Responses in population growth and reproduction of the freshwater rotifer Brachionus calyciflorus to microcystin-LR at different temperatures

Abstract

Microcystis blooms occur worldwide in eutrophic lakes. Microcystins (MCs) including microcystin-LR (MC-LR) released by Microcystis have adverse effects on aquatic organisms such as rotifers. To detect population growth and reproductive responses, the rotifer Brachionus calyciflorus was exposed to MC-LR at eight concentrations ranging from 0 to 200 μg.L-1 under different temperature (20, 25 and 30 C), and population growth rate (r), ovigerous females/non-ovigerous females (OF/NOF) ratio, mictic females/amictic females (MF/AF) ratio, mictic rate (MR), and 7-d resting egg (7-d RE) production were investigated. The results showed that higher temperatures stimulate the population growth of B. calyciflorus. B. calyciflorus showed high tolerance to MC-LR at concentrations lower than 200 μg.L-1 under different temperatures. Compared to the control, MC-LR at all concentrations increased the r (P<0.05), but decreased the OF/NOF and the MR of the rotifers at 30 C (P<0.01). A clear dose-response relationship existed between the r, the OF/NOF, and the MR of B. calyciflorus and MC-LR concentration at 30 C, respectively. These sensitive parameters could be used to monitor the ecological effects of low concentrations of MC-LR in natural water bodies at the high temperature. © 2012 EDP Sciences.