Researches on the effects of agricultural activities on sand dune lakes and measures to protect a lake ecosystem

新泻和秋田县31个沙丘湖泊水质普查。进行了富营养化评价。一些濒危物种的生活史或分布，如水仙和凤眼莲(Euryale ferox、)，以及优势种如菱。沙丘湖泊中的荷花也进行了研究。Sagata湖是新泻市一个典型的沙丘湖泊，西瓜、烟草和日本萝卜是该湖周边的主要农作物。对Sagata湖进行了密集的湖沼学研究，揭示了保护湖泊周围的芦苇带以减少农田硝态氮的重要性，以及覆盖TRapa植被以调节蓝藻有害水华的重要性。

General surveys on water quality of 31 sand dune lakes in Niigata and Akita Pref. were conducted to evaluate the eutrophication. Life cycle or distribution of some endangered species such as Nymphoides peltata and Euryale ferox、and dominant species such as Trapa spp. and Nelumbo nucifera inhabited in sand dune lakes were also studied. Intensive limnological studies of Lake Sagata, a typical sand dune lake in Niigata City, where watermelon, tobacco and Japanese radish are cultivated as main crops on the periphery of the lake, revealed the importance of protection of reed zone around the lake to decrease nitrate nitrogen from the farm land and covering of Trapa vegetation to regulate the harmful water bloom by cyanobacteria.