Low-dose exposure to alkylphenols adversely affects the sexual development of Atlantic cod (Gadus morhua): acceleration of the onset of puberty and delayed seasonal gonad development in mature female cod

Long-term exposure to aryl hydrocarbon receptor agonist neburon induces reproductive toxicity in male zebrafish (Danio rerio)

Neburon is a phenylurea herbicide that is widely used worldwide, but its toxicity is poorly studied. In our previous study, we found that neburon has strong aryl hydrocarbon receptor (AhR) agonist activity, but whether it causes reproductive toxicity is not clear. In the present study, zebrafish were conducted as a model organism to evaluate whether environmental concentrations of neburon (0.1, 1 and 10 µg/L) induce reproductive disorder in males. After exposure to neburon for 150 days from embryo to adult, that the average spawning egg number in high concentration group was 106.40, which was significantly lower than 193.00 in control group. This result was mainly due to the abnormal male reproductive behavior caused by abnormal transcription of genes associated with reproductive behavior in the brain, such as secretogranin-2a. The proportions of spermatozoa in the medium and high concentration groups were 82.40% and 83.84%, respectively, which were significantly lower than 89.45% in control group. This result was mainly caused by hormonal disturbances and an increased proportion of apoptotic cells. The hormonal disruption was due to the significant changes in the transcription levels of key genes in the hypothalamus-pituitary-gonadal axis following neburon treatment. Neburon treatment also significantly activated the AhR signaling pathway, causing oxidative stress damage and eventually leading to a significant increase in apoptosis in the exposed group. Together, these data filled the currently more vacant profile of neburon toxicity and might provide information to assess the ecotoxicity of neburon on male reproduction at environmentally relevant concentrations.

Transcriptomic and developmental effects of persistent organic pollutants in sentinel fishes collected near an arctic formerly used defense site

Alaska contains over 600 formerly used defense (FUD) sites, many of which serve as point sources of pollution. These sites are often co-located with rural communities that depend upon traditional subsistence foods, especially lipid-rich animals that bioaccumulate and biomagnify persistent organic pollutants (POPs). Many POPs are carcinogenic and endocrine-disrupting compounds that are associated with adverse health outcomes. Therefore, elevated exposure to POPs from point sources of pollution may contribute to disproportionate incidence of disease in arctic communities. We investigated PCB concentrations and the health implications of POP exposure in sentinel fishes collected near the Northeast Cape FUD site on Sivuqaq (St. Lawrence Island), Alaska. Sivuqaq residents are almost exclusively Yupik and rely on subsistence foods. At the request of the Sivuqaq community, we examined differential gene expression and developmental pathologies associated with exposure to POPs originating at the Northeast Cape FUD site. We found significantly higher levels of PCBs in Alaska blackfish (Dallia pectoralis) collected from contaminated sites downstream of the FUD site compared to fish collected from upstream reference sites. We compared transcriptomic profiles and histopathologies of these same blackfish. Blackfish from contaminated sites overexpressed genes involved in ribosomal and FoxO signaling pathways compared to blackfish from reference sites. Contaminated blackfish also had significantly fewer thyroid follicles and smaller pigmented macrophage aggregates. Conversely, we found that ninespine stickleback (Pungitius pungitius) from contaminated sites exhibited thyroid follicle hyperplasia. Despite our previous research reporting transcriptomic and endocrine differences in stickleback from contaminated vs. reference sites, we did not find significant differences in kidney or gonadal histomorphologies. Our results demonstrate that contaminants from the Northeast Cape FUD site are associated with altered gene expression and thyroid development in native fishes. These results are consistent with our prior work demonstrating disruption of the thyroid hormone axis in Sivuqaq residents.

