Water quality surveys in Culebra: comprehensive assessment of physical and chemical water characteristics 2023-02-08 to 2025-01-13

This record provides physical and chemical water quality metrics collected between February 2023 to January 2025 to provide reference data of nearshore and watershed water quality on the island of Culebra, Puerto Rico. The water quality monitoring was conducted at 18 fixed stations. Five stations were selected to quantify Land Based Sources of Pollution (LBSP) stressor loads at key points in the Cabra, Coronel, and Aeropuerto watersheds. Levels of LBSP exposure were measured at 13 nearshore stations co-located with long-term seagrass monitoring sites. Nearshore monitoring sites were selected to identify watershed discharge points, coastal hydrodynamics, as well as the existing level of LBSP exposure and anticipated changes to LBSP exposure due to management actions. Nearshore monitoring stations were designated based on their land based sources of pollution (LBSP management implementation status (LBSP Treatment Group), as follows: 1) LBSP Restoration stations: Located downstream where land-based pollutant management has or is being implemented. 2) LBSP Control stations: Represent a range of land-based pollutant impairments, including sites with no LBSP management, no known direct discharge of LBSP but are representative of the range of external factors that may be encountered at the LBSP Restoration stations. 3) Negative Reference stations of know significant -anecdotal and quantified- LBSP impairment. 4) Positive Reference stations of low LBSP impairment. Nearshore water quality parameter measurements were collected at two depths: surface (10-25 cm ) and bottom (2 m deep).

Metrics include:

1. Water physical properties: Temperature, Salinity, Dissolved Oxygen, and pH.

2. Indicators of water clarity threats: CDOM (Colored Dissolved Organic Matter), absorbs light in the blue and UV part of the electromagnetic spectrum giving water a yellow-brown color; Turbidity; Chlorophyll-a, used to gain insight of phytoplankton primary productivity, measured as the blue fluorescence emission; and Kd-PAR, the Attenuation coefficient of Photosynthetic Active Radiation.

3. Indicators of wastewater threats: Optical brighteners, which are whitening agents added to laundry soaps, detergents, toilet paper, and cleaning products to brighten fabrics and/or surfaces, are used to detect the presence of household effluent; and Monochloramines, long-lasting disinfectant used to treat drinking water protecting its quality as it moves through distribution pipes, primarily serving as a marker for the effectiveness of water treatment.

4. Indicators of fecal contamination: Fecal coliforms, the group of bacteria found in fecal matter from warm-blooded animals, including humans; Enterococcus, the group of fecal coliforms specifically used to assess water quality in marine and estuarine environments; and E. coli, a specific type of fecal coliform often considered a more reliable indicator due to its specific association with human waste.

The data presented herein was collected with financial support from NOAA Restoration Center and NOAA Coral Reef Conservation Program, and the National Fish and Wildlife Foundation (NFWF).

This work is an integral component of the Culebra Ridge-to-Reef Monitoring Program; a spatiotemporally coordinated effort designed to evaluate the effectiveness of the NOAA management strategies and actions in priority watersheds to reduce land-based sources of pollution (LBSP) impacts to the nearshore marine ecosystems of the island. This ridge-to-reef monitoring framework implements a Multiple Lines of Evidence approach consisting of: 1) Monitoring of LBSP stressors that are being managed through NOAA funding including sediment accumulation at unpaved road stabilization projects, water quality monitoring at key points throughout the watershed, and watershed modeling to estimate pollutant loads into the nearshore coastal environment. 2) Monitoring of LBSP exposure through nearshore water quality and sediment trap monitoring at nearshore fixed stations. 3) Monitoring of nearshore habitat responses that is co-located with the aforementioned nearshore water quality fixed stations and includes data collection via seagrass monitoring transects. Within this context, water quality is characterized and tracked to quantify the land-based pollutant loads and exposure levels in the receiving coastal environment and the associated seagrass and coral reef communities, which are ultimately the focal point of the NOAA LBSP management efforts on Culebra.

These data address LBSP pollutant exposure monitoring, specifically water quality, which together with LBSP stressor and LBSP habitat response monitoring represent the basis of Culebra's integrated LBSP Monitoring and Evaluation Framework with which to successfully assess progress and effectiveness toward achieving NOAA LBSP management goals and outcomes on Culebra. The parameters selected for monitoring are known to be good indicators of water quality condition (U.S. Coral Reef Taskforce Watershed Partnership Initiative Priority Ecosystem Indicators). In particular, indicators that are linked to both the LBSP management that is conducted in the watershed while also being linked to potential changes in habitat response.

https://www.ncei.noaa.gov/data/oceans/coris/library/NOAA/CRCP/NMFS/OHC/Projects/30033/Culebra_LBSP_RidgeToReef_Monitoring_Program/Vargas-Angel2024_Culebra_LBSP_RidgeToReef_Monitoring_Program.pdf

https://www.ncei.noaa.gov/data/oceans/coris/library/NOAA/CRCP/NMFS/OHC/Projects/30033/Culebra_LBSP_RidgeToReef_Monitoring_Program/Vargas-Angel2024c_Nearshore_WaterQuality_Monitoring_WorkPlan.pdf

https://www.ncei.noaa.gov/data/oceans/coris/library/NOAA/CRCP/NMFS/OHC/Projects/30033/Culebra_LBSP_RidgeToReef_Monitoring_Program/Vargas-Angel2024e_Seagrass_Monitoring_Transects_WorkPlan.pdf

https://www.ncei.noaa.gov/data/oceans/coris/library/NOAA/CRCP/NMFS/OHC/Projects/30033/Culebra_LBSP_RidgeToReef_Monitoring_Program/Vargas-Angel2024b_Watershed_WaterQuality_Monitoring_WorkPlan.pdf

https://www.ncei.noaa.gov/data/oceans/coris/library/NOAA/CRCP/NMFS/OHC/Projects/30033/Culebra_LBSP_RidgeToReef_Monitoring_Program/Vargas-Angel2024f_Appendix-A_Identifying_Priority_Fixed-Site_Monitoring_Locations.pdf

https://www.coris.noaa.gov/activities/uscrtf_watershed_tools/Priority_Ecosystem_Indicators_Final%202_18_16.pdf

In the field general water characteristics and clarity were quantified implementing the Eureka Manta 35 Water Quality Sonde; surface salinity was measured using the HANNA HI98319U portable marine salinometer, Monochloramine with the HACH SL100 Portable Analyzer, and optical brighteners with the Turner AquaFluor handheld fluorometer. PAR was assessed using the Apogee buoy-suspended light sensing system and estimates of KdPAR were computed as the normalized average of surface and bottom measurements. The Quanti-Tray system was implemented to detect the presence of fecal coliforms using the Most Probable Number (MPN) model. For further instrumentation and methodological details please review the Culebra Nearshore and Watershed Water Quality Monitoring Work Plans listed in "Other Citation Details" and "Lineages".