Individual and molecular level effects of produced water contaminants on nauplii and adult females of Calanus finmarchicus

Response of Microbial Communities to Naturally Occurring Radioactive Material-Contaminated Sediments: A Microcosm-Based Study

There is a growing need to understand the potential ecological impacts of contaminants in offshore oil and gas infrastructure, especially if that infrastructure is to be left in situ as a decommissioning option. Naturally occurring radioactive material (NORM) is one type of contaminant found in solid deposits on internal surfaces of infrastructure that poses potential ecological harm if released into the marine environment. Microbes are important components of marine sediment ecosystems because they provide ecosystem services, yet the impacts of NORM contamination to these communities are not well understood. The present study aimed to investigate the response of benthic microbial communities to NORM-contaminated scale, collected from an offshore oil and gas system, via controlled laboratory microcosm studies. Changes to microbial communities in natural sediment and sediments spiked with NORM at radium-226 activity concentrations ranging from 9.5 to 59.8 Bq/kg (in partial equilibria with progeny) over 7 and 28 days were investigated using high-throughput sequencing of environmental DNA extracted from experimental sediments. There were no significant differences in microbial community composition between control and scale-spiked sediments over 7 and 28 days. However, we observed a greater presence of Firmicutes in the scale-mixed treatment and Chloroflexi in the scale-surface treatments after 28 days. This could suggest selection for species with contaminant tolerance or potential resilience to radiation and metal toxicity. Further research is needed to explore microbial tolerance mechanisms and their potential as indicators of effects of radionuclide-contaminated sediments. The present study demonstrated that microcosm studies can provide valuable insights about the potential impacts of contamination from oil and gas infrastructure to sediment microbial communities. Environ Toxicol Chem 2024;43:1648-1661. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Zooplankton-based adverse outcome pathways: A tool for assessing endocrine disrupting compounds in aquatic environments

Endocrine disrupting compounds (EDCs) pose a significant ecological risk, particularly in aquatic ecosystems. EDCs have become a focal point in ecotoxicology, and their identification and regulation have become a priority. Zooplankton have gained global recognition as bioindicators, benefiting from rigorous standardization and regulatory validation processes. This review aims to provide a comprehensive summary of zooplankton-based adverse outcome pathways (AOPs) with a focus on EDCs as toxicants and the utilisation of freshwater zooplankton as bioindicators in ecotoxicological assessments. This review presents case studies in which zooplankton have been used in the development of AOPs, emphasizing the identification of molecular initiating events (MIEs) and key events (KEs) specific to zooplankton exposed to EDCs. Zooplankton-based AOPs may become an important resource for understanding the intricate processes by which EDCs impair the endocrine system. Furthermore, the data sources, experimental approaches, advantages, and challenges associated with zooplankton-based AOPs are discussed. Zooplankton-based AOPs framework can provide vital tools for consolidating toxicological knowledge into a structured toxicity pathway of EDCs, offering a transformative platform for facilitating enhanced risk assessment and chemical regulation.

Assessing the ecological impacts of NORM-contaminated scale on marine infauna using sediment microcosms

Naturally occurring radioactive materials (NORMs) can be found in decommissioned oil and gas infrastructure (e.g. pipelines), including scales. The effects of NORM contaminants from offshore infrastructure on benthic macroorganisms remain poorly understood. To test the potential ecological effects of NORM-contaminated scale, we exposed a marine amphipod, a clam and a polychaete to marine sediments spiked with low level concentrations of barium sulfate scale retrieved from a decommissioned subsea pipe. Only amphipods were included in further analysis due to treatment mortalities of the clam and polychaete. Barium (Ba) and copper (Cu) were elevated in the seawater overlying the spiked sediments, although no sediment metals exceeded guidelines. 210Po was the only NORM detected in the overlying waters while both 210Po and 226Ra were significantly elevated in the scale-contaminated sediments when compared with the control sediments. The whole-body burden of Ba and 226Ra were significantly higher in the scale-exposed amphipods. Using experiment- and scale-specific parameters in biota dose assessments suggested potential dose rates may elicit individual and population level effects. Future work is needed to assess the biological impacts and effects of NORM scale at elevated levels above background concentrations and the accumulation of NORM-associated contaminants by marine organisms.

