Award: OCE-1808233

This project assessed the impacts of back-to-back category 5 hurricanes Irma and Maria on the benthic communities inhabiting shallow coral reefs around St. Thomas, USVI. We compared pre-hurricane surveys of benthic communities on permanent transects at six sites with those conducted at 2, 6, 14, and 20 months post-hurricanes. At 2 months, there were no significant storm-related effects on coral and macroalgal cover, although sponge cover declined by 24.9%. Many individual upright sponges were lost but these losses were partially offset by an increase in the number of sponges encrusting on substrate and recruitment of new sponges (or regrowth of severely damaged individuals) was observed within 2 months of the hurricanes. Although sponge communities recovered to varying degrees at the sites over the subsequent two years, upright sponges only started to recover 14 months after the hurricanes. Coral cover declined following the hurricanes and showed mixed recovery over subsequent months, with some sites increasing in coral cover in late 2017 and early 2018 with other sites continuing to decline. The introduction of stony coral tissue loss disease at some sites beginning in late 2018 and continuing into 2019, which decimated coral communities, made analyses of coral cover at the later timepoints difficult. Macroalgal cover was extremely variable over time at the sites, but on the reefs where it increased may impact the recruitment, recovery or survival of small corals and sponges. The reefs did not return to pre-hurricane species assemblages during the duration of this project and it is not yet known when they will reach a stable community and what species will be present in that community. To help us understand how damaged reefs are repopulated, we sought to evaluate whether new sponge recruits were derived from larvae dispersed from spatially distant reefs or nearby individuals using population genetic analyses. Small samples of adult and newly recruited sponge individuals of three commonly occurring species were collected for this work and small changes in their genetic information are being examined to identify the sources for the new individuals. These studies are on-going. The scientists involved in this project provided training workshops on sponge ecology and identification for numerous graduate students and employees of various governmental agencies, non-profit organizations, and the University of the Virgin Island. Results from these studies have been provided to the USVI Department of Planning and Natural Resources annually and shared with other scientists at a variety of national and international scientific conferences and research seminars. Social media platforms such as Facebook and Twitter were used to distribute our findings with the broader USVI community along with annual presentations at Reef Fest. As the intensity of hurricanes continues to escalate, understanding their impacts, both on land and on nearshore environments, will be increasingly important to evaluate resilience. Last Modified: 02/07/2021 Submitted by: Julie B Olson