Ecotoxicological effects of salicylic acid in the freshwater fish Salmo trutta fario: antioxidant mechanisms and histological alterations

Acute toxicity of salicylic acid and its derivatives on the diatom Phaeodactylum tricornutum: Physico-Biochemical and transcriptomic insights

Salicylate pollutants (SAs) poses a serious threat to marine ecosystems as emerging contaminants. However, the toxic effects of SAs on marine phytoplankton, as well as the potential mechanisms and their ecological risks linked with them, are remain largely unknown. In this study, we aimed to evaluate the toxic effects of salicylic acid (SA) and its 5-substituted derivatives (5-sSA) on the marine diatom Phaeodactylum tricornutum, as well as the potential molecular mechanism involved in the toxicity. Physiological assays conducted on P. tricornutum revealed significant changes in photosynthetic pigments, chlorophyll fluorescence parameters, and antioxidant enzyme activities. The results showed that exposure of P. tricornutum to SAs caused a significant decline in chlorophyll contents and damage to the photosystem II (PSII) core resulting in the decline of photosynthesis. Although the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were enhanced, oxidative damage occurred. Transcriptome analysis showed that a large number of differentially expresses genes (DEGs) were significantly enriched in metabolic pathways such as porphyrin metabolism, terpenoid backbone biosynthesis, and carbon fixation in photosynthetic organisms after SA and 5-BrSA treatments. In addition, key genes in transcriptomic metabolic pathways were further analyzed and validated using weighted correlation network analysis (WGCNA) and real-time fluorescence quantitative PCR (qPCR). Considering the above results, SAs mainly inhibit the processes of photosynthesis by repressing the expression of genes involved in secondary metabolite synthesis and photosynthetic carbon sequestration pathways, thus exerting toxic effects on algal cells. The results of the study will provide key data for understanding the ecological risk and toxicity mechanisms of SA pollutants.

Aspirin exposure coupled with hypoxia interferes energy metabolism, antioxidant and autophagic processes and causes liver injury in estuarine goby Mugilogobius chulae

Toxicity assessments of pollutants often overlook the impact of environmental factors like hypoxia, which can alter chemical toxicity with unexpected consequences. In this study, Mugilogobius chulae, an estuarine fish, was used to investigate the effects of hypoxia (H), aspirin (ASA), and their combination (H_ASA) exposure over 24, 72, and 168 h. We employed RNA-seq analysis, expression of key gene expression profiling, enzymatic activity assays, and histopathological and ultrastructural examinations of liver tissue to explore the effects and mechanisms of ASA-coupled hypoxia exposure in fish. Results showed that glycolysis was inhibited, and lipolysis was enhanced in ASA/H_ASA groups. The PPAR signaling pathway was activated, increasing fatty acid β-oxidation and lipophagy to mitigate energy crisis. Both ASA and H_ASA exposures induced p53 expression and inhibited the TOR pathway to combat environmental stress. However, a greater energy demand and heightened sensitivity to ASA were observed in H_ASA compared to ASA exposure. Disruptions in energy and detoxification pathways led to increased stress responses, including enhanced antioxidant activities, autophagy, and apoptotic events, as observed in organelle structures. Overall, sub-chronic H_ASA exposure caused liver injury in M. chulae by affecting energy metabolism, antioxidant regulation, and autophagy processes. This study highlights the influence of hypoxia on ASA toxicity in fish, providing valuable insights for ecological risk assessment of NSAIDs.

A novel Escherichia coli cell-based bioreporter for quantification of salicylic acid in cosmetics

Transcription factor-based bioreporters have been extensively studied for monitoring and detecting environmental toxicants. In Escherichia coli, the multiple antibiotic resistance regulator (MarR) induces transcription upon binding to salicylic acid (SA). We generated SA-specific E. coli cell-based bioreporters utilizing the operator region of the mar operon and MarR as components of the reporter and sensing domains, respectively. Although bioreporters based on endogenous MarR and wild-type E. coli cells responded to SA, their sensitivity and selectivity were insufficient for practical sample monitoring. To improve these parameters, we genetically engineered host strains for optimal MarR expression, which enhanced the sensitivity of the biosensor to micromolar quantities of SA with increased selectivity. Under the optimized experimental conditions, the biosensor could quantify SA in environmental samples. For validation, the SA concentration in artificially contaminated SA-containing cosmetic samples was determined using the developed biosensor. Reliability assessment by comparing the concentrations determined using LC-MS/MS revealed > 90% accuracy of the bioreporters. Although bioreporters are not considered standard tools for environmental monitoring, bacterial cell-based bioreporters may serve as alternative tools owing to their affordability and simplicity. The SA biosensor developed in this study can potentially be a valuable tool for monitoring SA in environmental systems. KEY POINTS: • SA-responsive bioreporter is generated by employing mar operon system in E. coli • SA specificity and selectivity were enhanced by genetic/biochemical engineering • The novel bioreporter would be valuable for SA monitoring in environmental systems.

From metabolism to behaviour - Multilevel effects of environmental methamphetamine concentrations on fish

Methamphetamine (METH) is a concerning drug of abuse that produces strong psychostimulant effects. The use of this substance, along with the insufficient removal in the sewage treatment plants, leads to its occurrence in the environment at low concentrations. In this study, brown trout (Salmo trutta fario) were exposed to 1 μg/L of METH as environmental relevant concentration for 28 days in order to elucidate the complex effects resulting from the drug, including behaviour, energetics, brain and gonad histology, brain metabolomics, and their relations. Trout exposed to METH displayed lowered activity as well as metabolic rate (MR), an altered morphology of brain and gonads as well as changes in brain metabolome when compared to controls. Increased activity and MR were correlated to an increased incidence of histopathology in gonads (females - vascular fluid and gonad staging; males - apoptotic spermatozoa and peritubular cells) in exposed trout compared to controls. Higher amounts of melatonin in brain were detected in exposed fish compared to controls. Tyrosine hydroxylase expression in locus coeruleus was related to the MR in exposed fish, but not in the control. Brain metabolomics indicated significant differences in 115 brain signals between control and METH exposed individuals, described by the coordinates within the principal component analyses (PCA) axes. These coordinates were subsequently used as indicators of a direct link between brain metabolomics, physiology, and behaviour - as activity and MR varied according to their values. Exposed fish showed an increased MR correlated with the metabolite position in PC1 axes, whereas the control had proportionately lower MR and PC1 coordinates. Our findings emphasize the possible complex disturbances in aquatic fauna on multiple interconnected levels (metabolism, physiology, behaviour) as a result of the presence of METH in aquatic environments. Thus, these outcomes can be useful in the development of AOP's (Adverse Outcome Pathways).

