Application of an Algal Bloom Control Technique using Large Zooplankton Predators in An Eutrophic Agricultural Reservoir: A Preliminary Study

Massive nuisance algal blooms are a primary concern for the management of eutrophic reservoirs. The effects of biomanipulation using trophic cascade effects in the aquatic food chain vary with the conditions of applied water bodies and are controversial. However, this mode of biomanipulation has long been considered an ecosystem-friendly approach for the management of algal blooms. In the present study, herbivorous Daphnia similoides were artificially proliferated using a large culture system and were used to control algal blooms in a eutrophic agricultural reservoir. Introduced predators proliferated rapidly in the culture tanks, and high densities were subsequently sustained. Predators were then released into the reservoir at 1-week intervals during early summer and autumn, and 84.4% algal removal efficiency was observed and mean values of chlorophyll a concentration decreased from 219 to 34.2mgm(-3) during the algal bloom period in autumn. However, no apparent effects were observed during early summer when fish predation and water temperatures were high. These data suggest that continuous release of predators from our culture facility efficiently facilitates early expansion of zooplankton populations and maintenance of their populations in the reservoir. The effects of introduced zooplankton may be maximized with concurrent management of resident zooplanktivorous fish. Copyright (c) 2016 John Wiley & Sons, Ltd.