A study spectral reflectance of healthy and non-healthy coral (Acropora formosa) in Bidong Island water by using remote sensing technology

Abstract

Coral reefs in Malaysia are important as attractive tourist place because they are variety type of coral. The imp011ance of and worldwide threats to coral reef ecosystems have created an urgency to develop methods to study reefs on a global scale. In 1998, global coral bleaching event was the largest recorded historical disturbance of coral reefs and resulted in extensive habitat loss. The expulsion of pigmented zooxanthellae from corals during bleaching events results in a strong optical signal. In this study, a field program was designed to explore the differences in the spectral reflectance characteristics of various coral reef features especially between healthy and non-healthy coral. This study was conducted at Bidong Island, Karah Island and Tengkorah Island by using remote sensing application. In-situ upwelling and downwelling radiances were collected for 33 of measurements in range of wavelength 350 to 800 nm by using Satlantic underwater sensor just above the target substrate. This study is aimed to determine the optical wavelength in healthy and and non-healthy Acropora formosa. In order to discriminate between the target substrate further analyses were done such as hyperspectral reflectance, derivative and cluster analysis were applied. Stepwise wavelength selection revealed that reef species more accurate distinguished by using derivative analysis compared to hyperspectral reflectance or cluster analysis. The results from this study indicate that remote sensing technology may be feasible means of accurate identification and subsequent monitoring of change in coral health and overall well-being.