Joint effects of salinity and the antidepressant sertraline on the estuarine decapod Carcinus maenas

A Mini-review of the Toxicity of Pollutants to Fish Under Different Salinities

In recent years, with the development of the global economy, water pollution has increased. Pollutants migrate, accumulate, and diffuse in aquatic environments. Most of the pollutants eventually enter aquatic organisms. The accumulation of pollutants affects the development and reproduction of organisms, and many pollutants have teratogenic, carcinogenic, and/or mutagenic effects. Aquatic organisms in estuaries and coastal areas are under pressure due to both salinity and pollutants. Among them, salinity, as an environmental factor, may affect the behavior of pollutants in the aquatic environment, causing changes in their toxic effects on fishes. Salinity also directly affects the growth and development of fishes. Therefore, this paper focuses on metals and organic pollutants and discusses the toxic effects of pollutants on fish under different salinities. This research is of great significance to environmental protection and ecological risk assessment of aquatic environments.

The influence of salinity on the toxicity of remediated seawater

Mercury (Hg) is one of the most hazardous pollutants, due to its toxicity, biological magnification and worldwide persistence in aquatic systems. Thus, new efficient nanotechnologies (e.g. graphene oxide functionalized with polyethyleneimine (GO-PEI)) have been developed to remove this metal from the water. Aquatic environments, in particular transitional systems, are also subjected to disturbances resulting from climate change, such as salinity shifts. Salinity is one of the most relevant factors that influences the distribution and survival of aquatic species such as mussels. To our knowledge, no studies assessed the ecotoxicological impairments induced in marine organisms exposed to remediate seawater (RSW) under different salinity levels. For this, the focus of the present study was to evaluate the effects of seawater previously contaminated with Hg and remediated with GO-PEI, using the species Mytilus galloprovincialis, maintained at three different salinities (30, 20 and 40). The results obtained demonstrated similar histopathological and metabolic alterations, oxidative stress and neurotoxicity in mussels under RSW treatment at stressful salinity conditions (20 and 40) in comparison to control salinity (30). On the other hand, the present findings revealed toxicological effects including cellular damage and histopathological impairments in mussels exposed to Hg contaminated seawater in comparison to non-contaminated ones, at each salinity level. Overall, these results confirm the high efficiency of GO-PEI to sorb Hg from water with no noticeable toxic effects even under different salinities, leading to consider it a promising eco-friendly approach to remediate contaminated water.

Differential Molecular Responses of Zebrafish Larvae to Fluoxetine and Norfluoxetine

The occurrence of psychopharmaceuticals in aquatic ecosystems is a growing problem. Fluoxetine (FL) and its metabolite norfluoxetine (NF) are selective serotonin reuptake inhibitors. Although they may be potentially harmful to non-target species, available knowledge on the effects of NF is sparse, relative to FL. This study aimed at contributing to the body of knowledge about the modes-of-action (MoA) of these compounds and their underlying mechanisms eliciting hazardous effects during the early development of the teleost model zebrafish (Danio rerio). One hour post-fertilisation (hpf), embryos were exposed up to 80 hpf to these compounds at levels found in surface waters and higher (FL, 0.0015 and 0.05 µM; NF, 0.00006 and 0.0014 µM). Developmental anomalies were observed at 8, 32 and 80 hpf. Larvae were collected at 80 hpf to assess the expression of 34 genes related to FL and NF MoA and metabolism, using qPCR (quantitative reverse transcription PCR). Results showed that both compounds elicited an increased frequency of embryos exhibiting abnormal pigmentation, relative to controls. Gene expression alterations were more pronounced in FL- than in NF-exposed larvae. Cluster Analysis revealed two groups of genes discriminating between the drugs. for their marked opposing responses. Globally, downregulation of gene expression was typical of FL, whilst upregulation or no alteration was found for NF. These clusters identified were linked to the adrenergic pathway and to the retinoid and peroxisome proliferator-activated nuclear receptors. Overall, our data contradict the prevailing notion that NF is more toxic than FL and unveiled the expression levels of genes drd2b, 5-ht2c and abcc2 as possible markers of exposure to FL.