Differential gene expression and developmental pathologies associated with persistent organic pollutants in sentinel fish in Troutman Lake, Sivuqaq, Alaska

Persistent organic pollutants (POPs) are lipophilic compounds that bioaccumulate in animals and biomagnify within food webs. Many POPs are endocrine disrupting compounds that impact vertebrate development. POPs accumulate in the Arctic via global distillation and thereby impact high trophic level vertebrates as well as people who live a subsistence lifestyle. The Arctic also contains thousands of point sources of pollution, such as formerly used defense (FUD) sites. Sivuqaq (St. Lawrence Island), Alaska was used by the U.S. military during the Cold War and FUD sites on the island remain point sources of POP contamination. We examined the effects of POP exposure on ninespine stickleback (Pungitius pungitius) collected from Troutman Lake in the village of Gambell as a model for human exposure and disease. During the Cold War, Troutman Lake was used as a dump site by the U.S. military. We found that PCB concentrations in stickleback exceeded the U.S. Environmental Protection Agency's guideline for unlimited consumption despite these fish being low trophic level organisms. We examined effects at three levels of biological organization: gene expression, endocrinology, and histomorphology. We found that ninespine stickleback from Troutman Lake exhibited suppressed gonadal development compared to threespine stickleback (Gasterosteus aculeatus) studied elsewhere. Troutman Lake stickleback also displayed two distinct hepatic phenotypes, one with lipid accumulation and one with glycogen-type vacuolation. We compared the transcriptomic profiles of these liver phenotypes using RNA sequencing and found significant upregulation of genes involved in ribosomal and metabolic pathways in the lipid accumulation group. Additionally, stickleback displaying liver lipid accumulation had significantly fewer thyroid follicles than the vacuolated phenotype. Our study and previous work highlight health concerns for people and wildlife due to pollution hotspots in the Arctic, and the need for health-protective remediation.

The invisible Threat: Assessing the reproductive and transgenerational impacts of micro- and nanoplastics on fish

Micro- and nanoplastics (MNPs), emerging as pervasive environmental pollutants, present multifaceted threats to diverse ecosystems. This review critically examines the ability of MNPs to traverse biological barriers in fish, leading to their accumulation in gonadal tissues and subsequent reproductive toxicity. A focal concern is the potential transgenerational harm, where offspring not directly exposed to MNPs exhibit toxic effects. Characterized by extensive specific surface areas and marked surface hydrophobicity, MNPs readily adsorb and concentrate other environmental contaminants, potentially intensifying reproductive and transgenerational toxicity. This comprehensive analysis aims to provide profound insights into the repercussions of MNPs on fish reproductive health and progeny, highlighting the intricate interplay between MNPs and other pollutants. We delve into the mechanisms of MNPs-induced reproductive toxicity, including gonadal histopathologic alterations, oxidative stress, and disruptions in the hypothalamic-pituitary-gonadal axis. The review also underscores the urgency for future research to explore the size-specific toxic dynamics of MNPs and the long-term implications of chronic exposure. Understanding these aspects is crucial for assessing the ecological risks posed by MNPs and formulating strategies to safeguard aquatic life.

Nonylphenol reduced the number of haploids in in vitro spermatogenesis of the endangered cyprinid Gnathopogon caerulescens

Nonylphenol (NP), an endocrine disrupting chemical, is widely used in industrial and agricultural processes, causing NP influx into aquatic environments. NP induces hormonal imbalance, and male feminization, and reduces germ cell production during spermatogenesis; however, the mechanism by which it affects spermatogenesis remains unknown. Here, we investigated the effect of NP on spermatogenesis in honmoroko (Gnathopogon caerulescens), an endangered fish endemic to Lake Biwa, Japan, using an in vitro differentiation system. We collected spermatogonia from the testes of non-spawning G. caerulescens and subjected them to suspension culture. The spermatogonia differentiated into flagellated spermatozoa in 3 weeks, regardless of the presence of NP. NP concentrations as low as 1 nM caused a decrease in the number of germ cells in a dose-dependent manner, whereas the number of somatic cells decreased only at a high concentration of 1 μM. Flow cytometric analysis revealed that the decrease in germ cell number was attributed to haploids (spermatids and spermatozoa); the number of spermatogonia and spermatocytes was not affected by NP treatment. This result is consistent with the hypothesis that NP might repress the second meiosis or induce apoptosis in haploids. This study demonstrated that the combination of in vitro germ cell differentiation and flow cytometric analysis is useful for evaluating the direct effects of NP on germ cell differentiation in endangered endemic fish.

