Nippon Suisan Gakkaishi 75 (1), 45-53 (2009)

Development and testing of blocks made from Miyakejima Island volcanic ash for the restoration of Gelidium beds

KENJI TAKIO,1* KAZUTO ANDO,1a TAKASHI SUGINO,1b
ICHIRO KOMAZAWA,1a CHIHO NAKAMURA2c AND HISAYUKI ARAKAWA2

1Oshima Branch, Tokyo Metropolitan Islands Area Research and Development Center of Agriculture, Forestry and Fisheries, Oshima, Tokyo 100-0212, 2Department of Ocean Sciences, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, Japan

Using volcanic ash and/or scoria collected from Miyakejima Island, 6 blocks (L30×W30×H5 cm) of different compressive strengths and composition were formed and deployed in Sashikiji fishing harbor, Izu Oshima Island to compare the coverage of colonized marine algae with concrete blocks of the same type. The coverage of red algae on the upper surface of volcanic ash blocks was significantly lower than that on a concrete block. No significant differences were found among the coverages on the 6 volcanic ash blocks of different compressive strength and composition. Gelidiacean algae did not grow on the upper surface but on the edge and lateral surfaces of these blocks. In the second experiment, columnar blocks (φ5×H10 cm) were deployed in the same fishing harbor. Gelidiacean algae grew on the lateral surface of these blocks and the amount of these algae was only slightly smaller than that on concrete blocks of the same shape.


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