Does the antidepressant sertraline show chronic effects on aquatic invertebrates at environmentally relevant concentrations? A case study with the keystone amphipod, Gammarus locusta

Abstract

The increasing use of Sertraline (SER) as antidepressant and its consequent presence in the aquatic environment is raising concern about the chronic effects of this pharmaceutical to aquatic organisms. As the current concentrations of SER in surface waters are typically in the low ng/L range, acute toxicity is unlikely to occur. However, prolonged exposure to low concentrations of SER may lead to sub-lethal effects in aquatic organisms, including alterations in important physiological functions like growth, reproduction, behaviour, and also in key biochemical processes, such as those associated with neurotransmission and redox balance. To test this hypothesis, we selected the amphipod Gammarus locusta, a keystone species used in ecotoxicological hazard assessment. In the present study, juveniles' G. locusta from a permanent laboratory culture were chronically exposed to low concentrations of SER (8-1000 ng/L) in a bioassay that lasted for 48 days, allowing for a life-cycle study including effects on reproduction. At the lowest SER concentrations with environmental relevance (8, 40 and 200 ng/L) we detected no significant changes in key ecological endpoints such as survival, growth, reproduction and movement behaviour, or in any of the biochemical markers analysed. However, at 1000 ng/L SER (a concentration one order of magnitude higher than the levels reported in aquatic environments) females showed a significant increase in movement versus control, whereas no activity changes were observed in males. Overall, these findings indicate that G. locusta females are potentially more susceptible to the chronic effects of SER. Moreover, the current environmental SER concentrations are unlikely to affect amphipod's ecological endpoints because only SER concentrations higher than the levels reported in aquatic environments produced effects on the behaviour of G. locusta females. However, the increasing consumption of SER, highlights the importance of monitoring its chronic risk to the aquatic wildlife.

Keywords: Antidepressant; Behaviour; Crustaceans; Ecological relevant concentrations; Selective serotonin reuptake inhibitors (SSRIs); Sub-lethal effects.