The purpose of this study was to clarify the effect of the sunlight exposure treatment on gelidiaceae on the gel-forming ability of the agar. After sunlight exposure treatment to collected Gelidium elegans in August and October, agar was extracted and its molecular properties such as functional groups, molecular weight and molecular weight distribution and gel properties such as gelation temperature and rheological properties of gel were investigated. The treatment did not affect the mechanical properties of the agar gel. In addition, elimination of sulfate groups and decomposition of 3,6-anhydro-Lgalactose did not occur. However, the average molecular weight and molecular weight distribution of agar changed due to the treatment. It was suggested that the control of amount of ultraviolet rays of sunlight and temperature during the treatment is effective in producing agar having stable quality or desirable gel forming ability.

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An inexpensive and simple fertilizer application tool using plastic bottles fitted with a semipermeable membrane was tested in the laboratory and field for enhancement of nori cultivation. In the laboratory test, the amount of permeation of NO₃-N and NH₄-N from the fertilizer in the fertilizer application tools through the semipermeable membrane was continuous and stable. In the experimental cultivation of nori carried out in the Kii channel, Tokushima Prefecture, two areas were set in the nori cultivation system, i.e., an experimental fertilization area with numerous fertilizer application tools and a control area with no application tools. In the fertilization area, the growth and color tone of the nori thalli were better than control area and the Nori product value increased. This result indicates the effectiveness of this fertilizer application tool in the nori cultivation and the possibility of application to cultivation technologies of otheralgae.

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