Biomarker responses in fish exposed to polycyclic aromatic hydrocarbons (PAHs): Systematic review and meta-analysis

Exposure of Polycyclic Aromatic Hydrocarbons (PAHs) and Crude Oil to Atlantic Haddock (Melanogrammus aeglefinus): A Unique Snapshot of the Mercapturic Acid Pathway

Fish exposed to xenobiotics like petroleum-derived polycyclic aromatic hydrocarbons (PAHs) will immediately initiate detoxification systems through effective biotransformation reactions. Yet, there is a discrepancy between recognized metabolic pathways and the actual metabolites detected in fish following PAH exposure like oil pollution. To deepen our understanding of PAH detoxification, we conducted experiments exposing Atlantic haddock (Melanogrammus aeglefinus) to individual PAHs or complex oil mixtures. Bile extracts, analyzed by using an ion mobility quadrupole time-of-flight mass spectrometer, revealed novel metabolites associated with the mercapturic acid pathway. A dominant spectral feature recognized as PAH thiols set the basis for a screening strategy targeting (i) glutathione-, (ii) cysteinylglycine-, (iii) cysteine-, and (iv) mercapturic acid S-conjugates. Based on controlled single-exposure experiments, we constructed an interactive library of 33 metabolites originating from 8 PAHs (anthracene, phenanthrene, 1-methylphenanthrene, 1,4-dimethylphenanthrene, chrysene, benz[a]anthracene, benzo[a]pyrene, and dibenz[a,h]anthracene). By incorporation of the library in the analysis of samples from crude oil exposed fish, PAHs conjugated with glutathione and cysteinylglycine were uncovered. This qualitative study offers an exclusive glimpse into the rarely acknowledged mercapturic acid detoxification pathway in fish. Furthermore, this furnishes evidence that this metabolic pathway also succeeds for PAHs in complex pollution sources, a notable discovery not previously reported.

In vitro impacts of polystyrene microplastics and environmental pollutants on ethoxyresorufin-O-deethylase and glutathione S-transferase activity in Mossambica tilapia

Microplastic (MP) pollution is a potential threat to marine organisms. In vitro toxicity of MPs and other pollutants, such as pharmaceutically active compounds (PhACs) and brominated flame retardants (BFRs), has been understudied. This study aimed to investigate the effects of polystyrene microplastics (PS-MPs) with different particle sizes on two biomarkers: ethoxyresorufin-O-deethylase (EROD) and glutathione S-transferase (GST) in tilapia liver homogenates. The study also examined the combined effects of PS-MPs with various environmental contaminants, including three metal ions (Cu2+, Zn2+, Pb2+), three BFRs, and six PhACs. PS-MPs alone had no remarkable effects on the two biomarkers at the selected concentrations. However, PS-MPs combined with other pollutants significantly affected the two biomarkers in most situations. For EROD activity, PS + metal ions (except Zn2+ at 1000 μg/L), PS + BFRs (except decabromodiphenyl oxide (BDE-209)) or PS+ trimethoprim (TMP) significantly inhibited activity values, whereas PS+ 4-acetaminophen (AMP) induced EROD activity. For GST, PS together with most tested pollutants (except PS+ ibuprofen (IBF)) greatly decreased the activities. Accordingly, future research should focus on combined toxicity of mixtures to set more reasonable environmental safety evaluation standards.

Assessment of the Aryl Hydrocarbon Receptor-Mediated Effects of Aromatic Sensitizers in Paper Recycling Effluent Employing Zebrafish Embryos and in Silico Docking

Aromatic sensitizers and related substances (SRCs), which are crucial in the paper industry for facilitating color-forming and color-developing chemical reactions, inadvertently contaminate effluents during paper recycling. Owing to their structural resemblance to endocrine-disrupting aromatic organic compounds, concerns have arisen about potential adverse effects on aquatic organisms. We focused on SRC effects via the aryl hydrocarbon receptor (AHR), employing molecular docking simulations and zebrafish (Danio rerio) embryo exposure assessments. Molecular docking revealed heightened binding affinities between certain SRCs in the paper recycling effluents and zebrafish Ahr2 and human AHR, which are pivotal components in the SRC toxicity mechanism. Fertilized zebrafish eggs were exposed to SRCs for up to 96 h post fertilization; among these substances, benzyl 2-naphthyl ether (BNE) caused morphological abnormalities, such as pericardial edema and shortened body length, at relatively low concentrations (1 μM) during embryogenesis. Gene expression of cytochrome P450 1A (cyp1a) and ahr2 was also significantly increased by BNE. Co-exposure to the AHR antagonist CH-223191 only partially mitigated BNE's phenotypic effects, despite the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin being relatively well restored by CH-223191, indicating BNE's AHR-independent toxic mechanisms. Furthermore, some SRCs, including BNE, exhibited in silico binding affinity to the estrogen receptor and upregulation of cyp19a1b gene expression. Therefore, additional insights into the toxicity of SRCs and their mechanisms are essential. The present results provide important information on SRCs and other papermaking chemicals that could help minimize the environmental impact of the paper industry. Environ Toxicol Chem 2024;00:1-13. © 2024 SETAC.

Meta-analytical review of antioxidant mechanisms responses in animals exposed to herbicide 2,4-D herbicide

The 2,4-Dichlorophenoxyacetic acid (2,4-D) is a low-cost herbicide to eradicate broadleaf weeds. Since the development of 2,4-D resistant transgenic crops, it has been described as one of the most widely distributed pollutants in the world, increasing concern about its environmental impacts. This study aimed to elucidate the antioxidant system response in animals exposed to 2,4-D by different routes of exposure. It focused on determining if tissue, phylogenetic group, and herbicide formulation would influence the antioxidant mechanisms. A careful literature search of Scopus, WoS, and Science Direct retrieved 6983, 24,098, and 20,616 articles, respectively. The dataset comprised 390 control-treatment comparisons and included three routes of exposure: transgenerational, oral, and topical. The data set for transgenerational and oral exposure revealed oxidative stress through a decrease in enzymatic activities and the level of molecules of the antioxidant system. In contrast, topical exposure increased the oxidative stress. Tissue-specific analyses revealed that the transgenerational effects reduced hepatic catalase (CAT) activity. Oral exposure caused a variety of effects, including increased CAT activity in the prostate and decreased activity in various tissues. Mammals predominate in the transgenerational and oral groups, showing a significantly reduced activity of the antioxidant system. In contrast, in the topical exposure, an increased activity of oxidative stress biomarkers was observed in fish, earthworms, and mollusks. The effects of the 2,4-D formulation on oxidative stress responses showed significant differences between pure and commercial formulations, with oral exposure resulting in decreased activity and topical exposure increasing responses. In summary, orally exposed animals exhibited a clear decrease in enzyme activities, transgenerational exposure elicited tissue-specific prompted biochemical reductions, and topical exposure induced increased responses, emphasizing the need for unbiased exploration of the effects of 2,4-D on biomarkers of oxidative stress while addressing publication bias in oral and topical datasets.

The bioremediation of the typical persistent organic pollutants (POPs) by microalgae-bacteria consortia: A systematic review

With industrialisation and the rapidly growing agricultural demand, many organic compounds have been leaked into the environment, causing serious damage to the biosphere. Persistent organic pollutants (POPs) are a type of toxic chemicals that are resistant to degradation through normal chemical, biological or photolytic approaches. With their stable chemical structures, POPs can be accumulated in the environment, and transported through wind and water, causing global environmental issues. Many researches have been conducted to remediate POPs contamination using various kinds of biological methods, and significant results have been seen. Microalgae-bacteria consortium is a newly developed concept for biological technology in contamination treatment, with the synergetic effects between microalgae and bacteria, their potential for pollutants degradation can be further released. In this review, two types of POPs (polychlorinated biphenyls and polycyclic aromatic hydrocarbons) are selected as the targeted pollutants to give a systematic analysis of the biodegradation through microalgae and bacteria, including the species selection, the identification of dominant enzymes, as well as the real application performance of the consortia. In the end, some outlooks and suggestions are given to further guide the development of applying microalgae-bacteria consortia in remediating POPs contamination. In general, the coculturing of microalgae and bacteria is a novel and efficient way to fulfil the advanced treatment of POPs in soil or liquid phase, and both monooxygenase and dioxygenase belonging to oxygenase play a vital role in the biodegradation of PCBs and PAHs. This review provides a general guide in the future investigation of biological treatment of POPs.

Can environmental factors increase oxidative responses in fish exposed to polycyclic aromatic hydrocarbons (PAHs)?

