In vivo effects of environmental concentrations of produced water on the reproductive function of polar cod (Boreogadus saida)

A Critical Review of the Availability, Reliability, and Ecological Relevance of Arctic Species Toxicity Tests for Use in Environmental Risk Assessment

There is a pressing need to understand the impact of contaminants on Arctic ecosystems; however, most toxicity tests are based on temperate species, and there are issues with reliability and relevance of bioassays in general. Together this may result in an underestimation of harm to Arctic organisms and contribute to significant uncertainty in risk assessments. To help address these concerns, a critical review to assess reported effects for these species, quantify methodological and endpoint relevance gaps, and identify future research needs for testing was performed. We developed uniform criteria to score each study, allowing an objective comparison across experiments to quantify their reliability and relevance. We scored a total of 48 individual studies, capturing 39 tested compounds, 73 unique Arctic test species, and 95 distinct endpoints published from 1975 to 2021. Our analysis shows that of 253 test substance and species combinations scored (i.e., a unique toxicity test), 207 (82%) failed to meet at least one critical study criterion that contributes to data reliability for use in risk assessment. Arctic-focused toxicity testing needs to ensure that exposures can be analytically confirmed, include environmentally realistic exposure scenarios, and report test methods more thoroughly. Significant data gaps were identified as related to standardized toxicity testing with Arctic species, diversity of compounds tested with these organisms, and the inclusion of ecologically relevant sublethal and chronic endpoints assessed in Arctic toxicity testing. Overall, there needs to be ongoing improvement in test conduction and reporting in the scientific literature to support effective risk assessments in an Arctic context. Environ Toxicol Chem 2022;41:46-72. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Effects of water produced by oil segment on aquatic organisms after treatment using advanced oxidative processes

The water produced (PW) by the petroleum industry is a potential contaminant to aquatic biota, due to its complex mixture that may contain polycyclic aromatic hydrocarbons (PAHs), organic chemical compounds, including benzene, toluene, ethylbenzene and xylene (BTEX), metals and other components that are known to be toxic. The aim of this investigation was to examine the acute toxicity produced by a PW sample in aquatic organisms Vibrio fischeri and Daphnia similis prior to and after 4 treatments using advanced oxidative processes such as photocatalysis, photoelectrocatalysis, ozonation and photoelectrocatalytic ozonation. Data demonstrated that exposure to PW was toxic to both organisms, as evidenced by reduced luminescence in bacterium Vibrio fischeri and induced immobility in Daphnia similis. After treatment of PW with 4 different techniques, the PW remained toxic for both tested organisms. However, photoelectrocatalysis was more efficient in decreasing toxicity attributed to PW sample. Therefore, data demonstrate the importance of treating PW for later disposal in the environment in order to mitigate ecotoxicological impacts. Further photoelectrocatalysis appeared to be a promising tool for treating PW samples prior to disposal and exposure of aquatic ecosystems.

Susceptibility of polar cod (Boreogadus saida) to a model carcinogen

Studies that aim to characterise the susceptibility of the ecologically relevant and non-model fish polar cod (Boreogadus saida) to model carcinogens are required. Polar cod were exposed under laboratory conditions for six months to control, 0.03 μg BaP/g fish/week and 0.3 μg BaP/g fish/week dietary benzo(a)pyrene (BaP), a reference carcinogen. The concentrations of the 3-OH-BaP bile metabolite and transcriptional responses of genes involved in DNA adduct recognition (xpc), helicase activity (xpd), DNA repair (xpf, rad51) and tumour suppression (tp53) were assessed after 0, 1, 3 and 6 months of exposure, alongside body condition indexes (gonadosomatic index, hepatosomatic index and condition factor). Micronuclei and nuclear abnormalities in blood and spleen, and liver histopathological endpoints were assessed at the end of the experiment. Fish grew steadily over the whole experiment and no mortality was recorded. The concentrations of 3-OH-BaP increased significantly after 1 month of exposure to the highest BaP concentration and after 6 months of exposure to all BaP concentrations showing the biotransformation of the mother compound. Nevertheless, no significant induction of gene transcripts involved in DNA damage repair or tumour suppression were observed at the selected sampling times. These results together with the absence of chromosomal damage in blood and spleen cells, the subtle increase in nuclear abnormalities observed in spleen cells and the low occurrence of foci of cellular alteration suggested that the exposure was below the threshold of observable effects. Taken together, the results showed that polar cod was not susceptible to carcinogenesis using the BaP exposure regime employed herein.

