II. Species sensitivity distributions based on biomarkers and whole organism responses for integrated impact and risk assessment criteria

Advantages of model averaging of species sensitivity distributions used for regulating produced water discharges

Produced water (PW) generated by Australian offshore oil and gas activities is typically discharged to the ocean after treatment. These complex mixtures of organic and inorganic compounds can pose significant environmental risk to receiving waters, if not managed appropriately. Oil and gas operators in Australia are required to demonstrate that environmental impacts of their activity are managed to levels that are as low as reasonably practicable, for example, through risk assessments comparing predicted no-effect concentrations (PNECs) with predicted environmental concentrations of PW. Probabilistic species sensitivity distribution (SSD) approaches are increasingly being used to derive PW PNECs and subsequently calculating dilutions of PW (termed "safe" dilutions) required to protect a nominated percentage of species in the receiving environment (e.g., 95% and 99% or PC95 and PC99, respectively). Limitations associated with SSDs include fitting a single model to small (six to eight species) data sets, resulting in large uncertainty (very wide 95% confidence limits) in the region associated with PC99 and PC95 results. Recent advances in SSD methodology, in the form of model averaging, claim to overcome some of these limitations by applying the average model fit of multiple models to a data set. We assessed the advantages and limitations of four different SSD software packages for determining PNECs for five PWs from a gas and condensate platform off the North West Shelf of Australia. Model averaging reduced occurrences of extreme uncertainty around PC95 and PC99 values compared with single model fitting and was less prone to the derivation of overly conservative PC99 and PC95 values that resulted from lack of fit to single models. Our results support the use of model averaging for improved robustness in derived PNEC and subsequent "safe" dilution values for PW discharge management and risk assessment. In addition, we present and discuss the toxicity of PW considering the paucity of such information in peer-reviewed literature. Integr Environ Assess Manag 2024;20:498-517. © 2023 Commonwealth Scientific and Industrial Research Organisation. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Biomarker responses in mussels (Mytilus trossulus) from the Baltic Sea exposed to water-accommodated fraction of crude oil and a dispersant at different salinities

Oil spills pose significant environmental risks, particularly in cold seas. In the Baltic Sea, the low salinity (from 0 to 2 up to 18) affects the behaviour of the spilled oil as well as the efficiency and ecological impacts of oil spill response methods such as mechanical collection and the use of dispersants. In the present study, mussels (Mytilus trossulus) were exposed under winter conditions (5 °C) to the water-accommodated fraction (WAF) of Naphthenic North Atlantic crude oil prepared by mechanical dispersion or to the chemically enhanced fraction (CEWAF) obtained using the dispersant Finasol OSR 51 at salinities of 5.6 and 15.0. Especially at the lower salinity, high bioaccumulation of polycyclic aromatic hydrocarbons was recorded in mussels in the CEWAF treatments, accompanied by increased biomarker responses. In the WAF treatments these impacts were less evident. Thus, the use of dispersants in the Baltic Sea still needs to be carefully considered.

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

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

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.

Biomarker responses and accumulation of polycyclic aromatic hydrocarbons in Mytilus trossulus and Gammarus oceanicus during exposure to crude oil

