Award: OCE-1807807

In September 2017, two Category-5 hurricanes - Hurricanes Irma and Maria - hit the island of St. Thomas (U.S. Virgin Islands) within two weeks of each other. Two extreme hurricanes affecting the same location over such a short spatial scale was entirely unprecedented, and caused dramatic impacts on shallow reefs dominated by some of the most diverse sponge communities in the Caribbean. As corals have declined over the last several decades, sponges now represent significant biodiversity on Caribbean reefs and provide critical ecosystem services, including habitat, food, reef consolidation, water filtration and biogeochemical cycling. Many studies have evaluated the impacts of hurricanes on coral communities, but little was known about resilience, recovery, recruitment and early successional stages of Caribbean sponge communities in response to natural disasters. As climate change is predicted to increase the frequency and intensity of extreme storm events, understanding their impacts on already struggling coral reef communities is particularly timely. This project took advantage of the rare opportunity to evaluate short- and long-term resilience of sponges to extreme storm events on Caribbean reefs. Repeated surveys, experimental manipulation and genetic sampling addressed questions related to sponge resilience. Results identified an overall decline in sponge cover following the back-to-back hurricanes, but there were also winners and losers in the sponge communities. Upright sponges declined significantly while encrusting sponges increased in relative abundance post-hurricanes. Surprisingly, although coral cover appeared to decline slightly, there were no significant changes in coral cover at our sites. A coral disease outbreak affected two of the sites at the time of the final survey and has since spread throughout the U.S. Virgin Islands and broader Caribbean. This unprecedented disease outbreak ultimately resulted in a more dramatic decline in coral cover than did the hurricanes. Results also indicated that sponge recruitment and regrowth start rapidly after the hurricanes. There was site-specific variability in hurricane effects, in which sponge communities at some sites showed large storm-related changes and had not recovered to pre-hurricane states after at least 2 years. This project brought together graduate students, an early-career post-doc, as well as established research faculty on four research cruises, providing many opportunities for multi-level mentoring and cross-training. Over the course of the project, one female post-doctoral research associate from an under-represented minority (URM) background, 17 graduate students (12 female, 5 male; 4 from URM backgrounds), 1 female undergraduate, 3 female technicians, and a St. Thomas-based female resource manager were trained in field and laboratory methods focused on sponge community analysis. A second female post-doc from an URM background, 1 female graduate student and 3 undergraduates (2 female, 1 male) contributed to lab work related to sponge population genetics and taxonomy. Outcomes included the post-doctoral associate going on to become a tenure track Assistant Professor, two student theses, and an underwater sponge ID guide available online. Other project outcomes have so far included a peer-reviewed journal article, and presentations at local, regional, and international conferences. Last Modified: 01/20/2023 Submitted by: Deborah J Gochfeld