APPLICATION OF ALGAL BLOOM CONTROL TECHNIQUE USING NATURAL PREDATORS IN EUTROPHIC AGRICULTURAL RESERVOIR

摘要

Climate change resulting into temperature rise and drought promoted increased frequencyof algal bloom. Outbreaks of massive algal bloom in the eutrophic agricultural reservoirsare a main problem in water quality management. Various physical, chemical and biologicalmanagement skills had been applied on algal bloom, but most of those systems were notsatisfactory in terms of effects, cost and ecological security. Biomanipulation, is a safe way tomanage algal bloom and ecological health using predators on the food web of ecosystem, hasoften been applied to eutrophic reservoirs. In this study, proliferated herbivorous zooplanktonis applied to control algal bloom in the eutrophic reservoirs as ecological management.Among zooplankton, genus Daphnia has high control ability for most of algal species with theirsuperior predation. The development of applicable ecological algal control technique whichuses natural enemies, Daphnia, feeding algal bloom causing Cyanobacteria was carried outin this study. The purpose of the study was the practical application of proliferated naturalenemies, Daphnia for algal bloom control using fi eld growth facility and the assessment ofalgal control effi ciency in the eutrophic reservoir. The experiment was set up at small-sizedreservoir Jeondae. Massive cultured Daphnia as a natural enemy was supplied to the reservoirduring algal bloom period. Daphnia similoides and several similar species were selected andcultured as natural predators to reduce algal bloom caused by cyanobacteria. The targetorganism, D. similoides was confi rmed high-density enrichment in the culture tank within twoweeks after the initial inoculation. Individual growth rate was about 0.5, and population densitywas increased to double every two days in the tank. Algae removal effi ciency of 87% was veryhigh in the reservoir after discharging of the D. similoides and the mean values of chlorophyll-awere decreased from 243 to 31 mg•m-3 during algal bloom period. In conclusions, applicationof the natural predator, “Daphnia” as a top-down biomanipulation in this study showed astrong possibility of algal bloom control in a eutrophic reservoir. This management techniqueis a healthy and effective in algal bloom control.