Transcriptome responses in polar cod (Boreogadus saida) liver slice culture exposed to benzo[a]pyrene and ethynylestradiol: insights into anti-estrogenic effects

Polar cod (Boreogadus saida) is a key species in the arctic marine ecosystem vulnerable to effects of pollution, particularly from petroleum related activities. To facilitate studying the effects of those pollutants, we adapted a precision-cut liver slice culture protocol for this species. Using this system on board a research vessel, we studied gene expression in liver slice after exposure to the polycyclic aromatic hydrocarbon (PAH) benzo[a]pyrene (BaP), ethynylestradiol (EE2), and their mixtures, to map their molecular targets and examine possible anti-estrogenic effects of BaP. The exposure experiments were performed with BaP alone (0.1, 1, and 10 μM) or in combination with low concentrations of EE2 (5 nM) to mimic physiological estradiol levels in early vitellogenic female fish. Transcriptome analysis (RNA-seq) was performed after 72 h exposure in culture to map the genes and cellular pathways affected. The results provide a view of global transcriptome responses to BaP and EE2, which resulted in enrichment of many pathways such as the aryl hydrocarbon (Ahr) and estrogen receptor pathways. In the mixture exposure, BaP resulted in anti-estrogenic effects, shown by attenuation of EE2 activated transcription of many estrogen target genes. The results from this ex vivo experiment suggest that pollutants that activate the Ahr pathway such as the PAH compound BaP can result in anti-estrogenic effects that may lead to endocrine disruption in polar cod.

Quantifying the consequence of applying conservative assumptions in the assessment of oil spill effects on polar cod (Boreogadus saida) populations

In order to assess the potential impact from oil spills and decide the optimal response actions, prediction of population level effects of key resources is crucial. These assessments are usually based on acute toxicity data combined with precautionary assumptions because chronic data are often lacking. To better understand the consequences of applying precautionary approaches, two approaches for assessing population level effects on the Arctic keystone species polar cod (Boreogadus saida) were compared: a precautionary approach, where all exposed individuals die when exposed above a defined threshold concentration, and a refined (full-dose-response) approach. A matrix model was used to assess the population recovery duration of scenarios with various but constant exposure concentrations, durations and temperatures. The difference between the two approaches was largest for exposures with relatively low concentrations and short durations. Here, the recovery duration for the refined approach was less than eight times that found for the precautionary approach. Quantifying these differences helps to understand the consequences of precautionary assumptions applied to environmental risk assessment used in oil spill response decision making and it can feed into the discussion about the need for more chronic toxicity testing. An elasticity analysis of our model identified embryo and larval survival as crucial processes in the life cycle of polar cod and the impact assessment of oil spills on its population.

Environmental effects of offshore produced water discharges: A review focused on the Norwegian continental shelf

