A Numerical Modelling Approach to Coral Restoration and Management: Understanding Tobago's Hydrodynamics and Reef Connectivity

Ishmael-Lalla, M., Gopaul, N., Ganase, A., and Deonarine, A., 2024. A numerical modelling approach to coral restoration and management: Understanding Tobago's hydrodynamics and reef connectivity. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 644-648. Charlotte (North Carolina), ISSN 0749-0208. Numerical modelling was conducted to explore the interaction between ocean currents and reef systems in Tobago, an island in the southern Caribbean. Coral reef organisms have a bipartite life cycle, being reef-bound as adults and having pelagic larval stages that can disperse to other reefs. Larval dispersal and connectivity are crucial for population replenishment, habitat colonization, and overall reef expansion. Oceanographic factors significantly influence larval dispersal, affecting their viability and the natural reseeding of habitats. Factors such as waves, temperature, salinity, and current velocity are critical for coral reef rehabilitation. Therefore, understanding hydrodynamics in reef areas is vital for effective coral management and restoration. The DHI MIKE 21/3 hydrodynamic model, coupled with an Agent-Based Model (ABM), was used to assess reef connectivity of Tobago. This framework quantifies the interaction between hydrodynamics and larval traits, simulating the passive drifting of organisms during their pelagic phase. The ABM included factors such as settlement behavior and mortality. Dispersion from reefs off the Caribbean coast of Tobago was localized compared to Angel and Flying Reefs, due to lower currents and recirculation patterns along that coast. Coral larvae from Flying Reef, along Tobago's south coast, and Angel Reef in north-east Tobago dispersed more broadly due to stronger currents and deeper waters. These findings provide insights into the connectivity of Tobago's reefs based on oceanographic conditions, guiding spatial management of coral reefs and strategies in coral restoration.