Experimental Studies on the Role of Smaller Animals with Regard to the Degradation of AOKO

Abstract

Bio-film treatment process has been applied to the drinking water treatment plant used polluted lake water as source of water supply. It is said that this process have effect on removal and degradation of algae. But the role of smaller animals such as RotatoriaPhilodina erythrophthalmaand OligochaetaAeolosoma hemprichiinhabit in the bio-film has not been made clear yet sufficiently. Therefore, in this study, we spotlighted to these Rotatoria and Oligochaeta as smaller animals on the degradation of AOKO (bluegreen algal blooms), and then some experiments usingthese smaller animals in aerobic conditions with andwithout illuminations were made.The results may be summarised as follows. (1) The degradation of AOKO was promoted efficiently in dark conditions without photosynthesis. (2) Existence ofP.erythrophthamaandA. hemprichipromoted degradation of AOKO under both dark and light conditions. (3) Since detritus feederA. hemprichifeeds flocculated AOKO, and filter feederP. erythrophthalmafeeds dispersed AOKO deflocculated byA. hemprichiingestion, co-existence is much effective to promotly degradate the flocculated AOKO observed in the eutrophic lake. (4) The existence of smaller animals had direct and indirect functions to degradate AOKO.Direct one is degradation of AOKO, and indirect one is activation of total ecosystem through the food chain by increase of dissolved organic matter with degradation of AOKO.