Produced water (PW), a large byproduct of offshore oil and gas extraction, is reinjected to formations or discharged to the sea after treatment. The discharges contain dispersed crude oil, polycyclic aromatic hydrocarbons (PAHs), alkylphenols (APs), metals, and many other constituents of environmental relevance. Risk-based regulation, greener offshore chemicals and improved cleaning systems have reduced environmental risks of PW discharges, but PW is still the largest operational source of oil pollution to the sea from the offshore petroleum industry. Monitoring surveys find detectable exposures in caged mussel and fish several km downstream from PW outfalls, but biomarkers indicate only mild acute effects in these sentinels. On the other hand, increased concentrations of DNA adducts are found repeatedly in benthic fish populations, especially in haddock. It is uncertain whether increased adducts could be a long-term effect of sediment contamination due to ongoing PW discharges, or earlier discharges of oil-containing drilling waste. Another concern is uncertainty regarding the possible effect of PW discharges in the sub-Arctic Southern Barents Sea. So far, research suggests that sub-arctic species are largely comparable to temperate species in their sensitivity to PW exposure. Larval deformities and cardiac toxicity in fish early life stages are among the biomarkers and adverse outcome pathways that currently receive much attention in PW effect research. Herein, we summarize the accumulated ecotoxicological knowledge of offshore PW discharges and highlight some key remaining knowledge needs.

Growth and metabolism of adult polar cod (Boreogadus saida) in response to dietary crude oil

The increasing human presence in the Arctic shelf seas, with the expansion of oil and gas industries and maritime shipping, poses a risk for Arctic marine organisms such as the key species polar cod (Boreogadus saida). The impact of dietary crude oil on growth and metabolism of polar cod was investigated in the early spring (March-April) when individuals are expected to be in a vulnerable physiological state with poor energy stores. Adult polar cod were exposed dietarily to three doses of Kobbe crude oil during an eight weeks period and followed by two weeks of depuration. Significant dose-responses in exposure biomarkers (hepatic ethoxyresorufine-O-deethylase [EROD] activity and 1-OH phenanthrene metabolites in bile) indicated that polycyclic aromatic hydrocarbons (PAHs) were bioavailable. Condition indices (i.e. Fulton's condition factor, hepatosomatic index), growth, whole body respiration, and total lipid content in the liver were monitored over the course of the experiment. The majority of females were immature, while a few had spawned during the season and showed low hepatic lipid content during the experiment. In contrast, males were all, except for one immature individual, in a post-spawning stage and had larger hepatic energy stores than females. Most specimens, independent of sex, showed a loss in weight, that was exacerbated by exposure to crude oil and low hepatic liver lipids. Furthermore, females exposed to crude oil showed a significant elevation of oxygen consumption compared to controls, although not dose-dependent. This study highlights the importance of the energy status of individuals for their response to a crude oil exposure.

Transcriptomic analysis reveals dose-dependent modes of action of benzo(a)pyrene in polar cod (Boreogadus saida)

Polar cod (Boreogadus saida) has been used as a model Arctic species for hazard assessment of environmental stressors such as polycyclic aromatic hydrocarbons (PAHs). However, most of the PAH studies using polar cod rely on targeted biomarker-based analysis thus may not adequately address the complexity of the toxic mechanisms of the stressors. The present study was performed to develop a broad-content transcriptomic platform for polar cod and apply it for understanding the toxic mechanisms of a model PAH, benzo(a)pyrene (BaP). Hepatic transcriptional analysis using a combination of high-density polar cod oligonucleotide microarray and quantitative real-time RT-PCR was conducted to characterize the stress responses in polar cod after 14d repeated dietary exposure to 0.4 (Low) and 20.3 μg/g fish/feeding (High) BaP doses. Bile metabolic analysis was performed to identify the storage of a key BaP hepatic biotransformation product, 3-hydroxybenzo(a)pyrene (3-OH-BaP). The results clearly showed that 3-OH-BaP was detected in the bile of polar cod after both Low and High BaP exposure. Dose-dependent hepatic stress responses were identified, with Low BaP suppressing genes involved in the defense mechanisms and High BaP inducing genes associated with these pathways. The results suggested that activation of the aryl hydrocarbon receptor signaling, induction of oxidative stress, DNA damage and apoptosis were the common modes of action (MoA) of BaP between polar cod or other vertebrates, whereas induction of protein degradation and disturbance of mitochondrial functions were proposed as novel MoAs. Furthermore, conceptual toxicity pathways were proposed for BaP-mediated effects in Arctic fish. The present study has for the first time reported a transcriptome-wide analysis using a polar cod-specific microarray and suggested novel MoAs of BaP. The analytical tools, bioinformatics solutions and mechanistic knowledge generated by this study may facilitate mechanistically-based hazard assessment of environmental stressors in the Arctic using this important fish as a model species.

