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Evaluating the effects of drainage from paddy fields on Lake Biwa ecosystem

Research Project

Project/Area Number 16310011
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section一般
Research Field Environmental dynamic analysis
Research InstitutionThe University of Shiga Prefecture

Principal Investigator

BAN Syuhei  The University of Shiga Prefecture, School of Environmental Science, Associate Professor, 環境科学部, 助教授 (50238234)

Co-Investigator(Kenkyū-buntansha) OHTA Kei-ichi  The University of Shiga Prefecture, School of Environmental Science, Associate Professor, 環境科学部, 教授 (80022250)
SUDO Miki  The University of Shiga Prefecture, School of Environmental Science, Associate Professor, 環境科学部, 講師 (50206570)
KUMAGAI Michio  Lake Biwa Environmental Research Institute, Chief Scientist, 環境科学研究センター, 統括研究員 (40234512)
Project Period (FY) 2004 – 2006
Project Status Completed (Fiscal Year 2006)
Budget Amount *help
¥15,100,000 (Direct Cost: ¥15,100,000)
Fiscal Year 2006: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2005: ¥4,300,000 (Direct Cost: ¥4,300,000)
Fiscal Year 2004: ¥9,100,000 (Direct Cost: ¥9,100,000)
KeywordsDrainage from paddy fields / Lake Biwa / Subsurface maximum of ammonium / Phytoplankton production / Internal Kelvin wave / Nitrogen stable isotope / Material transport / Bottom sediments / セストンδ^<13>C / セストンのδ^<15>N / アンモニア / 植物プランクトン / 内部波 / アンモニアの排出 / 動物プランクトン
Research Abstract

In north basin of Lake Biwa, subsurface maximum of ammonium was found across the east to west transect of the lake from late April to early July. Phytoplankton was relaxed from nutrient limitation and primary production was enhanced in mid-May just after rice planting. According to stable isotope analysis, suspended particles originated from paddy fields run into the lake, and seemed to deposit to the bottom of the littoral area, where ammonium, and probably together with phosphate, was released from the bottom sediments, used by phytoplankton production. Experiments for zooplankton excretion showed that regenerated nitrogen from micro-and mesozooplankton may contribute to the subsurface maximum of ammonium, and that regenerated phosphate was not enough for phytoplankton growth. This does not necessarily suggest that the subsurface maximum of ammonium is proxy as supplying nutrients from littoral to pelagic area.
Survey using ADCP and thermister-chain showed that internal Kelvin wave was found after mid-May. Vertically mixing and wavy motion produced by the internal Kelvin wave can induce wavy motion oscillating to the shoreline due to the effect of the slope of the bottom, and it can transport materials such as nutrients from littoral to pelagic area of the lake. Pesticides as indicator of the water from paddy were found even at 20 m depth as well as at the surface in the lake. It also supports horizontal transportation under the thermocline, ca. 20 m. These results provide a scenario as described below. In Lake Biwa, turbid drainage from paddy fields just after rice planting run into the lake, and suspended materials from the paddy deposits on the bottom sediments. Nutrients, such as ammonium and phosphate, released from the interstitial water in the sediments by disturbance due to internal wave are transported to the pelagic area and enhance phytoplankton production. To confirm this hypothesis, further studies for analyzing nitrogen stable isotope are needed.

Report

(4 results)
  • 2006 Annual Research Report   Final Research Report Summary
  • 2005 Annual Research Report
  • 2004 Annual Research Report
  • Research Products

    (8 results)

All 2006 2005 2004

All Journal Article (8 results)

  • [Journal Article] In situ generation of refractory organic compounds in Lake Biwa, Japan.2006

    • Author(s)
      Nohda, C., M.Maruo, S.Ban, K.Ohta
    • Journal Title

      Proc. Second Japan-Korea Joint Symp. on Limnology

      Pages: 18-23

    • NAID

      130005021681

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] A lake as a natural integrator of linear processes : Application to Lake Kinneret (Israel) and Lake Biwa (Japan)2006

    • Author(s)
      Rimmer, A., M.Boger, Y.Aota, M.Kumagai
    • Journal Title

      Journal of Hydrology 319

      Pages: 163-175

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary 2005 Annual Research Report
  • [Journal Article] 自律型潜水ロボット「淡探」を用いた琵琶湖研究の高度化と展望2005

    • Author(s)
      熊谷道夫 他
    • Journal Title

      日本造船学会誌 883

      Pages: 52-56

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary 2004 Annual Research Report
  • [Journal Article] Application of autonomous underwater vehicle and image analysis for detecting 3D distribution of freshwater red-tide Uroglena americana (Chrysophyceae)2005

    • Author(s)
      Ishikawa, K., M.Kumagai, R.F.Ross
    • Journal Title

      Journal of Plankton Research 27

      Pages: 129-133

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary 2004 Annual Research Report
  • [Journal Article] Jiritsugata sensui robotto "TanTan" wo mochi-ita biwako kenkyu no koudo-ka to tenbo2005

    • Author(s)
      M.Kumagai et al.
    • Journal Title

      Nippon Zousen gakkai-shi 883

      Pages: 52-56

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Application of autonomous underwater vehicle and image analysis for detecting 3D distribution of freshwater red-tide Uroglena americana (Chrysophyceae)2005

    • Author(s)
      Ishikawa, K., M.Kumagai, RF.Ross
    • Journal Title

      Journal of Plankton Research 27

      Pages: 129-133

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary
  • [Journal Article] Spatial distribution and seasonal changes of pesticides in Lake Biwa (Japan)2004

    • Author(s)
      M.Sudo 他
    • Journal Title

      Limnology 5・2

      Pages: 77-86

    • NAID

      10013464119

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2006 Final Research Report Summary 2004 Annual Research Report
  • [Journal Article] Spatial distribution and seasonal changes of pesticides in Lake Biwa (Japan)2004

    • Author(s)
      M.Sudo et al.
    • Journal Title

      Limnology 5

      Pages: 77-86

    • NAID

      10013464119

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2006 Final Research Report Summary

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Published: 2004-04-01   Modified: 2016-04-21  

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