Relations among polycyclic aromatic hydrocarbons (PAHs), biomarkers of oxidative stress (lipid peroxidation, glutathione, and glutathione S-transferase activity), and the possible influence of environmental factors (temperature, pH, and salinity) were assessed in situ for specimens of Ramnogaster arcuata, a native estuarine fish. PAH levels found in the muscular tissue of R. arcuata ranged from 0.7 to 293.4 ng g-1 wet weight with petrogenic and pyrolytic inputs. Lipid peroxidation in the liver showed positive correlations (P < 0.05) with total PAHs (r = 0.66), 3-ring (r = 0.66) and 4-ring PAHs (r = 0.52) and glutathione in muscle (r = 0.58). Significant positive correlations (P < 0.05) were also evidenced between muscular glutathione with total (r = 0.62) and 3-ring PAHs (r = 0.75). Hepatic glutathione S-transferase negatively correlated with 4-ring PAHs (r = -0.58). These correlations suggest that lipid peroxidation and muscular glutathione could be good biomarkers for complex mixtures of PAHs, and hepatic glutathione S-transferase could be a suitable biomarker for 4-ring PAHs. Furthermore, significant correlations (P < 0.05) of environmental factors with PAH levels and biomarkers were observed, especially pH with 3-ring PAHs (r = -0.65), lipid peroxidation (r = -0.6), glutathione in the liver (r = -0.73) and muscle (r = -0.75); and temperature with 2-ring PAHs (r = -0.75) and glutathione in muscle (r = 0.51). The data suggest an influence of physicochemical parameters which could be driving a shift in PAH toxicity in R. arcuata. These results are essential for an integrated understanding of ecotoxicology and could help to predict environmental effects in present and future scenarios of ocean warming and acidification.

Mechanisms of the novel pesticide sodium dodecyl benzene sulfonate in the mitigation of protozoan ciliated pathogens during microalgal cultivation

Protozoan ciliates represent a common biological contaminant during microalgae cultivation, which will lead to a decline in microalgae productivity. This study investigated the effectiveness of sodium dodecyl benzene sulfonate (SDBS) in controlling ciliate populations within microalgae cultures. SDBS concentrations of 160 mg/L and 100 mg/L were found to effectively manage the representative species of ciliates contamination by Euplotes vannus and Uronema marinum during the cultivation of Synechococcus and Chlorella, and the growth vitality of microalgae has been restored. Additionally, SDBS at these concentrations reduced oxidative stress resistance and induced membrane damage to remove biological pollutants by modulating enzyme activity, affecting lipid, energy, amino acid metabolism pathways, and processes such as translation and protein folding. This research provides insights into the mechanisms through which SDBS effectively combats protozoan ciliates during the microalgal cultivation. This contributes to reduce biological pollution, ensure the overall productivity and healthy and sustainable management of microalgae ecosystems.

Relevance of flounder caging and proteomics to explore the impact of a major industrial accident caused by fire on the Seine estuarine water quality

On September 26th 2019, a major fire occurred in the Lubrizol factory located near the Seine estuary, in Rouen-France. Juvenile flounders were captured in the Canche estuary (a reference system) and caged one month in the Canche and in the Seine downstream the accident site. No significant increases of PAHs, PCBs and PFAS was detected in Seine vs Canche sediments after the accident, but a significant increase of dioxins and furans was observed in water and sewage sludge in the Rouen wastewater treatment plant. The proteomics approach highlighted a dysregulation of proteins associated with cholesterol synthesis and lipid metabolism, in fish caged in the Seine. The overall results suggested that the fire produced air borne dioxins and furans that got deposited on soil and subsequently entered in the Seine estuarine waters via runoff; thus contaminating fish preys and caged flounders in the Seine estuary.

Occurrence, sources and risk assessment of polycyclic aromatic hydrocarbons in the coral reef waters of the Lakshadweep Archipelago, Arabian Sea

The compound effects of anthropogenic disturbances on global and local scales threaten coral reef ecosystems of the Arabian Sea. The impacts of organic pollutants on the coral reefs and associated organisms have received less attention and are consequently less understood. This study examines the background levels, sources, and ecological implications of polycyclic aromatic hydrocarbons (PAHs) in the coral reef ecosystems of Lakshadweep Archipelago. Water and particulate matter were collected from four coral Islands (Kavaratti, Agatti, Bangaram and Perumal Par) of Lakshadweep Archipelago during January and December 2022 and analysed for 15 PAHs priority pollutants. The 15 PAHs congeners generally ranged from 2.77 to 250.47 ng/L in the dissolved form and 0.44 to 6469.86 ng/g in the particulate form. A comparison of available data among the coral reef ecosystems worldwide revealed relatively lower PAHs concentrations in the Lakshadweep coral ecosystems. The isomeric ratios of individual PAH congeners and principal component analysis (PCA) indicate mixed sources of PAHs in the water column derived from pyrogenic, low-temperature combustion and petrogenic. The risk quotient (RQ) values in the dissolved form indicate moderate risk to the aquatic organisms, while they indicate moderate to severe risk in the particulate form.

Nondestructive Evaluation of Metal Bioaccumulation and Biochemical Biomarkers in Blood of Broad-Snouted Caiman (Caiman latirostris) from Northeastern Brasil

Studies on the bioaccumulation and toxicity of contaminants in Crocodylians are scarce. We evaluated alterations in concentrations of the nondestructive biomarkers butyrylcholinesterase (BChE), glutathione-S-transferase (GST), superoxide dismutase (SOD), and reduced glutathione (GSH), together with bioaccumulation of the metals iron (Fe), copper (Cu), zinc (Zn), manganese (Mn), chronium (Cr), aluminium (Al), and lead (Pb) in Caiman latirostris captured in Tapacurá Reservoir (TR; São Lourenço da Mata, Pernambuco, Brasil), in urbanized areas of Pernambuco State (UA; Brasil) and from the AME Brasil caiman farm (AF; Marechal Deodoro, Alagoas, Brasil); the latter was used as a potential reference with low levels of contamination. For metal analysis, 500 µL of blood was digested in 65% HNO3 and 30% H2 O2 . The samples were analyzed by inductively coupled plasma-optical emission spectrometry. For analysis of biomarkers, an aliquot of blood was centrifuged to obtain plasma in which biochemical assays were performed. Blood concentrations of metals analyzed in animals from AF were lower compared with TR and UA, confirming that animals from the caiman farm could be used as references with low levels of contamination. Iron, Cu, Mn, Al, and Pb exceeded toxic levels for other vertebrates in animals from TR and UA. Butyrylcholinesterase activity showed significant reduction in adults from UA and TR compared with AF. An increase in the activity of GST and GSH, in adults of TR and UA in relation to AF, was verified. Superoxide dismutase activity showed a significant reduction in adults of TR in relation to AF, and the concentrations of Cu and Mn were negatively correlated with SOD activity. Animals from UA and TR showed greater concentrations of the analyzed metals compared with reference animals, and changes in biomarkers were seen, confirming the potential of these nondestructive chemical and biological parameters in blood of C. latirostris for biomonitoring of pollution. Environ Toxicol Chem 2024;00:1-18. © 2024 SETAC.

The association between exposure to polycyclic aromatic hydrocarbons and birth outcomes: A systematic review and meta-analysis of observational studies

Exposure to polycyclic aromatic hydrocarbons (PAHs) has been linked to adverse birth outcomes; however, to date, the available studies on such relations, with the exception of birth weight, has not been systematically synthesized. We conducted a systematic review and meta-analysis of the available observational studies on the association of maternal exposure to PAHs and their metabolites during pregnancy with indicators of fetal growth and gestational age at delivery. We searched Web of Science, PubMed and Scopus systematically for all relevant published papers in English until 13 January 2023. Random effects meta-analysis was applied to synthesize the association estimates. Publication bias was assessed using Egger's regression. A total of 31 articles were included in our review (n = 703,080 participants). Our quality assessment of reviewed papers showed that 19 research had excellent, nine had good, and three had fair quality. Most of the reviewed studies on exposure to PAHs and their metabolites with gestational age and preterm birth (seven studies) reported no statistically significant association. Eight studies were eligible for our meta-analysis. Results of the meta-analysis indicated that higher levels of maternal urinary 1-OHP was associated with lower birth weight, birth length and head circumference and a higher risk of low birth weight (LBW). However, these associations were not statistically significant. Similarly, the combined association between maternal urinary 1-OHP and newborn's Ponderal index (PI) and Cephalization index were not statistically significant. Overall, our systematic review and meta-analysis suggested a potential adverse impact of exposure to PAHs on LBW, HC, and CC; however, further studies are required to be able to draw concrete conclusions on such associations.

Polycyclic aromatic hydrocarbons distribution in fish tissues and human health risk assessment on consumption of four fish species collected from Lagos Lagoon, Nigeria

Lagos Lagoon is a very popular lagoon in Lagos state that receives effluents from neighboring industries. These effluents tend to increase the level of contaminants in the lagoon, thereby creating more stressors for aquatic animals. Determination of polycyclic aromatic hydrocarbons (PAHs) in four commonly consumed fish species from the lagoon and the prediction of possible health risks associated with their consumption were performed in this study. Various levels of PAH were detected in the fish tissues with the highest total concentration of PAH in Sarothoredon melanotheron. High concentrations of benzo(a)pyrene were noticed in Sarothoredon melanotheron and Ethmalosa fimbriata, and their values were above the guideline value of 0.002 μg/g. The dietary daily intake (DDI) value in S. melanotheron 82.00 ×10-5 μg/g/day was highest. Carcinogenic toxic equivalents (TEQ) showed that consumption of S. melanotheron had higher potential to pose carcinogenic risks, while the excess cancer risk (ECR) index for the PAHs in all the assessed fish species was beyond threshold values indicating potential carcinogenic risk from their consumption. No significant association was found between the concentration of PAHs and the size of the fish. Target hazard quotient (THQ) results suggested absence of potential non-carcinogenic risk if individual PAH in the fish are consumed frequently. The study however established possible carcinogenic human health risk from consumption of the fish obtained from Lagos Lagoon. The study recommends monitoring of contamination and consumption of fish from harvest sites within the study region.