Part B: Morphometric and transcriptomic responses to sub-chronic exposure to the polycyclic aromatic hydrocarbon phenanthrene in the fathead minnow (Pimephales promelas)

Phenanthrene is a tricyclic polycyclic aromatic hydrocarbon and environmental contaminant found in high concentrations around urban catchments and in the vicinity of oil extraction activities. Fish exposed to phenanthrene can exhibit altered reproductive hormone profiles and/or differences within gonadosomatic index and altered gamete proportions, but the mechanisms underlying these changes are not fully understood. In this study, we conducted a sub-chronic bioassay and measured transcriptional responses in the liver, the major tissue involved in generating lipids for oocyte growth. Adult male and female fathead minnow (Pimephales promelas) were exposed to an average measured concentration of 202 μg phenanthrene/L for a 7 week period. Condition factor was reduced in both males and females, while female fish also showed decreased gonadosomatic index relative to control females. In females exposed to phenanthrene, perinucleolar proportions were increased ∼1.9-fold relative to the control group whereas the proportions of vitellogenic oocytes decreased ∼8.8 fold. In males exposed to phenanthrene, spermatogonia proportions were increased ∼2.3 fold in testicular tissues compared to control fish. Thus, gametes were at an earlier stage of maturation in phenanthrene-treated fish compared to controls. However, no differences were detected in the production of 17β-estradiol or testosterone from the gonad in either sex. Catalase activity was also assessed in the liver as a measure of oxidative stress and this biomarker did not change in activity in either sex. In addition to endpoints in the ovary, the female hepatic transcriptome was measured, as this tissue produces lipids for oocyte maturation. Transcriptomic responses to phenanthrene exposure suggested a reduction in vitellogenin mRNA, and lipid metabolism and immune system pathways. Comparisons of hepatic transcriptome responses with Part A (72 h phenanthrene exposure) showed that energy homeostasis pathways were consistently altered following phenanthrene exposure over multiple durations and concentrations. We suggest that altered energy homeostasis may be adversely affecting reproductive efforts, as impaired reproduction has been observed in other studies investigating polycyclic aromatic hydrocarbons.

Effects of dietary crude oil exposure on molecular and physiological parameters related to lipid homeostasis in polar cod (Boreogadus saida)

Polar cod is an abundant Arctic key species, inhabiting an ecosystem that is subjected to rapid climate change and increased petroleum related activities. Few studies have investigated biological effects of crude oil on lipid metabolism in this species, despite lipids being a crucial compound for Arctic species to adapt to the high seasonality in food abundance in their habitat. This study examines the effects of dietary crude oil exposure on transcription levels of genes related to lipid metabolism (peroxisome proliferator-activated receptors [ppar-α, ppar-γ], retinoic X receptor [rxr-β], palmitoyl-CoA oxidase [aox1], cytochrome P4507A1 [cyp7α1]), reproduction (vitellogenin [vtg-β], gonad aromatase [cyp19a1]) and biotransformation (cytochrome P4501A1 [cyp1a1], aryl hydrocarbon receptor [ahr2]). Exposure effects were also examined through plasma chemistry parameters. Additional fish were exposed to a PPAR-α agonist (WY-14,643) to investigate the role of PPAR-α in their lipid metabolism. The dose-dependent up-regulation of cyp1a1 reflected the activation of genes related to PAH biotransformation upon crude oil exposure. The crude oil exposure did not significantly alter the mRNA expression of genes involved in lipid homeostasis except for cyp7α1 transcription levels. Plasma levels of cholesterol and alanine transaminase showed significant alterations in fish exposed to crude oil at the end of the experiment. WY exposure induced a down-regulation of ppar-α, an effect contrary to studies performed on other fish species. In conclusion, this study showed clear effects of dietary crude oil exposure at environmentally relevant concentrations on xenobiotic biotransformation but revealed only weak alterations in the lipid metabolism of polar cod.