In the brackish water Baltic Sea, oil pollution is an ever-present and significant environmental threat mainly due to the continuously increasing volume of oil transport in the area. In this study, effects of exposure to crude oil on two common Baltic Sea species, the mussel Mytilus trossulus and the amphipod Gammarus oceanicus, were investigated. The species were exposed for various time periods (M. trossulus 4, 7, and 14 days, G. oceanicus 4 and 11 days) to three oil concentrations (0.003, 0.04, and 0.30 mg L^-1 based on water measurements, nominally aimed at 0.015, 0.120, and 0.750 mg L^-1) obtained by mechanical dispersion (oil droplets). Biological effects of oil exposure were examined using a battery of biomarkers consisting of enzymes of the antioxidant defense system (ADS), lipid peroxidation, phase II detoxification (glutathione S-transferase), neurotoxicity (acetylcholinesterase inhibition), and geno- and cytotoxicity (micronuclei and other nuclear deformities). In mussels, the results on biomarker responses were examined in connection with data on the tissue accumulation of polycyclic aromatic hydrocarbons (PAH). In M. trossulus, during the first 4 days of exposure the accumulation of all PAHs in the two highest exposure concentrations was high and was thereafter reduced significantly. Significant increase in ADS responses was observed in M. trossulus at 4 and 7 days of exposure. At day 14, significantly elevated levels of geno- and cytotoxicity were detected in mussels. In G. oceanicus, the ADS responses followed a similar pattern to those recorded in M. trossulus at day 4; however, in G. oceanicus, the elevated ADS response was still maintained at day 11. Conclusively, the results obtained show marked biomarker responses in both study species under conceivable, environmentally realistic oil-in-seawater concentrations during an oil spill, and in mussels, they are related to the observed tissue accumulation of oil-derived compounds.

Dispersant application increases adverse long-term effects of oil on shrimp larvae (Pandalus borealis) after a six hour exposure

The application of chemical dispersants is one option of oil spill response (OSR). Here, Northern shrimp (Pandalus borealis) larvae were experimentally exposed for short periods (6 h and 1 h) to a realistic concentration of chemically dispersed oil (CDO) (~10 mg L^-1 THC), mechanically dispersed oil (MDO) (~7 mg L^-1 THC), and dispersant only (D). A control (C) with seawater served as reference. Short-term effects on survival and feeding were examined right after exposure and longer-term consequences on survival, feeding, growth and development following 30 days of recovery. Both exposure durations provoked long lasting effects on larval fitness, with 1 h exposure leading to minor effects on most of the selected endpoints. The 6 h exposure affected all endpoints with more adverse impacts after exposure to CDO. This study provides important data for assessing the best OSR option relevant to NEBA (Net Environmental Benefit Analysis).

Induction of nuclear abnormalities in herring (Clupea harengus membras), flounder (Platichthys flesus), and Atlantic cod (Gadus morhua) collected from the southern part of the Gotland Basin-the Baltic Sea (2010-2017)

Eight nuclear abnormalities of genotoxicity and cytotoxicity were studied in peripheral blood erythrocytes of herring (Clupea harengus membras), flounder (Platichthys flesus), and Atlantic cod (Gadus morhua) sampled (2010-2017) from the Polish and the Lithuanian Exclusive Economic Zones (EEZ) in the Baltic Sea. At all study stations, total genotoxicity (∑Gentox) was found to be higher than total cytotoxicity (∑Cytox). A significant time-related decrease in genotoxicity was detected in the Lithuanian EEZ (2015-2017), while in the Polish EEZ (2014-2016), the opposite tendency was revealed. The highest ∑Gentox and ∑Cytox values recorded in fish sampled at the study stations located relatively close to each other clearly indicate an increased environmental genotoxicity and cytotoxicity pressure for fish in these areas. Exceptionally high and high-level genotoxicity risks to herring followed by those to flounder and cod were determined at a higher percentage of the stations studied.

Acute exposure to water-soluble fractions of marine diesel oil: Evaluation of apoptosis and oxidative stress in an ascidian

To understand the mechanisms involved in organisms' responses to toxicity from oil pollution, we studied the effect of acute exposure (24 h) to the marine water-soluble fraction of diesel oil (WFDO) on the ascidian Styela plicata. We evaluated the mortality and behavior by means of the siphon reflex, and the response of blood cells (hemocytes) contained in the pharynx, by means of the production of nitric oxide (NO) and reactive oxygen species (ROS), in addition to the activity of the antioxidant enzyme catalase (CAT). We also correlated oxidative stress with the activation of apoptotic pathways. No mortality occurred 24 h after the ascidians were exposed to 5% and 10% marine WFDO; however, the siphon reflex, a behavioral test based on the time that the animals took to close their siphons, increased. We also observed an inflammatory response, as estimated by the increase in the number of hemocytes in the pharynx. NO and ROS production and CAT activity were reduced, whereas caspase-3, a signaling molecule involved in apoptosis, was activated. This suggests that in ascidians acutely exposed to oil, another mechanism can occur in addition to oxidative stress. Another possibility is that WFDO may directly interact with cellular macromolecules and activate caspase-3, independently of generating oxidative stress. The results showed that components of diesel oil affected a marine organism, which showed reduced ROS production in the pharynx cells, including hemocytes, and activation of apoptotic pathways.

