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Ocean acidification and increasing discharges of pharmaceutical contaminants into aquatic systems are among key and/or emerging drivers of environmental change affecting marine ecosystems. A growing body of evidence demonstrates that ocean acidification can have direct and indirect impacts on marine organisms although combined effects with other stressors, namely with pharmaceuticals, have received very little attention to date. The present study aimed to evaluate the impacts of the pharmaceutical drug Carbamazepine and pH 7.1, acting alone and in combination, on the clamScrobicularia plana. For this, a long-termexposure (28 days)was conducted and a set of oxidative stress markers was investigated. The results obtained showed that S. plana was able to develop mechanisms to prevent oxidative damage when under low pH for a long period, presenting higher survival when exposed to this stressor compared to CBZ or the combination of CBZ with pH 7.1. Furthermore, the toxicity of CBZ on S. plana was synergistically increased under ocean acidification conditions (CBZ + pH 7.1): specimens survival was reduced and oxidative stress was enhanced when compared to single exposures. These findings add to the growing body of evidence that ocean acidification will act to increase the toxicity of CBZ to marine organisms,which has clear implications for coastal benthic ecosystems suffering chronic pollution from pharmaceutical drugs.
Caffeine is known to be one of the most consumed psychoactive drugs. For this reason, caffeine is continuously released into the environment with potential impacts on inhabiting organisms. The current study evaluated the biochemical alterations induced in the clam species Ruditapes philippinarum after exposure for 28 days to caffeine (0.5, 3.0 and 18.0 mg/L). The results obtained showed that, with the increasing caffeine concentrations, an increase in clams defense mechanisms (such as antioxidant and biotransformation enzymes activity) was induced which was accompanied by an increase in protein content. Nevertheless, although an increase on defense mechanisms was observed, clams were not able to prevent cells from lipid peroxidation that increased with the increase of caffeine concentration. Furthermore, with the increase of exposure concentrations, clams increased their metabolic activity (measured by electron transport activity), reducing their energy reserves (glycogen content), to fight against oxidative stress. Overall, the present study demonstrated that caffeine may impact bivalves, even at environmentally relevant concentrations, inducing oxidative stress in organisms. The present study is an important contribution to address knowledge gaps regarding the impacts of long-term exposures to pharmaceuticals since most of the studies assessed the effects after acute exposures, most of them up to 96 h.
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, arithropogenically 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 mu g/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 mu g/L) after 14 days of exposure in which the clams from LAR accumulated ahigher CBZ concentration (LAR: similar to 10 ng/g FW) than clams from MIRA (MIRA: similar to 7 ng/g FW). LAR clams exhibited higher oxidative damage at this concentration, demonstrated by higher LPO levels over time (increase of similar to 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 similar to 40% in relation to the end of the exposure period) was accompanied by a decrease in CBZ tissue concentrations (decrease of similar to 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 similar to 80% relative to the end of the exposure period).
In the present study, the bivalve Scrobicularia plana, collected from two contrasting areas (pristine location and mercury contaminated area), was selected to assess the biochemical alterations imposed by pH decrease, carbamazepine (an antiepileptic) and the combined effect of both stressors. The effects on oxidative stress related biomarkers after 96 h exposure revealed that pH decrease and carbamazepine induced alterations on clams, with greater impacts on individuals from the contaminated area which presented higher mortality, higher lipid peroxidation and higher glutathione S-transferase activity. These results emphasize the risk of extrapolating results from one area to another, since the same species inhabiting different areas may be affected differently when exposed to the same stressors. Furthermore, the results obtained showed that, when combined, the impact of pH decrease and carbamazepine was lower than each stressor acting alone, which could be related to the defence mechanism of valves closure when bivalves are under higher stressful conditions.