Single and combined effects of caffeine and salicylic acid on mussel Mytilus galloprovincialis: Changes at histomorphological, molecular and biochemical levels

Caffeine (CAF) and salicylic acid (SA) are frequently detected in waterbody, though information on their biological impact is poor. This work assesses the effects of CAF (5ng/L to 10µg/L) and SA (0.05µg/L to 100µg/L) alone and combined as CAF+SA (5ng/L+0.05µg/L to 10µg/L+100µg/L) on mussel Mytilus galloprovincialis under 12-days exposure by histomorphology of digestive gland and oxidative stress defense at molecular and biochemical levels. Besides evaluating tissue accumulation, absence of histomorphological damage and haemocyte infiltration highlighted activation of defensive mechanisms. Up-regulation of Cu/Zn-sod, Mn-sod, cat and gst combined with increased catalase and glutathione S-transferase activity were found in CAF-exposed mussels, while SA reduced ROS production and mitochondrial activity. CAF+SA exposure induced differential responses, and the integrated biomarker response (IBR) revealed more pronounced effects of SA than CAF. These results enlarge knowledge on pharmaceuticals impact on non-target organisms, emphasizing the need for proper environmental risk assessment.

Toxic effects of a mixture of pharmaceuticals in Mytilus galloprovincialis: The case of 17α-ethinylestradiol and salicylic acid

The impact of pharmaceuticals on marine invertebrates has been a topic of rising concern, with an increasing number of studies regarding the impacts on bivalves. However, very few investigated the toxicity of mixtures of pharmaceuticals. This knowledge gap was investigated in the present study, where the toxicity of 17α-ethinylestradiol (EE2) and salicylic acid (SA) mixture was evaluated. To this end, Mytilus galloprovincialis mussels were chronically subjected to both pharmaceuticals, acting alone and in combination, and the effects at the cellular level were measured. The Independent Action (IA) model was performed aiming to compare obtained with predicted responses. The integrated biomarker response (IBR) index was used to assess the overall biochemical response given by mussels. The results obtained revealed that the most stressful condition was caused by the combined effect of EE2 and SA, with the highest metabolic capacity, antioxidant (catalase activity) and biotransformation (carboxylesterases activity) activation and cellular damage in organisms exposed to the mixture of both drugs in comparison to responses observed when each drug was acting alone. Predicted responses obtained from the IA model indicate that caution should be paid as frequent deviations to observed responses were found. This study highlights the need for future studies considering the mixture of pollutants, mimicking the actual environmental conditions.

Detection of Diclofenac-Induced Alterations in Rainbow Trout (Oncorhynchus mykiss) Using Quantitative Stereological Methods

In 2013, the nonsteroidal anti-inflammatory drug diclofenac (DCF) was included in the watch list for emerging pollutants under the European Union Water Framework Directive. Frequently, monitoring data revealed DCF concentrations in surface waters exceeding the proposed environmental quality standards of 0.04 µg L^-1 and 0.126 µg L^-1 . In recent literature, the possible effects of DCF on fish are discussed controversially. To contribute to a realistic risk assessment of DCF, a 28-day exposure experiment was carried on rainbow trout (Oncorhynchus mykiss). To warrant reliability of data, experiments were conducted considering the Criteria for Reporting and Evaluating Ecotoxicity Data. The test concentrations of DCF used (0.1, 0.5, 1, 5, 25, and 100 µg L^-1 ) also included environmentally relevant concentrations. The lowest-observed-effect concentration (LOEC) for a significant decrease in the plasma concentrations of the DCF biomarker prostaglandin E2 was 0.5 µg L^-1 (male fish). For objective evaluation of relevant histomorphological parameters of gills and trunk kidneys, unbiased quantitative stereological methods were applied. In the gills, significant increases in the thickness of the secondary lamella and in the true harmonic mean of barrier thickness in secondary lamellae were present at DCF concentrations of 25 µg L^-1 and 100 µg L^-1 . In the trunk kidneys, the absolute and relative volumes of nephrons were significantly decreased, paralleled by a significant increase of the volume of the interstitial renal tissue. With regard to quantitative histomorphological alterations in the trunk kidney, the observed LOEC was 0.5 µg L^-1 . The quantitative histomorphological analyses that were conducted allow identification and objective quantification of even subtle but significant morphological effects and thus provide an important contribution for the comparability of study results for the determination of no-observed-effect concentrations (NOEC). Environ Toxicol Chem 2023;42:859-872. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Triphenylmethane dye (C52H54N4O12) is potentially a hazardous substance in edible freshwater fish at trace level: toxicity, hematology, biochemistry, antioxidants, and molecular docking evaluation study

Malachite green (C₅₂H₅₄N₄O₁₂) is a synthetic dye that is used in textile industries as a colorant and in aquaculture sectors to contain microbial damage. Aquatic contamination of malachite green (MG) has been reported globally. Fish is the highest trophic organism among aquatic inhabitants, highly sensitive to waterborne contaminants (metals, coloring agents, etc.). Toxicity of waterborne chemicals on nontarget organisms can be determined by assessing biomarkers. Assessing blood parameters and tissue antioxidants (enzymatic and nonenzymatic) is useful to evaluate MG toxicity. To initiate the MG toxicity data for freshwater fish (Cyprinus carpio), the median lethal toxicity was primarily evaluated. Then, hematological, blood biochemical (glucose, protein, and cholesterol) and tissue biochemical (amino acids, lipids), and vital tissue (gills, liver, and kidney) antioxidant capacity (CAT, LPO, GST, GR, POxy, vitamin C, and GSH) of C. carpio were analyzed under acute (LC_50-96 h) and sublethal (Treatment I-1/10^th and Treatment II-1/5^th LC_50-96 h) exposure periods (28 days). Molecular docking for MG with hemoglobin was also obtained. Biomarkers examined were affected in the MG-treated groups with respect to the control group. Significant changes (p < 0.05) were observed in hematology (Hb, RBCs, and WBCs), glucose, proteins, lipids and tissue CAT, LPO, and GST activities under acute MG exposure. In sublethal treatment groups, biomarkers studied were significant (p < 0.05) throughout the study period. The potential for MG binding to hemoglobin was tested in this study. MG is potentially a multiorgan toxicant. Literally a chemical that is harmful to the aquatic environment if safety is concerned.

Time- and dose-dependent biological effects of a sub-chronic exposure to realistic doses of salicylic acid in the gills of mussel Mytilus galloprovincialis

Among nonsteroidal anti-inflammatory drugs (NSAIDs) commonly found in seawater and wastewater, salicylic acid (SA) represents one of the most persistent and hazardous compounds for aquatic organisms. This study was therefore designed to elucidate the biological effects of SA in mussel Mytilus galloprovincialis. During a sub-chronic exposure (12 days), mussels were exposed to five realistic concentrations of SA (C1: 0.05 μg/L; C2: 0.5 μg/L; C3: 5 μg/L; C4: 50 μg/L; C5: 100 μg/L) and gills, selected as the target organ, were collected at different time points (T3: 3 days; T5: 5 days; T12: 12 days). Exposure to SA induced no histological alterations in mussel gills, despite a relevant hemocyte infiltration was observed throughout the exposure as a defensive response to SA. Temporal modulation of glutathione S-transferase (GST), catalase (CAT), and superoxide dismutase (SOD) activities suggested the occurrence of antioxidant and detoxifying responses against SA exposure, while lipid peroxidation (LPO), except for a partial increase at T3, was prevented. Inhibition of the cholinergic system was also reported by reduced acetylcholinesterase (AChE) activity, mainly at T12. Overall, findings from this study contribute to enlarge the current knowledge on the cytotoxicity of SA, on non-target aquatic organisms, and might for the enhancement of new ecopharmacovigilance programs and optimization of the efficacy of wastewater treatment plants for mitigation of pharmaceutical pollution in coastal areas.