Heavy metal accumulation, risk assessment and integrated biomarker responses of local vegetables: A case study along the Le'an river

In this research, Ganzhou Chinese Cabbage (Brassica rapa pekinensis), Native Purple Garlic (Allium sativum L) and Leping Radish (Raphanus sativus L) widely planted and distributed along the Le'an River were chosen in the present study. Soil physical-chemical properties, nutrients contents as well as heavy metals elements accumulated in both soils and vegetables collected from 24 sites were analyzed by lab analysis combined with statistical method which was also used for calculation of contamination factor, pollution indexes and hazardous index. Heavy metals accumulation in soils were revealed with higher level, and copper and cadmium exceeded the background values by 8.82 and 16.73 times on average, which were also significantly related with the distribution of nonferrous metal processing enterprises. Heavy metal elements accumulated in vegetables were fully consistent with the finding of pollution characteristics in soils. Peroxidase biomarkers in vegetables, including superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), reduced glutathione (GSH) and lipoperoxidation (as TBARS), as well as integrated biomarker responses (IBR) were determined to give a reliable response after exposing of contaminants. Heavy metals accumulation ability and biomarker responses for three vegetables were usually determined in the following decrease trend: Ganzhou Chinese Cabbage > Native Purple Garlic > Leping Radish. Compared with peroxidase biomarkers activities or contents of control site, all the measured biomarkers in polluted sites showed significantly responses, indicating potential relationship between pollutants stresses and biomarker responses. This study also revealed that the IBR values were coordinated well with the pollutants concentrations.

III: Use of biomarkers as Risk Indicators in Environmental Risk Assessment of oil based discharges offshore

Offshore oil and gas activities are required not to cause adverse environmental effects, and risk based management has been established to meet environmental standards. In some risk assessment schemes, Risk Indicators (RIs) are parameters to monitor the development of risk affecting factors. RIs have not yet been established in the Environmental Risk Assessment procedures for management of oil based discharges offshore. This paper evaluates the usefulness of biomarkers as RIs, based on their properties, existing laboratory biomarker data and assessment methods. Data shows several correlations between oil concentrations and biomarker responses, and assessment principles exist that qualify biomarkers for integration into risk procedures. Different ways that these existing biomarkers and methods can be applied as RIs in a probabilistic risk assessment system when linked with whole organism responses are discussed. This can be a useful approach to integrate biomarkers into probabilistic risk assessment related to oil based discharges, representing a potential supplement to information that biomarkers already provide about environmental impact and risk related to these kind of discharges.

I: Biomarker quantification in fish exposed to crude oil as input to species sensitivity distributions and threshold values for environmental monitoring

The aim of this study was to determine a suitable set of biomarker based methods for environmental monitoring in sub-arctic and temperate offshore areas using scientific knowledge on the sensitivity of fish species to dispersed crude oil. Threshold values for environmental monitoring and risk assessment were obtained based on a quantitative comparison of biomarker responses. Turbot, halibut, salmon and sprat were exposed for up to 8 weeks to five different sub-lethal concentrations of dispersed crude oil. Biomarkers assessing PAH metabolites, oxidative stress, detoxification system I activity, genotoxicity, immunotoxicity, endocrine disruption, general cellular stress and histological changes were measured. Results showed that PAH metabolites, CYP1A/EROD, DNA adducts and histopathology rendered the most robust results across the different fish species, both in terms of sensitivity and dose-responsiveness. The reported results contributed to forming links between biomonitoring and risk assessment procedures by using biomarker species sensitivity distributions.