Effects of enrofloxacin, ciprofloxacin, and trimethoprim on two generations of Daphnia magna

Multigenerational tests on Daphnia magna were performed exposing two subsequent generation of the crustacean to enrofloxacin (EFX), his metabolite ciprofloxacin (CPX) and trimethoprim (TMP). Mortality rate of 100% and 50% was detected in F0 at concentrations of ≥12.5 mg L-1 (EFX) and 50 mg L-1 (TMP), respectively. In F1 with respect to F0, both for growth and reproduction, a worsening trend of the response with EFX, a similar response with CPX and an attenuating trend with TMP was observed. Furthermore, the lowest EC20 for reproduction inhibition (1.27 mg L-1) was calculated for F1 exposed to EFX. However, other experimentations, longer and more complex, are necessary in order to confirm that EFX is more hazardous to daphnids than CPX and TMP. EC50s measured for the three assayed antibacterials were in the 6.49-36.53 mg L-1 range and therefore environmental unrealistic, except in case of exceptional contaminations that may occur in relation to poorly controlled wastewaters from pharmaceutical factories or excessive use of prophylactic treatments in aquaculture.