Endocrine disruption of phenanthrene in the protogynous dusky grouper Epinephelus marginatus (Serranidae: Perciformes)

The dusky grouper Epinephelus marginatus is a protogynous hermaphrodite fish, that maintains high levels of plasma steroids as juveniles, as substrates for sex inversion. These fish are exposed to marine pollution from oil spills during cargo handling. Polycyclic aromatic hydrocarbons (PAHs), such as phenanthrene (Phe), are the main crude oil components and are toxic to fish, acting as endocrine disruptors (ED). This is the first study that investigated impacts of Phe as an ED in E. marginatus juveniles. An in vivo sublethal exposure (96h) to Phe was carried out at two concentrations (0.1mg/L and 1mg/L); exposure to the vehicle (ethanol; ETOH) was also performed. Plasma levels of 17β-estradiol (E₂), testosterone (T) and 11-ketotestosterone (11-KT) were measured by ELISA. Gonads, liver and spleen were processed for histological analysis. In an in vitro bioassay, gonad fragments were incubated with Phe (8.91mg/L) or ETOH. Steroid levels in the culture media were measured by ELISA. The in vivo exposure to Phe triggered an increase of the area of the hepatocytes, increased number of melanomacrophagic centers and hemosiderosis in the spleen; ETOH induced similar effects on spleen. E₂ and T levels did not change in plasma or in vitro media. In plasma, ETOH decreased 11-KT levels. Phenanthrene sharply reduced 11-KT levels in vitro. Although in vivo bioassay results were not unequivocal owing to ethanol effects, Phe might disrupt steroidogenesis in juvenile grouper, possibly causing dysfunctions during sex change and gonadal maturity, considering the importance of 11-KT in developing ovaries.

Antioxidant defenses in polar cod (Boreogadus saida) and responsiveness toward dietary crude oil exposure

Increasing anthropogenic activities in the Arctic pose the risk for accidental oil spills but our knowledge of ecotoxicological effects is still limited for Arctic organisms. This study aimed to provide insights in baseline levels of antioxidants in polar cod (Boreogadus saida) from different Arctic locations and investigate the susceptibility of this species to oxidative stress during a 32 day dietary crude oil exposure. Baseline levels of individual antioxidants and total oxyradical scavenging capacity (TOSC) varied among different Arctic fjords. Upon crude oil exposure, dose- and time-dependent polycyclic aromatic hydrocarbons (PAHs) biotransformation was evident through hepatic ethoxyresorufine-O-deethylase activity, glutathione S-transferase mRNA expression and biliary PAH metabolites. Changes in the activity of individual antioxidants and TOSC was, however, slight and transient upon exposure. In conclusion, biotransformation was clearly induced by the sub-lethal levels of crude oil in polar cod, while the antioxidant defense responded with high variability.

Effects of chronic dietary petroleum exposure on reproductive development in polar cod (Boreogadus saida)

