汽水湖沼におけるアオコおよび赤潮発生の制御に関する基礎的研究

Abstract

The relationship between salinity and the algal growth was investigated by algal assay procedure and by field survey in Lake Koyama-ike, Lake Togo-ike and Nakaumi which are located in Tottori prefecture.From the field investigation the following results were obtained. Water bloom of Microcystis spp. and Anabaena spp. were observed at less than 1200mg·l-1 of Cl- concentration and at more than 23°C and 18°C of water temperature, respectively. Red tide of Prorocentrum minimum occured at levels higher than 3500mg·l-1 of Cl- concentration and was observed between 5°C and 27°C.From the flask experiment significant negative correlation was observed between Microcystis aeruginosa or Anabaena affinis growth and Cl- concentration. M. aeruginosa growth was hindered at levels above 2300mg·l-1 of Cl- concentration and Anabaena affinis growth at levels above 2700mg·l-1.The yields for both species were halved at 1500mg·l-1 of Cl- concentration. A good positive correlation was observed between growth of both species and water temperature. Positive correlation was observed between P. minimum growth and Cl- concentration.It seemed that Cl- concentration and water temperature were very important factors to controlling the algal succession. There is a posibility that water bloom and red tide are hindered by controlling the Cl- concentration of brackish lakes.