Antidepressants in the sea: washed away or taken up? Quantifying Fluoxetine and Venlafaxine in cuttlefish and crabs

Prescriptions of antidepressants are still on the rise worldwide, and their excretion may result in a potential contamination of the aquatic compartments. Indeed, antidepressant residues such as fluoxetine (FLX) and venlafaxine (VEN) are currently detected at low concentrations, from ng.L-1 to μg.L-1. Due to bioaccumulation, however, the toxicity of these micropollutants is not necessarily represented by their concentration in the water body. Furthermore, these compounds conceived to treat depressive or anxiety disorders are worrisome because they can trigger neurobiological changes through targeting the serotonergic system of non-target organisms, such as marine invertebrates. Indeed, juvenile shore crabs and cuttlefish, which are particularly vulnerable to predators, thrive in the intertidal zone and coastal water. To study the effects of antidepressants at environmental concentrations, juvenile cuttlefish and crabs were exposed during 30 days to fluoxetine alone or in mixture with venlafaxine (i.e., 2.5 ng.L-1 and 5 ng.L-1). Behavioural test results showed an effect of the antidepressant on predation and camouflage. Now we investigate if VEN or FLX are bioaccumulated in these juvenile organisms at environmentally realistic concentrations. A former method from Robert et al (2017) was updated to allow detecting and quantifying the two antidepressants at very low concentrations (pg.mg-1). QuESChERS method was used for extraction and chemical analysis was done via LC-MS-MS.