Urbanization driving Ocypode quadrata burrow density, depth, and width across Caribbean beaches

Abstract

Globally, sandy beaches support local economies and are the most commonly-used type of coastline. This importance is perhaps most striking in the Caribbean; however, no study has assessed the morphological features of the U.S. Virgin Islands (USVI) sandy beaches or evaluated how their biodiversity is influenced by human activities. We addressed these gaps by sampling eight St. Thomas, USVI, beaches with different urbanization levels (Stumpy Bay, Santa Maria Bay, Caret Bay, Neltjeberg Bay, Lindberg Bay, Magens Bay, Coki Point Beach, and Sapphire Beach) multiple times during high- and low-tourist season. At each sampling site and occasion, we measured environmental features (i.e., grain size, waves, and slope), urbanization variables (e.g., solid waste, traffic of vehicles, and beach cleaning) and ghost crab (Ocypode quadrata) population parameters (i.e., burrow density, depth, and width). We found that all studied beaches have similar morphodynamic features, being generally characterized as wave dominated reflective. Urbanization variables were the main drivers of ghost crab populations, with visitor frequency, distance to urban center, and evidence of vehicles on sand exerting stronger roles than variations in physical beach characteristics. Overall, our results provide important information on the morphology of USVI beaches and the impact of beach use. We expect these results will increase understanding of the drivers and threats to local sandy beach biodiversity, inform future management decisions for the territory, while creating a baseline for ghost crab studies in the U.S. Virgin Islands.