In Vitro and in Vivo Studies of the Antiparasitic Effect of Aspirin Against Dactylogyrus Extensus (Monogenea) Invasion in Carp (Cyprinus carpio)

Aspirin is one of the most widely used medications globally as an analgesic and antipyretic drug. Aspirin use as an antiparasitic against fish parasites has never been tested. The parasite Dactylogyrus is considered a serious threat to freshwater aquaculture in relation to considerable losses. The present study is aimed to evaluate the antiparasitic effect of aspirin against Dactylogyrus extensus on Cyprinus carpio and alteration in gill histopathology. In vitro, aspirin exhibited antiparasitic activity with median effective concentration (EC50) values at one and six minutes of 8.137 g/L−1 and 1.629 g/L−1, were assessed for the first time. In vivo antiparasitic efficacy of aspirin to D. extensus was found to be 46.49%. Severe lesion profile was observed in histopathological evaluations of the gills.

Histological endpoints and oxidative stress transcriptional responses in the Mediterranean mussel Mytilus galloprovincialis exposed to realistic doses of salicylic acid

Despite the availability of analytic data, little is known about the toxicity of salicylic acid (SA) on aquatic non-target organisms. The present study aimed at evaluating the impact of SA through a short-term exposure of the Mediterranean mussel Mytilus galloprovincialis to five environmentally relevant concentrations of SA. A set of suitable biomarkers was applied at selected time-points on mussel digestive glands, including histological observations and expression of oxidative stress related genes. The obtained results showed a conspicuous hemocytic infiltration among mussel digestive tubules, as confirmed also by a flow cytometric approach that revealed an increase of halinocytes and granulocytes. Interestingly, a significant dose and time dependent decrease in the expression levels of oxidative stress related genes was found in mussels exposed to SA except for the glutathione S-transferase gene that was significantly up-regulated in a time-dependent manner confirming its important role against oxidant species and in the metabolism of pharmaceuticals.

A multi-biomarker approach for the early assessment of the toxicity of hospital wastewater using the freshwater organism Daphnia magna

Hospital wastewater (HWW) contains different hazardous substances resulting from a combination of medical and non-medical activities of hospitals, including pharmaceutical residues. These substances may represent a threat to the aquatic environment if they do not follow specific treatment processes. Therefore, we aimed to investigate the effects of the untreated effluent collected from a general hospital in Mahdia City (Tunisia) on neonatal stages of the freshwater crustacean Daphnia magna. Test organisms were exposed to three proportions (3.12%, 6.25%, and 12.5% v/v) of HWW. After 48 h of exposure, a battery of biomarkers was measured, including the quantification of antioxidant enzymes [catalase (CAT) and total and selenium-dependent glutathione peroxidase (total GPx; Se-GPx)], phase II biotransformation isoenzymes glutathione-S-transferases (GSTs), cyclooxygenases (COX) involved in the regulation of the inflammatory process, and total cholinesterases (ChEs) activities. Lipid peroxidation (LPO) was measured to estimate oxidative damage. The here-obtained results showed significant decreases of CAT and GSTs activities and also on LPO content in daphnids, whereas Se-GPx activity was significantly increased in a dose-dependent manner. Impairment of cholinesterasic and COX activities were also observed, with a significant decrease of ChEs and an increase of COX enzymatic activities. Considering these findings, HWW was capable of inducing an imbalance of the antioxidant defense system, but without resulting in oxidative damage in test organisms, suggesting that peroxidases and alternative detoxifying pathways were able to prevent the oxidant potential of several drugs, which were found in the tested effluents. In general, this study demonstrated the toxicity of hospital effluents, measured in terms of the potential impairment of key pathways, namely neurotransmission, antioxidant defense, and inflammatory homeostasis of crustaceans.

Toxicity of two drugs towards the marine filter feeder Mytilus spp, using biochemical and shell integrity parameters

The increasing presence of anthropogenic contaminants in the environment may constitute a challenge to non-target biota, considering that most contaminants can exert deleterious effects. Salicylic acid (SA) is a non-steroid anti-inflammatory drug (NSAID) which exerts its activity by inhibiting the enzyme cyclooxygenase (COX). Another class of drugs is that of the diuretics, in which acetazolamide (ACZ) is included. This pharmaceutical acts by inhibiting carbonic anhydrase (CA), a key enzyme in acid-base homeostasis, regulation of pH, being also responsible for the bio-availability of Ca²⁺ for shell biomineralization processes. In this work, we evaluated the chronic (28-day) ecotoxicological effects resulting from the exposures to SA and ACZ (alone, and in combination) on individuals of the marine mussel species Mytillus spp., using enzymatic (catalase (CAT), glutathione S-transferases (GSTs), COX and CA), non-enzymatic (lipid peroxidation, TBARS levels) and morphological and physiological (shell hardness, shell index and feeding behaviour) biomarkers. Exposure to ACZ and SA did not cause significant alterations in CAT and GSTs activities, and in TBARS levels. In terms of CA, this enzyme was inhibited by the highest concentration of ACZ in gills of exposed animals, but no effects occurred in the mantle tissue. The activity of COX was not altered after exposure to the single chemicals. However, animals exposed to the mixture of ACZ and SA evidenced a significant inhibition of COX activity. Morphological and physiological processes (namely, feeding, shell index, and shell hardness) were not affected by the here tested pharmaceutical drugs. Considering the general absence of adverse effects, further studies are needed to fully evaluate the effects of these pharmaceutical drugs on alternative biochemical and physiological pathways.

Integrated multi-biomarker responses of juvenile rainbow trout (Oncorhynchus mykiss) to an environmentally relevant pharmaceutical mixture

Pharmaceuticals are emerging pollutants of concern for aquatic ecosystems where they are occurring in complex mixtures. In the present study, the chronic toxicity of an environmentally relevant pharmaceutical mixture on juvenile rainbow trout (Oncorhynchus mykiss) was investigated. Five pharmaceuticals (paracetamol, carbamazepine, diclofenac, naproxen and irbesartan) were selected based on their detection frequency and concentration levels in the Meuse river (Belgium). Fish were exposed for 42 days to three different concentrations of the mixture, the median one detected in the Meuse river, 10-times and 100-times this concentration. Effects on the nervous, immune, antioxidant, and detoxification systems were evaluated throughout the exposure period and their response standardized using the Integrated Biomarker Response (IBRv2) index. IBRv2 scores increased over time in the fish exposed to the highest concentration. After 42 days, fish exposed to the highest concentration displayed significantly higher levels in lysozyme activity (p < 0.01). The mixture also caused significant changes in brain serotonin turnover (p < 0.05). In short, our results indicate that the subchronic waterborne exposure to a pharmaceutical mixture commonly occurring in freshwater ecosystems may affect the neuroendocrine and immune systems of juvenile rainbow trout.

Is ionizing radiation effective in removing pharmaceuticals from wastewater?

