Where Do Oyster Larvae Go? Analyzing Connectivity and Restoration Strategies Through Field-Calibrated Larval Transport Modeling in the Guana-Tolomato-Matanzas Estuary, Florida

Eastern oysters (Crassostrea virginica) are vital to estuarine ecosystems, providing habitat for various marine species, improving water quality, supporting fisheries, and protecting coastlines by dissipating waves, reducing erosion, and enhancing sediment deposition. The Guana-Tolomato-Matanzas Estuary in Florida, with its abundant populations of both live and dead oyster reefs, is an ideal area for studying their reproductive dynamics. This research investigates the environmental drivers influencing spawning activity by analyzing water temperature, tidal fluctuations, spat surveys, and oyster population characteristics, including reef location, density, and size. Key predictors, such as minimum temperature, temperature variation, tide level, and a temperature-based weight function, were integrated into a predictive model, which demonstrated high accuracy in forecasting the timing and intensity of spawning events over a three-year period. The GTM includes both live and dead oyster reefs. Initially, the study examines the connectivity of live reefs by analyzing larval dispersal during the 2018 spawning season using a coupled hydrodynamic and particle tracking model. The results show low local recruitment at the reef scale (~2% on average) but significantly higher local recruitment at watershed scale (~73.7 % on average), highlighting the importance of tidal dispersion in connectivity. These findings provide valuable insights for sustainable harvesting and restoration strategies in estuarine ecosystems. Furthermore, the research evaluates the effect of two stages of dead oyster reef restoration on connectivity: early-stage restoration, where reefs are only capable of recruiting larvae, and full restoration, where reefs both spawn and recruit. Simulations show that early restoration enhances larval recruitment and estuarine connectivity, while fully restored reefs maximize recruitment success. The study emphasizes the importance of restoration success in supporting population recovery and resilience, providing information to prioritize restoration efforts by identifying reefs with the highest potential for successful restoration. Overall, this research offers a comprehensive framework for understanding oyster reproductive dynamics, larval connectivity, and effective restoration strategies, contributing to the conservation and sustainable management of estuarine oyster populations.