Functional and molecular characterization of the Atlantic salmon gill epithelium cell line ASG-10; a tool for in vitro gill research

Fish gills are not only the respiratory organ, but also essential for ion-regulation, acid-base control, detoxification, waste excretion and host defense. Multifactorial gill diseases are common in farmed Atlantic salmon, and still poorly understood. Understanding gill pathophysiology is of paramount importance, but the sacrifice of large numbers of experimental animals for this purpose should be avoided. Therefore, in vitro models, such as cell lines, are urgently required to replace fish trials. An Atlantic salmon gill epithelial cell line, ASG-10, was established at the Norwegian Veterinary institute in 2018. This cell line forms a monolayer expressing cytokeratin, e-cadherin and desmosomes, hallmarks of a functional epithelial barrier. To determine the value of ASG-10 for comparative studies of gill functions, the characterization of ASG-10 was taken one step further by performing functional assays and comparing the cell proteome and transcriptome with those of gills from juvenile freshwater Atlantic salmon. The ASG-10 cell line appear to be a homogenous cell line consisting of epithelial cells, which express tight junction proteins. We demonstrated that ASG-10 forms a barrier, both alone and in co-culture with the Atlantic salmon gill fibroblast cell line ASG-13. ASG-10 cells can phagocytose and express several ATP-binding cassette transport proteins. Additionally, ASG-10 expresses genes involved in biotransformation of xenobiotics and immune responses. Taken together, this study provides an overview of functions that can be studied using ASG-10, which will be an important contribution to in vitro gill epithelial research of Atlantic salmon.

The goby fish Sicydium spp. as valuable sentinel species towards the chemical stress in freshwater bodies of West Indies

Implementation of the European Water Framework Directive in tropical areas such as the French West Indies (FWI) requires to select relevant aquatic sentinel species for investigating the ecological status of surface waters. The present work aimed to study the biological response of the widespread fish Sicydium spp. towards river chemical quality in Guadeloupe island through a set of proper biomarkers. During a 2-year survey, the hepatic EROD activity, the micronucleus formation and the level of primary DNA strand breaks in erythrocytes were measured respectively as an enzymatic biomarker of exposure and genotoxicity endpoints in fish living upstream and downstream of two chemically-contrasted rivers. Hepatic EROD activity was shown to be variable along the time but always significantly higher in fish from the most contaminated river (Rivière aux Herbes) compared to the low contaminated one (Grande Rivière de Vieux-Habitants). Fish size did not influence EROD activity. Female fish exhibited a lower EROD activity compared to males depending on the catching period. We observed significant temporal variation in micronucleus frequency and primary DNA damage level measured in fish erythrocytes that did not depend on the fish size. Micronucleus frequency and to a lesser extent DNA damage were significantly higher in fish from the Rivière aux Herbes compared to the Grande Rivière de Vieux-Habitants. Our results argue for the interest of using Sicydium spp. as sentinel species to assess river quality and chemical pressures in FWI.

Acute toxicity of organoarsenic chemical warfare agents to Danio rerio embryos

During the 20th century, thousands of tons of munitions containing organoarsenic chemical warfare agents (CWAs) were dumped into oceans, seas and inland waters around the world. As a result, organoarsenic CWAs continue to leak from corroding munitions into sediments and their environmental concentrations are expected to peak over the next few decades. There remains, however, a lack of knowledge about their potential toxicity to aquatic vertebrates, such as fish. The aim of this study was to fill in this gap in research, by investigating the acute toxicity of organoarsenic CWAs on fish embryos, using the model species, Danio rerio. To estimate the acute toxicity thresholds of organoarsenic CWAs (Clark I, Adamsite, PDCA), a CWA-related compound (TPA), as well as four organoarsenic CWA degradation products (Clark I[ox], Adamsite[ox], PDCA[ox], TPA[ox]), standardized tests were performed following the OECD no. 236 Fish Embryo Acute Toxicity Test guidelines. Additionally, the detoxification response in D. rerio embryos was investigated by analysing the mRNA expression of five genes encoding antioxidant enzymes (CAT, SOD, GPx, GR and GST). During the 96 h of exposure, organoarsenic CWAs induced lethal effects in D. rerio embryos at very low concentrations (classified as 1st category pollutants according to GHS categorization), and were therefore deemed to be serious environmental hazards. Although TPA and the four CWA degradation products caused no acute toxicity even at their maximum solubility, the transcription of antioxidant-related genes was altered upon exposure to these compounds, indicating the need for further testing for chronic toxicity. Incorporating the results of this study into ecological risk assessments will provide a more accurate prediction of the environmental hazards posed by CWA-related organoarsenicals.

Comparative analysis of two new zebrafish models: The cyp1a low-expression line and cyp1a knockout line under PAHs exposure

Cytochrome P450 1 (CYP1) is an important enzyme family involved in the metabolism of pollutants, and used as a biomarker to monitor environmental pollution. In this study, a fluorescence-labeled cyp1a zebrafish line, named as KI (cyp1a^+/+-T2A-mCherry) (KICM), was originally constructed to monitor dioxin-like compounds in the environment. However, the cyp1a gene expression in the KICM line was inhibited by the fluorescence labeling, thus leading to a significantly increased sensitivity of KICM zebrafish line to PAHs. Then, a cyp1a knockout zebrafish line, named KOC, were constructed for comparative analysis with the cyp1a low-expression line. Interestingly, knockout of the cyp1a gene did not increase the sensitivity of zebrafish to PAHs as significantly as the cyp1a low-expression line. So, the expression levels of related genes in the aryl hydrocarbon receptor pathway were analyzed and the results showed that the expression level of cyp1b in KOC group was significantly higher than that of wild type and KICM under the same PAH exposure. This indicated that the effect of losing cyp1a was compensated by inducing expression of cyp1b. In conclusion, two new zebrafish models including cyp1a low-expression line and cyp1a knockout line were constructed in this study, which may provide a convenient model for subsequent studies on the toxicity mechanism of PAHs and the role of cyp1a in detoxification.

Impacted estuaries on the Brazilian Amazon coast near port regions influence histological and enzymatic changes in Sciades herzbergii (Ariidae, Bloch, 1794)

Enzymatic (glutathione S-transferase, GST and catalase, CAT) and histological biomarkers in S. herzbergii are important for the analysis of impacted estuaries in port regions of the Brazilian Amazon coast. Fish specimens were collected in two areas in the rainy and dry seasons: Porto Grande (potentially impacted region) and Ilha dos Caranguejos (less impacted region). Sediment samples were collected for chemical analysis. Morphometric, histological, and enzymatic biomarker analyzes were performed. The analysis of the sediments collected in the potentially impacted region showed levels of iron, aluminum and polycyclic aromatic hydrocarbons above the limits allowed by CONAMA legislation. Histological changes in the gills and liver, as well as GST and CAT activities, were high in fish collected at the port. Analyzes suggest that fish in the potentially impacted region are subject to pollutants that compromise their health.

First study of bromophenols and hexabromocyclododecanes in seafood from North Africa (case of Bizerte Lagoon, Tunisia): occurrence and human health risk

In spite of the fact that bromophenols (BPs) and hexabromocyclododecanes (HBCDs) are widely used as flame retardants, no data was available until now on the levels of these two chemicals in North Africa biota. Seafood products might represent one of the main sources of dietary exposure to persistent organic pollutants such as non-dioxin-like polychlorinated biphenyls (ndl-PCBs), brominated flame retardants (BFRs), and polycyclic aromatic hydrocarbons (PAHs). In this study, the concentrations of the ndl-PCBs, PAH₄, and BFRs were determined in seafood products from a North African lagoon (Bizerte lagoon). Almost all the compounds were detected (15 out of 18) in the analyzed marine organisms. The accumulation of the contaminants followed the order BFRs > ndl-PCB > PAH₄. Mean contaminants concentrations ranged from 0.35 to 28.7 ng g^-1 ww for ∑ndl-PCBs; from below limit of quantification to 476 ng g^-1 ww for ∑BFRs and from below limit of quantification to 5.30 ng g^-1 ww for ∑PAH₄. PCB 138, 153, and 180 were the most frequently detected ndl-PCB congeners due to their high resistance to metabolic degradation. 2,4-dibromophenol (2,4-DBP) was the predominant BFR. Chrysene (Chr) was found to be the main contributor to the total PAH₄ concentration. Contaminant profiles varied significantly among seafood which may be due to the difference in lipid content, trophic level, feeding behavior, and metabolism. To assess the human health risks, the average daily dose exposure of ndl-PCBs, the dietary daily intake of PAHs and the estimated dietary intake of 3,3-,5,5-tetrabromobisphenol A (TBBPA) and HBCD from seafood were estimated. Findings indicated no adverse effects for human health from any of the analyzed contaminants, except for ndl-PCBs in eel.

