[Effects of Cd2+ concentration on life table demography of Brachionus calyciflorus under different Scenedesmus obliquus density].

In order to understand the chronic toxicity of a pollutant to an organism in an aquatic environment with different food density, and screen out sensitive endpoints for monitoring Cd2+ pollution with rotifers as test animals, this paper studied the effects of different concentration (2.5, 5.0, 10.0, 20.0 and 40.0 microg x L(-1)) Cd2+ on the life table demography of Bracionus calyciflorus at the Scenedesmus obliquus density being 1.0 x 10(6), 3.0 x 10(6), and 5.0 x 10(6) cells x ml(-1). The results showed that at 25 +/- 1 degrees C, the 24 h LC50 of Cd2+ to B. calyciflorus was 37.7 microg x L(-1). Compared with the controls at the same food density, when the S. obliquus density was 1.0 x 10(6) cells x ml(-1), 20.0 and 40.0 microg x L(-1) of Cd2+ prolonged the generation time of B. calyciflorus significantly, and 5.0 microg x L(-1) of Cd2+ increased the percentage of B. calyciflorus mictic offspring. When the S. obliquus density was 3.0 x 10(6) cells x ml(-1), the Cd2+ at all test concentrations except 5.0 microg x L(-1) decreased the percentage of mictic offspring; when the S. obliquus density was 5.0 x 10(6) cells x ml(-1), all test concentration Cd2+ had no effects on the life table demography (P > 0.05). S. obliquus density had significant effects on the generation time, life expectancy at birth, net reproduction rate, percentage of mictic offspring of B. calyciflorus (P < 0.05), Cd2+ concentration had significant effects on the generation time and the percentage of mictic offspring (P < 0.05), and the interaction of S. obliquus density and Cd2+ concentration had significant effects on the percentage of mictic offspring (P < 0.01). Among all the studied parameters, the generation time and the percentage of mictic offspring were more sensitive to Cd2+ pollution under the algal densities of 1.0 x 10(6) and 3.0 x 10(6) cells x ml(-1), with the latter being the most sensitive.