1996 Volume 40 Pages 371-376
The eutrophication and the increase of phytoplankton occur at the many lakes polluted with inorganic and organic matter all over the world. The water quality at lake Abashiri, in which the water quality accidents called as “Aoko” and “Aoshio” in Japanease have often happend, have been simulated numericaly by using “Soumiya” model. In order to analyze numericaly the basic relationship between phytoplankton and zooplankton, the trajector of solution on the phytoplankton-zooplankton phase plane for Lotka-Volterra equation was used. It was shown that phytoplankton could be decreased largely by increasing zooplankton in the period of increasing phytoplankton.