Changes in metabolic profiles of amphipods Allorchestes compressa after acute exposures to copper, pyrene, and their mixtures

Amphipods are ideal indicators for biomonitoring and ecotoxicological studies of environmental contaminants because they are extensively distributed in aquatic environments, are easy to collect and are important in nutrient cycling. Marine amphipods (Allorchestes compressa) were exposed to two concentrations of copper and pyrene, and their mixtures, for 24 and 48 h. Changes in polar metabolites were assessed using Gas Chromatography Mass Spectrometry (GC-MS)-based untargeted metabolomics. Generally, limited metabolite changes were observed for copper and pyrene single exposures (eight and two significant metabolites, respectively), while 28 metabolites had changed following exposures to mixtures. Furthermore, changes were mainly observed after 24 h but had seemingly returned to control levels after 48 h. Multiple types of metabolites were affected including amino acids, Tricarboxylic acid (TCA) cycle intermediates, sugars, fatty acids, and hormones. This study highlights the sensitivity of metabolomics in assessing the impacts of low concentrations of chemicals compared to traditional ecotoxicological endpoints.

Environmental risk assessment of petrogenic hydrocarbon spills in mangrove ecosystems: the Tumaco case study as a baseline, Colombian Pacific

Petrogenic hydrocarbon spills (PHS) are harmful to mangrove ecosystems along tropical coastlines in the short and long term. The aim of this study was to assess the environmental risk of recurrent PHS on mangrove ecosystems in Tumaco municipality, Colombian Pacific. Mangrove characteristics and management aspects led to subdividing the study area into 11 units-of-analysis (UAs) for which threats, vulnerability, potential impacts, and risks were assessed based on environmental factors and the formulation and use of indicators in a rating scale with five categories, which are very low, low, moderate, high, and very high. The results showed that all UAs are highly (64%; 15,525 ha) or moderately (36%; 4,464 ha) threatened by PHS, highly (45%; 13,478 ha) or moderately (55%; 6,511 ha) vulnerable to this kind of pollution, and susceptible to high (73%; 17,075 ha) or moderate (27%; 2,914 ha) potential impacts. The environmental risk was high in 73% (17,075 ha) of the UAs, indicating likely irreversible damage to mangrove ecosystems by PHS, thus pointing to the need of urgent intervention by responsible authorities to ease their recovery and conservation. The methodology and results of this study become technical inputs that serve for environmental control and monitoring, which can be incorporated into contingency and risk management plans.

Meta-analysis reveals the species-, dose- and duration-dependent effects of cadmium toxicities in marine bivalves

Cadmium (Cd) is a typical pollutant in marine environment. Increasing studies have focused on the toxicological effects of Cd in marine bivalves. However, there were many conflicting findings of toxicological effects of Cd in marine bivalves. An integrated analysis performed on the published data of Cd toxicity in marine bivalves is still absent. In this study, a meta-analysis was performed on the toxic endpoints in bivalves exposed to aqueous-phase Cd from 87 studies screened from 1519 papers. Subgroup analyses were conducted according to the categories of species, tissue, exposure dose and duration. The results showed significant species-, duration- and dose-dependent responses in bivalves to aqueous-phase Cd exposure. In details, clams were more sensitive to Cd than oysters, mussels and scallops, indicated by the largest effect size in clams. Gill, hepatopancreas and hemolymph were top three tissues used to indicate Cd-induced toxicity and did not present a significant tissue-specific manner among them. With regard to toxicological effect subgroups, oxidative stress and detoxification were top two subgroups indicating Cd toxicities. Detoxification and genotoxicity subgroups presented higher response magnitudes. What is more, toxicological effect subgroups presented multiple dose- and duration-dependent curves. Oxidative stress and genotoxicity related endpoints presented significant increase trends with Cd exposure dose and were preferable biomarkers to marine Cd pollution. Detoxification and energy metabolism related endpoints showed inverted U-shaped and U-shaped dose-response curves, both of which could be explained by hormesis. The linear decrease in oxidative stress and energy metabolism related endpoints over time suggested their involvement into the adaptive mechanism in bivalves. Overall, this study provided not only a better understanding the responsive mechanisms of marine bivalves to Cd stress, but also a selection reference for biomarkers to aqueous-phase Cd pollution in marine environment.

Early developmental toxicity of Atlantic salmon exposed to conventional and unconventional oils

Atlantic salmon is an important species for Canadian culture and economy and its importance extends beyond Canada to Scandinavia and Western Europe. However, it is a vulnerable species facing decline due to habitat contamination and destruction. Existing and new Canadian pipeline projects pose a threat to salmonid habitat. The effects of diluted bitumen (dilbit), the main oil circulating in pipelines, are less studied than those of conventional oils, especially during the critical early embryonic developmental stage occurring in freshwater ecosystems. Therefore, this study aimed to compare the effects of water-accommodated fractions (WAF) of the Clearwater McMurray dilbit and the Lloydminster Heavy conventional oil on Atlantic salmon embryos exposed either from fertilization or from eyed stage. The dilbit contained the highest concentrations of low molecular weight (LMW) compounds (including BTEX and C₆-C₁₀), while the conventional oil contained the highest concentrations of PAHs. The Clearwater dilbit caused a higher percentage of mortality and malformations than the conventional oil at similar WAF concentrations. In addition, the embryos exposed from fertilization suffered a higher mortality rate, more developmental delays, and malformations than embryos exposed from the eyed stage, suggesting that early development is the most sensitive developmental stage to oil exposure. Gene expression and enzymatic activity of the detoxification phase I and II enzymes (CYP1A and GST) were measured. Data showed increases in both cyp1a expression and GST activity with increasing WAF concentrations, while gst expression was not affected by the exposures. Also, gene expression of proteins involved in the biotransformation of vitamin A and DNA damage repair were modified by the oil exposures. Overall, this study indicates that Atlantic salmon is mostly affected by oil exposure at the beginning of its development, during which embryos accumulate deformities that may impact their survival at later life stages.

Interaction of Polycyclic Aromatic Hydrocarbon compounds in fish primary hepatocytes: From molecular mechanisms to genotoxic effects

Polycyclic Aromatic Hydrocarbons (PAHs) are persistent pollutants normally found in the environment as complex mixtures. Although several individual PAHs are classified as mutagenic and carcinogenic pollutants, the interaction effects between compounds in a mixture may trigger different toxicological mechanisms and, consequently, yield different effects to organisms which are not accounted for in risk assessment guidelines. Given the ubiquity of PAHs, understanding the mechanistic features of their mixtures is a pressing research need. Therefore, the present work aimed to disclose the interaction effects of three PAHs with different carcinogenic potential and chemical structure, in primary hepatocyte cells of gilt-headed seabreams (Sparus aurata). Hepatocytes were exposed to Phenanthrene (Phe), Benzo[a]pyrene (B[a]P) and Benzo[b]fluoranthene (B[b]F) and their mixtures at different proportions and several cellular responses were analyzed: cellular viability, CYP1A1 activity (EROD assay) and protein expression level (Western blot); transcript (mRNA) levels of CYP1A1, EPXH1 and GST-3 (qRT-PCR); genotoxic effects (DNA strand breakage) by the Comet assay. Results show that B[a]P induced CYP1A1 gene and protein expression increasing its activity and, therefore, increasing the production of metabolites that trigger genotoxic DNA damage (%). Most importantly, mixtures containing Phe and B[a]P increased even further CYP1A1 mRNA levels and DNA damage (up to 70 %) which suggests that, although Phe is considered a non-carcinogenic PAH, it potentiates CYP1A1 synthesis induced by B[a]P, increasing its genotoxicity. These findings indicate that the upregulation of CYP1A1 by carcinogenic PAHs will not weaken even when in mixtures with non-carcinogenic PAHs. On contrary, non-carcinogenic PAHs may potentiate the genotoxic effect of carcinogenic PAH and therefore mixture composition should be taken in account when assessing PAH toxicity. In fact, our results point to the need of redefining Environmental Risk Assessment protocols for mixtures of carcinogenic pollutants.

Field validated biomarker (ValidBIO) based assessment of impacts of various pollutants in water

The sensitivity of fish towards pollutants serves as an excellent tool for the analysis of water pollution. The effluents generated from various anthropogenic activities may contain heavy metals, pesticides, microplastics, and persistent organic pollutants (POPs) and ultimately find its way to aquatic environment. The enzymatic activities of fish collected from water bodies near major cities, oil spillage sites, agricultural land, and intensively industrialized areas have been reported to be significantly impacted in various field studies. These significant alterations in enzymatic activities act as a biomarker for monitoring purposes. The use of biomarkers not only helps in the identification of known and unknown pollutants and their detrimental health impacts, but also identifies the interaction between pollutants and organisms. The conventional method majorly used is physicochemical analysis, which is recognized as the backbone of the system for monitoring water quality. In physicochemical monitoring, major problems exist in assessing or predicting biological effects from chemical or physical data. Xenobiotic-induced enzymatic changes in fish may serve as an intuitive and efficient biomarker for determining contaminants in water bodies. Therefore, field validated biomarker (ValidBIO) approach needs to be integrated in water quality monitoring program for environmental health risk assessment of aquatic life impacted due to various point and non-point sources of water pollution.