Increasing human activities in the Arctic raise the risk of petroleum pollution, thus posing an elevated risk for Arctic organisms to be chronically exposed to petroleum compounds. The endocrine disrupting properties of some of these compounds (i.e. polycyclic aromatic hydrocarbons [PAHs]) present in crude oil may have negative effects on the long and energy intensive reproductive development of polar cod (Boreogadus saida), an Arctic keystone species. In the present study, selected reproductive parameters were examined in feral polar cod exposed to crude oil via a natural diet (0.11, 0.57 and 1.14μg crude oil/g fish/day [corresponding to low, medium and high treatments, respectively]) for 31 weeks prior to spawning. Fish maturing in the current reproductive period made up 92% of the experimental population while 5% were immature and 3% were identified as resting fish. Phase I metabolism of PAHs, indicated by ethoxyresorufin-O-deethylase (EROD) activity, showed a dose-dependent increase in high and medium crude oil treatments at week 6 and 22, respectively. Decreasing EROD activity and increasing PAH bile metabolite concentrations over the experimental period may be explained by reproductive maturity stage. Significant alterations in sperm motility were observed in crude oil exposed males compared to the controls. The investigated somatic indices (gonad and hepatic), germ cell development and plasma steroid levels (estradiol-17β [females], testosterone [males and females] and 11-ketotestosterone [males]) were not significantly altered by chronic dietary exposure to crude oil. The environmentally realistic doses polar cod were chronically exposed to in this study were likely not high enough to induce adverse effects in this ecologically important fish species. This study elucidated many baseline aspects of polar cod reproductive physiology and emphasized the influence of maturation state on biomarkers of PAH biotransformation (EROD and PAH bile metabolites).

Biological impact of environmental polycyclic aromatic hydrocarbons (ePAHs) as endocrine disruptors

Polycyclic aromatic hydrocarbons (PAHs) are often detected in the environment and are regarded as endocrine disruptors. We here designated mixtures of PAHs in the environment as environmental PAHs (ePAHs) to discuss their effects collectively, which could be different from the sum of the constituent PAHs. We first summarized the biological impact of environmental PAHs (ePAHs) found in the atmosphere, sediments, soils, and water as a result of human activities, accidents, or natural phenomena. ePAHs are characterized by their sources and forms, followed by their biological effects and social impact, and bioassays that are used to investigate their biological effects. The findings of the bioassays have demonstrated that ePAHs have the ability to affect the endocrine systems of humans and animals. The pathways that mediate cell signaling for the endocrine disruptions induced by ePAHs and PAHs have also been summarized in order to obtain a clearer understanding of the mechanisms responsible for these effects without animal tests; they include specific signaling pathways (MAPK and other signaling pathways), regulatory mechanisms (chromatin/epigenetic regulation, cell cycle/DNA damage control, and cytoskeletal/adhesion regulation), and cell functions (apoptosis, autophagy, immune responses/inflammation, neurological responses, and development/differentiation) induced by specific PAHs, such as benz[a]anthracene, benzo[a]pyrene, benz[l]aceanthrylene, cyclopenta[c,d]pyrene, 7,12-dimethylbenz[a]anthracene, fluoranthene, fluorene, 3-methylcholanthrene, perylene, phenanthrene, and pyrene as well as their derivatives. Estrogen signaling is one of the most studied pathways associated with the endocrine-disrupting activities of PAHs, and involves estrogen receptors and aryl hydrocarbon receptors. However, some of the actions of PAHs are contradictory, complex, and unexplainable. Although several possibilities have been suggested, such as direct interactions between PAHs and receptors and the suppression of their activities through other pathways, the mechanisms underlying the activities of PAHs remain unclear. Thus, standardized assay protocols for pathway-based assessments are considered to be important to overcome these issues.

Disruption of the rainbow trout reproductive endocrine axis by the polycyclic aromatic hydrocarbon benzo[a]pyrene

Successful reproduction in salmonids depends on a complex and highly regulated interplay between the pharmacokinetics and pharmacodynamics of naturally circulating sex steroids. The effects of a single intraperitoneal administration of the model PAH benzo[a]pyrene (B[a]P) on the kinetics of circulating levels of estradiol and testosterone through 7d post-injection in mature male and female rainbow trout (Oncorhynchus mykiss) in pre-spawning and spawning condition were investigated. Detailed measurements of the time course of injected E2 and excretion into the bile followed by pharmacokinetic modeling techniques were used to aid in identifying the potential mechanism of ED caused by B[a]P exposure. Plasma E2 and T concentrations were reduced significantly in both male and female trout. Administration of the GnRH analogue des-Gly(10)[D-Ala(6)]LH-RH-ethylamide, to induce spawning steroid profiles increased plasma E2 concentrations in control females, but not in B[a]P-treated fish. The mechanism underlying reductions in sex steroids in pre-spawning and spawning salmonids appears to be unrelated to the induction of P450 and related biotransformation enzymes by B[a]P. Induced biotransformation enzyme activities did not result in altered [(3)H]estradiol pharmacokinetics (e.g. terminal half-life) or elimination of steroid in bile, suggesting that B[a]P alters plasma E2 and T concentrations by other ED mechanisms in an anti-estrogenic manner.

