Use of biomarkers to investigate toxicological effects of produced water treated with conventional and innovative methods

EROD activity in the native fish Cnesterodon decemmaculatus as a biomarker for assessing aquatic pollution by AhR agonist chemicals within the Rio de la Plata Basin

The 7-ethoxyresorufin-O-deethylase (EROD) activity was first time characterized in the neotropical fish Cnesterodon decemmaculatus as a biomarker for assessing environmental health in aquatic ecosystems of the Rio de la Plata Basin impacted by organic pollutants agonist of the aryl-hydrocarbon receptor (AhR). Both laboratory and field studies were conducted. Laboratory experiments were run using β-naphthoflavone (BNF) as an AhR agonist model. A clear concentration-response relationship was found between 1 and 100 μg/L, with a NOEC and LOEC of 1 and 10 μg/L. A fast time-dependent response was observed with a significant induction after 24 h and a plateau from 24 to 48 h up to 264 h of exposure. Differences in basal activity were found between juveniles, females, and males, but induction levels were similar. Both basal activities and induction levels were distinct in the whole body, liver, gill, muscle, brain, and embryos. Fold-change inductions in the respective tissues were: 20, 114, 3, 5, 1, and 14. Maternal transfer and early cyp1a activation were unveiled by embryonic induction. Clear differences in EROD activity were found among juveniles collected in hydrocarbon-polluted streams, beside the La Plata Petrochemical hub, and a reference stream. Similar EROD activities were observed in laboratory and feral fish, usually with values below or above 1,000 pmol/min x mg protein for unexposed or exposed organisms. The study contributes with original information about EROD activity in C. decemmaculatus that encourages the use of both the response as a robust biomarker of exposure and the species as a good sentinel organism to be included in surveillant programs for assessing aquatic pollution by AhR agonist chemicals within the Rio de la Plata Basin within the One Health paradigm.

A blood-based multi-biomarker approach reveals different physiological responses of common kestrels to contrasting environments

The increase of urbanization and agricultural activities is causing a dramatic reduction of natural environments. As a consequence, animals need to physiologically adjust to these novel environments, in order to exploit them for foraging and breeding. The aim of this work was to compare the physiological status among nestling common kestrels (Falco tinnunculus) that were raised in nest-boxes located in more natural, rural, or urban areas in a landscape with a mosaic of land uses around Rome in Central Italy. A blood-based multi-biomarker approach was applied to evaluate physiological responses at multiple levels, including antioxidant concentrations, immunological functions, genotoxicity, and neurotoxicity. We found lower concentrations of glutathione and GSH:GSSG ratio values and higher proportions of monocytes in urban birds compared to the other areas. We also found higher DNA damage in rural compared to urban and natural krestels and inhibition of butyrylcholinesterase activity in urban and natural birds compared to rural area. Finally, we found similar values among study areas for respiratory burst, complement system, bactericidal capacity, and plasma non-enzymatic antioxidant capacity. These results suggest that (i) city life does not necessarily cause physiological alterations in kestrels compared to life in other habitats, and (ii) environmental pressures are likely to differ in typology and intensity across habitats requiring specific responses that a multi-biomarker approach can help to detect. Further studies are needed to assess which factors are responsible for the physiological differences among city, rural, and natural birds, and whether these differences are consistent across time and space.

Critical review of the OSPAR risk-based approach for offshore-produced water discharges

