Assemblage structure of fishes and invertebrates inhabiting the coral Pocillopora grandis in Hawaiʻi

Coral reefs are highly diverse ecosystems, and the relationship between reef structural complexity and the diversity of resident species has long been of interest. Corals in the genus Pocillopora, especially one of the largest species, P. grandis, are characterized by highly branching morphology that hosts many fishes and macroinvertebrates. I documented the general environment, surrounding reefscape, and colony-specific variables most correlated with resident assemblage structure on P. grandis on the island of Oʻahu, Hawai‘i. In general, surrounding reefscape had little effect on total assemblage structure, with most variation attributed to colony size, percent living tissue, and general environmental factors associated with each reef. Resident fish and invertebrate abundance, Shannon–Wiener composite α-diversity, species evenness, and species richness increased with colony size, and fish abundance and species richness increased with greater living colony tissue. However, invertebrate abundance and species richness remained unchanged across equally sized living and dead colonies, although live colonies supported more coral obligate decapods and dead colonies more facultative species. Live colonies detached from the seafloor yet otherwise mostly intact hosted more abundant and diverse residents than fully intact, attached colonies. The capability of P. grandis to grow to large sizes, host diverse resident assemblages, and tolerate moderate physical disturbance, after which assemblages may become larger and more diverse due to increases in habitat heterogeneity, makes this coral an ideal candidate for reef restoration efforts in Hawaiʻi.