Primary production and bacterioplankton in fish ponds with mono and polyculture

Abstract

Estimates of primary production in relation to bacterioplankton growth kinetics have been made in three fish ponds with mono and polyculture in the Fish Farm Nivka, Kiev, USSR. Since the basic process of primary production is dependent upon such prevailing conditions as temperature, light and nutrient rather than upon the introduction of fish species, almost similar production rates were obtained in these ponds, with the variance ratio found not significantly different from zero (P > 0.05). So was the case with bacterioplankton growth kinetics (P > 0.05). A maximal gross production coupled with a bacterioplankton peak was demonstrated in the summer month of July with the rise of temperature of the water, while minimal production was observed in September. The effect of season was highly significant (P < 0.001) upon both primary production and bacterioplankton. Extreme deficiency of the net photosynthetic production of O₂ was observed in summer due to less prevalence of phytoplanktonic algae as a consequence of heavy grazing by the herbivorous fishes at the time of their active growth. A plot of biochemical oxygen demand as function of the respiratory loss of O₂ due t0 bacterial population showed a direct linear relationship (P < 0.001). Lack of definite correlation (P > 0.05) was indicated between the BOD and the total bacterioplankton population. There existed no definite relationship (P > 0.05) between primary production and bacterioplankton, perhaps because of the very low percentage of autotrophic photosynthetic bacteria and abundance of heterotrophic bacteria in the composition of total bacterioplankton.