溜池における<i>Anabaena</i>の消長と環境条件との関係

Abstract

The succession of a molecular nitrogen fixing blue-green alga, Anabaena was investigated in a farm pond where chemical fertilizers applied in Nagano Prefecture during the years of 1954 to 1956. The results were obtained as follows: 1) Maintenance of the algal blooming and acceleration of their growth rate were not found to be affected by the application of phosphorus fertilizer. The phenomenon was interpreted that the assimilable carbon played possibly a role of limiting factor. 2) “Heterocyst frequency” proposed by FOGG (1953) showed the minimum value of 2 to 3% when the growth of Anabaena had attained the maximum, suggesting that their maximum growth might be determined by the estimation of the value of heterocyst frequency. The chemical fertilization was found to have affected more on the heterocyst formation than on the resting spore formation. It seemed reasonable to assume, therefore, that in the course of the algal growing the former plays role different from the latter. 3) In three-year period of the study A. Viguieri was determined dominant species in the pond water especially in June. In 1956, with nearly complete control of water plant growth affected by the stocking of grass-carp, other two species of algae A. contorta (in July) and A. flos-aquae (in August) were also detected dominant. 4) The maximum yield of Anabaena was suppressed by the growth of water plants in the pond water, which, however, did not effect on the growth rate of the former.