J.Technology and Education, Vol.32, No.1, pp.25-32 (2025)
研究論文

農業かんがい用ため池「門池」の水質とプランクトン

 

鈴木 雄心、芳野 恭士、竹口 昌之^*

沼津工業高等専門学校 物質工学科（〒410-8501 静岡県沼津市大岡3600）

*takeguch@numazu-ct.ac.jp

 

Water quality and plankton in agricultural irrigation pond “KADOIKE”

 

Yushin SUZUKI, Kyoji YOSHINO, Masayuki TAKEGUCHI*

Department of Chemistry and Biochemistry, National Institute of Technology, Numazu College

(3600 Ooka, Numazu, Shizuoka 410-8501, Japan)

 

(Received May 23, 2025; Accepted July 22, 2025)

 

A survey of the water quality and plankton populations in the agricultural irrigation pond “KADOIKE” was conducted from June 7 to December 24, 2019. An increase in chemical oxygen demand (COD) was observed from early June to early August at the inflow site. Concurrently, the water temperature exceeded 25°C, and there was an increase in sunshine hours after the end of the rainy season. Phytoplankton populations increased significantly from late July to early August, and Microcystis spp. covered the water surface, resulting in reduced transparency. The abnormal growth of phytoplankton is considered to have been caused by the following conditions: (1) eutrophication due to the inflow of high-COD water, (2) increased sunlight hours, (3) water temperatures above 25°C, and (4) increased water-stagnation time in the pond. The daily fluctuations in phytoplankton and zooplankton counts confirmed the predatory relationship of phytoplankton with zooplankton. The survey identified five predominant zooplankton species, suggesting that this pond exhibits a limited diversity of zooplankton species.

Keywords：agricultural irrigation pond, water quality, zooplankton, phytoplankton