Endocrine disrupting chemicals in the environment: Environmental sources, biological effects, remediation techniques, and perspective

Endocrine disrupting chemicals (EDCs) have been identified as emerging contaminants, which poses a great threat to human health and ecosystem. Pesticides, polycyclic aromatic hydrocarbons, dioxins, brominated flame retardants, steroid hormones and alkylphenols are representative of this type of contaminant, which are closely related to daily life. Unfortunately, many wastewater treatment plants (WWTPs) do not treat EDCs as targets in the normal treatment process, resulting in EDCs entering the environment. Few studies have systematically reviewed the related content of EDCs in terms of occurrence, harm and remediation. For this reason, in this article, the sources and exposure routes of common EDCs are systematically described. The existence of EDCs in the environment is mainly related to human activities (Wastewater discharges and industrial activities). The common hazards of these EDCs are clarified based on available toxicological data. At the same time, the mechanism and effect of some mainstream EDCs remediation technologies (such as adsorption, advanced oxidation, membrane bioreactor, constructed wetland, etc.) are separately mentioned. Moreover, our perspectives are provided for further research of EDCs.

Emergence of breeding tubercles and puberty onset in male zebrafish: evidence for a dependence on body growth

The presence of breeding tubercles (BTs) on the pectoral fins has been investigated as a typical male secondary sexual characteristic (SSC) that distinguish males from females in adult zebrafish. Nonetheless, the earliest occurrence of these tubercles and its association with puberty onset and body growth remain unclear. In this study, using morphological, histological and statistical analyses, the authors examined the first appearance of BTs and puberty onset in male zebrafish, with particular emphasis on the potential impact of body growth on them. The results of this study revealed that BTs distributed along the first five branched pectoral fin rays were the earliest manifestation of male SSCs, which is significantly strongly correlated with body weight (R²  = 0.9609, P < 0.001), and could be used as a "gold standard" for the earliest sex distinction (<0.1 g in weight). Using the first appearance of BTs (<0.20 mm² ) as a metric, the authors established that male puberty commenced at a body weight of c. 0.056 ± 0.015 g or a standard length of 10.99 ± 1.051 mm (mean ± S.D.). In this study, the authors thus established a simple method that can be used to sex live zebrafish at the pubertal stage and provides the first evidence for the relationship of BTs and male puberty initiation with body growth. These findings will accordingly lay a foundation for exploring mechanisms of the SSCs and male puberty onset in zebrafish and other teleost fish.

Determination of C0 -C9 alkyl phenols in produced-water-exposed fish eggs using gas chromatography/tandem mass spectrometry

RATIONALE

Produced water (PW) discharge from the oil and gas industry represents the largest intentional marine waste volume. Alkyl phenols (APs) are one of the main toxic component groups found in PW, with concentration of APs in discharged PW from the Norwegian Sector of the North Sea up to >16 mg/L. Several species of fish spawn in direct proximity to offshore production platforms and may be at risk of AP exposure. Therefore, a sensitive method to determine the potential for bioaccumulation of APs in fish eggs is needed.

METHODS

Fish eggs were extracted using liquid-solid extraction followed by gel permeation chromatography cleanup. Analysis was performed by gas chromatography coupled to triple quadrupole mass spectrometry. Extraction and analytical conditions were optimized for analysis of phenol and 30 APs (C₁ -C₉ ) with different degrees of branching in the alkyl chain. The method was verified and applied to analyze the body residue of APs in PW-exposed marine fish (Atlantic cod, Gadus morhua) eggs.

RESULTS

A comprehensive and sensitive method for the determination of C₀ -C₉ APs was developed. Detection limits were in the range 0.03-8 ng. Apart from a few compounds with poor recovery, the method generally provided reliable results with good precision (<15%).

CONCLUSIONS

We demonstrate the successful application of an optimized extraction method for APs in fish eggs and show first results of AP accumulation in cod embryos exposed to PW in the laboratory.

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.

