Acropora palmata (elkhorn coral) are essential, threatened reef-building corals found throughout the Caribbean and provide critical habitat complexity in shallow water reefs. The fact that they thrive in shallower regions with high wave actions makes them highly susceptible to hurricane damage. A. palmata has suffered extreme losses (90%) attributed largely to bleaching, disease, and hurricanes. Most recently, A. palmata in St. John, US Virgin Islands were hit by hurricanes Irma and Maria in 2017. As a case study to develop student- and citizen-science driven research teams of student-researchers have been surveying populations in Salt Pond Bay, St. John, USVI for the past three years as a part of a field course from Georgia State University straddling the 2017 hurricane events. This provides us with a unique opportunity to investigate hurricane impacts on coral population health and recovery. Underwater images were collected by students and images of corals before the storms and six and eighteen months after the storm events were visually analyzed and placed into three morphological stage classes (crust, fragment, and colony) in order to estimate the status, health and recovery rate of this critical species.
Results/Conclusions
Analysis of images from March 2018 indicate that the A. palmata population in Salt Pond Bay was devastated by hurricanes Irma and Maria in comparison to the 2017 pre-storm population. The 2018 population was dominated by crusts with much smaller proportions of fragments and colonies. By March 2019 A. palmata populations in Salt Pond showed qualitative as well as quantitative improvements. By March 2019 the overall population had nearly equal proportions of colonies and crusts, indicating a high transition rate to colonies. Preliminary analysis indicates a 50% transition rate crust à colony, with no colonies reverting to crusts or fragments. These recovery rates are significantly higher than those predicted by post-hurricane models (p<0.01), particularly regarding a hurricane of Irma’s intensity. Furthermore, the low-tech survey method conducted by the students shows promise for the development of similar monitoring methods that could be employed by courses or casual observers.