Wastewater and effluent discharges are the main causes of receiving water body pollution and important challenges in water quality management. Among the emerging contaminants, pharmaceuticals have increasingly drawn attention due to their incomplete removal during conventional biological treatment, inducing potential and actual risks to living organisms following residue discharges in river effluent. Electron beam irradiation (EBI) is a clean process technology for organic compound degradation and mineralization, as well as persistent pollutant detoxification. This study aimed to evaluate EBI effects on the degradation and toxicity removal of anti-inflammatory aspirin (ASA) in a single solution and in a fluoxetine (FLX) mixture. Results indicate that 98% of the single aspirin was degraded at 5.0 kGy. Aspirin toxicity to Daphnia similis, however, increased with increasing absorbed dose (1.0 to 5.0 kGy), possibly as a result of the presence of H₂O₂ and other byproducts formed during the oxidation process. Regarding the irradiated mixture, complete degradation was achieved for both pharmaceuticals. Toxicity removals for the mixture were of 56.2 ± 0.9% and 58.8 ± 5.4% for 1.0 and 2.5 kGy, respectively. These findings demonstrate that EBI can be an interesting alternative process to be applied as a pre-treatment followed by biological treatment.

Behavioral and physiological responses of Daphnia magna to salicylic acid

Salicylic acid (SA), a metabolite of acetylsalicylic acid is a monohydroxybenzoic acid a common non-steroidal analgesic and anti-inflammatory drug (NSAID) frequently detected in various aquatic ecosystems at concentrations up to 19.50 μg L^-1 in surface waters near livestock farms and 59.6 μg L^-1 in wastewaters. Little is known on the effects of short-term exposure of freshwater crustaceans to salicylic acid. Therefore, the aim of our study was to determine the effects of SA at concentrations of 5 μg L^-1, 500 μg L^-1, 5 mg L^-1, 50 mg L^-1 and 500 mg L^-1 on the behavior (swimming speed, swimming height, distance travelled) and physiological endpoints (heart rate, mandible movement) of Daphnia magna exposed for 24 h, 48 h and 72 h. The results showed that SA inhibited the swimming speed, swimming height and distance travelled, heart rate and mandible movement at 5 mg L^-1, 50 mg L^-1 and 500 mg L^-1 when compared to the control. On the other hand, SA at 5 μg L^-1 and 500 μg L^-1 transiently increased swimming speed and distance travelled after 24 h of the exposure, except for swimming height. Behavioral and physiological disturbances were observed much earlier than lethality. Our study showed SA at environmental levels may be an ecotoxicological agent imparing behavior and physiology of freshwater crustaceans.

Evaluation of single and combined effects of two pharmaceuticals on the marine gastropod Phorcus lineatus enzymatic activity under two different exposure periods

Pharmaceutical drugs are among the most used chemicals for human and veterinary medicines, aquaculture and agriculture. Pharmaceuticals are environmentally persistent, biologically active molecules, thereby having the potential to exert biological effects on non-target species. Among the most used pharmaceuticals, one may find salicylic acid (SA), a non-steroid anti-inflammatory drug (NSAID) that acts by inhibiting the enzymes cyclooxigenases; it is also possible to identify acetazolamide (ACZ), a diuretic that acts by inhibiting the activity of carbonic anhydrase (CA). In this work, the effects of both single and combined effects of these drugs were assessed on the marine gastropod Phorcus lineatus, by measuring key enzymatic activities, namely carbonic anhydrase (CA) and cyclooxygenase (COX), under two different exposure periods (14 and 28 days). We observed no straightforward pattern of enzymatic response in all treatments of both pharmaceuticals, on both analyzed tissues (gut and gills), and for both exposure regimes. We assume that this species is not responsive to the hereby tested pharmaceuticals, a finding that may be due to general mechanisms of response to adverse conditions, such as reduction of metabolism, of heart rate, of filtration rates, and to the increase production of mucus. All these functional adaptations can mitigate the deleterious effects caused by adverse conditions, without triggering biochemical responses. In conclusion, the species P. lineatus seems not to be sensitive in terms of these specific enzymatic pathways to these contaminants, under the adopted conditions.

Occurrence, seasonal variations, and ecological risk of pharmaceuticals and personal care products in River Ganges at two holy cities of India

Occurrence of 15 different pharmaceuticals and personal care products (PPCPs) (ibuprofen, diclofenac, ketoprofen, acetaminophen, ciprofloxacin, erythromycin, amoxicillin, ofloxacin, tetracycline, metoprolol, triclosan, salicylic acid, N, N diethyl-meta-toluamide, caffeine and β-Estradiol) belongs to eight different classes in an urban stretch of River Ganges were detected for three seasons in two holy cities Rishikesh and Haridwar (India). The overall concentration of PPCPs in the River Ganges ranged between Below Detectable Limit (BDL) to 1104.84 ng/L, with higher concentrations at anthropogenically influenced lower reaches of the River Ganges at Haridwar. Acetaminophen, triclosan, N, N diethyl-meta-toluamide (DEET), tetracycline, and caffeine showed the highest detection frequency (>90-100%) in the river. PPCPs concentration, especially for NSAIDs (Ibuprofen, ketoprofen and acetaminophen), antibiotics (ciprofloxacin, tetracycline and ofloxacin) and metabolite (salicylic acid) was found to be higher in winter compared to summer in the Ganges, possibly due to the lower biodegradation efficiency related to lesser temperatures and inadequate sunlight. While metoprolol (beta-blockers), triclosan (antibacterial), DEET (insect repellent) and caffeine (human indicator) showed a higher load in summer, possibly due to their intense uses during this period. Results of risk quiescent (RQ) revealed higher ecological risk for algae while the moderate risk for river fish biota.

Prioritization of contaminants and biological process targets in the North Sea using toxicity data from ToxCast

The increasing number of chemicals detected in the marine environment underlines the need for appropriate prioritization strategies prior to further testing and potential inclusion into monitoring programs. Here, a prioritization strategy is proposed for chemicals detected in the North Sea over the last decade, through the development of a Concern Index (CI) using exposure and toxicity data obtained from peer-review publications and the ToxCast database, respectively. A total of 158 chemicals were ranked and the most sensitive tested assay endpoints were identified. Additionally, similar analysis was performed for the classes of chemicals and Biological Process Targets (BPTs). By first ranking chemicals currently acknowledged for their high toxicity to the aquatic environment, i.e. naphthalene, salicylic acid and simazine, the obtained results not only reinforce the risk posed by these but also promote a confident extrapolation from mammalian in vitro toxicity data to fish. Furthermore, genes targeted by the most sensitive assays, related to basic cell maintenance processes and immune defense, are highly evolutionarily conserved across species. The identification of these assays further reinforces the importance of a shift from traditional toxicity endpoints to lower levels of biological organization, allowing the detection of adverse effects at lower concentrations.

