reefs

Discovering the Deep ROV assisted data collection to understand the status of Mesophotic Coral Ecosystems around Bonaire

Abstract The coral reefs of Bonaire, providing resources and environmental services, are often ranked among the richest, most resilient and least degraded in the Caribbean, but they are not escaping the global degrading trend in coral reefs. Identifying and combatting local stressors, increases the resilience to global stressors. Research has shown that even the deeper, relatively unexplored reefs, mesophotic coral ecosystems (MCE), ranging from 30 to 150m in depth, are being impacted by anthropogenic disturbances. As the MCEs start where Scuba diving stops, and submersibles are often too costly, this study deployed an ROV to explore and monitor the shallow (5-20m) and the upper-mesophotic (40- 60m) reefs at eight sites along the leeward coast of Bonaire. These sites were subdivided into different zones, showing a gradient in human impact and water quality. The imagery obtained by the ROV is of adequate quality, allowing for identification to genus level if not species level, and showed comparable results in estimated percentage coral cover with other recent studies. The benthic community composition changed along the vertical (depth) and horizontal (human impact and water quality) gradient. Benthic cyanobacterial mats were found around 40-60m depth, covering large parts of the ocean floor. Hard and soft corals, sponges, macroalgae and crustose coralline algae occurred at 40m depth at six of the eight monitored sites, indicating the presence of MCEs, and only at one site (Karpata), hard corals were present at 60m depth. Coral cover showed a clear increasing trend with decreasing human impact, addressing the need for a better understanding of heterogeneity among sites and local conservation measures. Developments in underwater robotics and machine learning enable more research on these hidden coral reefs and identification of the effect of local stressors on MCEs.

Date
2022
Data type
Research report
Theme
Research and monitoring
Report number
Master Research GEO4-1520
Geographic location
Bonaire

Protecting Bonaire against Coastal Flooding A participatory multi-criteria analysis of coastal adaptation options

Part of the larger The impacts of climate change on Bonaire (2022-present) report available here.
 

Summary

Coastal hazards pose a significant threat to small islands, especially in combination with Sea Level Rise (SLR). Currently, the small Caribbean island of Bonaire is poorly protected against coastal flooding and there is a lack of local knowledge on potential adaptation options and their benefits and trade-offs. This study aims to fill this gap by evaluating how different coastal adaptation options to protect Bonaire are valued, considering economic, social, environmental, and technical criteria. This is evaluated using a participatory Multi-Criteria Analysis (MCA) that includes key stakeholders through semistructured interviews and the use of an online questionnaire. A wide variety of coastal adaptation options, ranging from grey infrastructure to softer Nature-based Solutions (NbS), is assessed based on an interdisciplinary set of 10 different criteria, providing a holistic view of the consequences of each option. The results show that NbS, especially mangrove restoration, and spatial zoning measures are overall perceived to be most beneficial. The least favourable adaptation strategies include the construction of any type of seawall and doing nothing. While an MCA does not lead to a final perfect solution, it does provide valuable comparative information about potential future adaptation strategies for Bonaire, which can be used to aid policy makers in the decision-making process. Moving forward, it is important to further strengthen the results of this study by conducting additional quantified analyses, including an evaluation of the spatial suitability of specific measures or combinations of measures. Moreover, to ensure public support for any final policy decisions, regardless of the specific measures that a

Date
2022
Data type
Research report
Theme
Education and outreach
Research and monitoring
Geographic location
Bonaire