Effects of mine tailing exposure on the development of early life stages of the marine copepod Calanus finmarchicus

The demand for mineral resources is increasing mining activities worldwide. In Norway, marine tailing disposal (MTD) is practiced, introducing mineral particles into fjord ecosystems. We investigated the effects of two concentrations (high and low) of fine tailings from a CaCO3 processing plant on early life stages of the marine copepod Calanus finmarchicus. Results show that the exposure did not significantly impact hatching success or development in non- and early feeding life stages. However, feeding stage nauplii ingested tailings, which caused a significantly slower development in later nauplii stages in high exposure groups, with most individuals being two stages behind the control group. Further, high mortality occurred in late nauplii and early copepodite stages in low exposure groups, which could be caused by insufficient energy accumulation and depleted energy reserves during development. Individuals exposed to high exposure concentrations seemed to survive by arresting development and potentially by reduced activity, thereby conserving energy reserves. In nature, slower development could affect lipid storage buildup and reproduction.

Magnetized vermiculite as a tool for the treatment of produced water generated by oil companies: Effects on aquatic organisms before and after treatment

Produced water (PW) generated by oil companies is a highly impacting waste that contains chemicals such as metals and organic and inorganic compounds. Given its polluting potential, PW requires effective treatment before being discharged into the environment. Conventional treatments have limited efficiency in removing PW toxicity, so alternative approaches must be developed and standardized. In this context, treatment with adsorbent materials like magnetized vermiculite (VMT-mag) is highlighted. This work aimed to evaluate the efficiency of treatment with VMT-mag in reducing PW toxicity to aquatic biota. For this purpose, three aquatic species (the midge Chironomus riparius, the planarian Girardia tigrina, and the crustacean Daphnia magna) were exposed to untreated PW and to PW treated with VMT-mag at laboratory conditions. The assessed endpoints included mortality, growth, emergence, and developmental time of C. riparius; mortality, locomotion, feeding, and head regeneration of G. tigrina; and intrinsic population growth rate (r) and reproductive output of D. magna. The results showed that all the species exposed to raw PW were impaired: C. riparius had delayed development, G. tigrina had reduced locomotor activity and delayed head regeneration, and D. magna had reduced reproduction and delayed intrinsic population growth rate (r). Most of the analyzed parameters showed that treatment with VMT-mag diminished PW toxicity. Therefore, using VMT-mag to treat PW may be the key to reducing the PW effects on aquatic organisms.

Radiological risk assessment to marine biota from exposure to NORM from a decommissioned offshore oil and gas pipeline

Scale residues can accumulate on the interior surfaces of subsea petroleum pipes and may incorporate naturally occurring radioactive materials (NORM). The persistent nature of 'NORM scale' may result in a radiological dose to the organisms living on or near intact pipelines. Following a scenario of in-situ decommissioning of a subsea pipeline, marine organisms occupying the exteriors or interiors of petroleum structures may have close contact with the scale or other NORM-associated contaminated substances and suffer subsequent radiological effects. This case study used radiological dose modelling software, including the ERICA Tool (v2.0), MicroShield® Pro and mathematical equations, to estimate the likely radiological doses and risks of effects from NORM-contaminated scale to marine biota from a decommissioned offshore oil and gas pipeline. Using activity concentrations of NORM (²²⁶Ra, ²¹⁰Po, ²¹⁰Pb, ²²⁸Ra, ²²⁸Th) from a subsea pipeline from Australia, environmental realistic exposure scenarios including radiological exposures from both an intact pipe (external only; accounting for radiation shielding by a cylindrical carbon steel pipe) and a decommissioned pipeline with corrosive breakthrough (resulting in both internal and external radiological exposure) were simulated to estimate doses to model marine organisms. Predicted dose rates for both the external only exposure (ranging from 26 μGy/h to 33 μGy/h) and a corroded pipeline (ranging from 300 μGy/h to 16,000 μGy/h) exceeded screening levels for radiological doses to environmental receptors. The study highlighted the importance of using scale-specific solubility data (i.e., K_d) values for individual NORM radionuclides for ERICA assessments. This study provides an approach for conducting marine organism dose assessments for NORM-contaminated subsea pipelines and highlights scientific gaps required to undertake risk assessments necessary to inform infrastructure decommissioning planning.