Comparison of produced water toxicity to Arctic and temperate species

Produced water is the main discharge stream from oil and gas production. For offshore activities this water is usually discharged to the marine environment. Produced water contains traces of hydrocarbons such as polycyclic aromatic hydrocarbons as well as alkylphenols, which are relatively resistant to biodegradation and have been reported to cause adverse effects to marine organisms in laboratory studies. For management of produced water, risk-based tools have been developed using toxicity data for mainly non-Arctic species. Reliable risk assessment approaches for Arctic environments are requested to manage potential impacts of produced water associated with increased oil and gas activities in Arctic regions. In order to assess the applicability of existing risk tools for Arctic areas, basic knowledge on the sensitivity of Arctic species has to be developed. In the present study, acute and chronic toxicity of artificial produced water for 6 Arctic and 6 temperate species was experimentally tested and evaluated. The hazardous concentrations affecting 5% and 50% of the species were calculated from species sensitivity distribution curves. Hazardous concentrations were compared to elucidate whether temperate toxicity data used in risk assessment are sufficiently representative for Arctic species. From the study it can be concluded that hazardous concentration derived from individual species' toxicity data of temperate and Arctic species are comparable. However, the manner in which Arctic and non-Arctic populations and communities respond to exposure levels above established thresholds remains to be investigated. Hence, responses at higher levels of biological organization should be studied to reveal potential differences in sensitivities to produced water between Arctic and non-Arctic ecosystems.

Scales of freshwater fish Labeo rohita as bioindicators of water pollution in Tung Dhab Drain, Amritsar, Punjab, India

This study examined the impact of municipal wastewater on scale morphology of freshwater fish Labeo rohita. Fish were exposed to sublethal concentrations (17.7, 26.6, or 35.4%) of municipal wastewater for durations of 15, 30, and 60 d. Recovery experiments were also performed for a duration of 60 d. Scales were extracted after respective exposure periods, cleaned, and processed for scanning electron microscopy. Results showed concentration- and exposure duration-dependent alterations in the morphology of scales. Severe damage was observed at the anterior and posterior portions of scales in the form of lepidontal breakage and uprooting, destructions at the base of circuli and radii along with complete structural loss in the focal region and adjacent circuli and radii, and alterations in structure of tubercles. Data indicate that scales of fish L. rohita may be employed as bioindicators of water pollution and could be incorporated into water monitoring surveillance.

Evidence of altered fertility in female roach (Rutilus rutilus) from the River Seine (France)

A large variety of anthropogenic chemicals present in the aquatic environment have been shown to be able to alter the endocrine system of exposed organisms, potentially impacting their reproductive function. The aim of this study was to assess the effects of environmental pollution on the reproductive system of wild female roach (Rutilus rutilus) from the Seine River (Normandy, France). A suite of biomarkers of endocrine disruption including gonado-somatic index, plasmatic vitellogenin, gonadal aromatase activity and histological parameters (oocyte diameter and gonad maturation) were studied. Female fish from the polluted sites showed a number of reproductive alterations, including inhibited gonad maturation, reduced oocyte growth, reduced levels of plasmatic vitellogenin and 3-fold lower gonadal aromatase activity than females collected in the reference site. Overall, these results highlight the presence of endocrine disruption in female roach from the Seine River.