Effects of atrazine and carbaryl on growth and reproduction of the rotifer Brachionus calyciflorus Pallas

Abstract

The functioning of freshwater ecosystems can be altered if rotifers are stressed by atrazine and carbaryl. To detect reproductive responses, rotifer (Brachionus calyciflorus) populations were exposed to atrazine and carbaryl at six concentrations ranging from 0 to 5.12 mg L−1 and the 2-d population growth rate, 3-d mictic rate (MR), 7-d resting egg production (RE), and 3-d resting egg hatching rate (HR) were measured. Data showed that the no effect concentration (NOEC) and lowest effect concentration (LOEC) of atrazine and carbaryl were highest for growth rate. In sexual reproduction, the NOEC and LOEC of atrazine for MR were 0.32 and 1.28 mg L−1. However, carbaryl did not show similar results because 0.06 mg L−1 carbaryl increased the MR compared with the control. The NOEC and LOEC of atrazine for RE and HR were the same (0.08 and 0.32 mg L−1) and the NOEC and LOEC of carbaryl for RE were slightly lower. HR was the most sensitive of all indices with NOEC and LOEC of atrazine ranging from 0.02 to 0.32 mg L−1 nominal concentration.