire abyssal communities.