Abstract-The bivalve Anodonta woodiana is widely distributed throughout Chinese freshwaters and is an important economic pearl mollusk. Recently, A. woodiana as a biomanipulation tool in Chinese lakes due to its strong suppression of phytoplankton, has been attracted increasingly more attention. In order to examine whether A. woodiana can exert grazing pressure on Microcystis and to evaluate the different effects of each algae diet on mussels' potential growth, a comparative study was carried out on the acute physiological responses to variable microalgae diets including toxic microcystin-producing cyanobacteria Microcystis aeruginosa and non-toxic green algae Scenedesmus obliquus. The values of filtration rate, absorption efficiency, oxygen consumption rate and ammonia excretion rate of A. woodiana were measured and finally the scope for growth (SFG) value as a measure of metabolic energy balance for A. woodiana was calculated and compared. The results showed that the mussel A. woodiana has a higher grazing ability on the toxic M. aeruginosa compared with the green algae S. obliquus; furthermore, the effects of different algae diets on SFG of A. woodiana demonstrated that the toxic M. aeruginosa may supply more energy for A. woodiana's potential growth. These results indicated that A. woodiana has strong adaptation ability when they were exposed to toxic Microcystis solution in this study, which implied that there is high application feasibility of A. woodiana as a toxic Microcystis-blooming controller in practice.Index Terms-Anodonta woodiana, microcystis aeruginosa, scenedesmus obliquus, scope for growth (SFG). I. INTRODUCTIONLake Taihu is the third largest freshwater lake in China and situated in the Yangtze delta. Since 1980's, however, the development of industry and agriculture in the lake region, as well as a rapid increase in the population has resulted in pollutants being produced and discharged into rivers and the lake. With the deterioration of inflow water quality, eutrophication and cyanobacterial blooms have occurred. Recently, cyanobacterial blooms have extended its coverage and persisted throughout the summer, which affected the function of the lake as a drinking water supply [1].

The occurrence and distribution of microcystins were investigated in Lake Taihu, the third largest lake in China. An extensive survey, larger and broader in scale than previous studies, was conducted in summer 2010. The highest microcystin concentration was found at southern part of Taihu, which was newly included in this survey. In northern coastal areas, total cellular concentrations of 20 to 44 μg/L were observed. In northern offshore waters, levels were up to 4.8 μg/L. Microcystin occurrence was highly correlated with chemical oxygen demand, turbidity, and chlorophyll-a. Extracellular/total cellular microcystin (E/T) ratios were calculated and compared to other water quality parameters. A higher correlation was found using E/T ratios than original microcystin values. These results show that algal blooms are having a severe impact on Lake Taihu, and further and extensive monitoring and research are required to suppress blooms effectively.

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