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タイトル: Introduction of underwater video system for the observation of coastal macroalgal vegetation
著者: Hayashizaki, Ken-Ichi
Ogawa, Hisao
キーワード: macroalgae
GPS
abundance
underwater video
発行日: 2006年4月28日
出版者: International Coastal Research Center, Ocean Research Institute, the University of Tokyo
掲載誌情報: Coastal marine science. Vol.30No.1, 2006.4, pp. 196-200
抄録: Benthic vegetation has important roles in coastal ecosystems. Vegetation analysis and biomass estimation are urgently required for proper utilization and conservation of coastal area and also for sustainable fisheries. Although remote sensing methods such as aerial photography and satellite imaging give us efficient ways for vegetation mapping on wide area, these methods are limited to shallow and flat bottom waters where seagrasses mainly occur. For macroalgae, predominant on rocky littoral and sub-littoral zones, direct visual observation with SCUBA has been used. The accuracy of species identification is expected to be high, but the time consuming procedures result in limited coverage of area. To overcome the limitation we have developed a monitoring system for seaweed vegetation in conjunction with underwater video, GPS and depth sounder. Although limited resolution of the image might affect the accuracy of species identification, the synchronized recordings of video image and three-dimensional positioning of vegetation enabled quick monitoring to cover certain spread of area. It was possible to deploy the system in different ways, from traditional quadrat placement on transect line, to serial towing, so that the diversity of species and bottom environments could be adequately observed. Bathymetry and monitoring of bottom substrate and invertebrates were also enabled with the system. For the effective extraction of information from observation and also aimed to improve the accuracy of biomass estimation, we developed a numerical analysis using generalized additive models (GAMs). The two distinctive properties of GAMs analysis, constraint free smoothing and model selection by AIC, enabled versatile modeling of macroalgae distribution in direct/indirect association with environmental factors. Together with categorization by life forms of macroalgae, it was possible to deduce a possible vegetation pattern and a numerical prediction of standing stock biomass for each category even from small samplesized quadrat observations. The application of this system in the Otsuchi bay, Tohoku districts, Japan was introduced, and further expansion of the methods to include tropical waters were discussed.
URI: http://hdl.handle.net/2261/5632
ISSN: 13493000
出現カテゴリ:Coastal Marine Science
Coastal Marine Science

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