Michael will be presenting a portion of his dissertation research at the upcoming European Coral Reef Symposium, and will be graduating from FAU in May 2018.
Coral reef ecosystems worldwide are facing increasing degradation due to disease, anthropogenic damage, and climate change, particularly in the Tropical Western Atlantic. Mesophotic coral ecosystems (MCEs 30–150 m) have been recently gaining attention through increased characterization as continuations of shallow reefs below traditional SCUBA depths. As MCEs appear to be sheltered from many of the stressors affecting shallow reefs, it has been proposed that deeper reefs may act as a coral refuge and provide larvae to nearby shallow reefs. The Deep Reef Refugia Hypothesis (DRRH) posits that shallow and mesophotic reefs may be genetically connected and that individual coral species are equally compatible in both habitats. Empirical support for the DRRH has been mixed, however. The research presented here addresses key questions that underlie this theory and advances our knowledge of coral connectivity and functional ecology on MCEs using the depth-generalist coral model species Montastraea cavernosa. Chapter 1 presents an overview of the DRRH, description of mesophotic coral ecosystems in the Gulf of Mexico (GOM), and the framework of research questions within existing reef management infrastructure in the GOM. Through microsatellite genotyping, Chapter 2 identifies high connectivity among shallow and mesophotic reefs in the northwest GOM, despite evidence for relative isolation between depth zones in Belize and the southeast GOM. Further, historical migration and vertical connectivity models predict Gulf-wide population panmixia. Chapter 3 focuses on population structure within the northwest GOM, identifying an overall lack in significant population structure. Dominant migration patterns estimate a net downstream to upstream movement of gene flow, suggesting mesophotic populations currently considered for National Marine Sanctuary protection were benefitting the Flower Garden Banks. Chapter 4 quantifies the level of morphological variation between shallow and mesophotic M. cavernosa, revealing two distinct morphotypes that may represent photoadaptive tradeoffs. Chapter 5 examines the transcriptomic mechanisms behind coral plasticity between depth zones, discovering a relatively consistent response to mesophotic conditions across regions. Additionally, this chapter identifies variable plasticity of mesophotic corals resulting from transplantation to shallow depths, and potential differences in bleaching resilience between shallow and mesophotic corals. The final section synthesizes the results of these chapters as they pertain to connectivity of shallow and mesophotic corals in the Gulf of Mexico, and suggests future research that will aid in further understanding of MCE ecological connectivity. This research was specifically designed to provide data for improved regional protection of existing management infrastructure and to strengthen collaborative marine research through the Cooperative Institute for Ocean Exploration, Research, and Technology (CIOERT).