EFFECTS OF TEMPERATURES AND MICROCYSTIS AERUGINOSA TOXICITY ON LIFE-TABLE PARAMETERS OF BRACHIONUS CALYCIFLORUS

To investigate the effects of two strains of Microcystis aeruginosa (microcystin-producing and microcystin-free) at different concentrations on the life table parameters of Brachionus calyciflorus, we conducted a life-table study at 25℃ and investigated the responses of life table parameters of B. calyciflorus to microcystin-producing M. aeruginosa concentrations at five temperature gradients. The results showed that both M. aeruginosa toxicity and concentration significantly mediated the net reproduction rate (R₀; F=31.83, P<0.01; F=30.36, P<0.01) and intrinsic growth rate (r_m; F=34.67, P<0.01; F=18.73, P<0.01) of B. calyciflorus with a significant interactive effect, and that temperature and microcystin-producing M. aeruginosa concentration had significant independent and interactive effects on the net reproduction rate (R₀; F=13.51, P<0.01) and intrinsic growth rate (r_m; F=12.99, P<0.01) of B. calyciflorus. Microcystin-free M. aeruginosa promoted the rotifer population and it could be used as a food source for rotifers at low concentration (1×10⁴ cells/mL), but its food quality was low due to the lack of fatty acids and other nutrients. High concentration of Microcystin-free M. aeruginosa (1×10⁵ cells/mL and 5×10⁵ cells/mL) obviously inhibited the growth of rotifers because rotifers prefer microcystin-free M. aeruginosa. The net reproductive rate and intrinsic growth rate of B. calyciflorus increased significantly by increasing concentration of microcystin-producing M. aeruginosa. Moreover, high temperature (30℃ and 35℃) accelerated their reproduction and growth rate, shorten the generation time, and promoted inhibitory effect of microcystin-free M. aeruginosa on rotifers.