Toxicity associated to uptake and depuration of carbamazepine in the clam Scrobicularia plana under a chronic exposure

Carbamazepine (CBZ) is an antiepileptic drug commonly detected in aquatic systems, with toxic effects to inhabiting organisms. Limited information is known on stress response biomarkers associated to bioconcentration and depuration of CBZ in aquatic organisms. Moreover, few studies addressed if the response and recovery of organisms to a contaminant can change when they are collected in a contaminated site. This study intended to understand the bioconcentration and depuration of CBZ combined with its toxicological impact in Scrobicularia plana clams collected from two contrasting areas (MIRA, Mira channel, non-contaminated and LAR, Laranjo bay, anthropogenically impacted) from the Ria de Aveiro (Portugal). The clams were exposed for 14 days to environmentally relevant CBZ concentrations (0.0, 4.0 and 8.0 μg/L), followed by a 14 day depuration period. CBZ concentrations in S. plana tissues were rapidly bioconcentrated during the exposure period. In the depuration period CBZ was eliminated, in some extent. The main toxic effects occurred at the highest concentration (8.0 μg/L) after 14 days of exposure in which the clams from LAR accumulated a higher CBZ concentration (LAR: ~ 10 ng/g FW) than clams from MIRA (MIRA: ~ 7 ng/g FW). LAR clams exhibited higher oxidative damage at this concentration, demonstrated by higher LPO levels over time (increase of ~ 1.4% relative to control) and, in comparison with MIRA clams (LAR: 17.7 nmol/g FW; MIRA: 11.4 nmol/g FW). After the depuration period, LAR clams recovered from the stress induced by CBZ. A decrease in LPO for LAR (decrease of ~ 40% in relation to the end of the exposure period) was accompanied by a decrease in CBZ tissue concentrations (decrease of ~ 61% relative to the end of the exposure period). MIRA clams were not oxidatively injured (low LPO levels remained unchanged after the depuration and CBZ decreased ~ 80% relative to the end of the exposure period).