Toxicity of five antidepressant drugs on embryo-larval development and metamorphosis sucess in the Pacific oyster, <i>Crassostrea gigas</i>

Unlike conventional pollutants, pharmaceutical residues are continuously discharged at low levels (low to mid ng l−1 concentrations), which results in the chronic contamination of non-target organisms, but little is known about the effects of these residues. The purpose of this study was to provide the first assessment of the ecotoxicity of five antidepressants (selective serotonin reuptake inhibitors [SSRIs] fluoxetine and sertraline, tricyclic antidepressants [TCAs] clomipramine and amitriptyline, and serotonin norepinephrine reuptake inhibitor [SNRI] duloxetine) at a wide range of concentrations from 0.1 to 100,000 $μ$g l−1 on two early life stages in the Pacific oyster. The toxicity was quantified in D-shaped larvae after 36 h of exposure, and in 21-day-old pediveliger larvae after 24 h of exposure using the percentage of normal larval development and the metamorphosis rate as endpoints, respectively. The embryotoxicity assays reported that the EC50 values were within the same range of concentrations (67 to 192 $μ$g l−1) for all of the tested molecules. The metamorphosis tests revealed that the antidepressants can be ranked along an increasing severity gradient: clomipramine < amitriptyline < duloxetine \~{} fluoxetine. Sertraline appeared to be the less toxic molecule on this endpoint; however, a different concentration range was used. The embryotoxicity test was more sensitive than the metamorphosis bioassay for three of the five molecules tested, but the latter test showed more practical benefits. Overall, the obtained toxicity values were at least 10,000-fold higher than the reported environmental concentrations.