At present, our nation's self support ratio of food provisions in marine product is extremely low. Therefore, it is important to improve this situation as well as its stable supply. Regardless to say, to improve marine biological growth environment is one of urgent tasks for stable supply. Generally, once concrete block are submerged in the water, occasionally, converting the surrounding water area into strong alkaline region for sea water and this is not good for any marine plant and organism.
So, due to prevent strong alkaline composition liquid out from surface of the concrete block, coating technology which transfer concrete surface with ferrous sulfate which is an essential element for seaweed growth was developed and availabilities of this technology were tested and examined by many users.

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This paper is a study of the use of light emitting diodes (LEDs) as a light source instead of the sun or fluorescent lamps for the growth of a photosynthetic microorganism, Euglena gracilis, which is classified both as a green algae in the plant kingdom and a protozoan in the animal kingdom. LEDs for blue light of 450nm and LEDs for red light of 660nm were used. For the testing of the growth of Euglena under light, a luminaire consisting of 1064 LEDs on a 230mm (width) ×320mm (height) panel was manufactured, on which 532 LEDs were red and the others were blue. The luminous intensity of each light source was controlled by a power supply separately attached. For full illumination, an electric power of 80W was supplied to the luminaire. These two kinds of lights were introduced to the Euglena in the cultivation vessel. The Euglenagrown by LEDs were about 2 times greater than by ordinary fluorescent lamps. From the results, we concluded that light emitting diodes are not only useful for microalgal-biomass production but also for efficient conversion of electric energy to photosynthetic energy.

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The oxygen regeneration system is one of the most important subsystems in CELSS. Algae photosynthesis is useful for oxygen regeneration. In this study, in order to obtain basic knowledge regarding oxygen regeneration using algae, a culture system based on the turbidostat method was constructed. Culture experiments, using Spirulina platensis, were conducted for the purpose of investigating the relationship between oxygen production rate and cell density. Spirulina was cultured with several different cell densities and oxygen production rate, dilution rate and chlorophyll content were measured for each treatment. The maximum oxygen production rate was obtained with the highest cell density, but in spite of that, photosynthesis and growth were enhanced in the lower density treatments. In the algal suspension with high cell density, the obtainable light energy in the culture vessel decreased so drastically that photosynthesis of Spirulinamay have been inhibited. There was such a large amount of Spirulina cells in the culture vessel that despite the lower levels of photosynthesis, the oxygen production rate remained high. The chlorophyll content was less in the lower density treatments. The high light intensity may have caused the decrease in chlorophyll content.

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