EVEN MODERATE LEVELS OF TOURISM PRESSURE ARE SUFFICIENT TO DEPLETE ORGANISM ABUNDANCE AND BIODIVERSITY IN THE FRINGING CORAL REEFS OF ST. JOHN, U.S. VIRGIN ISLANDS

Tourism is critical to many islands with coral reefs, but the threshold for tourist activity that balances economic needs and reef conservation is unclear. This study examines how pressure from snorkeling and other tourist activities impact the biodiversity and abundance of reef-building and inhabiting organisms around the island of St. John in the U.S. Virgin Islands. The fringing reefs on St. John differ in their regulations and accessibility to tourists. For example, many bays on St. John fall within the Virgin Islands National Park, which provides protections like no-fishing and no-anchoring zones. To investigate the impact of tourism on biological abundance and diversity, we conducted a census of reef organisms in six bays with varied tourist pressure. Organism occurrences were counted at the family level. Tourist pressure was determined from field observations. Our findings show that even moderate levels of estimated tourist pressure had a statistically significant impact on reef-organism abundance and diversity. Specifically, we found a decrease in coral and sponge abundance and an increase in motile invertebrates with increased tourism pressure. Soft coral families (Gorgoniidae and Plexauridae), stony coral families (Siderastreidae and Merulinidae), and sponge families (Niphatidae, Irciniidae, and Aplysinidae) show the largest response to tourism pressure. These families are abundant at bays with little tourism pressure and limited or absent at bays with high tourism. Poritidae, a stony coral family, appears unaffected by tourism levels and is found in high abundance at all bays. In contrast, bays with higher levels of tourism pressure saw higher numbers of motile invertebrates, especially urchins. There was a decrease in family-level diversity of corals and sponges across all bays with an increase in tourist pressure. Our findings that even moderate levels of tourism are sufficient to degrade reefs suggest that improved strategies for balancing tourism and natural resource preservation are needed. While tourism is important to the economy of islands with reef ecosystems, it must be carefully regulated to prevent reef degradation and biodiversity loss.