The scleractinian coral Pocillopora damicornis relies on neuroendocrine regulation to cope with polycyclic aromatic hydrocarbons under heat stress

Polycyclic aromatic hydrocarbons (PAHs) are highly toxic environmental pollutants and are threatening scleractinian corals. In this study, PAHs treatment did not induce significant physiological responses of the coral Pocillopora damicornis and its algal symbionts, but biological processes including response to toxin, drug metabolic, and oxidation reduction were triggered at the mRNA level. These results implied that PAHs could be a group of slow-acting environmental toxicants, whose effects were moderate but persistent. Besides, it was interesting to find that PAHs activated the neuroendocrine system in the coral by triggering the expression of monoaminergic and acetylcholinergic system related genes, indicating that PAHs might function as environmental hormones. Moreover, the combined treatments of PAHs and heat caused a much obvious effect on the coral and its algal symbionts by elevating antioxidant activity and suppressing photosynthesis in the symbionts. Results from the transcriptome data further indicated that corals might perform stress responses upon PAHs and heat challenges through the TNF and apoptosis pathways, which perhaps was modulated by the neuroendocrine system of corals. Collectively, our survey demonstrates that the PAHs can function as environmental hormones and activate the neuroendocrine regulation in scleractinian corals, which may contribute to the stress responses of symbiotic association by modulating photosynthesis, antioxidation, and apoptosis.

An ecotoxicological risk model for the microplastics in arctic waters

The risk posed to Arctic marine life by microplastics, a Contaminants of Emerging Arctic Concern (CEAC), is poorly known. The reason is the limited understanding of the dose-response relationship due to the region's peculiar environmental and geophysical properties and the unique physiological properties of the species living there. The properties of microplastics in the region and their distribution across the oceanic profile further complicate the problem. This paper addresses the knowledge gap by proposing a novel comprehensive ecotoxicity model. The model uses oxidative stress caused by the Reactive Oxygen Species (ROS) to assess cell mortality. Cell mortality has been used as an indicator of ecological risk. The model is implemented in the Bayesian Network (BN) framework to evaluate the cytotoxicity, measured as the probability of causing mortality. The work enhances the understanding and assessment of the cytotoxicity of microplastics in polar cod and associated risks.

Age matters: Comparing life-stage responses to diluted bitumen exposure in coho salmon (Oncorhynchus kisutch)

Millions of liters of diluted bitumen (dilbit), a crude oil product from Canada's oil sands region, is transported through critical Pacific salmon habitat each day. While the toxicity of the water-soluble fraction of dilbit (WSFd) to early life-stages of salmon is known, quantitative data on life-stage differences in sensitivity to WSFd is missing. To fill this knowledge gap, we exposed two juvenile life-stages of coho salmon (O. kisutch) in parallel to very low (parts per billion), environmentally-relevant concentrations of WSFd for acute (48 h) and sub-chronic (4 wk) durations. The relative sensitivities of the two life-stages (fry and parr) were assessed by comparing the timing and magnitude of biological responses using common organismal and molecular endpoints of crude oil exposure. A significant reduction in body condition occurred in both fry and parr after 4 wk exposure to WSFd. Both life-stages also experienced a concentration-dependent decrease in time-to-loss-of-equilibrium during a hypoxia challenge test at both 48 h and 4 wk of exposure. Although organismal responses were similar, molecular responses were distinct between life-stages. In general, unexposed fry had higher baseline values of hepatic phase I biotransformation indicators than unexposed parr, but induction of EROD activity and cyp1a mRNA expression in response to WSFd exposure was greater in parr than in fry. Neither gst nor hsp70 mRNA expression, markers of phase II biotransformation and cell stress, respectively, were reliably altered by WSFd exposure in either life-stage. Taken together, results of this study do not support differential sensitivities of coho fry and parr to WSFd. All the same, the potential for ontogenic differences in the expression and induction of phase I biotransformation need to be considered because age does matter for these endpoints if they are used as bioindicators of exposure in post-spill impact assessments.

From molecular endpoints to modeling longer-term effects in fish embryos exposed to the elutriate from Doce River

Sediments represent a major sink and also a main source of contaminants to aquatic environments. An environmental disaster from a mining dam breakage in 2015 in South-East Brazil re-suspended complex mixtures of chemicals deposited in the sediment, spreading contaminants along the Doce River Basin (DRB) major river course. While high levels of contaminants in sediment were well described, toxicological effects in aquatic organisms were poorly investigated. Thus, the effects of these potentially toxic chemicals were assessed in the present study through different endpoints (biochemical to populational levels) in fish embryos of the South-American silver catfish exposed to elutriates from different sites of the DRB. Despite no significant mortality observed, our results showed that exposure to the elutriates, especially those from the closest site to the dam collapse, caused higher deformities rates and DNA damage in the fish embryos than in the control group. Multivariate analysis showed that these sublethal effects may be related to the high levels of metals introduced by mining activities, compromising long-term survival and reproduction success. In addition, it was possible to observe the influence of other sources of pollutants along the river. According to our data, the mathematical model simulated a significant impact on the population density at longer-term exposure, for the sites that showed the most prominent toxicity responses. The fish embryo toxicity test proved to be an effective assay to assess the ecotoxicological effects of the pollutants from a major river contaminated by a mining dam collapse and showed that the survival rate per se was not a suitable endpoint to assess the toxicity of the pollutants. As a consequence, we contributed to shed a light on a potential underestimated impact of pollutants in sediments of the DRB on the native organisms at distinct biological levels of organizations.

Chronic toxicity of tire crumb rubber particles to mummichog (Fundulus heteroclitus) in episodic exposures

Microrubber (MR) encompasses all tire-related particles in the micro-scale and has recently drawn increased attention as a subclass of the broader group of microplastics. While tire particles entered the environment since the introduction of rubber tires for vehicles, the concern regarding tire wear particles (TWP) as an environmental contaminant is relatively new. Recent studies have examined physical and chemical toxicity of MR particles and leachates to a variety of organisms. However, there is a lack of information on the long-term effects of tire particle exposure under environmentally realistic conditions. The current study examined the chronic toxicity of crumb rubber (CR) particles to the estuarine fish species, mummichog (Fundulus heteroclitus) under episodic exposures at environmentally relevant concentrations. Immunohistochemistry (IHC) of fish gill, intestine, and liver was performed to assess CYP1A induction in these organs. Bile fluorescence was measured as an indicator of exposure to polycyclic aromatic hydrocarbons (PAHs) from CR. DNA damage was measured through the formation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) together with other oxidative stress measures as lipid peroxidation (TBARS assay), free glutathione (GSH), and oxidized glutathione (GSSG) concentrations. Upregulation of CYP1A in gill, intestine, and liver was observed especially in gill filaments and general vasculature. Increased bile fluorescence demonstrated exposure to aromatic compounds, especially pyrene-like PAHs. Data for DNA damage indicated greater plasma 8-OHdG concentrations as a result of increased DNA repair. There was a decrease in malondialdehyde (MDA) production and an increase in total GSH at higher concentrations of CR. It appeared that under long-term repeated dosing, antioxidant systems in mummichog were upregulated to deal with exogenous stressors released by the CR particles. Combined, these data demonstrate that fish exposed to tire crumb rubber particles illicit significant biomarker responses under environmentally relevant CR concentrations, but induced antioxidant and detoxification pathways may prevent mortality and serious physiological effects in F. heteroclitus when exposed to environmentally relevant concentrations of CR.

Nanotechnology in agriculture: Comparison of the toxicity between conventional and nano-based agrochemicals on non-target aquatic species

Increased crop production is necessary to keep up with rising food demand. However, conventional agricultural practices and agrochemicals are unable to sustain further increases without serious risk of adverse environmental consequences. The implementation of nanotechnology in agriculture practices has been increasing in recent years and has shown tremendous potential to boost crop production. The rapid growth in development and use of nano-agrochemicals in agriculture will inevitably result in more chemicals reaching water bodies. Some unique properties of nanoformulations may also alter the toxicity of the AI on aquatic organisms when compared to their conventional counterparts. Results from studies on conventional formulations may not properly represent the toxicity of new nanoformulations in the aquatic environment. As a result, current guidelines derived from conventional formulations may not be suitable to regulate those newly developed nanoformulations. Current knowledge on the toxicity of nano-agrochemicals on aquatic organisms is limited, especially in an ecologically relevant setting. This review complies and analyzes 18 primary studies based on 7 criteria to provide a comprehensive analysis of the available toxicity information of nano-agrochemicals and their conventional counterparts on aquatic organisms. Our analysis demonstrates that the overall toxicity of nano-agrochemicals on non-target aquatic species is significantly lower as compared to conventional counterparts. However, further dividing formulations into three categories (organic, bulk and ionic) shows that some nanoformulations can be more toxic when compared to bulk materials but less toxic as compared to ionic formulations while organic nanopesticides do not show a general trend in overall toxicity. Moreover, our analysis reveals the limitations of current studies and provides recommendations for future toxicity studies to ensure the effective and sustainable application of nano-agrochemicals, which will be beneficial to both the agrochemical industry and regulatory agencies alike.