Current understanding and research needs for ecological risk assessments of naturally occurring radioactive materials (NORM) in subsea oil and gas pipelines

Thousands of offshore oil and gas facilities are coming to the end of their life in jurisdictions worldwide and will require decommissioning. In-situ decommissioning, where the subsea components of that infrastructure are left in the marine environment following the end of its productive life, has been proposed as an option that delivers net benefits, including from: ecological benefits from the establishment of artificial reefs, economic benefits from associated fisheries, reduced costs and improved human safety outcomes for operators. However, potential negative impacts, such as the ecological risk of residual contaminants, are not well understood. Naturally occurring radioactive materials (NORM) are a class of contaminants found in some oil and gas infrastructure (e.g. pipelines) and includes radionuclides of uranium, thorium, radium, radon, lead, and polonium. NORM are ubiquitous in oil and gas reservoirs around the world and may form contamination products including scales and sludges in subsea infrastructure due to their chemistries and the physical processes of oil and gas extraction. The risk that NORM from these sources pose to marine ecosystems is not yet understood meaning that decisions made about decommissioning may not deliver the best outcomes for environments. In this review, we consider the life of NORM-contamination products in oil and gas systems, their expected exposure pathways in the marine environment, and possible ecological impacts following release. These are accompanied by the key research priorities that need to better describe risk associated with decommissioning options.

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.

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.

The State-of-the Art of Environmental Toxicogenomics: Challenges and Perspectives of "Omics" Approaches Directed to Toxicant Mixtures

The last decade witnessed extraordinary advances in “omics” methods, particularly transcriptomics, proteomics and metabolomics, enabling toxicologists to integrate toxicokinetics and toxicodynamics with mechanistic insights on the mode-of-action of noxious chemicals, single or combined. The toxicology of mixtures is, nonetheless, a most challenging enterprise, especially for environmental toxicologists and ecotoxicologists, who invariably deal with chemical mixtures, many of which contain unknowns. Despite costs and demanding computations, the systems toxicology framework, of which “omics” is a major component, endeavors extracting adverse outcome pathways for complex mixtures. Still, the interplay between the multiple components of gene expression and cell metabolism tends to be overlooked. As an example, the proteome allocates DNA methyltransferases whose altered transcription or loss of function by action of chemicals can have a global impact on gene expression in the cell. On the other hand, chemical insult can produce reactive metabolites and radicals that can intercalate or bind to DNA as well as to enzymes and structural proteins, compromising their activity. These examples illustrate the importance of exploring multiple “omes” and the purpose of “omics” and multi-“omics” for building truly predictive models of hazard and risk. Here we will review the state-of-the-art of toxicogenomics highlighting successes, shortcomings and perspectives for next-generation environmental toxicologists.

Exposure to chemically-dispersed oil is more harmful to early developmental stages of the Northern shrimp Pandalus borealis than mechanically-dispersed oil

Knowledge of key species sensitivity for oil spill response (OSR) options is needed to support decision-making and mitigate impact on sensitive life stages of keystone species. Here, Northern shrimp (Pandalus borealis) larvae were exposed for 24 h to a gradient (H-High, M-Medium: 10 times dilution and L-Low: 100 times dilution) of mechanically- (MDO) (H < 6 mg/L total hydrocarbon content) and chemically- (CDO) dispersed oil (Slickgone NS, H < 20 mg/L total hydrocarbon content), followed by a recovery period. Larval mortality, feeding rate and development were evaluated. Overall, the results show that 24 h exposure to field-realistic concentrations of CDO lead to lower survival, reduced feeding rate and slower larval development in P. borealis larvae compared to MDO. These effects persisted during recovery, indicating a higher vulnerability with dispersant use and the need for longer observation periods post-exposure to fully evaluate the consequences for sensitive life-stages from OSR.

Gamma radiation induces dose-dependent oxidative stress and transcriptional alterations in the freshwater crustacean Daphnia magna

