The recent domestic aquaculture production of Okinawamozuku (
Cladosiphon okamuranus) is unstable, ranging from 5,000 to 20,000 tons per year. Therefore, technical development to ensure Okinawamozuku stable production is required. A lot of ecological and biological research on Mozuku cultivation methods hitherto have been reported, although there has been little information about the optical environments for the growth. Fluctuations in Mozuku production is intricately involved not only in the natural environment as well such as market price and production techniques. The aquaculture production is known to be mostly depended on water temperature and light condition, however basic scientific information were very limited. Therefore experimental equipment that can be used for basic research of algae growth in coral reef waters was necessary. We developed a culture system to examine optical environment for algae cultivation in coral zone. Algae are cultivated in special optical environmental condition imitating reflected light from seabed in a coral reef region in addition to directly light from the sun. It is necessary to use an artificial cultivation device to keep stable condition for consideration of the environmental effect on the growth without direct light from the sun. Taking into consideration the reflected light from a submerged coral reef, a device with down and up lighting was developed. In this study, we describe the calculating method to simulate a natural optical environment and the development of the culture device. Based on the differences in light intensity between measured value for the developed system and calculated value both for up and down lighting, developed apparatus can be used to examine optimum light condition for the growth of algae in coral reef region.
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