Effects of perfluoroalkyl substances (PFASs) and benzo[a]pyrene (BaP) co-exposure on phase I biotransformation in rainbow trout (Oncorhynchus mykiss)

The presence of perfluoroalkyl substances (PFASs) in the environment, especially in aquatic ecosystems, continues to be a significant concern for human and environmental health. Previous studies have suggested that several PFASs do not undergo biotransformation due to their chemical stability, yet perfluorooctanesulfonic acid (PFOS)- and perfluorooctanoic acid (PFOA)-exposed organisms have presented altered activity of important biotransformation pathways. Given the fundamental role of biotransformation in biological organisms and the significant distribution of PFAS in aquatic environments, the present study investigated the influence of PFOA and PFOS on phase I biotransformation enzymes in vitro using the rainbow trout liver RTL-W1 cell line and in vivo using juvenile rainbow trout. Cells and fish were exposed and co-exposed to environmentally relevant concentrations of PFOA, PFOS, and benzo[a]pyrene (BaP), for 72 h and 10 days, respectively, prior to measurements of cytotoxicity and biotransformation ability through measurements of CYP1A1-, CYP1A2-, and CYP3A4-like activities. Our results indicate that exposure to PFAS-BaP binary mixtures altered CYP1A-like activity in vivo; however, those alterations were not observed in vitro. Similarly, while BaP did not significantly induce CYP3A4 in vivo, exposure to the PFAS led to significantly lower enzymatic activity relative to basal levels. These observations may have implications for organisms simultaneously exposed to PFASs and other environmental pollutants for which biotransformation is necessary, especially in detoxification mechanisms. Furthermore, the interference with biotransformation pathways could potentially predispose exposed organisms to a compromised physiology, which may increase their vulnerability to other stressors and erode their survival fitness.

Chemical pollution impairs the health of fish species and fishery activities along the Algeria coastline, Mediterranean Sea

Chronic exposure to multiple pollutants affects aquatic organisms, even at low concentrations, and can impair fishery activities along marine coastlines. The bioavailability of toxic metals and the presence of metals and polycyclic aromatic hydrocarbons (PAHs) in both water and sediment can explain the worst-case scenario of fish health and fishery production decline along the Algeria coastline. The hepatosomatic index (HIS), gonadosomatic index (GSI), and condition factor (K) in the studied species from the Algiers, Bou Ismail, and Zemmouri bays are the first indicators of the poor environmental health along the studied region. These findings could be explained by the bioavailability of Zn, Cu, Cr, Mn, Hg, and Ni and the detection of PAHs in the water and sediment of these bays. Additionally, histopathological damage in the liver is described in sardine (Sardina pilchardus), anchovy (Engraulis encrasicolus), and sardinelle (Sardinella aurita) highlights the current study in the investigation of the risk of exposure to biota or human populations. The occurrence of permanent lesions in the livers of fish impairs organ function and increases the incidence of diseases affecting the fish community. Furthermore, the factor analysis with principal component analysis (FA/PCA) dataset explains the physiological disturbances described in all studied species. These findings revealed that Zemmouri bay is the most affected by chemicals, suggesting that S. pilchardus is the most sensitive species. Finally, the results showed that the bioavailability of chemicals present in the studied bays confirms poor water quality, which can explain the decrease in fishery production along the Algerian Coastline.

A review on polycyclic aromatic hydrocarbons distribution in freshwater ecosystems and their toxicity to benthic fauna

Polycyclic aromatic hydrocarbons (PAHs) are a group of organic compounds, found ubiquitously in all environmental compartments. PAHs are considered hazardous pollutants, being of concern to both the environmental and human health. In the aquatic environment, PAHs tend to accumulate in the sediment due to their high hydrophobicity, and thus sediments can be considered their ultimate sink. Concurrently, sediments comprise important habitats for benthic species. This raises concern over the toxic effects of PAHs to benthic communities. Despite PAHs have been the subject of several reviews, their toxicity to freshwater benthic species has not been comprehensively discussed. This review aimed to provide an overview on PAHs distribution in freshwater environments and on their toxicity to benthic fauna species. The distribution of PAHs between sediments and the overlying water column, given by the sediment-water partition coefficient, revealed that PAHs concentrations were 2 to 4 orders of magnitude higher in sediments than in water. The sediment-water partition coefficient was positively correlated to PAHs hydrophobicity. Toxicity of PAHs to benthic fauna was addressed through Species Sensitivity Distributions. The derived hazardous concentration for 5% of the species (HC₅) decreased as follows: NAP (376 μg L^-1) > PHE > PYR > FLT > ANT (0.854 μg L^-1), varying by 3 orders of magnitude. The hazardous concentrations (HC₅) to benthic species were inversely correlated to the hydrophobicity of the individual PAHs. These findings are pertinent for environmental risk assessment of these compounds. This review also identified future challenges regarding the environmental toxicity of PAHs to freshwater benthic communities, namely the need for updating the PAHs priority list and the importance of comprehensively and more realistically assess the toxicity of PAHs in combination with other stressors, both chemical and climate-related.

Fire and rain: A systematic review of the impacts of wildfire and associated runoff on aquatic fauna

Climate and land-use changes are expected to increase the future occurrence of wildfires, with potentially devastating consequences for freshwater species and ecosystems. Wildfires that burn in close proximity to freshwater systems can significantly alter the physicochemical properties of water. Following wildfires and heavy rain, freshwater species must contend with complex combinations of wildfire ash components (nutrients, polycyclic aromatic hydrocarbons, and metals), altered light and thermal regimes, and periods of low oxygen that together can lead to mass mortality events. However, the responses of aquatic fauna to wildfire disturbances are poorly understood. Here we provide a systematic review of available evidence on how aquatic animals respond to and recover from wildfire disturbance. Two databases (Web of Science and Scopus) were used to identify key literature. A total of 83 studies from across 11 countries were identified to have assessed the risk of wildfires on aquatic animals. We provide a summary of the main ecosystem-level changes associated with wildfires and the main responses of aquatic fauna to such disturbances. We pay special focus to physiological tools and biomarkers used to assess how wildfires impact aquatic animals. We conclude by providing an overview of how physiological biomarkers can further our understanding of wildfire-related impacts on aquatic fauna, and how different physiological tools can be incorporated into management and conservation plans and serve as early warning signs of wildfire disturbances.

Occurrences, Sources, and Human Health Risk Assessments of Polycyclic Aromatic Hydrocarbons in Marine Organisms From Temperate Coastal Area

The pollution characteristics of 16 polycyclic aromatic hydrocarbons (PAHs) in marine organism species (6 species of fishes and 2 species of crustaceans) from the coastal area of the East China Sea were determined. The concentrations of 16 PAHs in the studied organisms ranged from 29.73 to 87.02 ng/g dw and 2- and 3-ring PAHs were the most abundant compounds in the aquatic organisms. The habitat, diet and predator-prey relationship have posed potential effects on the PAH accumulation in marine organisms. The source identification of PAHs was performed by using the molecular diagnostic ratios and principal component analysis (PCA). The results showed that the main sources of PAHs in the marine organisms were coal combustion, followed by mixture of gasoline combustion, oil combustion, crude oil spill and vehicle emissions. The incremental lifetime cancer risk of human via ingestion process of marine organisms in this sea area was also estimated and the assessment showed that it posed an acceptable but non-negligible risk to human health.

Screening of the Toxicity of Polystyrene Nano- and Microplastics Alone and in Combination with Benzo(a)pyrene in Brine Shrimp Larvae and Zebrafish Embryos

The occurrence of nanoplastics (NPs) and microplastics (MPs) in aquatic ecosystems and their capacity to sorb hydrophobic pollutants is nowadays an issue of great concern. This study aimed to assess the potential bioavailability and acute toxicity of polystyrene (PS) NPs (50 and 500 nm) and of MPs (4.5 µm), alone and with sorbed benzo(a)pyrene (B(a)P), in the embryo/larval stages of brine shrimps and zebrafish. Exposure to pristine plastics up to 50.1 mg PS/L did not cause significant impact on brine shrimp survival, while some treatments of plastics-B(a)P and all concentrations of B(a)P (0.1–10 mg/L) resulted acutely toxic. In zebrafish, only the highest concentrations of MPs-B(a)P and B(a)P caused a significant increase of malformation prevalence. Ingestion of NPs was observed by 24–48 h of exposure in the two organisms (from 0.069 to 6.87 mg PS/L). In brine shrimps, NPs were observed over the body surface and within the digestive tract, associated with feces. In zebrafish, NPs were localized in the eyes, yolk sac, and tail at 72 h, showing their capacity to translocate and spread into the embryo. MP ingestion was only demonstrated for brine shrimps. In zebrafish embryos exposed to plastics-B(a)P, B(a)P appeared in the yolk sac of the embryos. The presence of B(a)P was also noticeable in brine shrimps exposed to 500 nm NPs-B(a)P. In conclusion, NPs entered and spread into the zebrafish embryo and PS NPs, and MPs were successful vectors of B(a)P to brine shrimp and zebrafish embryos. Particle size played a significant role in explaining the toxicity of plastics–B(a)P. Our study provides support for the idea that plastics may pose a risk to aquatic organisms when combined with persistent organic pollutants such as B(a)P.

