Chronic Effects of Bromate on Sexual Reproduction of Freshwater Rotifer Brachionus calyciflorus.

The effects of potassium bromate (KBrO3), sodium bromate (NaBrO3), and potassium bromide (KBr) on the sexual reproduction of the rotifer Brachionus calyciflorus were studied by 2-d population growth, 4-d sexual reproduction, and 7-d resting egg production tests. The results showed that low concentrations of bromate promote 2-d and 4-d rotifer population growth, while high concentrations limit it. Bromate stress significantly affected parameters of rotifer sexual reproduction, including the ratio of mictic to amictic females, the mictic rate of rotifers, and the fertilization rate of mictic females. KBrO3 at 0.001, 0.01, 1, and 10 mg/L, NaBrO3 at 1 and 10 mg/L, and KBr at 100 and 200 mg/L significantly increased resting egg production, while KBrO3 at 100 and 200 mg/L, and NaBrO3 at 200 mg/L significantly decreased it. Resting egg production appears to provide a sensitive endpoint in evaluating the effect of bromate on rotifer sexual reproduction.