HCNSO Student Theses and Dissertations

Defense Date


Document Type


Degree Name

M.S. Marine Biology

First Advisor

Dr David Gilliam

Second Advisor

Dr Joana Figueiredo

Third Advisor

Dr Matthew Johnston


High-latitude reefs have been postulated as refugia, centers for resilience or the first areas to undergo re-organization under climate change. The Southeast Florida Reef Tract (SEFRT) is a high-latitude reef system (>25 °N) running parallel to the highly urbanized coastline of southeast Florida. With a benthic community comprised of a mixture of coral reef associated assemblages, the SEFRT is towards the northern limit of stony coral cover due to temperature constraints. This study analyzed spatial variations in benthic cover, spatiotemporal changes in the benthic community and the impact of spatial and temporal fluctuations in temperature on benthic cover on the SEFRT, from 2007-2016. Photographic data from two long term monitoring projects was used to calculate the percent cover of taxonomic assemblages in the benthic community. In situ temperature data and modelled data from HYCOM were used in combination to assess the impact of temperature fluctuations and thermal stress events. Data was split on a latitudinal gradient into six defined ecosystem regions based on biogeographic boundaries and at major port channels. These accounted for any possible range expansion and spatiotemporal variations on the SEFRT. Statistical analysis via generalized linear models (GLM) identified significant changes in the major benthic taxa, stony coral, octocoral, sponges and macroalgae. Ecosystem regions showed strong clustering by their taxonomic composition and this was in part created by temperature variation. Stony coral cover significantly declined on the SEFRT and a concomitant significant increase in macroalgae cover may create a negative feedback loop which hinders recovery. Spatiotemporal variations in benthic cover were found between ecosystem regions and thermal stress events, both hot and cold, had immediate and latent impacts on benthic cover. This has resulted in biotic homogenization on the SEFRT with a retraction of outlier regions towards the mean. Anthropogenically influenced high-latitude reefs are significantly impacted by thermal stress. As oceans continue to warm, populations expand, coastlines continue to develop and pollutants persist, the benefits of potential thermal refugia are negated.