Massive infection of Cystidicoloides ephemeridarum in brown trout Salmo trutta with skeletal deformities

We investigated the cause of skeletal deformities found in brown trout from the Aspromonte mountain area in Reggio Calabria, Italy. Toxicological, histopathological and parasitological analyses were carried out on 14 fish with evident macro-morphological alterations from 2 different locations in the same river, and 4 control fish without morphological alterations from a different river (far from the first river but still within the area under study). Histopathological and radiological observations confirmed severe skeletal deformities in the specimens investigated. Parasitological examinations highlighted the presence of the nematode Cystidicoloides ephemeridarum, found only within the gastrointestinal tract of specimens showing deformities. Moreover, a direct correlation between parasite number and fish size was found. Given the low heavy metal levels and the presence of a massive parasitosis in teleosts showing deformities, we postulate a correlation between skeletal deformities and nematode infestation: the parasites caused a serious vitamin and mineral deficiency in the fish, which led to a dysplastic vertebral column. The low calcium levels found in malformed specimens compared with negative controls effectively confirm this hypothesis.

Antibiotics control in aquaculture requires more than antibiotic-free feeds: A tilapia farming case

Public concern over the health implications of antimicrobials employed in aquaculture has resulted in adoption of strict regulations for their use. This study employed a high-throughput protocol covering 86 compounds in six pharmaceutical groups to screen feed and sediments from 20 tilapia ponds randomly in 18 farms of an aquacultural unit in southern China, one of important tilapia fillet suppliers in the world. Seventeen samples of commercial feeds from manufacturer-sealed bags in the farms were tetracyclines-free but not antibiotic-free. All the sealed-bag feeds contained quinolones and two feeds had sulfonamides (up to 140 μg kg^-1). Meanwhile, seven leftover-feeds in opened bags contained added antimicrobials: tetracyclines (570-2790 μg kg^-1) in all and florfenicol (20-294 μg kg^-1) in four. All the feeds regardless sealed or not had large amounts (221-2642 μg kg^-1) of salicylic acid (possible antimicrobial substitute) and caffeine, and one sealed-bag feed even was quantified with medroxyprogesterone. Surface sediments (0-10 cm) from the ponds were detected with 36 compounds and sublayer sediments (10-20) with 8 compounds. Large amounts of salicylic acid were present in both surface and sublayer sediments accounting up to 10% of total pharmaceutical residues. Surface sediments were dominated by antibiotics (5.2-172 μg kg^-1), mainly sulfonamides and quinolones, contributing 68% of the total quantitative compound mass. Sublayer sediments were also enriched in quinolones (up to 260 μg kg^-1). Surprisingly, all sediments contained progesterone (up to 8.0 μg kg^-1) in coincidence to the feed with medroxyprogesterone, perhaps arising from endocrine abuses or cross-contamination. Although high levels of other pharmacologic residues (caffeine) in sediment posed greater than medium ecological risks, antibiotic residues contributed only 2-35% to the risk. These findings suggest that antibiotic-free feed may be insufficient to control antibiotic abuse in aquaculture and that additional regulatory actions may be necessary, such as veterinary prescription as human antibiotic uses.

Impacts of salicylic acid in Mytilus galloprovincialis exposed to warming conditions

While many studies have been conducted on drug-inducing alterations in the aquatic environment, little is known about their interaction with climate change, such as rising temperatures. To increase knowledge on this topic, Mytilus galloprovincialis mussels were exposed to two different temperatures 17 ± 1 °C (control) and 21 ± 1 °C in the absence and presence of salicylic acid (SA) (4 mg/L) for 28 days. Salicylic acid in the water and tissues was measured and its impact reported through biomarker responses including: energy metabolism (electron transport system (ETS) activity, glycogen (GLY), protein (PROT) and lipids (LIP) contents), oxidative stress markers (activity of the enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx)), glutathione balance between the reduced and the oxidized forms (GSH/GSSG), and damage to membrane lipids (lipid peroxidation - LPO). The mussels responded differently if the stresses imposed were single or combined, with greater impacts when both stressors were acting together. Contaminated mussels exposed to high temperatures were unable to increase their metabolic capacity to restore their defence mechanisms, reducing the expenditure of LIP. In the presence of SA and increased temperature antioxidant defences respond differently, with higher SOD levels and inhibition of CAT. The present study highlights not only the negative impact of warming and SA, but especially how temperature increase will promote the impact of SA in M. galloprovincialis, which under predicted climate change scenarios may greatly impair population maintenance and ecosystem biodiversity.

Environmental concentration of methamphetamine induces pathological changes in brown trout (Salmo trutta fario)

Methamphetamine, mainly consumed as an illicit drug, is a potent addictive psychostimulant that has been detected in surface water at concentrations ranging from nanograms to micrograms per litre, especially in Middle and East Europe. The aim of this study was to expose brown trout (Salmo trutta fario) to environmental (1 μg L^-1) and higher (50 μg L^-1) concentrations of methamphetamine for 35 days with a four-day depuration phase to assess the possible negative effects on fish health. Degenerative liver and heart alterations, similar to those described in mammals, were observed at both concentrations, although at different intensities. Apoptotic changes in hepatocytes, revealed by activated caspase-3, were found in exposed fish. The parent compound and a metabolite (amphetamine) were detected in fish tissues in both concentration groups, in the order of kidney > liver > brain > muscle > plasma. Bioconcentration factors ranged from 0.13 to 80. A therapeutic plasma concentration was reached for both compounds in the high-concentration treatment. This study indicates that chronic environmental concentrations of methamphetamine can lead to health issues in aquatic organisms.

The use of Hediste diversicolor in the study of emerging contaminants

The contamination of aquatic environments has been the focus of research to understand effects on ecosystems and its species. Benthic organisms are considered potential targets since sediments act as sources and sinks for environmental contaminants. This review presents information on the effects of three types of emerging contaminants: pharmaceuticals (tested concentrations between 0.1 ng/L - 250 mg/L and 0.01 ng/g - 2.5 μg/g), metal-based nanoparticles (<100 nm) (tested concentrations between 10 μg/L - 1 mg/L and 5 - 140 μg/g) and micro(nano)plastics (tested concentrations between 5 μg/L - 50 mg/L and 10 - 50 mg/kg), on the polychaete Hediste diversicolor, a key species in estuarine/coastal ecosystems. Data shows that these contaminants promote alterations in burrowing activity (lowest concentration inducing effects: 10 ng/L), neurotransmission and damage related parameters (lowest concentration inducing effects: 100 ng/L). The characteristics of this polychaete, such as regenerative capacity, make the use of this species in biomedical studies involving environmental contaminants valuable.

Effects of pH on salicylic acid toxicity in terms of biomarkers determined in the marine gastropod Gibbula umbilicalis

Alterations of the physical-chemical properties of the oceans due to anthropogenic activities are, at present, one of the most concerning environmental issues studied by researchers. One of these issues is ocean acidification, mainly caused by overproduction and release of carbon dioxide (CO₂) from anthropogenic sources. Another component of environmental degradation is related to the production and release of potential toxic compounds, namely active pharmaceutical ingredients, into the aquatic environment that, combined with oceanic acidification, can cause unpredictable and never before considered deleterious effects on non-target marine organisms. Regarding this issue, the hereby study used predictions of future ocean acidification to simulate realistic scenarios of environmental exposure to a common therapeutic drug, salicylic acid (SA), in the marine gastropod Gibbula umbilicalis under different pH values. This species was exposed to a range of pH values (8.2, 7.9 and 7.6), and to already reported environmentally realistic concentrations (5, 25 and 125 μg/L) of SA. To evaluate the effects of these environmental stressors, key physiological biomarkers (GSTs, CAT, TBARS, AChE and COX) and shell hardness (SH) were quantified. Results from the present study showed that CAT and GSTs activities were enhanced by SA under water acidification; increased lipid peroxidation was also observed in organisms exposed to SA in more acidic media. In addition, the hereby study demonstrated the neurotoxic effects of SA through the inhibition of AChE. Effects were also observed in terms of COX activity, showing that SA absorption may be affected by water acidification. In terms of SH, the obtained data suggest that SA may alter the physical integrity of shells of exposed organisms. It is possible to conclude that the combination of seawater acidification and exposure to toxic xenobiotics (namely to the drug SA) may be strenuous to marine communities, making aquatic biota more susceptible to xenobiotics, and consequently endangering marine life in an unpredictable extent.