Ecotoxicological characterization of emissions from steel coatings in contact with water

In order to prevent corrosion damage, steel structures need to be protected. Coating systems achieve this by the isolation of the steel from its environment. Common binding agents are epoxide and polyurethane resins which harden by polyaddition reactions. In contact with water, various organic substances might be leached out and released into the aquatic environment potentially causing adverse effects. So far, no legal requirements are mandatory for the environmental sustainability of coating systems. To characterize emissions from steel coatings, recommendations for the ecotoxicological assessment of construction products were utilized. Seven different coating systems based on epoxide or polyurethane resins were leached in 8 steps (6 h-64 d), followed by the testing of acute toxic effects on bacteria and algae as well as estrogen-like and mutagenic effects. In addition, chemical analysis by GC-MS was performed to identify potentially toxic compounds released from the coating systems. Two systems tested did not show any significant effects in the bioassays. One coating system caused significant algal toxicity, none was found to cause mutagenic effects. The other coating systems mainly showed estrogenic effects and bacterial toxicity. The effects increased with increasing leaching time. 4-tert-butylphenol, which is used in epoxy resins as a hardener, was identified as the main contributor to acute and estrogenic effects in two coatings. The release mechanism of 4-tert-butylphenol was characterized by two different modelling approaches. It was found that the release from the most toxic coating is not explainable by an elevated content of 4-tert-butylphenol but more likely by the release mechanism that - in contrast to the less toxic coating - is controlled not only by diffusion. This finding might indicate a sub-optimal formulation of this coating system resulting in a less stable layer and thus an increased release of toxic compounds.

Biodegradation in seawater of PAH and alkylphenols from produced water of a North Sea platform

Operational planned discharges of produced water (PW) to the marine environment from offshore oil production installations, contain low concentrations of dispersed oil compounds, like polycyclic aromatic hydrocarbons (PAHs) and alkylated phenols (APs). Biotransformation in natural seawater (SW) of naphthalenes/PAHs and phenol/APs in field-collected PW from a North Sea platform was investigated in this biodegradation study. The PW was diluted in SW from a Norwegian fjord, and the biodegradation study was performed in slowly rotating carousels at 13 °C over a period of 62 days. Naphthalenes/PAHs and phenol/APs biotransformation was determined by first-order rate kinetics, after normalization against the recalcitrant biomarker 17α(H),21β(H)-Hopane. The results from this study showed total biotransformation half-lives ranging from 10 to 19 days for groups of naphthalenes and PAHs, while half-lives for APs (C0- to C9-alkylated) were 10-14 days. Biotransformation half-lives of single compounds ranged from 8 to >100 days for naphthalenes and PAHs (median 16 days), and from 5 to 70 days (median 15 days) for phenols and APs. Four of the tested PAHs (chrysene, benzo(b)fluoranthene, benzo(e)pyrene, benzo(g,h,i)perylene) and one AP (4-tert-butylphenol) showed biotransformation half-lives >50 days. This is one of a few studies that has investigated the potential for biodegradation of PW in natural SW. Methods and data from this study may be used as a part of Risk Based Approaches (RBA) for assessments of environmental fate of PW released to the marine environment and as part of the persistence related to risk.

Reproductive toxicity of inorganic mercury exposure in adult zebrafish: Histological damage, oxidative stress, and alterations of sex hormone and gene expression in the hypothalamic-pituitary-gonadal axis

Mercury (Hg) is a prominent environmental contaminant that causes a variety of adverse effects on aquatic organisms. However, the mechanisms underlying inorganic Hg-induced reproductive impairment in fish remains largely unknown. In this study, adult zebrafish were exposed to 0 (control), 15 and 30μg Hg/l (added as mercuric chloride, HgCl2) for 30days, and the effects on histological structure, antioxidant status and sex hormone levels in the ovary and testis, as well as the mRNA expression of genes involved in the hypothalamic-pituitary-gonadal (HPG) axis were analyzed. Exposure to Hg caused pathological lesions in zebrafish gonads, and changed the activities and mRNA levels of antioxidant enzymes (catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx)) as well as the content of glutathione (GSH) and malondialdehyde (MDA). In females, although ovarian 17β-estradiol (E2) content remained relatively stable, significant down-regulation of lhβ, gnrh2, gnrh3, lhr and erα were observed. In males, testosterone (T) levels in the testis significantly decreased after Hg exposure, accompanied by down-regulated expression of gnrh2, gnrh3, fshβ and lhβ in the brain as well as fshr, lhr, ar, cyp17 and cyp11b in the testis. Thus, our study indicated that waterborne inorganic Hg exposure caused histological damage and oxidative stress in the gonads of zebrafish, and altered sex hormone levels by disrupting the transcription of related HPG-axis genes, which could subsequently impair the reproduction of fish. Different response of the antioxidant defense system, sex hormone and HPG-axis genes between females and males exposed to inorganic Hg indicated the gender-specific regulatory effect by Hg. To our knowledge, this is the first time to explore the effects and mechanisms of inorganic Hg exposure on reproduction at the histological, enzymatic and molecular levels, which will greatly extend our understanding on the mechanisms underlying of reproductive toxicity of inorganic Hg in fish.

