Abstract
The actual conditions of physical, chemical and biological properties and interrelationship between them in the eutrophic Lake Koyama in Tottori were investigated in 1991 and 1992.
In the both years, the blue-green algae made bloom in early summer (dominantly, Anabaena solitaria) and fall (dominantly, Microcystis wesenbergii). The outbreak of Anabaena might be brought about by low N, especially water soluble N of the water in May and June. Anabaena made the water rich in the non-soluble N. The soluble N of the water increased after the disappearance of Anabaena.
Microcystis became dominant soon after the disappearance of Anabaena. It made bloom in October. It seemed difficult to explain the outbreak of Microcystis by the change in the N concentration of the water. The concentration of P, however, was always enough for the growth of blue-green algae. It was found out that the both blue-green algae suppressed the growth of other algae.
The water temperature became maximum in August and seemed one of the major factors of bloom outbreak. It, however, was also difficult to explain the outbreak of Microcystis by the change in the water temperature.
The peak time of the CFU was close to that of the algae, which suggested the interrelationship between bacteria and algae.