Effect of the preparation method and metal content on the synthesis of metal modified titanium oxide used for the removal of salicylic acid under UV light

Titanium dioxide modified with Ag and Fe was synthesized using two preparation methods, characterized and applied to the photocatalytic degradation of salicylic acid in aqueous solution. The modified TiO₂ samples were prepared by the sol-gel and wet impregnation methods starting from titanium(IV) isopropoxide and using AgNO₃ and Fe(NO₃)₃·9H₂O as precursors of the modifiers, with their content varying between 0 and 5 wt.%. Catalysts characterization was based on powder X-ray diffraction (PXRD), nitrogen physisorption at 77 K, temperature programmed reduction (H₂-TPR), chemisorption of NH₃ at 343 K and X-ray photoelectron spectroscopy (XPS). The photocatalytic degradation of salicylic acid by modified TiO₂ was investigated under ultraviolet irradiation at 298 K considering various concentrations of the catalyst, between 100 and 1000 mg_catalyst/dm³, and of the organic molecule, between 0 and 15 mg/dm³. The catalysts most active in the degradation of salicylic acid were those having the highest Fe content.

Combined effects of salinity changes and salicylic acid exposure in Mytilus galloprovincialis

Pharmaceuticals and Personal care products (PPCPs) are frequently released into several marine matrices, representing significant environmental and ecotoxicological risks. Among the widest spread PPCPs in aquatic systems is Salicylic acid (SA), with known negative effects on marine and freshwater species. Nevertheless, the toxicity resulting from these emerging pollutants, including SA, together with climate change has still received little attention up to date. Among climate change related factors salinity is one that most affects aquatic organisms. To better understand the combined impacts of SA and salinity, the present study evaluated the biochemical alterations induced in Mytilus galloprovincialis mussels exposed to SA and different salinity levels, acting individually and in combination. The effects observed clearly highlighted that cellular damages were mainly observed at higher salinity (35), with no additive or synergistic effects derived from the combined presence of SA. Higher antioxidant capacity of mussels in the presence of SA may prevent increased LPO levels in comparison to uncontaminated mussels. Nevertheless, in the presence of SA mussels revealed loss of redox balance, regardless of the salinity level. Furthermore, mussels exposed to SA at control salinity showed increased metabolic capacity which decreased when exposed to salinities 25 and 35. These findings may indicate the protective capacity of mussels towards higher stressful conditions, with lower energy reserves expenditure when in the presence of SA and salinities out of their optimal range. Although limited cellular damages were observed, changes on mussel's redox balance, antioxidant mechanisms and metabolism derived from the combined exposure to SA and salinity changes may compromise mussel's growth and reproduction. Overall, the present study highlights the need to investigate the impacts induced by pollutants under present and future climate change scenarios, towards a more realistic environmental risk assessment.

Toxicity and bioaccumulation of Cadmium, Copper and Zinc in a direct comparison at equitoxic concentrations in common carp (Cyprinus carpio) juveniles

The individual toxicity and bioaccumulation of cadmium, copper and zinc for common carp juveniles was evaluated in a direct comparison in two experimental setups. First, fish were exposed for 10 days to different metal concentrations in order to link metal bioaccumulation to LC₅₀ values (concentration lethal to 50% of the animals) and incipient lethal levels (ILL, concentration where 50% survives indefinitely). Accumulated metals showed a positive dose dependent uptake for cadmium and copper, but not for zinc. Toxicity was in the order cadmium>copper>zinc with 96h LC₅₀ values for cadmium at 0.20±0.16 μM, for copper at 0.77±0.03 μM, and for zinc at 29.89±9.03 μM respectively. For copper, the 96h exposure was sufficient to calculate the incipient lethal level and therefore 96h LC₅₀ and ILL levels were the same, while for cadmium and zinc 5 to 6 days were needed to reach ILL resulting in slightly lower values at 0.16 μM and 28.33 μM respectively. Subsequently, a subacute exposure experiment was conducted, where carp juveniles were exposed to 2 equitoxic concentrations (10% and 50% of LC₅₀ 96 h) of the three metals for 1, 3 and 7 days. Again a significant dose-dependent increase in gill cadmium and copper, but not in zinc, was observed during the 7-day exposure. Copper clearly affected sodium levels in gill tissue, while zinc and cadmium did not significantly alter any of the gill electrolytes. The overall histopathological effects (e.g. hyperemia and hypertrophy) of the metal exposures were mild for most of the alterations. Our study showed that copper an cadmium (but not zinc) showed dose dependent metal accumulation, however this bioaccumulation was only correlated with mortality for cadmium. Metal specific alterations were reduced gill sodium levels in copper exposed fish and oedema of the primary epithelium which typically occurred in both levels of zinc exposure.

Biochemical and physiological responses induced in Mytilus galloprovincialis after a chronic exposure to salicylic acid

A vast variety of substances currently reaches the aquatic environment, including newly developed chemicals and products. Lack of appropriate analytical methods for trace determinations in aquatic ecosystem compartments and lack of information regarding their toxicity explains existing regulation gaps. However, suspicion of their toxicity assigned them as Contaminants of Emerging Concern (CECs). Among CECs are Pharmaceuticals including Salicylic Acid (SA), which is the active metabolite of acetylsalicylic acid (ASA; aspirin). The aim of the present study was to evaluate the potential effects of SA on the mussel Mytilus galloprovincialis. For this, organisms were exposed for 28 days to different concentrations of SA (0.005; 0.05; 0.5 and 5 mg/L), resembling low to highly polluted sites, after which different physiological and biochemical parameters were evaluated to assess organism's respiration rate, neurotoxic, metabolic and oxidative stress status. Our results clearly showed that SA strongly reduced the respiration capacity of mussels. Also, SA inhibited the activity of superoxide dismutase (SOD) and catalase (CAT) enzymes, but increased the activity of glutathione peroxidase (GPx) and glutathione-S-transferases (GSTs), which prevented the occurrence of lipid peroxidation (LPO). Nevertheless, oxidative stress was confirmed by the strong decrease of the ratio between reduce glutathione (GSH) and oxidized (GSSG) glutathione in contaminated mussels. Moreover, neurotoxicity was observed in mussels exposed to SA. Overall, this study demonstrates the metabolic, neurotoxic and oxidative stress impacts of SA in M. galloprovincialis, which may result in negative consequences at the population level.