Elasmobranchs as bioindicators of pollution in the marine environment

Bioindicator species are increasingly valuable in environmental pollution monitoring, and elasmobranch species include many suitable candidates for that role. By measuring contaminants and employing biomarkers of effect in relevant elasmobranch species, scientists may gain important insights about the impacts of pollution in marine ecosystems. This review compiles biomarkers applied in elasmobranchs to assess the effect of pollutants (e.g., metals, persistent organic pollutants, and plastics), and the environmental changes induced by anthropogenic activities (e.g., shifts in marine temperature, pH, and oxygenation). Over 30 biomarkers measured in more than 12 species were examined, including biotransformation biomarkers (e.g., cytochrome P450 1A), oxidative stress-related biomarkers (e.g., superoxide anion, lipid peroxidation, catalase, and vitamins), stress proteins (e.g., heat shock protein 70), reproductive and endocrine biomarkers (e.g., vitellogenin), osmoregulation biomarkers (e.g., trimethylamine N-oxide, Na⁺/K⁺-ATPase, and plasma ions), energetic and neurotoxic biomarkers (e.g., lactate dehydrogenase, lactate, and cholinesterases), and histopathological and morphologic biomarkers (e.g., tissue lesions and gross indices).

A meta-analytic review of fish antioxidant defense and biotransformation systems following pesticide exposure

Pesticides reach aquatic ecosystems and interact with various targets in cells of fish and other living organisms. Toxicity originates during the metabolization process, which may produce toxic metabolites or reactive oxygen species (ROS). Ethoxyresorufin-O-deethylase (EROD), glutathione S-transferase (GST), catalase (CAT), superoxide dismutase (SOD) activities, and levels of reduced glutathione (GSH) indicate toxicants interacted with drug-metabolizing and antioxidant systems, i.e., they are biomarkers of biotransformation and oxidative stress. We meta-analytically quantified the impact of pesticides on the mean response and variability of these biomarkers. Our goals were to verify (i) the overall effect of pesticides on oxidative stress and biotransformation, and how each biomarker respond to exposure; (ii) how the life stage of fish (juvenile and adult) influence biomarkers variability and mean activity; (iii) to what extent fish sex (male, female or mixed-sex groups) modify pesticides toxicity; (iv) how different classes of pesticides, and the combination of their concentration and time of exposure, affect each biomarker. Overall, pesticides induced oxidative stress and the biotransformation system. Regardless of life stage, EROD mean activity increased significantly. In exposed juveniles, CAT and GST variability decreased and increased, respectively. CAT mean activity was higher in females, while EROD and GST activities increased in males after pesticide exposure. Organophosphorus (OPs) and organochlorine insecticides, along with imidazole and triazole fungicides, affected biomarkers the most, however the combined effect of concentration and time of exposure of OPs was not detected. Notably, imidazoles and triazoles classes increased EROD by more than 100%. Additionally, we identified research gaps, such as the lack of effect estimates of relevant pesticides on EROD (e.g., pyrethroids and neonicotinoids) and the small number of studies evaluating GSH on female fish. Future researchers may use these gaps as a guide towards enhanced experimental designs and, consequently, a better understanding of pesticide toxic effects on fish.

In vitro-in vivo biotransformation and phase I metabolite profiling of benzo[a]pyrene in Gulf killifish (Fundulus grandis) populations with different exposure histories

Chronic exposure to pollution may lead populations to display evolutionary adaptations associated with cellular and physiological mechanisms of defense against xenobiotics. This could result in differences in the way individuals of the same species, but inhabiting different areas, cope with chemical exposure. In the present study, we explore two Gulf killifish (Fundulus grandis) populations with different exposure histories for potential differences in the biotransformation of benzo[a]pyrene (BaP), and conduct a comparative evaluation of in vitro and in vivo approaches to describe the applicability of new approach methodologies (NAMs) for biotransformation assessments. Pollution-adapted and non-adapted F. grandis were subjected to intraperitoneal (IP) injections of BaP in time-course exposures, prior to measurements of CYP biotransformation activity, BaP liver concentrations, and the identification and quantification of phase I metabolites. Additionally, substrate depletion bioassays using liver S9 fractions were employed for measurements of intrinsic hepatic clearance and to evaluate the production of metabolites in vitro. Pollution-adapted F. grandis presented significantly lower CYP1A activity and intrinsic clearance rates that were 3 to 4 times lower than non-adapted fish. The metabolite profiling of BaP showed the presence of 1‑hydroxy-benzo[a]pyrene in both the in vitro and in vivo approaches but with no significant population differences. Contrarily, 9‑hydroxy-benzo[a]pyrene and benzo[a]pyrene-4,5-dihydrodiol, only identified through the in vivo approach, presented higher concentrations in the bile of pollution-adapted fish relative to non-adapted individuals. These observations further the understanding of the evolutionary adaptation of F. grandis inhabiting heavily polluted environments in the Houston Ship Channel, TX, USA, and highlight the need to consider the evolutionary history of populations of interest during the implementation of NAMs.

Transformation Products of Emerging Pollutants Explored Using Non-Target Screening: Perspective in the Transformation Pathway and Toxicity Mechanism—A Review

The scientific community has increasingly focused on forming transformation products (TPs) from environmental organic pollutants. However, there is still a lot of discussion over how these TPs are generated and how harmful they are to living terrestrial or aquatic organisms. Potential transformation pathways, TP toxicity, and their mechanisms require more investigation. Non-target screening (NTS) via high-resolution mass spectrometry (HRMS) in model organisms to identify TPs and the formation mechanism on various organisms is the focus of this review. Furthermore, uptake, accumulation process, and potential toxicity with their detrimental consequences are summarized in various organisms. Finally, challenges and future research initiatives, such as performing NTS in a model organism, characterizing and quantifying TPs, and evaluating future toxicity studies on TPs, are also included in this review.

Red Blood Cell Cytotoxicity Associated to Heavy Metals and Hydrocarbons Exposure in Flounder Fish from Two Regions of the Gulf of Mexico

In this study, the genotoxic effect of contaminants was assessed through detection of DNA damage using the micronucleus (MNs) test in erythrocytes from 149 flounder fish collected in two regions of the Gulf of Mexico (GoM). The frequency of microcytes (MCs) was also evaluated in the same group of fish collected from the Perdido Foldbelt (PF) and the Yucatan Platform (YP). The MCs frequency was different among locations of the YP (p = 0.011), while MNs frequency varied among locations of PF (p = 0.024). MCs and MNs values correlated with heavy metals from fish muscle, fish species and localities. Mean number, prevalence, and intensity of MCs and MNs correlated with Al, PAHs, depth, and locality. MNs frequency showed a species-specific association (p = 0.004). MNs and MCs were associated with heavy metals and PAHs from fish muscle and sediments, and the MNs frequency was species dependent.

Transient exposure to sublethal concentrations of a pesticide mixture (chlorpyrifos-difenoconazole) caused different responses in fish species from different trophic levels of the same community

The assessment of early effects caused in biota by sublethal exposure to pesticide mixtures should enhance the realism in the ecological risk assessment for agricultural landscapes. This study aimed to evaluate sub-individual responses in fish, which can be linked with outcomes at higher levels of biological organization and affect their trophic relationships. A multilevel biomarker approach was applied to assess the effects of a 48 h exposure of two freshwater mesoamerican fish species (Parachromis dovii and Poecilia gillii) to a mixture of sublethal concentrations of chlorpyrifos (5 μg/L) and difenoconazole (325 μg/L). Transcriptomic induction of cyp1A and the activities of 7-ethoxy-resorufin-O-distillase (EROD) and glutathione S-transferase (GST) were measured as biotransformation-related biomarkers; cholinesterase activity (ChE) was assessed as a neurotoxicity biomarker; resting metabolic rate (RMR) was measured as a physiological biomarker; and the movement of fish in a dark-light environment as a behavior biomarker. The exposure to the mixture had evident effects on P. gillii, with significant induction of cyp1A transcription, increased EROD activity, ChE inhibition in muscle, and increased permanence in the light side of the dark-light environment. Meanwhile, P. dovii only showed significant induction of cyp1A, without evidence of neurotoxicity or changes in behavior. This study demonstrates that the severity of the effects caused by the exposure to a mixture of pesticides can differ among species from the same trophic chain. The potential impairment of predator-prey relationships is a relevant effect that pesticide pollution can cause and it should be considered for the risk assessment of such contaminants.

