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Proceedings Paper

Impact of huge tsunami in March 2011 on seaweed bed distributions in Shizugawa Bay, Sanriku Coast, revealed by remote sensing
Author(s): Shingo X. Sakamoto; Shuji Sasa; Shuhei Sawayama; Ryo Tsujimoto; Genki Terauchi; Hiroshi Yagi; Teruhisa Komatsu
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Paper Abstract

Seaweed beds are very important for abalones and sea urchins as a habitat. In Sanriku Coast, these animals are target species of coastal fisheries. The huge tsunami hit Sanriku Coast facing Pacific Ocean on 11 March 2011. It is needed for fishermen to know present situation of seaweed beds and understand damages of the huge tsunami on natural environments to recover coastal fisheries. We selected Shizugawa Bay as a study site because abalone catch of Shizugawa Bay occupied the first position in Sanriku Coast. To evaluate impact of tsunami on seaweed beds, we compared high spatial resolution satellite image of Shizugawa Bay before the tsunami with that after the tsunami by remote sensing with ground surveys to know impact of the tsunami on seaweed beds. We used two multi-band imageries of commercial high-resolution satellite, Geoeye-1, which were taken on 4 November 2009 before the tsunami and on 22 February 2012 after the tsunami. Although divers observed the tsunami damaged a very small part of Eisenia bicyclis distributions on rock substrates at the bay head, it was not observed clearly by satellite image analysis. On the other hand, we found increase in seaweed beds after the tsunami from the image analysis. The tsunami broke concrete breakwaters, entrained a large amount of rocks and pebble from land to the sea, and disseminated them in the bay. Thus, hard substrates suitable for attachment of seaweeds were increased. Ground surveys revealed that seaweeds consisting of E. bicyclis, Sargassum and Laminaria species grew on these hard substrates on the sandy bottom.

Paper Details

Date Published: 11 December 2012
PDF: 7 pages
Proc. SPIE 8525, Remote Sensing of the Marine Environment II, 85251B (11 December 2012); doi: 10.1117/12.999308
Show Author Affiliations
Shingo X. Sakamoto, The Univ. of Tokyo (Japan)
Shuji Sasa, The Univ. of Tokyo (Japan)
Shuhei Sawayama, The Univ. of Tokyo (Japan)
Ryo Tsujimoto, Northwest Pacific Region Environmental Cooperation Ctr. (Japan)
Genki Terauchi, Northwest Pacific Region Environmental Cooperation Ctr. (Japan)
Hiroshi Yagi, VisionTech Inc. (Japan)
Teruhisa Komatsu, The Univ. of Tokyo (Japan)
Japan Science and Technology Agency (Japan)

Published in SPIE Proceedings Vol. 8525:
Remote Sensing of the Marine Environment II
Robert J. Frouin; Naoto Ebuchi; Delu Pan; Toshiro Saino, Editor(s)

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