Loss of Genetic Diversity in the UTRs of the MSH4 Gene in Orbicella faveolata from Great Abaco, The Bahamas.

Coral reefs are extremely important ecosystems essential for marine biodiversity. Even though they only cover 0.2% of the ocean floor they host an approximate 25% of marine species. Reefs are also important sources of fish protein for millions of people in tropical countries as they are local fishing hotspots, while at the same time providing protection from shoreline erosion by reducing wave energies. The strain inflicted on coral reefs from the effects of climate change and local human activity is greatly affecting their stability and prosperity. Coral reefs are incredibly dynamic and resistant to some variations in their environment however, the overwhelming shifts in atmospheric CO2 levels in combination with biotic and abiotic oceanic conditions have been too rapid and dramatic for a majority of organisms to tolerate. Coral coverage in Caribbean reefs has seen a decline of more than 80% since 1970, with reefs worldwide projected to mirror this decline in years to come. The Great Abaco region in The Bahamas experienced a warming event in 2015 that caused many of its coral to bleach. However, unusually high thermal tolerance was observed in an Orbicella faveolata colony in Mermaid Reef (MR). Water temperatures reaching 33°C, which dramatically exceeded its local bleaching threshold of 30.4°C. This project aimed to explore the unique characteristics of the tolerant colony in Mermaid Reef in comparison with the sensitive colony in Sandy Cay Reef (SC). This was done by sequencing the untranslated regions (UTRs) of the MSH4 gene, which is important in organisms' stress response mechanism. By comparing the tolerant and sensitive coral a significant loss in the number of polymorphic sites was observed in the Mermaid Reef colony. As genetic diversity is strongly associated with an organism's fitness, the loss of genetic diversity in MR's O. faveolata could be an indicator of its reduced fitness. However, it could also be an indicator of the extreme selective pressure that has allowed the coral to survive these specific conditions. By comparing the number of polymorphic sites between MR and SC, we can begin to investigate the degree of clonality seen in MR and the potential fitness trade-offs for MR's increased survival rate.