The influence of salinity on sodium lauryl sulfate toxicity in Mytilus galloprovincialis

The influence of salinity on the effects of sodium lauryl sulfate (SLS) was evaluated using the Mediterranean mussel Mytilus galloprovincialis, exposed for 28 days to SLS (control-0.0 and 4.0 mg/L) under three salinity levels (Control-30, 25 and 35). The effects were monitored using biomarkers related to metabolism and energy reserves, defence mechanisms (antioxidant and biotransformation enzymes) and cellular damage. The results revealed that non-contaminated mussels tended to maintain their metabolic capacity regardless of salinity, without activation of antioxidant defence strategies. On the contrary, although contaminated mussels presented decreased metabolic capacity at salinities 25 and 35, they were able to activate their antioxidant mechanisms, preventing cellular damage. Overall, the present findings indicate that SLS, especially under stressful salinity levels, might potentially jeopardize population survival and reproduction success since reduced metabolism and alterations on mussels' antioxidant mechanisms will impair their biochemical and, consequently, physiological performance.

Norfluoxetine and venlafaxine in zebrafish larvae: Single and combined toxicity of two pharmaceutical products relevant for risk assessment

Antidepressant metabolites are found in natural and waste waters. However, investigation of their toxic effects on aquatic animals, single or in mixture with other occurring psychoactive drugs, has been neglected. Here, effects of 80hpf exposure to norfluoxetine (0.64-400 ng/L), venlafaxine (16-10000 ng/L) or their combination (3.2 ng/L +2000 ng/L, respectively) were investigated in embryos and zebrafish larvae. Mortality, embryonic malformations, sensorymotor reflexes and the expression of 34 genes involved in the toxicants mode-of-action (MoA) and metabolism were evaluated (i.e. monoamine receptors and transporters, nuclear receptors, and detoxification transporters and enzymes). Compared to controls, norfluoxetine treatments only caused depigmentation of embryos and larvae. Venlafaxine-exposed larvae exhibited depigmentation and spinal deformities, impaired sensorymotor reflexes, alterations in the expression of genes belonging to the serotonergic, noradrenergic and dopaminergic pathways, as well as nuclear receptors related to lipid and drug metabolism. The mixture elicited distinct interaction effects, depending on the level of biological organisation analysed and the neurotransmitter pathways affected; synergism (lethality), no interaction (sensorymotor reflexes), antagonism and inverse agonism (gene expression). The results call for investigation of the toxicity of pharmaceutical metabolites single and in mixture, as well as their risk assessment in approaches accounting for possible interactions with other endocrine-disrupting compounds.

Current issues confounding the rapid toxicological assessment of oil spills

Oil spills of varying magnitude occur every year, each presenting a unique challenge to the local ecosystem. The complex, changeable nature of oil makes standardised risk assessment difficult. Our review of the state of science regarding oil's unique complexity; biological impact of oil spills and use of rapid assessment tools, including commercial toxicity kits and bioassays, allows us to explore the current issues preventing effective, rapid risk assessment of oils. We found that despite the advantages to monitoring programmes of using well validated standardised tests, which investigate impacts across trophic levels at environmentally relevant concentrations, only a small percentage of the available tests are specialised for use within the marine environment, or validated for the assessment of crude oil toxicity. We discuss the use of rapid tests at low trophic levels in addition to relevant sublethal toxicity assays to allow the characterisation of oil, dispersant and oil and dispersant mixture toxicity. We identify novel, passive dosing techniques as a practical and reproducible means of improving the accuracy and maintenance of nominal concentrations. Future work should explore the possibility of linking this tiered testing system with ecosystem models to allow the prediction and risk assessment of the entire ecosystem.

