Hyperspectral Remote Sensing of Water Quality Parameters Impacting Coral Reef Health in Puerto Rico Roy A. Armstrong, Ph.D. Department of Marine Sciences University of Puerto Rico at Mayaguez Progress Report October 1, 2016 to January 31, 2017
Introduction Water quality is of great concern to coral reef managers in Puerto Rico and to most partners and stakeholders. There is an urgent need to monitor sedimentation and nutrients discharges into the coral reefs and the anthropogenic activities causing them. By the end of this project we anticipate having developed methods and algorithms that use hyperspectral in situ data to quantify water quality parameters in coastal waters. In addition, we anticipate developing satellite products using multispectral data for water quality indicators that can be related to coral reef status. Tasks and Issues During the Reporting Period Monthly field data collection of optical and water quality data have been completed during this reporting period. For the field sampling of optical measurements a Satlantic free-falling Hyperspectral Optical Profiler was used to measure the downwelling irradiance and upwelling radiance at different sites in La Parguera and Guánica, southwestern Puerto Rico. These measurements are used for deriving the attenuation coefficients of downwelling irradiance (Kd) and the water-leaving radiance (Lw) for validation and calibration of satellite-derived ocean color products. These data have been made available to NOAA scientists for calibration/validation of the VIIRS water quality products. Water samples were collected and processed to estimate Chl-a, CDOM and TSS concentrations at various stations. Results and Findings All water samples and optical data from the start of the project to this date has been processed. The sampled stations include a turbidity gradient that can be observed under high river flow conditions from inside Guanica Bay to the shelf edge. Stations in La Parguera represent coral reefs areas where long-term benthic characterization has been conducted. Other stations include Bioluminescent Bay and a deep-water station offshore from the bay. Field Kd (490) values were obtained from the Satlantic spectroradiometer for the various sampling dates and represent an index of turbidity in the water column. The highest values of Kd 490 are from inside Guanica Bay (Figure 1). Chlorophyll a values were determined from water samples obtained at each station. Highest Chlorophyll a values are from Guanica Bay (Gua1) followed by Bioluminescent