Development of a coral monitoring system for the use of underwater vehicle

The purpose of this research is to develop a coral monitoring system for the use of underwater vehicles. Reef coral is very sensitive about changes of ocean environment, such as unusual climate changes or increase of crown-of-thorns starfish resulting from the global warming. Coral can thus be an index of ocean environment. It is widely known that some kinds of corals have an inherent characteristic of fluorescence due to `coral fluorescent protein (CFP).' The authors are developing an oceangoing solar-powered underwater glider, named `Tonai60'. The operational depth of the Tonai60 glider is 60m, for ocean environmental monitoring in twilight ocean zone. The Tonai60 glider is equipped with an ocean-environment monitoring data logger `RINKO-Profiler' of JFE Advantech Co., Ltd. and an underwater passive acoustic data logger `A-tag' of Marine Micro Technology Corp. for monitoring marine mammals. Measuring items of RINKO-Profiler are depth, temperature, conductivity, salinity, dissolved oxygen, chlorophyll and turbidity. The glider is also equipped with a coral monitoring system at the forefront of its fuselage. This system consists of a network camera and 3-axis digital compass. Coral can be detected from an image binarised with a certain threshold. This paper deals with a coral monitoring system using ultraviolet LEDs and image analyses.