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

¹ Provincial Key Laboratories of Conservation and Utilization for Important Biological Resource in Anhui and Biotic Environment and Ecological Safety, College of Life Sciences, Anhui Normal University, Wuhu, Anhui 241000, China
² College of Biological and Pharmaceutical Engineering, WestAnhui University, Lu'an, Anhui 237012, China

^* Corresponding author: ylxi1965@yahoo.com.cn

Received: 2 September 2012
Accepted: 4 November 2012

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.