THE EVALUATION OF SINANODONTA WOODIANA APPLICATION FEASIBILITY AS A MICROCYSTIS-BLOOMING REMOVAL TOOL IN MICROCOSM EXPERIMENTS

Abstract

Sinanodonta woodiana is widely distributed throughout Chinese freshwaters and is an important economic pearl mollusk. In order to evaluate the application feasibility of S. woodiana as a Microcystis-blooming removal tool, a series of microcosm experiments were performed. Firstthe 6-day feeding responses experiment was carried out with naturally blooming pond water and the bivalves in laboratory, which was lasted for 6 days. In this experiment, phytoplankton abundances and community structure were analyzed on 0-day and 6-day for both control and treatment microcosms; also, filtration rate, absorption efficiency, oxygen consumption rate and ammonia excretion rate of S. woodiana were measured on 0-day and 6-day and finally the scope for growth (SFG) value as a measure of metabolic energy balance for S. woodiana was calculated and compared. The results showed that Microcystis spp. of colony and unicell were reduced obviously on the 6-day; meanwhile, after six days' exposure to Microcystis-blooming pond water, the SFG value for S. woodiana increased. Furthermore, in the extended long-term grazing experiment, bivalves were fed with highly concentrated toxic Microcystis-blooming water and non-toxic Chlorella at the constant concentration (Chl.a=424.5 mg/m 3) in two respective tanks for 12 days. No bivalve mortality was registered on both Chlorella group and blooming water group. In addition, SFGs were significantly higher for the blooming water group, compared with them for Chlorella group on 3-day, 6-day and 12-day. These results indicated that toxic Microcystis spp. in natural eutrophic water can be removed greatly by S. woodiana; moreover, the bivalves themselves have strong adaptation ability when they were exposed to toxic natural eutrophic water. Therefore, it can be inferred that there is high application feasibility of S. woodiana as a Microcystis-blooming controller in practice.