The management of produced water (PW) discharges from offshore oil and gas installations in the North Atlantic is under the auspices of OSPAR (Oslo/Paris convention for Protection of the Marine Environment of the North-East Atlantic). In 2010, OSPAR introduced the risk-based approach (RBA) for PW management. The RBA includes a hazard assessment estimating PW ecotoxicity using two approaches: whole-effluent toxicity (WET) and substance-based (SB). Set against the framework of the WET and SB approach, we conducted a literature review on the magnitude and cause of PW ecotoxicity, respectively, and on the challenges of estimating these. A large variability in the reported magnitude of PW WET was found, with EC50 or LC50 values ranging from <1% to >100%, and a median of 11% (n = 301). Across the literature, metals, hydrocarbons, and production chemicals were identified as causing ecotoxicity. However, this review reveals how knowledge gaps on PW composition and high sample and species dependency of PW ecotoxicity make clear identification and generalization difficult. It also highlights how limitations regarding the availability and reliability of ecotoxicity data result in large uncertainties in the subsequent risk estimates, which is not adequately reflected in the RBA output (e.g., environmental impact factors). Thus, it is recommended to increase the focus on improving ecotoxicity data quality before further use in the RBA, and that WET should play a more pronounced role in the testing strategy. To increase the reliability of the SB approach, more attention should be paid to the actual composition of PW. Bioassay-directed chemical analysis, combining outcomes of WET and SB in toxicity identification evaluations, may hold the key to identifying drivers of ecotoxicity in PW. Finally, an uncertainty appraisal must be an integrated part of all reporting of risk estimates in the RBA, to avoid mitigation actions based on uncertainties rather than reliable ecotoxicity estimations. Integr Environ Assess Manag 2023;19:1172-1187. © 2022 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Effects of microplastics on head kidney gene expression and enzymatic biomarkers in adult zebrafish

Due to massive production, improper use, and disposal of plastics, microplastics have become global environmental pollutants affecting both freshwater and marine ecosystems. Several studies have documented the uptake of microplastics in wild species and the correlated biological effects, such as epithelial damage, inflammation, metabolic alterations, and neurotoxicity. However, the effects of microplastics are not fully understood yet. In this study, adult zebrafish have been exposed for twenty days to two concentrations of a mix of polystyrene and high-density polyethylene microplastics. The biological effects were investigated through the expression levels of a set of selected genes in head kidney samples and two enzymatic biomarkers, acetylcholinesterase and lactate dehydrogenase, in head and body homogenates respectively. The lowest microplastic concentration up-regulated genes involved in xenobiotics catabolic processes (cyp2p8), and adaptive immunity (tcra). Acetylcholinesterase activity was inhibited by the highest microplastics exposure, while a weaker and no significant inhibition was induced by the lowest concentration. No significant effects on lactate dehydrogenase activity were observed. The results presented in this study support the hypothesis that MPs exposure could induce the activation of an immune response and the xenobiotic metabolism, suggesting also that the cytochrome P450 enzyme cyp2p8 and acetylcholinesterase may be sensitive to MPs contamination.

Comparison of in situ sediment remediation amendments: Risk perspectives from species sensitivity distribution

Contaminated sediment is a major issue for aquatic environments, but attention must be kept even during remediation activities that can negatively affect resident biota especially when applied in situ. For the first time, the species sensitivity distribution (SSD) approach was applied to amendments used for in situ sediment remediation considering 39 papers including both freshwater (F) and saltwater (S) effect data (i.e. n = 17 only F, n = 19 only S, and n = 3 both F and S). Toxicity data related to the application of activated carbon (AC), nano-Zero-Valent-Iron (nZVI), apatite (A), organoclay (OC) and zeolite (Z) were collected and analyzed. SSD curves were constructed by lognormal model providing comprehensive comparisons of the sensitivities of different species to the relative testing methods. Results indicated that Bacteria were the most sensitive group of testing organisms, while Crustaceans were the less sensitive. The hazardous concentration for 5% of the affected species (HC5) were derived to determine the concentration protecting 95% of the species. OC, A and Z presented both acute and chronic toxicity. The HC5 values in descending order are: AC (4.79 g/L) > nZVI (0.02 g/L) > OC, A and Z (1.77E-04 g/L). AC and nZVI can be considered safer than OC, A and Z in sediment remediation activities, even if in situ long-term effects remained still underexplored.

Offshore produced water management: A review of current practice and challenges in harsh/Arctic environments

Increasing offshore oil and gas exploration and development in harsh/Arctic environments require more effective offshore produced water management, as these environments are much more sensitive to changes in water quality than more temperate climates. However, the number and scope of studies of offshore produced water management in harsh/Arctic environments are limited. This paper reviews the current state of offshore produced water management, impacts, and policies, as well as the vulnerability, implications and operational challenges in harsh/Arctic environments. The findings show that the primary contaminant(s) of concern are contained in both the dissolved oil and the dispersed oil. The application of emerging technologies that can tackle this issue is significantly limited by the challenges of offshore operations in harsh/Arctic environments. Therefore, there is a need to develop more efficient and suitable management systems since more stringent policies are being implemented due to the increased vulnerability of harsh/Arctic environments.

