COI metabarcoding study of pelagic ARMS communities deployed in Mendexa, Basque Country

Difficulties on the development of standardized tools to monitor marine benthic communities and tracking the trajectory and fate of propagules and larvae have limited our knowledge of mechanisms of maintenance of species biodiversity and dispersal strategies. Here, we present a new application to monitor and characterize benthic spatial biodiversity patterns combining DNA metabarcoding and imagery on Autonomous Reef Monitoring Structures (ARMS) deployed in pelagic systems across the Bay of Biscay's Basque Coast. Results reveal a remarkably lower biodiversity in pelagic- relative to benthic ARMS and a clear spatial patterning showing well-defined clusters in benthic community composition with the pelagic ARMS greatly differing to the benthic ones according both to metabarcoding (ANOSIM R= 0.82; p = 0.002) and image analysis (ANOSIM R = 0.87; p = 0.001). We also show that a large portion of the benthic community inhabiting the pelagic ARMS (83.5%) probably originates from benthic habitats, while the benthic community shared across pelagic and benthic habitats is considerably lower (24.9%). Further, we also identified which benthic species successfully use the pelagic environment as “steppingstone” to disperse across the ocean from nearshore coast, and found that the unique taxa inhabiting the pelagic ARMS consist of organisms with typically larger dispersal distances relative to strictly sessile taxa with direct larvae development found only in benthic ARMS. Overall, these findings suggest that the benthic system acts as population source delivering species towards a less diverse pelagic domain. Taken together, his novel application of ARMS deployed in pelagic systems has the potential to identify the often overlooked yet critically important benthic community structure, as well as to unveil how dispersal pathways across benthic and pelagic habitats can shape biodiversity patterns of coastal ecosystems.