Abstract: The purpose of this microcosm experiment was to determine whether the freshwater gastropod Bellamya aeruginosa affected zooplankton community in the water body experiencing a cyanobacterial bloom. Three treatments of different snail densities (low, medium, and high) and a control (no snails) were set up. The abundance of zooplankton was determined on days 0, 3, 7, 11, 15, 23, 31, 46, and 61. A total of 52 species from 33 genera were identified, which consisted of 15 species of Protozoa, 28 species of Rotifera, 6 species of Cladoera and 3 species of Copepoda. According to the abundance and occurrence, nauplius, Asplanchra, Polyarthra, and Brachionus were considered as the dominant taxa. Principal response curves showed that zooplankton community in all treatments was consistently different from that in the control. The highest decrease in abundance was found for Keratella cochlearis, K. valga and Difflugia sp. The abundances of these species decreased from 481, 545.3 and 359.7 ind·L^-1 to 0.1, 0.1 and 9.2 ind·L^-1 in the high density treatment, respectively. The populations of testate amoebae, tintinnid ciliate and rotifer were significantly negatively affected by the snails. Additionally, the presence of snails also caused the increase in the biomass of Cyclops sp. The abundance of Cyclops sp. increased from 46.4 ind·L^-1 to 420.1 ind·L^-1 in the high density treatment. These results indicate that the presence of snails resulted in a significant change of zooplankton community in cyanobacterial bloom. The dynamic of zooplankton community was more subject to the indirect impact than direct filterfeeding of snails.

Key words: rice, low temperature, panicle initiation, spikelets, floral organ, grain filling.