Pilot study on levels of chemical contaminants and porphyrins in Caretta caretta from the Mediterranean Sea

Perfluorinated compounds (PFCs), synthetic musks compounds (SMCs), bisphenol A (BPA), para-nonylphenol (p-NP) and polybrominated diphenyl ethers (PBDEs) are known for their toxicity and ability to interfere with the endocrine system. The aim of this study was to determine levels and distribution of the above mentioned compounds in liver samples of Caretta caretta and levels of porphyrins that have been proposed as sensitive biomarkers of exposure to contaminants. This paper reports the results for 9 specimens yet analysed. Musk ketone was never detected, PFOA was found in one sample, while PFOS was the prevalent contaminant. For PFCs the levels are lower than the results of studies of comparison. The porphyrins profile showed a predominance of protoporphyrins on coproporphyrins and uroporphyrins, with a positive statistical correlation between levels of PFOS and uroporphyrins. These data represent, for several parameters, the first evidence of contaminant levels and biomarker responses in loggerhead turtles.

Effects of water accommodated fractions of crude oils and diesel on a suite of biomarkers in Atlantic cod (Gadus morhua)

The aim of this study was to characterize concentration- and time-dependent responses in juvenile Atlantic cod (Gadus morhua) following exposure for one and three weeks to the water-soluble fraction (WAF) of three weathered oils: Arabian Light crude oil (ALC), North Sea crude oil (NSC) and ship-diesel. The sum of polycyclic aromatic hydrocarbons (PAH) in water was highest after one week of exposure and within environmentally relevant concentrations. PAH metabolites in bile confirmed exposure to and uptake of PAHs. Hepatic cytochrome P450 1A (CYP1A) gene expression (mRNA quantification) increased dramatically following exposure to all three oil types (fold-change up to 165) and there was a time lag between gene and protein expression. Hepatic CYP1A protein concentration and ethoxyresorufin-O-deethylase (EROD) activity were more variable among individuals and treatments than gene expression. EROD activity in liver and gills increased in fish exposed to WAF from the two crude oils, but not in fish exposed to WAF from diesel. Exposure to diesel appeared to induce oxidative stress to a greater extent than exposure to crude oils. Other biomarkers (glutathione S-transferases, acetylcholine esterase, vitellogenin) did not appear to respond to the exposure and hence did not discriminate among oils. Biomarker responses in cod after exposure to weathered crude oils and diesel suggested that the CYP1A system and oxidative stress markers have the highest potential for discriminating among different oil types and to monitor the environmental consequences of spills.

Sodium fluxes in tamoatá, Hoplosternum litoralle, exposed to formation water from Urucu Reserve (Amazon, Brazil)

Formation water (produce water or oil field brine) from oil and gas production usually has high concentrations of soluble salts and metals. The objective of this study was to examine the effect of formation water from Urucu Reserve, Amazon, on whole-body uptake and internal distribution of newly accumulated Na+ in juvenile tamoatá, Hoplosternum litoralle. Groups of fish were submitted to nine treatments for 3 h in 400-ml chambers: control (well water), 5% formation water, and well water with respective concentrations of 5% formation water of Ca2+, Fe, Mn, Ba2+, Fe+Ca2+, Mn+Ca2+, and Ba+Ca2+ added. Specimens of tamoatá exposed to 5% formation water presented a very high Na+ influx, probably due to the high Na+ levels in this water. Waterborne Fe and Mn stimulated Na+ influx, but Fe increased Na+ efflux, causing Na+ loss. Waterborne Mn, on the other hand, decreased Na+ efflux, reducing Na+ loss by this species. Waterborne Ca2+ also affected Na+ influx but had no significant effect on net Na+ fluxes. These results demonstrated that spilling of formation water in ion-poor Amazon rivers would dramatically disrupt osmoregulatory balance of tamoatá and probably other Amazon fish species, impairing their survival and reduce biodiversity.