Walnut Polyphenol Extract Attenuates Immunotoxicity Induced by 4-Pentylphenol and 3-methyl-4-nitrophenol in Murine Splenic Lymphocyte

4-pentylphenol (PP) and 3-methyl-4-nitrophenol (PNMC), two important components of vehicle emissions, have been shown to confer toxicity in splenocytes. Certain natural products, such as those derived from walnuts, exhibit a range of antioxidative, antitumor, and anti-inflammatory properties. Here, we investigated the effects of walnut polyphenol extract (WPE) on immunotoxicity induced by PP and PNMC in murine splenic lymphocytes. Treatment with WPE was shown to significantly enhance proliferation of splenocytes exposed to PP or PNMC, characterized by increases in the percentages of splenic T lymphocytes (CD3+ T cells) and T cell subsets (CD4+ and CD8+ T cells), as well as the production of T cell-related cytokines and granzymes (interleukin-2, interleukin-4, and granzyme-B) in cells exposed to PP or PNMC. These effects were associated with a decrease in oxidative stress, as evidenced by changes in OH, SOD, GSH-Px, and MDA levels. The total phenolic content of WPE was 34,800 ± 200 mg gallic acid equivalents/100 g, consisting of at least 16 unique phenols, including ellagitannins, quercetin, valoneic acid dilactone, and gallic acid. Taken together, these results suggest that walnut polyphenols significantly attenuated PP and PNMC-mediated immunotoxicity and improved immune function by inhibiting oxidative stress.

Endocrine effects of real-life mixtures of persistent organic pollutants (POP) in experimental models and wild fish

A series of studies have assessed the occurrence, levels, and potential adverse effects of persistent organic pollutants (POP) in fish from Lake Mjøsa. In this lake, high levels of various POP were detected in biota. Fish from the nearby Lake Losna contain background levels of POP and served as reference (controls) in these studies. Significantly higher prevalence of mycobacteriosis and pathological changes were documented in burbot (Lota lota) from Mjøsa compared to burbot from Losna. Further, transcriptional profiling identified changes in gene expression in burbot from Mjøsa compared to burbot from Losna associated with drug metabolism enzymes and oxidative stress. POP extracted from burbot liver oil from the two lakes was used to expose zebrafish (Danio rerio) during two consecutive generations. During both generations, POP mixtures from both lakes increased the rate of mortality, induced earlier onset of puberty, and skewed sex ratio toward males. However, opposite effects on weight gain were found in exposure groups compared to controls during the two generations. Exposure to POP from both lakes was associated with suppression of ovarian follicle development. Analyses of genome-wide transcription profiling identified functional networks of genes associated with weight homeostasis, steroid hormone functions, and insulin signaling. In human cell studies using adrenocortical H295R and primary porcine theca and granulosa cells, exposure to lake extracts from both populations modulated steroid hormone production with significant difference from controls. The results suggest that POP from both lakes may possess the potential to induce endocrine disruption and may adversely affect health in wild fish.

Altered levels of endocrine biomarkers in juvenile barramundi (Lates calcarifer; Bloch) following exposure to commercial herbicide and surfactant formulations