Two antidepressants fluoxetine and sertraline cause growth retardation and oxidative stress in the marine rotifer Brachionus koreanus

To understand effects of two widely used antidepressant on the antioxidant defense mechanism in the marine rotifer Brachionus koreanus, we assessed acute toxicity and measured population growth, reactive oxygen species (ROS) levels, glutathione (GSH) levels, and antioxidant enzymatic activities (GST, GR, and SOD) in response to fluoxetine hydrochloride (FLX) and sertraline hydrochloride (SER). The no observed effect concentration-24 h of fluoxetine and sertraline were 1000 μg/L and 450 μg/L, respectively, whereas the median lethal concentration (LC50)-24 h of fluoxetine and sertraline were 1560 μg/L and 507 μg/L, respectively. Both fluoxetine and sertraline caused significant reduction (P < 0.05) in the population growth rate indicating that both antidepressants have a potential adverse effect on life cycle parameters of B. koreanus. The intracellular ROS level and GSH level were significantly modulated (P < 0.05) in response to fluoxetine and sertraline. In addition, antioxidant enzymatic activities have shown significant modulation (P < 0.05) in response to FLX and SER in B. koreanus. Furthermore, transcriptional profiles of antioxidant genes (GSTs, SODs, and GR) have shown modulation in response to FLX compared to SER-exposed B. koreanus. Our results indicate that fluoxetine and sertraline induce oxidative stress, leading to reduction in the population density and modulation of antioxidant defense mechanism in the marine rotifer B. koreanus.

Interactive effects of biotic and abiotic environmental stressors on carbamazepine toxicity in the non-biting midge Chironomus riparius

The toxicity of contaminants in freshwater ecosystems can increase in combination with environmental stress, leading to a potential underestimation of risk in conventional assessments. The number of multiple-stress experiments in ecotoxicology is growing constantly, but pharmaceuticals have mostly been disregarded. As an omnipresent pharmaceutical in the water cycle, the antiepileptic drug carbamazepine (CBZ) was chosen as test substance for our 28-day binary stress experiments with the non-biting midge Chironomus riparius. Elevated population densities, food limitation, temperature, and a reduction of organic matter (OM) were chosen as relevant environmental stressors. In five stress intensities, they were combined with the 10% lethal concentration (LC₁₀) of CBZ to investigate the joint effect of stress and CBZ exposure. We were able to demonstrate that the toxicity of CBZ increased with higher larval densities and reduced OM. Mortality of the midges exposed to CBZ increased by a factor of 1.69 with 100 larvae per vessel and by a factor of 2.87 at 0.25% OM compared to the conventional test protocol, while the stressors alone did not reduce survival. Conventional low-stress laboratory tests as conducted for the risk assessment of chemicals would have underestimated the toxicity of CBZ. Even though it is necessary that more than binary stressor combinations are included in future experiments, the present results extend our knowledge about the toxicity of pharmaceuticals, such as CBZ, in stressful environments and emphasize the importance of including pharmaceuticals in multiple stress experiments.

Living in a multi-stressors environment: An integrated biomarker approach to assess the ecotoxicological response of meagre (Argyrosomus regius) to venlafaxine, warming and acidification

Pharmaceuticals, such as the antidepressant venlafaxine (VFX), have been frequently detected in coastal waters and marine biota, and there is a growing body of evidence that these pollutants can be toxic to non-target marine biota, even at low concentrations. Alongside, climate change effects (e.g. warming and acidification) can also affect marine species' physiological fitness and, consequently, compromising their ability to cope with the presence of pollutants. Yet, information regarding interactive effects between pollutants and climate change-related stressors is still scarce. Within this context, the present study aims to assess the differential ecotoxicological responses (antioxidant activity, heat shock response, protein degradation, endocrine disruption and neurotoxicity) of juvenile fish (Argyrosomus regius) tissues (muscle, gills, liver and brain) exposed to VFX (via water or feed), as well as to the interactive effects of warming (ΔT °C = +5 °C) and acidification (ΔpCO₂ ~ +1000 µatm, equivalent to ΔpH = -0.4 units), using an integrated multi-biomarker response (IBR) approach. Overall, results showed that VFX toxicity was strongly influenced by the uptake pathway, as well as by warming and acidification. More significant changes (e.g. increases surpassing 100% in lipid peroxidation, LPO, heat shock response protein content, HSP70/HSC70, and total ubiquitin content, Ub,) and higher IBR index values were observed when VFX exposure occurred via water (i.e. average IBR = 19, against 17 in VFX-feed treatment). The co-exposure to climate change-related stressors either enhanced (e.g. glutathione S-transferases activity (GST) in fish muscle was further increased by warming) or attenuated the changes elicited by VFX (e.g. vitellogenin, VTG, liver content increased with VFX feed exposure acting alone, but not when co-exposed with acidification). Yet, increased stress severity was observed when the three stressors acted simultaneously, particularly in fish exposed to VFX via water (i.e. average IBR = 21). Hence, the distinct fish tissues responses elicited by the different scenarios emphasized the relevance of performing multi-stressors ecotoxicological studies, as such approach enables a better estimation of the environmental hazards posed by pollutants in a changing ocean and, consequently, the development of strategies to mitigate them.

