Epifaunal communities differ between tropical and polar mesophotic marine animal forests

Understanding marine biodiversity in polar regions remains limited compared to tropical ecosystems, where coastal habitats have been more extensively studied; however, both regions exhibit a substantial lack of knowledge regarding mesophotic marine biota. Marine Animal Forests (MAFs), key components of oceanic biodiversity, remain largely unexplored at mesophotic depths (30–200 m) due to accessibility constraints. Here, we examined epifaunal assemblages associated with mesophotic MAFs in polar (Arctic) and tropical (Caribbean) regions, analysing taxonomic and phylogenetic diversity, along with body size as a key functional trait. Community structure differed notably between regions: amphipods dominated in the Arctic, while decapods were more abundant in the Caribbean. Individuals from both groups were significantly larger in the Arctic, with decapods reaching up to four times and amphipods up to two times the body size of their tropical counterparts, supporting the biogeographic pattern described by the Bergmann’s rule. Overall, our results provided a comparative analysis of epifaunal communities associated with mesophotic MAFs in two biogeographically contrasting regions and established an initial framework for understanding latitudinal trends in epifaunal diversity within mesophotic ecosystems.