Effects of commonly used therapeutic drugs, paracetamol, and acetylsalicylic acid, on key physiological traits of the sea snail Gibbula umbilicalis

Over time, the consumption of pharmaceutical drugs has highly augmented, directly contributing for an increase of the discharges of these substances into sewage water due to excretion, and their direct release to the environment, with or without adequate treatment. Considering that part of the sewage water is dumped into rivers and seas, this is the major source of contamination of the aquatic environment. Paracetamol and acetylsalicylic acid are among the most worldwide consumed pharmaceutical drugs, frequently found in wastewater discharges and consequently in the aquatic environment in considerable amounts, posing ecotoxicity concerns especially towards aquatic non-target species. Thus, it is important to study the ecotoxicological implications that these drugs might pose to organisms from aquatic environments. The objective of this study was to assess the toxic effects of these two compounds on key biochemical features (antioxidant defenses and damage, metabolism, and cholinergic neurotoxicity) of the marine snail species Gibbula umbilicalis after an acute (96 h) exposure, simulating pulses of contamination. In order to understand the effects that those drugs have on this species, the biochemical biomarkers analyzed were the activities of catalase (CAT), glutathione-S-transferases (GSTs), cholinesterases (ChEs), and the levels of lipid peroxidation (TBARS). After acute exposure to paracetamol, catalase activity decreased significantly in organisms exposed to both highest concentrations; no significant alterations were observed for glutathione-S-transferases activity; TBARS concentration decreased significantly in organisms exposed to the intermediate and both highest concentrations, and cholinesterase activity increased significantly in animals exposed to the lowest concentration. However, after acute exposure to acetylsalicylic acid, catalase activity increased significantly; no significant alterations were observed for glutathione-S-transferases activity, and TBARS concentrations and cholinesterase activity increased. This set of data shows that G. umbilicalis is highly responsive to the presence of the tested drugs, and may thus be a promising species to serve as test organism in future marine ecotoxicological testing. The adoption of this species may broaden the offer of highly ecologically representative test organisms to be included in biomonitoring projects of the coastal and marine environment. Furthermore, it is possible to suggest that both drugs may pose significant deleterious effects of pro-oxidative origin to the physiology of the selected species, with potential adverse ecological consequences, even after short periods of exposure. The absence of neurotoxicity showed that despite being able to trigger antioxidant mechanisms, both drugs did not affect neurotransmission.

Worms on drugs: ecotoxicological effects of acetylsalicylic acid on the Polychaeta species Hediste diversicolor in terms of biochemical and histological alterations

Pharmaceuticals are important environmental stressors since they have a worldwide use; they are usually released in the aquatic compartment without adequate treatment, and because of their intrinsic properties, they may affect several non-target organisms. Acetylsalicylic acid (ASA), the active substance of aspirin, is a non-steroidal anti-inflammatory drug, being one of the most widely prescribed analgesics in human medical care. Consequently, this compound is systematically reported to occur in the wild, where it may exert toxic effects on non-target species, which are mostly uncharacterized so far. The objective of the present work was to assess the acute and chronic effects of ASA on selected oxidative stress biomarkers [catalase (CAT), glutathione reductase (GRed), glutathione peroxidase (GPx), glutathione S-transferase (GST)], lipid peroxidation (thiobarbituric acid-reactive substance), and histological alterations in the polychaete Hediste diversicolor (Annelida: Polychaeta). The obtained data showed that ASA is not exempt of toxicity, since it was responsible for significant, albeit transient, changes in biomarkers related to the redox status of the organisms, occurring as an increase in the activity of catalase in the individuals exposed acutely to ASA. Chronic exposure to ecologically relevant concentrations of this drug showed to be mostly ineffective in promoting any significant biochemical alteration in H. diversicolor. However, histochemical observations revealed proliferation of mucous cells in the tegument of chronically exposed individuals to ASA.

Histopathological effects in gills and liver of Sparus aurata following acute and chronic exposures to erythromycin and oxytetracycline

Due to their worldwide use and environmental persistence, antibiotics are frequently detected in various aquatic compartments. Their toxic properties raise environmental concerns to non-target organisms. Histopathology data is frequently applied in ecotoxicology studies to assess the effects of different classes of environmental stressors in fish, including antibiotics. Tissue alterations in gills and liver of gilthead seabream (Sparus aurata) individuals acutely (96 h) and chronically (28 days) exposed to environmentally relevant concentrations of the antibiotics erythromycin (ERY: 0.0002-200 μg/L) and oxytetracycline (OTC: 0.0004-400 μg/L), including a control non-exposed group, were evaluated. Several disorders (circulatory, regressive, progressive, and inflammatory) were observed in both organs of all exposed animals. The hereby obtained data showed a higher and significant increase in gill histopathological index of organisms acutely exposed to ERY and of those chronically exposed to OTC. In terms of categorical lesions, only a significant increase of regressive and progressive alterations occurred in gills after chronic exposure to OTC. For the liver, a significant increase in pathological index was also detected, as well as regressive changes, after chronic exposure to OTC. Furthermore, the present study indicates that most of the changes observed in gills and liver were of mild to moderate severity, which might be adaptive or protective, non-specific, and mostly reversible. Despite being observed, irreversible lesions were not significant in any of the fish organs analyzed. Although there were histological changes, gill apparatus was considered still functionally normal, as well as liver tissue, not supporting the occurrence of severe toxicity. In general, the observed histological changes were not stressor-specific, and toxicological mechanistic explanations for the alterations observed in gills and liver are presented. The obtained data showed that histopathological biomarkers can be successfully applied in ecotoxicological studies, evidencing their relevance, responsivity, and complementarity to other biochemical biomarker-based approaches.

Acute ecotoxicological effects of salicylic acid on the Polychaeta species Hediste diversicolor: evidences of low to moderate pro-oxidative effects

Contamination of the aquatic environment by pharmaceutical drugs is an emerging issue in ecotoxicology. Aquatic organisms, in the presence of xenobiotics, tend to activate defensive mechanisms against toxic effects in order to mitigate and/or compensate for the toxic damages that frequently result from these interactions. Salicylic acid (SA) is a common drug, widely used in human medicine due to its analgesic, anti-inflammatory, and antipyretic properties, as well as its activity in terms of preventing platelet aggregation, among other clinical and cosmetic uses. It is commonly found in levels of the nanograms per liter to the micrograms per liter range in receiving waters, and its presence has been related to toxic effects in aquatic organisms, including oxidative stress. However, the number of studies that characterize the ecotoxicological profile of salicylates is still scarce and no studies have been published about the putative toxic effects of SA, especially in marine polychaetes. In order to determine the potential ecotoxicological effects caused by SA, individuals of the marine Polychaeta species Hediste diversicolor were exposed for 96 h to ecologically relevant concentrations of this compound, and several biochemical endpoints were evaluated, namely the activity of the antioxidant enzymes glutathione peroxidase (GPx) and catalase (CAT), the phase II biotransformation isoenzymes glutathione S-transferases (GSTs), the cholinergic enzyme acetylcholinesterase (AChE), and the determination of lipoperoxidative damage (thiobarbituric acid-reactive substances (TBARS) assay). The obtained results demonstrated that despite the pro-oxidative effects elicited by SA, exposure to realistic levels of this compound was not able to generate a state of oxidative stress, and the adaptive protective responses elicited by exposed individuals were effective enough to minimize and/or inhibit the damage potentially caused by overproduced reactive oxygen species.

