Freshwater anostracan, Branchinella kugenumaensis, as a potential controlling consumer species on toxic cyanobacteria Microcystis aeruginosa

To evaluate the potential of Branchinella kugenumaensis for cyanobacterial bloom control relative to Daphnia, we conducted several feeding experiments on microcystin-free and microcystin-containing unicellular strains of Microcystis aeruginosa and colonial forms of Microcystis using B. kugenumaensis and Daphnia magna in a laboratory. Branchinella kugenumaensis showed higher filtration rates than those of D. magna in all treatments. In particular, the microcystin-containing unicellular strain supported the highest filtration rates of B. kugenumaensis among treatments. Daphnia magna reduced colonies less than 75 mu m in length, whereas B. kugenumaensis could graze colonies less than 100 mu m. The middle-sized group of B. kugenumaensis had a higher filtration rate than the small and large sized groups in a continuous feeding experiment for 4 days. In survival experiments, survivorships were not different between the two species, whereas ages at the beginning of the experiments affected their survival time. Our results showed that B. kugenumaensis grazed on toxic and colonial cyanobacteria at relatively high rates, indicating that locally abundant grazers like Branchinella may offer a better potential for bloom control than Daphnia.