Characterization and Distribution of Seagrass Habitats in a Caribbean Nature Reserve using High-Resolution Satellite Imagery and Field Sampling

Abstract

León-Pérez, M.C.; Hernández, W.J., and Armstrong, R.A., 2019. Characterization and distribution of seagrass habitats in a Caribbean nature reserve using high-resolution satellite imagery and field sampling. Journal of Coastal Research, 35(5), 937–947. Coconut Creek (Florida), ISSN 0749-0208.Effective management of seagrass habitats requires detailed information about seagrass condition and distribution. This paper addresses the first step of a larger study to assess long-term changes in seagrass distribution within Caja de Muertos Island Nature Reserve, Puerto Rico. A high-spatial-resolution characterization of seagrass beds in the reserve was conducted using a WorldView-2 (WV-2) image and field data set. The WV-2–derived seafloor reflectance and bathymetry data were used to conduct an object-based image analysis (OBIA). The selection of bands for this analysis was based on in situ spectral water attenuation measurements. The resulting polygons of the OBIA were classified through a supervised classification and contextual editing. Calibration and validation of the image were conducted using 164 sampling sites. Together with traditional accuracy assessment tools, a reliability map was created to provide another metric for evaluating the map accuracy. Overall accuracy was 96.59%, and the total seagrass accuracy was 100%. Seagrass beds were found mainly west and north of the island and were mostly composed of a combination of Thalassia testudinum and Syringodium filiforme. Results suggested that light availability was not a limiting factor for seagrass colonization at the study area and that strong wave energy may be an important factor in regulating seagrass distribution. This seagrass habitat map improved upon previous mapping efforts and represents the first high-spatial-resolution map for the reserve. The data and methods used proved to be effective for mapping seagrass habitats within a highly complex benthic environment.