Changing Biogeochemistry and Invertebrate Community Composition at Newly Deployed Artificial Reefs in the Northeast Gulf of Mexico

Artificial reefs have been deployed throughout US coastal waters since the late 1970s, primarily to enhance fisheries. Although numerous studies have examined their effects on fish communities, few have examined interactions between artificial reefs and primary producers or their effects on biogeochemistry of the surrounding water column. Understanding how reefs may alter biogeochemistry and primary producers is key to understanding overall reef productivity. In this study, we examined the relationships among epifauna, algae, and biogeochemical processes on artificial reefs located on the shallow Florida shelf in the Northeast Gulf of Mexico over a year following their deployment. We measured oxygen and nutrient fluxes, attached chlorophyll a, and invertebrate macrofauna. Temporal differences in biomass and chlorophyll a production occurred due to changes in in situ conditions including fluctuations in bottom-water temperature over the year as well as decreasing bottom-water oxygen and increasing chlorophyll a fluorescence during the summer. Invertebrate biomass was greater than micro- or macroalgal biomass. Biomass of the invertebrate epifaunal community increased exponentially during the first 5 months of this study. The reef was net heterotrophic with few differences between oxygen or nutrient fluxes in the light and dark. Positive nitrate and nitrite fluxes and abundances of amoA genes in the microbiomes of benthic invertebrates indicate significant nitrification associated with the epifaunal community. Reef biogeochemistry was directly related to the composition and biomass of the epifaunal community at the reef sites.