Effects of the antidepressant, mianserin, on early development of fish embryos at low environmentally relevant concentrations

Pharmaceuticals have been considered as emerging organic contaminants in the environment that might pose huge risk to the non-target aquatic organisms. Mianserin, a tetracyclic antidepressant, is present at low detectable concentrations in the aquatic environment; however, limited attention has been devoted to its potential adverse effects on the aquatic animals. In the present study, we first performed an acute toxicity test for mianserin exposure using zebrafish (Danio rerio) embryos during 4-124h post fertilization (hpf). Time-dependent lethal concentrations of mianserin exposure on the zebrafish embryos were firstly determined at mg/L levels. Then, a series of sublethal concentrations of 0.01, 0.1, 1, 10, 100, and 1000μg/L of mianserin were prepared for the short-term exposure of zebrafish embryos for 120h. The results showed that mianserin exposure reduced the body length of zebrafish larvae, in addition to altering multiple physiological and biochemical parameters in the exposed embryos/larvae. A dose-dependent inhibition of the total antioxidant capacity and total cholinesterase activity was revealed in the exposed fish larvae upon increasing the concentrations of mianserin exposure. A U-shaped concentration-dependent response curve was observed for the adrenocorticotropic hormone; however, an inversed U-shaped response curve was obtained for the monoamine oxidase level in response to mianserin exposure. Activities of the total adenosine triphosphatase (T-ATPase), Na⁺/K⁺-ATPase, and Ca²⁺/Mg²⁺-ATPase were significantly increased in the fish larvae exposed to relatively high doses of mianserin; interestingly however, low dose of mianserin at 10ng/L inhibited their Na⁺/K⁺-ATPase and T-ATPase activities. Additionally, the coordinated regulation of cyclic adenosine monophosphate and protein kinase A was observed in the mianserin-exposed fish larvae, implying a reserved signaling pathway involved in the fish response to the antidepressant. Therefore, our study demonstrated that mianserin exposure significantly affected the early development of fish embryos at environmentally relevant concentrations, and suggested that the risk of pharmaceutical contamination of the aquatic environment, even at low doses, should receive more attention.

Toxicokinetics, disposition and metabolism of fluoxetine in crabs

The disposition and metabolism of fluoxetine in the European shore crab and the Dungeness crab were assessed. Crabs received intracardiac doses of either 0.13 μg/kg or 0.5 mg/kg fluoxetine, respectively. In addition, fluoxetine was administered to Metacarcinus cancer by oral gavage at 7.8 mg/kg. The distribution of fluoxetine was quantified in haemolymph and digestive gland for both crabs, as well as brain, muscle, and testis of Carcinus maenas, over 12 days. The metabolite norfluoxetine, was also measured in C. maenas. Fluoxetine was mainly found in lipid rich tissues. Distribution coefficients increased for digestive gland until three days after fluoxetine administration and then decreased until the end of the observations. The highest distribution coefficients were obtained for brain. Norfluoxetine displayed continuously high levels in digestive gland and brain. The strong decrease in fluoxetine and the concomitant increase in norfluoxetine demonstrates that decapod crustaceans metabolise fluoxetine into the more biologically active norfluoxetine. Fluoxetine levels in the haemolymph of M. cancer declined within 20 h, but showed a second peak 25 h later, suggesting remobilisation from tissues sequestering the compound. The steady state volume distribution and the total body clearance of fluoxetine were high, consistent with high diffusion of fluoxetine into the peripheral tissues and biotransformation as an important elimination pathway. Oral administration of fluoxetine prolonged its half-life in M. cancer, but bioavailability was low. These results confirm the high distribution into nervous tissue, extensive biotransformation into the highly active norfluoxetine and a half-life similar to that observed in vertebrates.

