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1996 Fiscal Year Final Research Report Summary

Prediction of interannual changes in summer chlorophyll-a concentration in a reservoir using environmental conditions of the preceding spring

Research Project

Project/Area Number 07680557
Research Category

Grant-in-Aid for Scientific Research (C)

Allocation TypeSingle-year Grants
Section一般
Research Field Environmental dynamic analysis
Research InstitutionEhime University

Principal Investigator

KAGAWA Hisanori  Ehime University, Faculty of Agriculture, Professor, 農学部, 教授 (40003777)

Co-Investigator(Kenkyū-buntansha) HIROTANI Hiroshi  Ehime University, Faculty of Agriculture, Assistant, 農学部, 助手 (70218858)
Project Period (FY) 1995 – 1996
Keywordsreservoir / chlorophyll-a / interannual changes / prediction / Mg / K ratio
Research Abstract

In the Ishitegawa Reservoir in Japan, the mean chlorophyll-a concentration at 0.5m depth during July, August and September (C^s, mugl^<-1>) is predictable by the conductivity in May (E_5, mScm^<-1> at 25゚C) and the mean air temperature in May (T_5, ゚C). In this report the authors intended to make clear the actual substances corresponding to E_5 mainly by regression analyzes of 14 years of monthly data 1983 through 1996. The C_s in a logarithm (logC_s) correlated positively with chlorophyll-a concentration (mugl^<-1>) in May in a logarithm (logChl-a_5) (gamma=0.89, P<0.01). Only one factor in May, a ratio of concentrations (mmoll^<-1>) between dissolved magnesium and potassium, (Mg/K)_5, was found to correlate positively both with logChl-a_5 (gamma=0.72, P<0.05) and E_5 (gamma=0.67, P<0.05) among calcium, magnesium, sodium and potassium concentrations and each ratio. Potassium concentration was always low in the reservoir, and that in May correlated negatively with logChl-a_5 (gamma=-0.78, P<0.01), which might be due to the result of potassium absorption by algae, so the positive effects of the magnesium part of Mg/K on algal growth were examined by culture experiments of Chlorella vulgaris under definite potassium, phosphorus and nitrogen concentrations. The results of the culture experiments showed positive effects of magnesium on the growth of C.vulgaris under usual magnesium concentrations in the reservoir. Finally, using (Mg/K)_5, the authors were able to induce a new regression equation predicting the chlorophyll-a concentration in the summer, "logC_s=0.578 (Mg/K)_5 -0.44" (R^2=0.77, P<0.01). The residuals of observation minus prediction showed an interannual trend to become larger in minus values, correlating negatively with summer nitrite and acid-soluble iron concentrations.

  • Research Products

    (2 results)

All Other

All Publications (2 results)

  • [Publications] Hisanori KAGAWA: "Predicting the summer chlorophyll a concentration in a reservoir based on the environmental conditions of the preceding spring" Hydrobiologia. 310. 59-70 (1995)

    • Description
      「研究成果報告書概要(和文)」より
  • [Publications] Kagawa, H.& Hirotani, H.: "Predicting the summer chlorophyll alpha concentration in a reservoir based on the environmental conditions of the preceding spring" Hydrobiologia. 310. 59-70 (1995)

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 1999-03-09  

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