How are Southeast Florida’s coral reef communities changing under climate change?

Guy Harvey Oceanographic Center Facility

The Southeast Florida Reef Tract (SEFRT) is a high latitude (>25°N) reef system running parallel to the heavily urbanized coastline of southeast Florida. With a benthic community composed of coral reef associated assemblages, the SEFRT is toward the northern limit of stony coral distribution. Range expansion of coral species further north is predicted to be limited by present day hydrographic processes (Walker and Gilliam, 2013), therefore the impact of ocean warming on the coral reef community in the region is of particular interest. The Southeast Florida Coral Reef Evaluation and Monitoring Project and the Broward Annual Monitoring Project (Annual) provide long-term benthic cover data via annual image analysis of permanent sites along the SEFRT. Combining data from these two projects enables comprehensive coverage of the benthic community along the SEFRT. This analysis focuses on the spatiotemporal change in coral reef community cover and the impact of climate change, specifically water temperatures and thermal stress events, from 2007-2016. Mean and minimum sea surface temperatures have significantly increased over the 10-year study period and the SEFRT has experienced periodic cold-water anomalies and consecutive El Niño induced bleaching years. Spatiotemporal change in benthic cover composition suggests potential temperature induced shifts, with statistical analysis identifying significant changes in stony coral, macroalgae, octocoral and sponge assemblages at monitored sites during the study period. The SEFRT covers an extensive latitudinal gradient and therefore the impact of climate change on the benthic community is expected to change with latitude. To assess benthic changes on a latitudinal scale, the SEFRT has been separated by known biogeographic boundaries (Walker, 2012) and major ports into 7 coral reef ecosystem regions. Combining in situ temperature data with modelled data from the Hybrid Coordinate Ocean Model (HYCOM), analysis of spatiotemporal temperature fluctuations and thermal extreme events has been conducted to assess the impact of climate change on the SEFRT coral reef community and the temporal changes seen within coral reef ecosystem regions.