Environmental behavior and eco-toxicity of xylene in aquatic environments: A review

With the demand for chemicals and fuels increasing continuously, the occurrence of accidental leakage poses great risks to the aquatic environment. Xylene, a hazardous and noxious substance, has been major concerns with regard to heterogeneity and eco-toxicity towards aquatic organisms. This review focused on the ecotoxicological hazards of m-, o-, and p-xylene, as well as mixed xylene, on aquatic organisms. The mechanism of action of xylenes was also demonstrated in details. The purpose of this review was to further understand transfer and diffusion of toxicity on marine and freshwater organisms of xylene in the aquatic environment. Another aim was to screen sensitive biomarkers which were suitable for ecotoxicological assessment and monitoring in an aquatic system.

Toxicity of seven priority hazardous and noxious substances (HNSs) to marine organisms: Current status, knowledge gaps and recommendations for future research

Shipping industry and seaborne trade have rapidly increased over the last fifty years, mainly due to the continuous increasing demand for chemicals and fuels. Consequently, despite current regulations, the occurrence of accidental spills poses an important risk. Hazardous and noxious substances (HNSs) have been raising major concern among environmental managers and scientific community for their heterogeneity, hazardous potential towards aquatic organisms and associated social-economic impacts. A literature review on ecotoxicological hazards to aquatic organisms was conducted for seven HNSs: acrylonitrile, n-butyl acrylate, cyclohexylbenzene, hexane, isononanol, trichloroethylene and xylene. Information on the mechanisms of action of the selected HNS was also reviewed. The main purpose was to identify: i) knowledge gaps in need of being addressed in future research; and ii) a set of possible biomarkers suitable for ecotoxicological assessment and monitoring in both estuarine and marine systems. Main gaps found concern the scarcity of information available on ecotoxicological effects of HNS towards marine species and their poorly understood mode of action in wildlife. Differences were found between the sensitivity of freshwater and seawater organisms, so endpoints produced in the former may not be straightforwardly employed in evaluations for the marine environment. The relationship between sub-individual effects and higher level detrimental alterations (e.g. behavioural, morphological, reproductive effects and mortality) are not fully understood. In this context, a set of biomarkers associated to neurotoxicity, detoxification and anti-oxidant defences is suggested as potential indicators of toxic exposure/effects of HNS in marine organisms. Overall, to support the development of contingency plans and the establishment of environmental safety thresholds, it will be necessary to undertake targeted research on HNS ecotoxicity in the marine environment. Research should address these issues under more realistic exposure scenarios reflecting the prevailing spatial and temporal variability in ecological and environmental conditions.

Behavioral and biochemical responses in freshwater fish Carassius auratus exposed to sertraline

Sertraline is one of the most commonly prescribed selective serotonin reuptake inhibitors and is frequently detected in the aquatic environment. However, knowledge regarding relationships among molecular or biochemical endpoints involved in modes of action (MOAs) of sertraline and ecologically important behavioral responses of fish is insufficient. The present study aimed to investigate the bioconcentration and possible adverse outcomes pathways (AOPs) in crucian carp (Carassius auratus) exposed to various concentrations of sertraline (4.36, 21.3 and 116 μg L(-1)) for 7 d. Bioconcentration factor values were in the range of 19.5-626 in liver, 6.94-285 in brain, 4.01-146 in gill and 0.625-43.1 in muscle during the entire period of exposure. Liver superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) activities and brain acetylcholinesterase (AChE) activity were selected as biochemical endpoints associated with MOAs. Swimming activity, shoaling, feeding rate and food consumption were determined to assess behavioral responses. Fish plasma levels of sertraline exceeding human therapeutic doses were also predicted from external exposure concentrations. Significant enhancements in CAT, GPx, AChE and swimming activities and decreases in shoaling tendency, feeding rate and food consumption were observed when fish plasma levels exceeded human therapeutic thresholds. Shoaling, feeding rate and food consumption were correlated with the activities of SOD, CAT and GST. A significant positive correlation between swimming activity and AChE activity was also observed. As such, our study provides important AOPs linking biochemical responses with ultimate ecologically relevant behavioral endpoints.