The coral reef ecosystems of Culebra Island, Puerto Rico
The coral reef ecosystems of Culebra are among the more pristine habitats within the northeastern portions of Puerto Rico. However, the combination of declining coral cover and research showing coastal development and increased land-based pollution as possible causes led to the development of Culebra’s Integrated Watershed Management Plan in 2013. Unpaved roads, failing septic systems, and the local wastewater treatment plant were found to be primary contributors of sediment and nutrient loads to the island’s coastal ecosystem. These findings helped establish the initial priorities for land-based sources of pollution management on Culebra. Then, in 2014, with the Culebra’s designation as part of the Caribbean region’s Habitat Focus Area, NOAA’s investments in land-based sources of pollution management on Culebra were re-evaluated, scaled-up, and prioritized to targeted locations which would provide the greatest pollution reduction and benefit to the coastal resources.
Aerial view of the coral reefs and characteristic spur and groove formations fringing Punta Soldado, Culebra.
Since then, NOAA and partners have stabilized 32.7 miles of unpaved roads, which represent about 60% of the island's unpaved road network. This project has built and installed over 250 erosion control measures, including cross-drains and culverts, sediment traps, resurfacing, paving, and slope stabilization. Also, more than 750 check dams have been constructed to slow down and divert water flow, promote infiltration, reduce total runoff volume, and improve water quality.
Monitoring effectiveness of management actions on Culebra Island
To assess the effectiveness of land-based sources of pollution management strategies, actions, and investments, a Monitoring and Evaluation Framework was implemented, which integrates experimental, on-site, and simulation data. Through this work, a coordinated Ridge-to-Reef Monitoring Program was started and a number of products developed, including:
- Standard protocols for monitoring of pollutant loads at management sites, pollutant exposure through nearshore water quality and sediment traps, and habitat responses via seagrass transects;
- Guidance to inform the selection of fixed nearshore monitoring locations together with recommendations for long-term monitoring and cost-savings;
- Outfitting an on-island laboratory and field station; multiple monitoring approaches, instruments, and protocols tested; and building local capacity for water quality monitoring; and,
- Transferrable geospatial inventory tools and small island watershed models.
Examples of NOAA-funded management strategies and actions to reduce land-based pollution stressor loads from unpaved roads on Culebra. A–B) Regrading, compaction, and slope stabilization; C–D) ditches, cross drains, and culverts; E) check dams; and F) sediment trap. Photo credits: Protectores de Cuencas.
Monitoring and evaluation confirmed the strong association between rainfall and nearshore water quality as well as the best ecosystem indicators of land-based pollution impacts on Culebra. This work also demonstrates that implemented management practices have prevented, on average, approximately 3,900 metric tons of sediment delivery to the coastal habitats per year. This equates to about 300 dump trucks of sediments not reaching the coastline. Also, preliminary Before and After Control Impact (BACI) analyses suggest seagrass habitat has improved downstream of at least one restored site compared to a control site. This is particularly reassuring given the influence of disturbances such as coastal development and legacy contamination, together with hurricanes that can still impact these nearshore m ecosystems.
Culebra’s Ridge-to-Reef Monitoring Program activities include A) Land-based stressor monitoring via Best Management Practice implementation inventories and road condition assessments. B–D) Pollutant exposure monitoring through nearshore water quality and sediment accumulation measurements. E) Habitat response monitoring of seagrass community status and trends. F) Outreach and local capacity building. Photo credits: Protectores de Cuencas.
Positive effects both locally and regionally
The work on Culebra Island has demonstrated the effectiveness of different road stabilization techniques, developed technical drainage design guidance, and an unpaved road standards manual for the Caribbean. This project has also trained and employed Culebra municipal staff to maintain these roads and developed and implemented maintenance agreements with landowners. This work by NOAA and partners has resulted in private landowners requesting construction of roads that meet these new standards, which are aimed at minimizing environmental impacts while maximizing sustainability. The approach and work on Culebra are actively being applied in other island jurisdictions. For more information, visit the Culebra Project web page.
Related Material
Management and planning
- Culebra’s Integrated Watershed Management Plan
- Unpaved road assessment and prioritization of NOAA investments on Culebra Island, Puerto Rico
Monitoring
- Identifying Priority Fixed-Site Monitoring Locations
- Culebra Nearshore Water Quality Monitoring Program Workplan
- Culebra Sediment Trap Monitoring Work Plan
- Culebra Seagrass Monitoring Work Plan
- Culebra LBSP Ridge to reef monitoring: equipment, instrument, and supply budget list