BENTHIC HABITAT MAPPING OF BONAIRE, CARIBBEAN NETHERLAND ANTILLES: APPLICATION OF IMAGE CLASSIFICATION IN ARCGIS TO REMOTELY SENSED UNDERWATER ORTHOMOSAICS

The island of Bonaire, Caribbean Netherlands, is home to some of the world’s most diverse coral reefs, which provide critical habitat and ecosystem services. Due to the threat of large-scale coral bleaching events, changing climate, and anthropogenic activity, action is needed. However, there is currently a lack of foundational mapping of the coastal benthic habitats and species that comprise Bonaire’s coral reefs. This study focuses on developing benthic habitat maps of multiple reef locations, which primarily contain hard corals, sponges, and sand. Orthomosaics were produced in Pix4D Mapper from field surveys collected by our underwater drone (a QYSEA FIFISH V6 EXPERT) over a single field season. Different image classification techniques in ArcGIS Pro were tested to find the most accurate identification and continuous delineation of the benthic features. Supervised image classification failed to produce accurate feature geometries for both the object-based and pixel-based classification methods. These methods did not produce accurate maps, due to (1) the complex (amorphous) structure of the reef, (2) the spectral inconsistency among the same features, and (3) the similarity of spectra between different features. Through many different trials, it was found that unsupervised image classification produced the best results, yet further manual identification was needed to create the most accurate maps. The new benthic habitat maps presented here contribute to the understanding of current coral reef dynamics and species populations. Moreover, time-integrated maps (through repeat surveys) can be used for monitoring and to identify areas of focus for conservation and management strategies to help reduce the impact of increasing pressures on Bonaire’s coral reefs, such as bleaching events and diseases like Stony Coral Tissue Loss Disease currently widespread throughout the Caribbean.