Environmental genotoxicity and cytotoxicity in the offshore zones of the Baltic and the North Seas

Micronuclei (MN), nuclear buds (NB) and fragmented-apoptotic cells (FA) were analyzed in mature peripheral blood and immature cephalic kidney erythrocytes of flounder (Platichthys flesus), dab (Limanda limanda) and cod (Gadus morhua) from 12 offshore sites in the Baltic Sea (479 specimens) and 11 sites in the North Sea (291 specimens), which were collected during three research vessel cruises in December 2002, 2003 and in September 2004. The highest levels of environmental genotoxicity (frequencies of MN up to 0.5 per thousand, NB - up to 0.75 per thousand) and cytotoxicity (FA - up to 0.53 per thousand) were observed in flatfishes from areas close to oil and gas platforms in the North Sea and in zones related to the extensive shipping and potentially influenced by contamination from large European Rivers (Elbe, Vistula, Oder). In dab from the offshore zones of the North Sea, the levels of nuclear abnormalities were higher as compared to those in dab from the Baltic Sea. Responses in immature kidney erythrocytes were higher than in mature erythrocytes from peripheral blood. MN frequency lower than 0.05 per thousand (the Baltic Sea) and lower than 0.1 per thousand (the North Sea) could be suspected as a reference level in the peripheral blood erythrocytes of flatfish.

Development of a laboratory exposure system using marine fish to carry out realistic effect studies with produced water discharged from offshore oil production

A biotest system for environmentally realistic exposure of fish to produced water (PW) was developed and tested. Authentic PW was collected at an oil production platform in the North Sea and preserved by freezing in multiple aliquots a 25L. After transport to the test laboratory onshore, daily PW aliquots were thawed, homogenised and administered to the test fish, Atlantic cod (Gadus morhua), in two diluted exposure concentrations, 0.1% and 0.5%, during a 15 d period, using a continuous flow-through exposure setup. Positive control groups were exposed to two crude oil treatments for comparison. Chemical analyses showed that alkylphenol (AP) and PAH concentrations in PW exposure waters were very low. Observations of significantly increased AP and PAH metabolite levels in PW exposed fish demonstrated the suitability of the biotest system for its use in biological exposure/effect studies of PW, and it also demonstrated the sensitivity of bile metabolites as PW exposure markers in fish. The relevance of the biotest system for PW effect studies and for validating modelled environmental risk estimates of PW dischargers from offshore oil production is discussed.

Uptake and tissue distribution of C4-C7 alkylphenols in Atlantic cod (Gadus morhua): relevance for biomonitoring of produced water discharges from oil production

The sensitivity of different tissues for assessment of chronic low-dose environmental exposure of fish to alkylphenols (APs) was investigated. We exposed Atlantic cod (Gadus morhua) in the laboratory to tritium labelled 4-tert-butylphenol, 4n-pentylphenol, 4n-hexylphenol, and 4n-heptylphenol via seawater (8 ng/l) and via contaminated feed (5 microg/kg fish per day). Measurements of different fish tissues during eight days of exposure and eight subsequent days of recovery revealed that APs administered via spiked seawater were readily taken up whereas the uptake was far less efficient when APs were administered in spiked feed. AP residues were mainly located in the bile fluid whereas the concentrations in liver were very low, indicating a rapid excretion and the liver-bile axis to be the major route of elimination. The biological half-life of APs in the exposed cod was short, between 10 and 20 h. Our study shows that in connection with biomonitoring of AP exposure in fish, assessment of AP metabolites in bile fluid is a more sensitive tool than detection of parent AP levels in liver or other internal tissues.

