Underwater hyperspectral classification of deep sea corals exposed to 2-methylnaphthalene

Tropical corals are routinely monitored from satellite and aeroplane using remote sensing techniques, revealing the health of coral reefs. Notably, coral bleaching is continuously monitored using multi- or hyperspectral imagery from satellites and aeroplanes. For deep-water corals, however, no established remote sensing technique exists, and for this reason, much less is known about the status of their habitats over time. The purpose of the present work was to evaluate the use of underwater hyperspectral imaging to detect changes in health status of both orange and white color morphs of the coral species L. pertusa. In this study, we examine the feasibility of similar ecosystem health monitoring by the use of underwater hyperspectral imagery. A total of 66 coral samples were exposed to 2-methylnaphthalene concentrations from 0 mg L-1 to 3.5 mg L-1, resulting in corals of varying health condition. By use of a machine learning model for classification of reflectance spectra, we were able to classify exposed corals according to lethal concentration (LC) levels LC5 (5% mortality) and LC25 (25% mortality). This is a first step in developing a remote sensing technique able to assess environmental impact on deep-water coral habitats over larger areas underwater.