The concentrations of abamectin were measured in
water samples containing 0.1, 0.3, 0.5, 0.7, 0.9 and 1.1 lg/l
both initially and at the end of the experiment (Fig. 1).
With the exception of the first sample containing 0.1 lg/
l of abamectin, the concentrations of abamectin decreased
by about 40% in a few hours and then remained constant
for 48 h (Fig. 1). The calculated EC values for daphnids in
Table 2 are based on the measured exposure concentrations.
In our study, the EC
values based on the mobility
of daphnids (Table 2) were similar to those reported by
Wislocki et al. (1989) despite the fact that his toxicity
endpoint was mortality for which the 48 h LC
50
of
abamectin was reported to be 0.34 lg/l.
50