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Black corals are important components of mesophotic and deep-water marine habitats. Their presence at great depths (e.g., 50 to 200 m) makes accessibility difficult, limiting our understanding of the associated biodiversity. Amphipods dominate vagile epifauna in marine habitats around the world, fulfilling important ecosystem functions. However, there are no studies on amphipods exclusively associated with black corals, including relationships between their ecological patterns (e.g., abundances) and the size of coral colonies. We investigated the epifaunal composition and abundance associated with black coral colonies of Antipathella wollastoni in the subtropical eastern Atlantic Ocean. In total, 1,736 epifaunal individuals were identified, of which 1,706 (98.27%) were amphipods, belonging to 6 taxa. We identified and described a new amphipod genus and species within the Stenothoidae family, Wollastenothoe minuta gen. nov., sp. nov., which outnumbered the amphipod assemblage (86.15%) and provided a complete taxonomic key of Stenothoidae family including this new finding. For the first time, the association between an amphipod species and a black coral was described, including a strong correlation between coral colony size and amphipod abundances. This study demonstrates that epifauna associated with mesophotic black corals remains largely undescribed. [ABSTRACT FROM AUTHOR]

Rhodolith seabeds are 'ecosystem engineers' composed of free-living calcareous red macroalgae, which create extensive marine habitats. This study addressed how depth influenced the structure (size and morphology) of rhodoliths and the abundance of associated floral and faunal epibionts across the Eastern Atlantic Ocean. Sampling was carried out at two sites within five regions (Brittany, Galicia, Madeira, Gran Canaria, and Principe Island), from temperate to tropical, covering a latitudinal gradient of 47°, in three depth strata (shallow, intermediate and deep), according to the rhodolith bathymetrical range in each region. Depth typically affected the rhodolith size at all regions; the largest nodules were found in the intermediate and deep strata, while rhodolith sphericity was larger at the shallow depth strata. Higher biomasses of attached macroalgae (epiphytes) were observed at depths where rhodoliths were larger. The abundance of epifauna was variable across regions and depth strata. In general, the occurrence, structure, and abundance of the associated biota across rhodolith habitats were affected by depth, with local variability (i.e., sites within regions) often displaying a more significant influence than the regional (large-scale) variation. Overall, this study showed that the rhodolith morphology and associated epibionts (flora and fauna) were mostly affected by depth, irrespective of latitude. [ABSTRACT FROM AUTHOR]