Megabenthic assemblages from South Adriatic marine mesophotic environments

Mesophotic habitats in the Mediterranean Sea host rich and diverse benthic assemblages, dominated by invertebrates alongside sciaphilous algae. Recent findings suggest that certain mesophotic bioconstructions built by invertebrates, while classified under the coralligenous definition, differ significantly in their taxonomic composition. This study investigates diversity patterns in megabenthic assemblages associated with algal and invertebrate bioconstructions along the Apulian coast, using alpha- and beta-diversity metrics derived from an image analysis approach. Across 360 analyzed frames, 81 taxa were identified, revealing distinct coverage patterns that separate mesophotic algal assemblages from both coral and oyster bioconstructions. Morphological seabed features and primary bioconstructors played a key role in shaping the associated communities. These findings highlight the substantial differences between upper and deeper megabenthic assemblages and emphasize the ecological importance of mesophotic bioconstructions as biodiversity hotspots, underscoring their role in supporting Mediterranean marine ecosystems and the need for targeted conservation strategies.