Biodiversity and ecosystem function of shallow bank systems within Florida Keys National Marine Sanctuary (FKNMS)

Bank systems, clusters of shallow banks and associated channels located in the shallow waters between Florida Bay and the Florida Keys, are distinctive benthic features of Florida Keys National Marine Sanctuary (FKNMS). The banks are aggregations of Porites coral rubble and Halimeda sand covered with a veneer of seagrass, macroalgae and a wide diversity of invertebrate taxa. Bank systems provide a mosaic of essential fish habitat, such as juvenile nurseries and foraging and sheltering grounds for adults, including high densities of economically important reef fishes. Surveys of three bank systems (Moser Channel, Bamboo, and Channel Key Banks) showed that their associated fish assemblages consistently resembled assemblages of coral reefs and had higher diversity and biomass than the assemblages of surrounding basins. As in most reef fish assemblages, a high proportion of the biomass of the bank system community consisted of "homing" species that shelter in channels during the day and forage nocturnally in surrounding habitats. The species composition and the high density and diversity of the fish assemblage indicate bank systems provide a key structural component supporting the biodiversity and productivity of the FKNMS. Given their integral role in the ecology of the FKNMS and the vulnerability of bank systems to environmental and anthropogenic stressors, we recommend they receive additional protection through inclusion in a management zone better suited to protect the structure and function of these critical habitats.