Bryozoan diversity in the Marzamemi (SE Sicily, SW Ionian Sea) and Mediterranean coralligenous habitats

Abstract Although coralligenous is considered a priority habitat for conservation within European directives largely considering its complex 3D structure promoting spatial and ecological heterogeneity and related high biodiversity, detailed information on species richness and composition is still scant, at least for some taxonomic groups, including bryozoans, notwithstanding their ecological relevance within the habitat. Focusing on the bryozoan community associated with six build-ups sampled between 33 and 37 m depth offshore Marzamemi (SE Sicily, SW Ionian Sea), this study contributes to improve knowledge on coralligenous bryozoan biodiversity, from a locality in the still understudied eastern Mediterranean. A total of 127 species were recorded, raising to 145 and 257 species the coralligenous bryozoan diversity currently known for Marzamemi and the entire Mediterranean, respectively, the latter representing a high proportion (44%) of the overall Mediterranean bryozoan diversity (588 species). Heterogeneity was detected at small spatial scale, among build-ups in the Marzamemi area, and at the Mediterranean scale through comparison with the scant existing literature, which mostly focused on the western basin. Facies differentiation and related ecological heterogeneity, rather than geographic distance, are considered the main drivers. Finally, our results emphasise the critical importance of microscopic and SEM examination of specimens for species detection.