Spring bloom in a hypereutrophic lake, Lake Kasumigaura, Japan—V : Factors controlling natural population of phytoplankters

Temperature was the limiting factor controlling the multiplication rate and standing stock of natural population density of phytoplankters in the lake of Tsuchiura Harbor during the spring bloom of 1980. The temperature relationship of the multiplication rate could be expressed as an Arrhenius equation during the spring bloom. The species composition of the natural phytoplankton community, on the other hand, was affected chiefly by combination of the ambient nutrient concentrations of ammonium, nitrate, phosphate and silicate. Although many phytoplankton species occurred, one temperature relationship appeared to hold for mixed species of the natural community from 4.4 to 24.9° C.     

Spring bloom in a hypereutrophic lake, Lake Kasumigaura, Japan—IV : Inductive factors for phytoplankton bloom

The limiting factor for inducing the spring bloom of phytoplankters in 1980 at Tsuchiura Harbor of Lake Kasumigaura was shown to be temperature. The bloom started at a water temperature higher than 10°C and lasted until the temperature was up to approx. 20°C. The concentration of inorganic nitrogen in the lake was found to have a profound effect on the induction of the spring bloom as a nonlimiting factor. Other inorganic nutrients contributed mostly to the species succession of phytoplankters comprising the spring bloom.