Black coral and gorgonian assemblages of Santo Antão (Cabo Verde): diversity, distribution, and demographic structure

• First systematic mapping and characterization of black coral and gorgonian assemblages at shallow and upper mesophotic depths (18–50 m) around Santo Antão, Cabo Verde, East Atlantic Ocean. • 11 black coral and gorgonian species identified, showing distinct spatial distribution patterns. • Densities of Stichopathes luetkeni (46.0 colonies/m 2 ) and Tanacetipathes spinescens (23.2 colonies/m 2 ) are among the highest reported globally. • Morpho-functional traits linked to hydrodynamic conditions and species-specific distribution. • Findings highlight the critical roles of these species as habitat providers in coastal ecosystems. • Study supports the need for marine protected areas and community-based conservation initiatives. Black coral and gorgonian assemblages are vital components of marine ecosytems, providing complex habitats that support high biodiversity. Despite their importance, these coral communities remain underexplored in the Cabo Verde Archipelago, a region of significant ecological value. This study provides the first systematic assessment of black coral and gorgonian assemblages in Santo Antão, examining their distribution, density, size structure, and morpho-functional traits through in situ surveys. Our findings identified 11 species of black corals and gorgonians,and three key patterns: (1) Coral assemblages in Santo Antão are divided into black coral-dominated, gorgonian-dominated, and mixed assemblages with high diversity, particularly in the Northeast (NE) and Southeast (SE) regions. (2) Large, bushy and/or unbranched erect black corals thrived in high-current environments, whereas large, planar gorgonians flourished in gentler hydrodynamic conditions. Notably, mean (± SD) densities of black corals, such as Stichopathes luetkeni Brook, 1889 (46.0 ± 50.5 colonies/m 2 ) and Tanacetipathes spinescens Gray, 1857 (23.2 ± 15.5 colonies/m 2 ), were among the highest reported globally. Gates of Eden (SE) emerged as the most coral-abundant location. (3) Functional richness (FRic) varied across locations, with distinct spatial patterns observed at Hanging Garden Flat (SE) and Cruzinha hotel (NW).Overall, the observed patterns in taxonomic (species richness, evenness, and Shannon-Wiener) and functional diversity (FRic) reinforce the presence of distinct assemblages across Santo Antão: high-diversity hotspots in the NE and SE regions, low-diversity communities dominated by a few species and traits in the NW, and variable patterns in the SW and S regions. This study establishes a crucial baseline for the diversity and ecological role of blackcoral and gorgonians in Santo AntãoOur findings underscorethe need for target conservation strategies, including the establishment of marine protected areas (MPAs)regulatory measures and community-based conservation initiatives to safeguard these vital ecosystems.