Determining the health status of coral reefs: a case-study of the Saba Bank in the Dutch Caribbean

Student Report 

Coral reefs are impacted by temperature rise, ocean acidification and various local anthropogenic stressors, causing global degradation. To apply appropriate conservation strategies, it is necessary to have a clear understanding of the health status of coral reefs. The Reef Health Index (RHI) is an assessment tool for this purpose, using four indicators and set thresholds to determine reef health. However, only shallow reefs have been assessed by the RHI. In this study, the applicability of the RHI for deeper reefs was analyzed. The Saba Bank, a submerged atoll located in the Dutch Caribbean, contains relatively deep reefs (15 m – 30 m) which are less affected by human activity and relatively unstudied. The benthic composition of 12 reef sites of the Saba Bank was assessed by conducting an image analysis. Along with existing data, the health status was then scored using the RHI. This score was compared to an alternative assessment using multiple environmental indicators. As the scores of the two assessment tools differed significantly with a negative bias towards deeper sites, it has been suggested that the RHI adjusts it’s indicators or thresholds to give a realistic representation of reef health for deeper reefs such as on the Saba Bank. 

Keywords

Saba Bank, Coral reefs, Fish, Benthic composition, Reef Health Index, Caribbean