Transcriptome aberration associated with altered locomotor behavior of zebrafish (Danio rerio) caused by Waterborne Benzo[a]pyrene

Waterborne Benzo[a]pyrene (B[a]P) pollution is a global threat to aquatic organisms. The exposure to waterborne B[a]P can disrupt the normal locomotor behavior of zebrafish (Danio rerio), however, how it affect the locomotor behavior of adult zebrafish remains unclear. Herein, B[a]P at two concentrations (0.8 μg/L and 2.0 μg/L) were selected to investigate the molecular mechanisms of the affected locomotor behavior of zebrafish by B[a]P based on transcriptome profiling. Adverse effects of B[a]P exposure affecting locomotor behavior in zebrafish were studied by RNA sequencing, and the locomotion phenotype was acquired. The gene enrichment results showed that the differentially highly expressed genes (atp2a1, cdh2, aurka, fxyd1, clstn1, apoc1, mt-co1, tnnt3b, and fads2) of zebrafish are mainly enriched in adrenergic signaling in cardiomyocytes (dre04261) and locomotory behavior (GO:0007626). The movement trajectory plots showed an increase in the locomotor distance and velocity of zebrafish in the 0.8 μg/L group and the opposite in the 2.0 μg/L group. The results showed that B[a]P affects the variety of genes in zebrafish, including motor nerves, muscles, and energy supply, and ultimately leads to altered locomotor behavior.

Gene expression analysis on growth, development and toxicity pathways of male Nile tilapia (Oreochromis niloticus), after acute and sub-chronic benzo (α) pyrene exposures

Benzo[α]pyrene (BaP), a lipophilic polycyclic aromatic hydrocarbon (PAH), is a contaminant widely distributed in aquatic systems. Its presence in freshwater organisms is of great concern; particularly in Nile tilapia (Oreochromis niloticus), due to its economic relevance. The aim of this study is to evaluate the effects of acute and sub-chronic BaP exposures on molecular growth/development responses, toxicity to DNA pathways and xenobiotic metabolism. Negative morphometric changes (the growth condition factor, hepatosomatic and gonadosomatic indices), the fluorescent aromatic compounds (FACs) in bile were also studied in order to understand the mechanisms of action of BaP. Genes involved in the growth hormone GH/insulin-like growth factor 1 (IGF-1) were measured, such as IGF1-2 with the growth hormone receptor gene expression GHR1-2, and the endocrine disruption biomarker vitellogenin (VTG). Acute exposure elicited changes in the GH/IGF axis, mainly in the GHR1 and in IGF1 mRNA levels without affecting the GHR2 expression. While sub-chronic exposure had less effect on both GHR and IGF genes. The most notable tissue-specific effects and morphometric endpoints were observed upon sub-chronic exposure, such as changes in key genes involved in detoxification, DNA damage, and altered reproductive morphological endpoints; showing that sub-chronic BaP doses have longer-lasting toxic effects. This study shows that sub-chronic BaP exposure may compromise the health of Nile tilapia and sheds light on the changes of the GH/IGF axis and the biotransformation of the xenobiotics due to the presence of this contaminant.

Assessment of seasonal relationship between polycyclic aromatic hydrocarbon accumulation and expression patterns of oxidative stress-related genes in muscle tissues of red mullet (M. barbatus) from the Northern Adriatic Sea

In this study, we examined the seasonal association between Polycyclic Aromatic Hydrocarbon (PAH) concentrations and mRNA expression profiles of some antioxidant genes (i.e. CAT, GST and SOD), as well as lipid peroxidation (LPO), in muscle of sexually inactive females of red mullet (Mullus barbatus). Fish were captured in a fishery area of the Northern Adriatic Sea during both winter and summer. We found significantly (p < 0.05) higher ∑HMW-PAHs concentrations in muscle of specimens caught during winter than summer. On the basis of sampling season, red mullets exhibited different gene expression profiles of antioxidant enzymes showing lower levels of both CAT and GST in winter than in summer. Accordingly, CAT was found to be negatively associated with ∑PAH concentrations, especially ∑LMW-PAH, in individuals collected during winter. Seasonal-related downregulation of some oxidative stress biomarker expression is suggestive of greater susceptibility of red mullets to PAHs during winter.

Correlating seasonal changes of naturally produced brominated compounds to biomarkers in perch from the Baltic Sea

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs), naturally produced by algae and cyanobacteria in the Baltic Sea, are potent disrupters of energy metabolism as well as endocrine disruptors and neurotoxins. In this study, European perch (Perca fluviatilis) from the Baltic Sea were sampled from May until October. OH-PBDEs and ten biomarkers were measured in each individual (n = 84 over 18 sampling time points) to study potential correlations between exposure to OH-PBDEs and changes in biomarkers. Several biomarkers showed significant non-linear seasonal variation. In the perch, ethoxyresorufin-O-deethylase (EROD) activity, plasma lactate concentration, and plasma glucose concentration showed a significant positive log-linear correlation with OH-PBDEs, whereas lipid percentage and liver somatic index showed a significant negative log-linear correlation with OH-PBDEs. These results strengthen the concern that OH-PBDEs could cause negative health effects for fish in the Baltic Sea.

Biomarkers of exposure and effect in the armoured catfish Hoplosternum littorale during a rice production cycle

Fish cultivation in rice fields is a valuable resource in some rural areas of the world. Fish is a source of protein and an additional source of income for local farmers. However, the use of pesticides may impact fish and consumer health. The aim of this study was to evaluate exposure and effect biomarkers in native fish inhabiting a rice field during a production cycle. Samples of fish, water and sediment from a rice field in Santa Fe, Argentina were collected during a cultivation season (at the beginning: November 2017, in the middle: December 2017 and at the end: February 2018). At each sampling period, fish biomarkers of effect (biometric indices, hematological parameters, energy reserves, oxidative stress and neurotoxicity) were assessed together with pesticide screening in water, sediment, and fish samples. Only herbicides were present in water and sediment samples in agreement with land treatment before rice sowing stage, where only herbicides were applied. In general, the greatest water concentrations of bentazone, glyphosate and aminomethylphosphonic acid (AMPA), and the lowest sediment glyphosate and AMPA levels were observed at the beginning of the farming cycle. Fish bioaccumulated AMPA residues at all sampling periods and showed biological responses to cope with a stressful environment. Alterations in hematological parameters, mobilization of energetic reserves and activation of the antioxidant system were detected. However, no oxidative damage nor neurotoxic effects were present along the production cycle. Under a real exposure scenario, the present work demonstrates that biological changes are induced in fish to cope with stressors present in a rice field. Fish-rice coculture is an efficient and ecologically sustainable approach to increase food supplies, and a better understanding of the effect of this particular environment on fish would allow a greater and safer development of this promising productive activity in South American rice producing countries.

Suspended solids-associated toxicity of hydraulic fracturing flowback and produced water on early life stages of zebrafish (Danio rerio)

Hydraulic fracturing flowback and produced water (HF-FPW), which contains polyaromatic hydrocarbons (PAHs) and numerous other potential contaminants, is a complex wastewater produced during the recovery of tight hydrocarbon resources. Previous studies on HF-FPW have demonstrated various toxicological responses of aquatic organisms as consequences of combined exposure to high salinity, dissolved organic compounds and particle/suspended solids-bound pollutants. Noteworthy is the lack of studies illustrating the potentially toxic effects of the FPW suspended solids (FPW-SS). In this study, we investigated the acute and sublethal toxicity of suspended solids filtered from six authentic FPW sample collected from two fracturing wells, using a sediment contact assay based on early-life stages of zebrafish (Danio rerio). PAHs profiles and acute toxicity tests provided initial information on the toxic potency of the six samples. Upon exposure to sediment mixture at two selected doses (1.6 and 3.1 mg/mL), results showed adverse effects in larval zebrafish, as revealed by increased Ethoxyresorufin-O-deethylase (EROD) activity. Transcriptional alterations were also observed in xenobiotic biotransformation (ahr, pxr, cyp1a, cyp1b1, cyp1c1, cyp1c2, cyp3a65, udpgt1a1, udpgt5g1), antioxidant response (sod1, sod2, gpx1a, gpx1b) and hormone receptor signaling (esr1, esr2a, cyp19a1a, vtg1) genes. The results demonstrated that even separated from the complex aqueous FPW mixture, FPW-SS can induce toxicological responses in aquatic organisms' early life stages. Since FPW-SS could sediment to the bottom of natural wetland acting as a continuous source of contaminants, the current findings imply the likelihood of long-term environmental risks of polluted sediments on aquatic ecosystems due to FPW spills.

Enzymatic, morphological, and genotoxic effects of benzo[a]pyrene in rainbow trout (Oncorhynchus mykiss)

Fish have defense systems that are capable of repairing damages caused by xenobiotics like benzo[a]pyrene (BaP), so the aims of this study were to identify BaP toxicity in melanomacrophages (MMs) cytoskeleton, evaluate the melanin area in MMs, and analyze genotoxicity. Rainbow trout juveniles (n = 24) were split in 48h and 7d treatments that received 2 mg/kg of BaP. After the experiment, blood samples were collected and liver was removed, to proceed with the analysis: EROD activity, MMs melanin area quantification, melanosomes movements, and a genotoxicity test. The results revealed increased in EROD activity after 48-h and 7-day BaP exposure. The group 7d displayed a reduction in MMs pigmented area, melanosomes aggregation, in addition to an increased frequency of micronucleus. By means of the EROD assay, it was possible to confirm the activation of BaP biotransformation system. The impairment of the melanosomes' movements possibly by an inactivation of the protein responsible for the pigment dispersion consequently affects the melanin area and thus might negatively impact the MMs detoxification capacity. In addition to this cytotoxicity, the increased frequency of micronucleus might also indicate the genotoxicity of BaP in this important fish species.