Agricultural pesticides that are known endocrine disrupting chemicals have been detected in waters in the Great Barrier Reef catchment and lagoon. Altered transcription levels of liver vitellogenin (vtg) have been documented in wild populations of 2 Great Barrier Reef fisheries species and were strongly associated with pesticide-containing runoff from sugarcane plantations. The present study examined endocrine and physiological biomarkers in juvenile barramundi (Lates calcarifer) exposed to environmentally relevant concentrations of commercial herbicide (ATRADEX(®) WG Herbicide, DIUREX(®) WG Herbicide) and surfactant (ACTIVATOR(®) 90) formulations commonly used on sugarcane in the Great Barrier Reef catchment. Estrogenic biomarkers (namely, liver vtg messenger RNA and plasma 17β-estradiol) increased following exposure to commercial mixtures but not to the analytical grade chemical, suggesting an estrogenic response to the additives. In contrast, brain aromatase (cyp19a1b) transcription levels, plasma testosterone and 11-ketotestosterone concentrations, and gill ventilation rates were not affected by any of the experimental exposures. These findings support the assertion that exposure to pesticide-containing runoff from sugarcane plantations is a potential causative agent of altered liver vtg transcription levels in wild barramundi. Whether exposure patterns in the Great Barrier Reef catchment and lagoon are sufficient to impair fish sexual and reproductive development and ultimately influence fish population dynamics remains to be determined. These findings highlight the need to consider both active and so-called inert ingredients in commercial pesticide formulations for environmental risk assessments.

Dispersants have limited effects on exposure rates of oil spills on fish eggs and larvae in shelf seas

Early life stages of fish are particularly vulnerable to oil spills. Simulations of overlap of fish eggs and larvae with oil from different oil-spill scenarios, both without and with the dispersant Corexit 9500, enable quantitative comparisons of dispersants as a mitigation alternative. We have used model simulations of a blow out of 4500 m(3) of crude oil per day (Statfjord light crude) for 30 days at three locations along the Norwegian coast. Eggs were released from nine different known spawning grounds, in the period from March 1st until the end of April, and all spawning products were followed for 90 days from the spill start at April first independent of time for spawning. We have modeled overlap between spawning products and oil concentrations giving a total polycyclic hydrocarbon (TPAH) concentration of more than 1.0 or 0.1 ppb (μg/l). At these orders of magnitude, we expect acute mortality or sublethal effects, respectively. In general, adding dispersants results in higher concentrations of TPAHs in a reduced volume of water compared to not adding dispersants. Also, the TPAHs are displaced deeper in the water column. Model simulations of the spill scenarios showed that addition of chemical dispersant in general moderately decreased the fraction of eggs and larvae that were exposed above the selected threshold values.

Structural and functional effects of early exposure to 4-nonylphenol on gonadal development of Nile tilapia (Oreochromis niloticus): a-histological alterations in ovaries

The present study investigated the gonads alterations of mature female Oreochromis niloticus caused by different concentrations (0, 40, 60, 100 μg/L) of 4-nonylphenol (NP) and also its effect on steroidogenesis. A tendency for a dose-dependent reduction in the gonadosomatic index, fecundity and oocytes diameter in the NP-exposed groups was observed. Histological examination revealed that NP impairs gonadal growth clearly shown in the oocyte development and differentiation. Also, the estrogenic activity of such NP was identified through 11-ketotestosterone, 17b-estradiol and vitellogenin which were affected significantly by the applied concentrations. The study indicates that NP has estrogenic potency-induced marked alteration in the sexual development including gonadal maturation, spawning time and egg production.

Environmental impacts of produced water and drilling waste discharges from the Norwegian offshore petroleum industry

Operational discharges of produced water and drill cuttings from offshore oil and gas platforms are a continuous source of contaminants to continental shelf ecosystems. This paper reviews recent research on the biological effects of such discharges with focus on the Norwegian Continental Shelf. The greatest concern is linked to effects of produced water. Alkylphenols (AP) and polyaromatic hydrocarbons (PAH) from produced water accumulate in cod and blue mussel caged near outlets, but are rapidly metabolized in cod. APs, naphtenic acids, and PAHs may disturb reproductive functions, and affect several chemical, biochemical and genetic biomarkers. Toxic concentrations seem restricted to <2 km distance. At the peak of discharge of oil-contaminated cuttings fauna disturbance was found at more than 5 km from some platforms, but is now seldom detected beyond 500 m. Water-based cuttings may seriously affect biomarkers in filter feeding bivalves, and cause elevated sediment oxygen consumption and mortality in benthic fauna. Effects levels occur within 0.5-1 km distance. The stress is mainly physical. The risk of widespread, long term impact from the operational discharges on populations and the ecosystem is presently considered low, but this cannot be verified from the published literature.

