Comparative diversity of anemone-associated fishes and decapod crustaceans in a Belizean coral reef and seagrass system

Abstract

Within tropical coastal habitats such as coral reefs and seagrass meadows, sea anemones (Actiniaria) provide microhabitats for a diverse range of fauna. However, the mechanisms that enable these interactions, and how actiniarian diversity and abundance mediates associate assemblages, remains poorly understood. Here, we compared sea anemone species richness and abundance with that of their associated decapod crustaceans and teleost fishes across adjacent coral reef and seagrass habitats at Carrie Bow Cay, Belize. At least 16 decapod and seven fish species were associated with anemones across both habitats, including several previously undocumented associations. While overall anemone-associate richness did not differ between habitats, seagrass anemones had the greatest mean abundance and diversity of both decapod and fish associates. This suggests that the importance of anemones as microhabitat reflected broader benthic complexity and shelter availability, with species aggregating on sea anemones when access to alternative shelter, such as corals, was limited. Patterns of associate distributions on anemones were also highly structured, in terms of both associate and anemone species, with these patterns likely reflecting a combination of associate specialization, intraspecific competition, and anemone morphology and toxicity. The diverse multi-species associate complexes observed suggest that sea anemones provide an important refuge for both specialized and generalist species and so have the potential to increase faunal diversity and abundance within tropical coastal habitats.