Impact of the NSAID diclofenac on survival, development, behaviour and health of embryonic and juvenile stages of brown trout, Salmo trutta f. fario

The NSAID diclofenac is controversially discussed with respect to its environmental relevance. Since further information is need to assess whether diclofenac should be included as substance of priority in the EU water framework directive, we investigated the impact of this analgesic on the embryonic development of brown trout (Salmo trutta f. fario) from fertilized egg until the end of sac-fry stage and studied effects in juvenile fish six months post hatch. Embryos were exposed to five test concentrations (0.1, 0.5, 1, 10, 100μg/L) over 127days at 7°C. None of the treatments affected mortality, hatching, development or heart rate. Six months old juveniles exposed to five concentrations (0.1, 1, 10, 100, 200μg/L) over 25days at 7°C, however, showed increased mortality, reaching significance at 100μg/L. Furthermore, a significantly higher proportion of juvenile animals bore injuries at concentrations higher 10μg/L. Neither the levels of the stress protein Hsp70, nor the amount of lipid peroxides was affected by any of the treatments. Histological analyses of gill, liver and kidney revealed visible tissue reactions in fish from all experimental groups. Histological responses in livers of diclofenac-exposed fish outstripped the status of laboratory control fish, particularly when exposed to the two highest concentrations. Chemical analyses of fish muscle tissue revealed concentration-dependent uptake of DCF into the animal, but no relevant bioconcentration. Our study supports earlier findings indicating a lower sensitivity of trout early life stages compared to older individuals, suggesting that studies for risk assessment of diclofenac should predominantly focus on later life stages. Furthermore, fish mortality was found to increase with rising diclofenac concentrations, and the lowest observed effect concentration of 10μg/L on the organismic level emphasises the classification of diclofenac as a micropollutant that requires close attention.

The effect of hydraulic flowback and produced water on gill morphology, oxidative stress and antioxidant response in rainbow trout (Oncorhynchus mykiss)

Hydraulic fracturing fluid are complex mixtures containing high concentrations of salts (up to 330,000 ppm), organic, and metal contaminants. However, little data exist on the potential mechanisms of toxicity of these flowback and produced wastewaters (FPW) on aquatic biota. Juvenile rainbow trout were exposed to either control, FPW (2.5 or 7.5%), FPW that had been treated with activated charcoal (AC), or a custom salt-matched control (SW; replicating only the salt content of FPW) for 48 hours. Gill histology revealed decreases in interlamellar cell mass (ILCM) and mean lamellar length in all treatments (FPW, AC and SW) compared to control, indicative of hyperosmotic stress. Liver CYP1A1 activity was significantly elevated by 7.5-fold in the FPW 7.5% treatment only, indicative of Phase I metabolism. Superoxide dismutase activity significantly decreased in the gills to all treatments with the lowest activity occurring in the 7.5% FPW group. Catalase activity increased in liver with the highest values noted in fish exposed to 7.5% FPW. No changes were observed with respect to glutathione-S-transferase, while increased lipid peroxidation was only observed in both FPW treatments (2.5, 7.5%). These data suggest a characteristic signature of FPW impact which may help in risk assessment and biomonitoring of FPW spills.

The Effects of Salicylic Acid on Juvenile Zebrafish Danio rerio Under Flow-Through Conditions

The aquatic environment is becoming increasingly contaminated with pharmaceuticals. Salicylic acid (SA), which can be used individually or appear as a degradation product of the widely used acetylsalicylic acid was chosen for testing. Juvenile zebrafish Danio rerio were subjected to OECD test No. 215 (fish, juvenile growth test) with salicylic acid concentrations of 0.004; 0.04; 0.4; 4 and 40 mg/L. Specific growth rate (SGR), histological changes, and parameters of oxidative stress were evaluated. SA had no effects on histological changes, SGR, glutathione reductase, and lipid peroxidation. Increased catalytic activity of GPx was found at 0.04 mg/L compared to control, increased catalytic activity of catalase was found at 0.04 and 4 mg/L compared to control, and increased catalytic activity of glutathione-S-transferase was found at 0.004 and 0.04 mg/L compared to control (P < 0.05). Juvenile zebrafish turned out to be relatively insensitive to both environmentally relevant (0.004 mg/L) and higher concentrations of salicylic acid.

Effects of chronic exposure to benzalkonium chloride in Oncorhynchus mykiss: cholinergic neurotoxicity, oxidative stress, peroxidative damage and genotoxicity

Benzalkonium chloride (BAC) is one of the most used conservatives in pharmaceutical preparations. However, its use is limited to a small set of external use formulations, due to its high toxicity. Benzalkonium chloride effects are related to the potential exertion of deleterious effects, mediated via oxidative stress and through interaction with membrane enzymes, leading to cellular damage. To address the ecotoxicity of this specific compound rainbow trouts were chronically exposed to BAC at environmental relevant concentrations (ranging from 0.100 to 1.050mg/L), and the biological response of cholinergic neurotoxicity, modulation of the antioxidant defense, phase II metabolism, lipid peroxidation and genotoxicity was studied. The obtained results showed a dual pattern of antioxidant response, with significant alterations in catalase activity (starting at 0.180mg/L), and lipid peroxidation, for intermediate (0.180 and 0.324mg/L) concentrations. No significant alterations occurred for glutathione-S-transferases activity. An unexpected increased of the acetylcholinesterase activity was also recorded for the individuals exposed to higher concentrations of BAC (starting at 0.180mg/L). Furthermore, exposure to BAC resulted in the establishment of genotoxic alterations, observable (for the specific case of the comet assay results) for all tested BAC concentrations. However, and considering that the oxidative response was not devisable, other mechanisms may be involved in the genotoxic effects reported here.

Chronic Effects of Realistic Concentrations of Non-essential and Essential Metals (Lead and Zinc) on Oxidative Stress Biomarkers of the Mosquitofish, Gambusia holbrooki

Metallic contamination is widespread, particularly in areas impacted by human activities. Human activities result in high loads of metals being discarded into the aquatic compartment, reinforcing the need to evaluate their toxic effects especially on exposed fish. The purpose of this study was to determine the toxic response (namely, antioxidant levels and lipoperoxidative damage) in both liver and gills of the freshwater fish species Gambusia holbrooki, exposed to lead and zinc. Fish were exposed for 28 days (chronic exposure) to ecologically relevant concentrations of the selected compounds. The following oxidative stress/damage biomarkers were evaluated: glutathione-S-transferases (GSTs), glutathione reductase (GR), and thiobarbituric acid reactive substances (TBARS). The results indicate that lead caused a significant oxidative response, with significant increase of the enzymatic antioxidant defense (GSTs activity in hepatic tissue, and GR activity in branchial tissue) of exposed organisms. On the other hand, zinc caused a significant inhibition of G. holbrooki hepatic GR, a biological response that may be related to the antioxidant activity exhibited by this metal. The obtained results are of high importance, especially if one considers that the obtained toxic responses occurred at low, albeit ecologically relevant, levels of exposure.