Assessing the use of connectivity index and water turbidity measurements to identify major sediment runoff areas and their effect on coral reef cover

Coral reefs are a crucial ecosystem for marine biodiversity worldwide, yet they are threatened by a range of anthropogenic stressors, including sediment runoff. This thesis employs a multidisciplinary approach composed of remote sensing modelling, water quality surveys and benthic cover assessments to comprehend the relationship between sediment runoff, reef health and water quality in the Dutch Caribbean Island of Saba. Remote sensing modelling utilizes satellite images to identify potential sediment sources and assess sediment connectivity between Saba's watersheds and the sea. Water quality surveys measure turbidity around the island and gauge the impact of sediment on water quality. Benthic community surveys evaluate coral reef health, and possibly correlate it to sediment runoff and turbidity. The findings from this study determine that remote sensing connectivity models can identifying areas with the highest likelihood of sediment runoff. Refining the model could improve its
capacity to explain variations in water turbidity based on watershed characteristics. Water quality results reveal that turbidity does not pose an imminent threat to Saba’s corals. However, the lack of evidence from the surveys does not exclude the possibility of short-term high turbidity events during heavy rainfalls causing sediment stress. Further studies are needed to ascertain this possibility. Benthic community surveys reveal a concerning trend of increasing coral loss and emergence of turf algae and macroalgae as dominant groups within benthic communities. Site-specific analyses indicate areas adjacent to the harbor and the airport as of major concern for sediment runoff and in dire need of management. Overall, this thesis reveals intricate dynamics linking sediment runoff, water quality, and reef health in the Caribbean. The integrated approach we adopted is just the first step towards an understanding of watershed dynamics and their effect on water quality. Future studies hold the potential to enhance our capacity to create effective management strategies to protect vital marine habitats from sediment stress.