Coral health monitoring: linking coral colour and remote sensing techniques

Percent of living coral cover is an indicator commonly used to assess reef status. This study tested whether Coral Health Chart scores could be used as a proxy for spectral reflectance, which would provide a basis for mapping living coral cover at a finer scale (colour) using remote sensing techniques. A total of 1264 spectral reflectance measurements were taken in situ from corals representing the colour scores on the Coral Health Chart at Heron Island, Great Barrier Reef, Australia. Spectral analyses of reflectance magnitude showed that living coral could be classified with 72.41% overall accuracy into three colour categories: bleached, medium, and dark coral. First- and second-order derivative analyses did not improve the accuracy of classifying coral spectra into colour categories. Spectral analyses using only coral spectra from the genus Acropora also failed to improve classification results significantly, consistent with suggestions that coral reflectance is independent of taxonomy at the genus level. The results of this study provide a foundation for using the Coral Health Chart as a proxy to map and monitor living coral condition using remote sensing techniques.