Toxicity and developmental effects of Arctic fuel oil types on early life stages of Atlantic cod (Gadus morhua)

Stranded heavy fuel oil exposure causes deformities, cardiac dysfunction, and oxidative stress in marine medaka Oryzias melastigma using an oiled-gravel-column system

Heavy fuel oil (HFO) stranded on the coastline poses a potential threat to the health of marine fish after an oil spill. In this study, an oiled-gravel-column (OGC) system was established to investigate the toxic effects of stranded HFO on marine medaka Oryzias melastigma. HFO 380# (sulfur content 2.9%) was chosen as one type of high sulfur fuel oil for acute toxicity tests. The marine medaka larvae were exposed to the OGC system effluents with oil loading rates of 0 (control), 400, 800, 1600, and 3200 µg HFO/g gravel for 144 h, respectively. Results showed that a prevalence of blue sac disease signs presented teratogenic effects, including decreased circulation, ventricular stretch, cardiac hemorrhage, and pericardial edema. Moreover, the treatments (800, 1600, and 3200 µg oil/g gravel) induced severe cardiotoxicity, characterized by significant bradycardia and reduced stroke volume with an overt decrease in cardiac output. Additionally, the antioxidant enzyme activities, including catalase (CAT), peroxidase (POD), and glutathione S-transferase (GST) were significantly upregulated at 800-3200 µg oil/g gravel except for a marked inhibition of CAT activity at 3200 µg oil/g gravel. Furthermore, significantly elevated protein carbonyl (PCO) levels were detected, suggesting that the organisms suffered severe protein oxidative damage subjected to the exposure. Overall, stranded HFO 380# exposure activated the antioxidant defense system (up-regulated POD and GST activities) of marine medaka and disrupted CAT activity, which could result in an oxidative stress state (elevated PCO levels) and might further contribute to cardiac dysfunction, deformities, and mortality.

A review of oil spill research in Canadian Arctic marine environments

The Canadian Arctic is a large and diverse geographic area that encompasses a wide variety of environmental conditions and ecosystems. Over recent decades, marine transportation has increased across the Arctic and, as a result, so has the likelihood of an oil spill. The study of oil spills in the Arctic presents unique challenges compared to temperate marine environments, due to remoteness, cold temperatures and the presence of snow and ice throughout much of the year. This review summarizes and discusses the fate of oil in the Canadian Arctic. A brief introduction to the Canadian Arctic and sources of potential petroleum spills is provided, followed by discussions of the behaviour of oil in ice and freezing temperatures, oil-sediment interactions, and the weathering and natural remediation of oil under Arctic conditions. A summary of perspectives concludes the review, with emphasis on possible areas of future work to address research gaps.

Dilute concentrations of maritime fuel can modify sediment reworking activity of high-latitude marine invertebrates

Multiple expressions of climate change, in particular warming-induced reductions in the type, extent and thickness of sea ice, are opening access and providing new viable development opportunities in high-latitude regions. Coastal margins are facing these challenges, but the vulnerability of species and ecosystems to the effects of fuel contamination associated with increased maritime traffic is largely unknown. Here, we show that low concentrations of the water-accommodated fraction of marine fuel oil, representative of a dilute fuel oil spill, can alter functionally important aspects of the behaviour of sediment-dwelling invertebrates. We find that the response to contamination is species specific, but that the range in response among individuals is modified by increasing fuel concentrations. Our study provides evidence that species responses to novel and/or unprecedented levels of anthropogenic activity associated with the opening up of high-latitude regions can have substantive ecological effects, even when human impacts are at, or below, commonly accepted safe thresholds. These secondary responses are often overlooked in broad-scale environmental assessments and marine planning yet, critically, they may act as an early warning signal for impending and more pronounced ecological transitions.

Mind the gap - Relevant design for laboratory oil exposure of fish as informed by a numerical impact assessment model

Laboratory experiments provide knowledge of species-specific effects thresholds that are used to parameterize impact assessment models of oil contamination on marine ecosystems. Such experiments typically place individuals of species and life stages in tanks with different contaminant concentrations. Exposure concentrations are usually fixed, and the individuals experience a shock treatment being moved from clean water directly into contaminated water and then back to clean water. In this study, we use a coupled numerical model that simulates ocean currents and state, oil dispersal and fate, and early life stages of fish to quantify oil exposure histories, specifically addressing oil spill scenarios of high rates and long durations. By including uptake modelling we also investigate the potential of buffering transient high peaks in exposure. Our simulation results are the basis for a recommendation on the design of laboratory experiments to improve impact assessment model development and parameterization. We recommend an exposure profile with three main phases: i) a gradual increase in concentration, ii) a transient peak that is well above the subsequent level, and iii) a plateau of fixed concentration lasting ∼3 days. In addition, a fourth phase with a slow decrease may be added.

No observed developmental effects in early life stages of capelin (Mallotus villosus) exposed to a water-soluble fraction of crude oil during embryonic development

The rise in offshore oil and gas operations, maritime shipping, and tourism in northern latitudes enhances the risk of oil spills to sub-Arctic and Arctic coastal environments. Therefore, there is a need to understand the potential adverse effects of petroleum on key species in these areas. Here, we investigated the effects of oil exposure on the early life stages of capelin (Mallotus villosus), an ecologically and commercially important Barents Sea forage fish species that spawns along the coast of Northern Norway. Capelin embryos were exposed to five different concentrations (corresponding to 0.5-19 µg/L total PAHs) of water-soluble fraction (WSF) of crude oil from 6 days post fertilization (dpf) until hatch (25 dpf), and development of larvae in clean seawater was monitored until 52 dpf. None of the investigated endpoints (embryo development, larval length, heart rate, arrhythmia, and larval mortality) showed any effects. Our results suggest that the early life stages of capelin may be more robust to crude oil exposure than similar life stages of other fish species.