Among aquatic organisms, invertebrate species such as the freshwater crustacean Daphnia magna are believed to be sensitive to gamma radiation, although information on responses at the individual, biochemical and molecular level is scarce. Following gamma radiation exposure, biological effects are attributed to the formation of free radicals, formation of reactive oxygen species (ROS) and subsequently oxidative damage to lipids, proteins and DNA in exposed organisms. Thus, in the present study, effects and modes of action (MoA) have been investigated in D. magna exposed to gamma radiation (dose rates: 0.41, 1.1, 4.3, 10.7, 42.9 and 106 mGy/h) after short-term exposure (24 and 48 h). Several individual, cellular and molecular endpoints were addressed, such as ROS formation, lipid peroxidation, DNA damage and global transcriptional changes. The results showed that oxidative stress is one of the main toxic effects in gamma radiation exposed D. magna, mediated by the dose-dependent increase in ROS formation and consequently oxidative damage to lipids and DNA over time. Global transcriptional analysis verified oxidative stress as one of the main MoA of gamma radiation at high dose rates, and identified a number of additional MoAs that may be of toxicological relevance. The present study confirmed that acute exposure to gamma radiation caused a range of cellular and molecular effects in D. magna exposed to intermediate dose rates, and highlights the need for assessing effects at longer and more environmentally relevant exposure durations in future studies.

Toxicity of dissolved and precipitated forms of barium to a freshwater alga (Chlorella sp. 12) and water flea (Ceriodaphnia dubia)

Barium is present at elevated concentrations in oil and gas produced waters, and there is no international water quality guideline value to assess the potential risk of adverse effects to aquatic biota. Sulfate concentration largely controls the solubility of barium in aquatic systems, with insoluble barium sulfate (barite) assumed to be less bioavailable and less toxic than dissolved barium. We exposed aquatic biota to dissolved barium only and to a mixture of dissolved and precipitated barium. The chronic dissolved barium 48-h growth rate inhibition effect concentrations, (EC10 and EC50) for the tropical freshwater alga Chlorella sp. 12 were 40 mg/L (27-54 mg/L 95% confidence limits [CL]), and 240 mg/L (200-280 mg/L 95% CL), respectively. The acute EC10 and EC50 values for 48-h immobilization of the water flea (Ceriodaphnia dubia) by dissolved barium were 14 mg/L (13-15 mg/L 95% CL) and 17 mg/L (16-18 mg/L 95% CL), respectively. Chlorella sp. 12 was significantly more sensitive to precipitated barium than to dissolved barium, whereas the opposite seemed likely for C. dubia. Ceriodaphnia dubia was predicted to be chronically sensitive to dissolved barium at concentrations measured in produced waters and receiving waters, based on a predicted chronic EC10 of 1.7 mg/L derived from the acute EC50/10. Further chronic toxicity data that account for barium toxicity in dissolved and precipitated forms are required to derive a barium guideline for freshwater biota. Environ Toxicol Chem 2018;37:1632-1642. © 2018 SETAC.

Deciphering the Combined Effects of Environmental Stressors on Gene Transcription: A Conceptual Approach

The use of classical mixture toxicity models to predict the combined effects of environmental stressors based on toxicogenomics (OMICS) data is still in its infancy. Although several studies have made attempts to implement mixture modeling in OMICS analysis to understand the low-dose interactions of stressors, it is not clear how interactions occur at the molecular level and how results generated from such approaches can be better used to inform future studies and cumulative hazard assessment of multiple stressors. The present work was therefore conducted to propose a conceptual approach for combined effect assessment using global gene expression data, as illustrated by a case study on assessment of combined effects of gamma radiation and depleted uranium (DU) on Atlantic salmon ( Salmo salar). Implementation of the independent action (IA) model in reanalysis of a previously published microarray gene expression dataset was performed to describe gene expression patterns of combined effects and identify key gene sets and pathways that were relevant for understanding the interactive effects of these stressors. By using this approach, 3120 differentially expressed genes (DEGs) were found to display additive effects, whereas 279 (273 synergistic, 6 antagonistic) were found to deviate from additivity. Functional analysis further revealed that multiple toxicity pathways, such as oxidative stress responses, cell cycle regulation, lipid metabolism, and immune responses were enriched by DEGs showing synergistic gene expression. A key toxicity pathway of DNA damage leading to enhanced tumorigenesis signaling is highlighted and discussed in detail as an example of how to take advantage of the approach. Furthermore, a conceptual workflow describing the integration of combined effect modeling, OMICS analysis, and bioinformatics is proposed. The present study presents a conceptual framework for utilizing OMICS data in combined effect assessment and may provide novel strategies for dealing with data analysis and interpretation of molecular responses of multiple stressors.

