Ecotoxicological assessment of the effects of fluoxetine on Daphnia magna based on acute toxicity, multigenerational reproduction effects, and attraction-repellence responses

Fluoxetine, a common pharmaceutical used as an antidepressant, is already considered potentially hazardous to biota due to its increasing use and detection in European, North American, and Asian rivers. We studied the effects of fluoxetine on Daphnia magna, as we hypothesized that fluoxetine might have harmful effects, short and long-term, at different levels: survival, behaviour, and reproduction (offspring production). We applied two different approaches: (i) a scenario at environmentally relevant concentrations (0.1-1.0 μg/L) and (ii) a scenario simulating a future worsening of contamination (1-800 μg/L) until the reach of lethal concentrations. In the former, we examined whether there are multigenerational effects on reproduction and on the avoidance/colonisation behaviour in previously exposed populations. In the latter, three responses were assessed: survival, avoidance behaviour and reproduction. We did not detect differences in the reproduction output of D. magna among the treatments over the three generations examined. Irrespective of the multigenerational treatment, D. magna colonised the environments with fluoxetine in a similar way. In the second scenario, we determined the lethal concentration for 50% of the population (96 h-LC50 = 365 μg/L), which, in spite of the toxic effect, was attractive to organisms during the avoidance tests (24 h); in fact, D. magna were attracted (no repellence) even to the highest concentrations of fluoxetine tested (800 μg/L). Lastly, in a 21-day chronic toxicity test the reproduction output of D. magna increased with higher concentrations of fluoxetine. This effect might be related to the fact that the organisms in the contaminated treatment began their first reproduction earlier, when compared to that in the control treatments. In conclusion, this study discusses an identified hazard for aquatic biota due to the fluoxetine attraction effect and a predictive assessment of the consequences expected if its indiscriminate use increases.H. Stremmel thanks the PROMOS scholarship of the DAAD and the RUB. C.V.M. Araújo is grateful for the grant (Ramón y Cajal contract: RYC-2017-22324) funded by MCIN/AEI/10.13039/501100011033 and “ESF Investing in your future”. This research was funded by MCIN/AEI/10.13039/501100011033 (BrEStress project: PID 2019-105868RA-I00).Peer reviewe