Observation of a coccolithophore Gephyrocapsa oceanica bloom in the temperate coastal waters of Sagami Bay, Japan

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  • Yano Koichi
    Graduate School of Science and Engineering, Soka University
  • Takayama Yoshiki
    Institute of Plankton Eco-engineering, Soka University Manazuru Marine Center for Environmental Research and Education, Graduate School of Environment and Information Sciences, Yokohama National University Japan Agency for Marine-Earth Science and Technology (JAMSTEC)
  • Shimode Shinji
    Manazuru Marine Center for Environmental Research and Education, Graduate School of Environment and Information Sciences, Yokohama National University
  • Toratani Mitsuhiro
    Department of Civil Engineering, School of Architecture and Urban Planning, Tokai University
  • Murakami Hiroshi
    Earth Observation Research Center (EORC), Japan Aerospace Exploration Agency (JAXA)
  • Kuwahara Victor S.
    Graduate School of Science and Engineering, Soka University

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タイトル別名
  • Observation of a coccolithophore <i>Gephyrocapsa oceanica</i> bloom in the temperate coastal waters of Sagami Bay, Japan

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<p>In mid-May 2020, a coccolithophore bloom of Gephyrocapsa oceanica Kamptner, 1943 was observed in Sagami Bay, Japan, possibly for the first time in 25 years. This species is a common yet elusive taxon in the waters around Japan, but there has only been one report of a bloom observation in Sagami Bay in 1995. The G. oceanica bloom in 2020 was observed by the combined approach of the JAXA ocean color remote sensing satellite “Shikisai” and field surveys. The true-color RGB images from the satellite showed the initial bloom in Tokyo Bay appears to have advected into Sagami Bay on May 5. On May 15, ad hoc field sampling was conducted based on visual confirmation from the shore. Nitrate, nitrite and phosphate concentrations at the sea surface were 3.28 µM, 0.11 µM and 0.29 µM, respectively, and higher than the median of May from 1997 to 2019. Chlorophyll a concentration was 2.23 µg L−1 at the sea surface, and cell density was 5.3 × 103 cells mL−1. The large bloom appears to have reached the western shorelines of the bay, and dispersed counterclockwise within the bay. The bloom reached an estimated 1119.02 km2 surface expression on May 17, and completely disappeared by May 24. Further, the median value of 19′-hexanoyloxyfucoxanthin (a signature pigment of haptophytes, including coccolithophores) concentration has been increasing from 2017 to 2020, and the coastal area of Sagami Bay may have changed to a region favorable for haptophytes.</p>

収録刊行物

  • Plankton and Benthos Research

    Plankton and Benthos Research 19 (1), 37-50, 2024-02-28

    日本プランクトン学会、日本ベントス学会

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