Effects of chronic crude oil exposure on early developmental stages of the Northern krill (Meganyctiphanes norvegica)

Rising oil and gas activities in northern high latitudes have led to an increased risk of petroleum pollution in these ecosystems. Further, seasonal high UV radiation at high latitudes may elevate photo-enhanced toxicity of petroleum pollution to marine organisms. Zooplanktons are a key ecological component of northern ecosystems; therefore, it is important to assess their sensitivity to potential pollutants of oil and gas activity. As ontogenetic development may be particularly sensitive, the aim of this study was to examine the impact of chronic exposure to oil water dispersion (OWD) on development and feeding of early life stages of the Northern krill, Meganyctiphanes norvegica. In a range of experiments, embryonic, nonfeeding, and feeding larval stages were exposed to concentrations of between 0.01 and 0.1 mg/L of oil or photo-modified oil for 19 and 21 d. No significant effects on egg respiration, hatching success, development, length and larval survival were observed from these treatments. Similarly, evolution of fatty acid composition patterns during ontogenetic development was unaffected. The results indicates a high degree of resilience of these early developmental stages to such types and concentrations of pollutants. However, feeding and motility in later calyptopis-stage larvae were significantly impaired at exposure of 0.1 mg/L oil. Data indicate that feeding larval stage of krill was more sensitive to OWD than early nonfeeding life stages. This might be attributed to the narcotic effects of oil pollutants, their direct ingestion, or accumulated adverse effects over early development.

Maternal polycyclic aromatic hydrocarbon (PAH) transfer and effects on offspring of copepods exposed to dispersed oil with and without oil droplets

Copepods of the genus Calanus have the potential for accumulating lipophilic oil components due to their high lipid content and found to filter and ingest oil droplets during exposure. As female copepods produce eggs at the expense of lipid storage, there is a concern for transfer of lipophilic contaminants to offspring. To assess the potential for maternal transfer of oil components, ovigerous female copepods (Calanus finmarchicus) were exposed to filtered and unfiltered oil dispersions for 4 days, collected and eggs maintained in clean seawater and hatching and gene expression examined in hatched nauplii. Oil droplet exposure contributed to polycyclic aromatic hydrocarbon (PAH) uptake in dispersion-treated adult copepods, as displayed through PAH body residue analyses and fluorescence microscopy. Applying the latter methodology, transfer of heavy PAH from copepod mothers to offspring were detected Subtle effects were observed in offspring as evidenced by a temporal reduction in hatching success appear to be occurring only when mothers were exposed to the unfiltered oil dispersions. Offspring reared in clean water through to late naupliar stages were collected for RNA extraction and preparation of libraries for high-throughput transcriptome sequencing. Differentially expressed genes were identified through pairwise comparisons between treatments. Among these, several expressed genes have known roles in responses to chemical stress including xenobiotic metabolism enzymes, antioxidants, chaperones, and components of the inflammatory response. While gene expression results suggest a transgenerational activation of stress responses, the increase in relatively small number of differentially expressed genes suggests a minor long-term effect on offspring following maternal exposure.

Acute hydrogen peroxide (H2O2) exposure does not cause oxidative stress in late-copepodite stage of Calanus finmarchicus

Use of hydrogen peroxide (H₂O₂) for removal of salmon lice in the aquaculture industry has created concern that non-target organisms might be affected during treatment scenarios. The aim of the present study was to examine the potential for H₂O₂ to produce oxidative stress and reduce survival in one of the most abundant zooplankton species in Norwegian coastal areas, the copepod Calanus finmarchicus. Copepods were subjected to two 96-hr tests: (1) acute toxicity test where mortality was determined and (2) treated copepods were exposed to concentrations below the No Observed Effect Concentration (0.75 mg/L) H₂O₂ and analyzed for antioxidant enzyme activities, as well as levels of glutathione (GSH) and malondialdehyde (MDA). Compared to available and comparable LC₅₀ values from the literature, our results suggest that C. finmarchicus is highly sensitive to H₂O₂. However, 96-hr exposure of C. finmarchicus to 0.75 mg H₂O₂/L did not significantly affect the antioxidant systems even though the concentration is just below the level where mortality is expected. Data suggest that aqueous H₂O₂ exposure did not cause cellular accumulation with associated oxidative stress, but rather produced acute effects on copepod surface (carapace). Further investigation is required to ensure that aqueous exposure during H₂O₂ treatment in salmon fish farms does not exert adverse effects on local non-target crustacean species and populations. In particular, studies on copepod developmental stages with a more permeable carapace are warranted.