Genotoxic effects of produced waters in mosquito fish (Gambusia affinis)

The aim of this study was to assess the potential genotoxic effects of produced water (PW) from an Italian on-shore oil plant. Produced water is a complex mixture containing residual hydrocarbons, trace elements, naturally occurring radioactive material and potentially toxic treatment chemicals such as biocides, dispersants, detergents and scale inhibitors used in oil production. The test organism, mosquito fish (Gambusia affinis), was divided into male and female groups and exposed for 8 days in the laboratory to 50% concentrations of different produced waters: PW before treatment and after settling treatment. The fish were also exposed to lower concentrations (10%) of the same PW for 30 days. DNA damage was evaluated in erythrocytes by single cell gel electrophoresis (Comet assay) and micronucleus test, while an oxidative stress biomarker, was assessed. Polycyclic aromatic hydrocarbons (PAH) metabolites in bile were also evaluated. A higher sensitivity in biomarker responses was found in females in comparison to males. An increase in DNA strand breaks was observed in both genders after 30 days exposure and a statistically significant increase of micronucleated cells was found in females after 8 days exposure. A positive correlation between presence of micronucleated cells and PAH metabolites in bile was also observed.

Differential gene expression and biomarkers in zebrafish (Danio rerio) following exposure to produced water components

The main effluent from oil and gas production is produced water (PW), a waste that contains low to moderate concentrations of oil-derived substances such as polycyclic aromatic hydrocarbons (PAHs) and alkylphenols (APs). PW components may be present in seawater at low concentrations over large areas in the vicinity of oil and gas production facilities. In this study, zebrafish (Danio rerio) were exposed to control and three treatments (high-, pulsed-, low-dose) of a synthetic PW mixture for 1, 7 and 13 weeks. The aim was to investigate the development of transcriptome and biomarker responses as well as relationships between early responses and population-relevant effects. The synthetic PW contained a mixture of low-molecular-weight PAHs (<5 ring) and short-chain APs (C1-C4). The water-borne exposure levels (sum PAH) ranged from 0.54 ppb (low dose) to 5.4 ppb (high dose). Bile pyrene metabolites ranged from 17-133 ng g(-1) bile in the control group to 23-1081 ng g(-1) bile in the high exposure group. Similar levels have been observed in wild fish, confirming an environmentally relevant exposure. The expression of mRNAs of hepatic genes was investigated in the high exposure group using the Zebrafish OligoLibrary from Compugen. Functional clustering analysis revealed effects in the reproductive system, the nervous system, the respiratory system, the immune system, lipid metabolism, connective tissue and in a range of functional categories related to cell cycle and cancer. The majority of differentially expressed mRNAs of genes were down-regulated, suggesting reduction in gene transcription to be as relevant as up-regulation or induction when assessing biological responses to PW exposure. Biomarkers for effects of PAHs (cytochrome P450 1A) and environmental estrogens (vitellogenin) did not appear to be affected by the chronic exposure to low concentration of PW components. Effects at the population level included a reduction in condition factor in male fish from all exposed groups and spinal column deformations in the F1 generation of exposed groups. The different exposure regimes did not produce any significant differences in reproduction or recruitment. The results from this study demonstrate that environmentally relevant concentrations of PW affect gene expression and population-relevant endpoints in zebrafish, although links between the two were not obvious.

Biomonitoring of polybrominated diphenyl ether (PBDE) pollution: a field study

Polybrominated diphenyl ethers (PBDEs) and cytochrome P450 enzyme activities were investigated in European eels (Anguilla anguilla) collected from seven sites in a coastal lagoon in the north-western Mediterranean Sea, Orbetello lagoon (Italy). Twelve PBDE congeners were measured in muscle and two CYP1A enzyme activities, 7-ethoxyresorufin-O-deethylase (EROD) and benzo(a)pyrene monooxygenase (BP(a)PMO), were investigated in liver microsomal fraction in order to obtain insights into the health of the lagoon environment. PBDE muscle levels were low and the most abundant congeners were 2,2',4,4'-tetrabromodiphenylether (BDE-47), 2,2',4,4',5,5'-hexaBDE (BDE-153) and 2,2',4,5'-tetraBDE (BDE-49). EROD and B(a)PMO activities were also low and no differences were observed between eels from different sites. Multivariate analysis (PCA) did not indicate correlations between PBDEs and either P450 activities.