In vivo endocrine effects of naphthenic acids in fish

Oil pollution from various sources, including exploration, production and transportation, is a growing global concern. The highest toxicity of hydrocarbon pollutants is associated with the water-soluble phase compounds, including naphthenic acids, a known component found in all hydrocarbon deposits. Recently, naphthenic acids (NAs) have shown estrogenic and anti-androgenic effects in vitro. For this reason we investigated the potential effects of two commercial mixtures of naphthenic acids on fish in vivo, using the three-spined stickleback (Gasterosteus aculeatus) as a model species. Anti-androgenic and estrogenic properties of tested compounds were evaluated using the androgenized female stickleback screen (AFSS) and a variant of the 21-d fish screen (TG230) respectively. One-dimensional gas chromatography-mass spectrometry (GC-MS) showed that the complex commercial NAs mixtures were dominated by acyclic carboxylic acids. In one experiment (freshwater) we found a clear effect of NA exposure on spiggin levels; this was contrary to our hypothesis since NAs enhanced the androgenic potency of DHT (when co-administered) without inducing spiggin when tested in the absence of DHT. Exposure to NAs did not have a statistically significant effect on vitellogenin (Vtg) production in male stickleback, although the Vtg responses were increasing with increasing exposure concentrations. This study shows that in contrast to previous in vitro data, NAs did not exhibit either estrogenic or anti-androgenic properties in vivo, at the concentrations tested. On the contrary, at least in freshwater, NAs appear to have an overall androgenic effect that is not mediated via the androgen receptor involved in spiggin synthesis. Possible reasons for this discrepancy between in vitro and in vivo results as well as between our studies are discussed.

Acute exposure to offshore produced water has an effect on stress- and secondary stress responses in three-spined stickleback Gasterosteus aculeatus

Pollution is one of today's greatest problems, and the release of contaminants into the environment can cause adverse changes in vitally important biological pathways. In this study, we exposed three-spined stickleback Gasterosteus aculeatus to produced water (PW), i.e. wastewater from offshore petroleum production. PW contains substances such as alkylphenols (APs) and aromatic hydrocarbons (PAHs) known to induce toxicant stress and endocrine disruption in a variety of organisms. Following exposure to PW, a standardized confinement treatment was applied as a second stressor (PW-stress), testing how fish already under stress from the pollutant would respond to an additional stressor. The endpoint for analysis was a combination of blood levels of cortisol and glucose, in addition to transcribed levels of a set of genes related to toxicant stress, endocrine disruption and general stress. The findings of this study indicate that low doses of PW do not induce vitellogenin in immature female stickleback, but do cause an upregulation of cytochrome (CYP1A) and UDP-glucuronsyltransferase (UDP-GT), two biomarkers related to toxicant stress. However, when the second stressor was applied, both genes were downregulated, indicating that the confinement exposure had a suppressive effect on the expression of toxicant biomarkers (CYP1A and UDP-GT). Further, two of the stress related genes, heat shock protein 90 (HSP90) and stress-induced phosphoprotein (STIP), were upregulated in both PW- and PW-stress-treatment, but not in the water control confinement treatment, indicating that PW posed as a larger stress-factor than confinement for these genes. The confinement stressor caused an increased level of glucose in both control and PW-treated fish, indicating hyperglycemia, a commonly reported stress response in fish.

Effects of oil pollution and persistent organic pollutants (POPs) on glycerophospholipids in liver and brain of male Atlantic cod (Gadus morhua)

Fish in the North Sea are exposed to relatively high levels of halogenated compounds in addition to the pollutants released by oil production activities. In this study male Atlantic cod (Gadus morhua) were orally exposed to environmental realistic levels (low and high) of weathered crude oil and/or a mixture of POPs for 4weeks. Lipid composition in brain and in liver extracts were analysed in order to assess the effects of the various pollutants on membrane lipid composition and fatty acid profiles. Transcriptional effects in the liver were studied by microarray and quantitative real-time RT-PCR. Chemical analyses confirmed uptake of polychlorinated biphenyls (PCBs) and chlorinated pesticides, polybrominated diphenyl ethers (PBDEs) and perfluorooctanesulfonate (PFOS) in the liver and excretion of metabolites of polyaromatic hydrocarbons (PAHs) in the bile. Treatment with POPs and/or crude oil did not induce significant changes in lipid composition in cod liver. Only a few minor changes were observed in the fatty acid profile of the brain and the lipid classes in the liver. The hypothesis that pollution from oil or POPs at environmental realistic levels alters the lipid composition in marine fish was therefore not confirmed in this study. However, the transcriptional data suggest that the fish were affected by the treatment at the mRNA level. This study suggests that a combination of oil and POPs induce the CYP1a detoxification system and gives an increase in the metabolism and clearing rate of PAHs and POPs, but with no effects on membrane lipids in male Atlantic cod.

