To investigate the effect of electrical treatment on storage behavior for fresh spinach leaves during cold storage, sample leaves with various leaf lengths were put on the AC high voltage electrode and were examined for changes in moisture content, SPAD value as a leaf color index and L-ascorbic acid content during storage. The sample leaves were sorted into sizes S (20-25 cm), M (26-37 cm) and L (38-50 cm) as samples of different shape. Each sample leaf was put on a stainless-steel shelf at 9.4°C in 84.9% RH. One of the shelves received an AC voltage of 2000 V and a frequency of 50 Hz for 8 weeks, and another shelf was electrostatic shielded as a control condition. The moisture content of all samples was significantly decreased after 4 weeks of storage. The moisture content for the voltage applied sample of M size at 2 weeks storage and L size at 4 weeks was statistically lower than the control (P < 0.05), though the SPAD values showed no significant differences for electrical treatment. There was also no significant difference for the L-Ascorbic Acid content in the 2 weeks storage. The result of this study indicated that there should be no effect of electrical treatment using an AC high voltage electrode on the spinach leaf attributes during cold storage for 2 weeks except for moisture content.

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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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On the implications for mariculture, the effects of breeding with algal food supply to promote maturity of sea urchin, Strongylocentrotus intermedius (A. Agassiz) were examined from December 2000 to November 2001.Urchins were reared in tank under artificial condition with algal food supply as experimental urchins (EU). Maturity of the EU was compared with that of wild urchins (WU) to reveal the effects of algal food supply. Before spawning, the changes in gonad index (GI) and maturity stage of EU were similar to these of WU, which implied that the food supply breeding did not accelerate maturity of sea urchins. However, significant differences were observed in GI and maturity stage between experimental groups in spawning season. Satiation feeding of algae is considered to extend spawning period and slow gonad reduction for sea urchin S. intermedius.

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