Environmental risk assessment of alkylphenols from offshore produced water on fish reproduction

Concern has been raised over whether environmental release of alkylphenols (AP) in produced water (PW) discharges from the offshore oil industry could impose a risk to the reproduction of fish stocks in the North Sea. An environmental risk assessment (ERA) was performed to determine if environmental exposure to PW APs in North Sea fish populations is likely to be high enough to give effects on reproduction endpoints. The DREAM (Dose related Risk and Effect Assessment Model) software was used in the study and the inputs to the ERA model included PW discharge data, fate information of PW plumes, fish distribution information, as well as uptake and elimination information of PW APs. Toxicodynamic data from effect studies with Atlantic cod (Gadus morhua) exposed to APs were used to establish a conservative environmental risk threshold value for AP concentration in seawater. By using the DREAM software to 1) identify the areas of highest potential risk and 2) integrate fish movement and uptake/elimination rates of APs for the chosen areas we found that the environmental exposure of fish to APs from PW is most likely too low to affect reproduction in wild populations of fish in the North Sea. The implications related to risk management of offshore PW and uncertainties in the risk assessment performed are discussed.

An estrogen-responsive plasma protein expression signature in Atlantic cod (Gadus morhua) revealed by SELDI-TOF MS

Compound-specific protein expression signatures (PESs) can be revealed by proteomic techniques. The SELDI-TOF MS approach is advantageous due to its simplicity and high-throughput capacity, however, there are concerns regarding the reproducibility of this method. The aim of this study was to define an estrogen-responsive PES in plasma of Atlantic cod (Gadus morhua) using the SELDI-TOF MS technique. Protein expression analysis of male cod exposed to 17β-estradiol (E₂) showed that 27 plasma peaks were differentially expressed following exposure. The reproducibility of this result was evaluated by reanalyzing the samples six months later, and a significant change in expression was confirmed for 13 of the 27 peaks detected in the first analysis. The performance of the reproducible E₂-responsive PES, constituting these 13 peaks, was then tested on samples from juvenile cod exposed to 4-nonylphenol, North Sea oil, or North Sea oil spiked with alkylphenols. Principal component analysis revealed that nonylphenol-exposed cod could be separated from unexposed cod based on the E₂-responsive PES, indicating that the PES can be used to assess estrogenic exposure of both juvenile and adult specimens of cod. A targeted antibody-assisted SELDI-TOF MS approach was carried out in an attempt to identify the E₂-responsive peaks. Results indicated that 2 peaks were fragments of the well-known biomarkers VTG and/or ZRP. In this study, the SELDI-TOF MS technology has shown its potential for defining compound-specific PESs in fish. Nevertheless, thorough validation of reproducibility, specificity and sensitivity of a PES is required before it can be applied in environmental monitoring.

SELDI-TOF MS analysis of alkylphenol exposed Atlantic cod with phenotypic variation in gonadosomatic index

Proteomics is a new and promising approach to evaluate potential effects of pollution. In order to investigate if there is a direct link between the protein expression profiles obtained by the SELDI-TOF MS technology and effects observed at the organism level in fish, plasma samples from unexposed and 20 ppb alkylphenol exposed female Atlantic cod (Gadus morhua) with high phenotypic variation in gonadosomatic index (GSI) were analyzed by SELDI-TOF MS. Principle component analysis (PCA) showed that the major proteomic variation present in the dataset (i.e. 23.6%) could be significantly correlated to the individual variation in GSI, which indicates that SELDI-TOF MS data can reflect effects observed at higher levels of organization in fish. Further exploration of the other principal components revealed an additional proteomic pattern specific for the alkylphenol exposed females. Hence, this study supports the usefulness of SELDI-TOF MS as a proteomic tool in ecotoxicological research.