Experimental evaluation of DPF performance loaded over Pt and sulfur-resisting material for marine diesel engines

Different from vehicle engines, Diesel Particulate Filter (DPF) inactivation is an unavoidable issue for low-speed marine diesel engines fueled with Heavy Fuel Oil (HFO). This paper introduced a sulfur resisting material in Silicon Carbide (SiC)-DPF to improve DPF performance. The results of bench-scale experiments showed that the Balance Point Temperature of the modified DPF module was 300°C and DPF modules had a good filtration performance, with Particulate Matters (PMs) residual being less than 0.6 g per cycle. In pilot-scale tests, PMs emissions of unit power decreased with engine load going up, filtration efficiency of nucleation mode PMs being only 36% under 100% load, while DPF still had a good performance in accumulation mode PMs control, being 94.2% under the same load. DPF modules showed excellent regeneration durability in the 205h endurance test, with a regeneration period of 1.5-2h under 380°C. There was no obvious degeneration in the DPF module structure, with no cracks or breakage. Besides, the DPF module could also control gaseous emissions, total emissions decreased by 10.53% for NO and 57.19% for CO, respectively. The results suggested that introducing sulfur-resisting material in DPF could greatly improve the DPF performance of low-speed marine diesel engines fueled with HFO.

Intraspecific Variation in the Sublethal Effects of Physically and Chemically Dispersed Crude Oil on Early Life Stages of Atlantic Cod (Gadus morhua)

The offshore oil industry in Atlantic Canada necessitates a greater understanding of the potential impacts of oil exposure and spill response measures on cold-water marine species. We used a standardized scoring index to characterize sublethal developmental impacts of physically and chemically dispersed crude oil in early life stages of Atlantic cod (Gadus morhua) and assessed intraspecific variation in the response among cod families. Cod (origin: Scotian Shelf, Canada) were laboratory-crossed to produce embryos from five specific families, which were subsequently exposed prehatch to gradient dilutions of a water-accommodated fraction (WAF) and a chemically enhanced WAF (CEWAF; prepared with Corexit 9500A) for 24 h. Postexposure, live embryos were transferred into filtered seawater and monitored to hatch; then, all live fish had sublethal endpoints assessed using the blue-sac disease (BSD) severity index. In both WAF and CEWAF groups, increasing exposure concentrations (measured as total petroleum hydrocarbons) resulted in an increased incidence of BSD symptoms (impaired swimming ability, increased degree of spinal curvature, yolk-sac edemas) in cod across all families. This positive concentration-dependent increase in BSD was similar between physically (WAF) versus chemically (CEWAF) dispersed oil exposures, indicating that dispersant addition does not exacerbate the effect of crude oil on BSD incidence in cod. Sensitivity varied between families, with some families having less BSD than others with increasing exposure concentrations. To our knowledge, our study is the first to demonstrate the occurrence in fishes of intraspecific variation among families in sublethal responses to oil and dispersant exposure. Our results suggest that sublethal effects of crude oil exposure will not be uniformly observed across cod populations and that sensitivity depends on genetic background. Environ Toxicol Chem 2022;41:1967-1976. © 2022 SETAC.

Application of chemical herders do not increase acute crude oil toxicity to cold-water marine species

Chemical herders may be used to sequester and thicken surface oil slicks to increase the time window for performing in situ burning of spilled oil on the sea surface. For herder use to be an environmentally safe oil spill response option, information regarding their potential ecotoxicity both alone and in combination with oil is needed. This study aimed at assessing if using herders can cause toxicity to cold-water marine organisms. Our objective was to test the two chemical herders Siltech OP-40 (OP-40) and ThickSlick-6535 (TS-6535) with and without oil for toxicity using sensitive life stages of cold-water marine copepod (Calanus finmarchicus) and fish (Gadus morhua). For herders alone, OP-40 was consistently more toxic than TS-6535. To test herders in combination with oil, low-energy water accommodated fractions (LE-WAFs, without vortex) with Alaskan North Slope crude oils were prepared with and without herders. Dissolution of oil components from surface oil was somewhat delayed following herder application, due to herder-induced reduction in contact area between water and oil. The LE-WAFs were also used for toxicity testing, and we observed no significant differences in toxicity thresholds between treatments to LE-WAFs generated with oil alone and oil treated with herders. The operational herder-to-oil ratio is very low (1:500), and the herders tested in the present work displayed acute toxicity at concentrations well above what would be expected following in situ application. Application of chemical herders to oil slicks is not expected to add significant effects to that of the oil for cold-water marine species exposed to herder-treated oil slicks.

The effects of dissolved petroleum hydrocarbons on benthic organisms: Chironomids and amphipods

The oil sands industry in Canada, produces heavy unconventional oils, diluted for transport and called diluted bitumen. However, despite advances in our knowledge of the ecotoxicological risk that these products represent, their effects on benthic organisms following a spill are still largely unknown. In order to fill these gaps, this study aims to determine the lethal and sublethal effects of two diluted bitumens (Bluesky and Cold Lake) and one conventional oil (Lloydminster) for two freshwater benthic invertebrates: Chironomus riparius and Hyalella azteca. The objective of this study is to assess the toxicity of dissolved hydrocarbons, resulting from the physical dispersion of oil, immediately after a spill on the benthic invertebrates. To this end, organisms were exposed for 7 days for chironomids and 14 days for amphipods to a fraction containing soluble hydrocarbons (WAF: water accommodated fraction; 10 g/L, 18 h of agitation, followed by 6 h of sedimentation) with natural or artificial sediment. After exposure, the effects of hydrocarbons were determined using size, mortality, and antioxidant capacities. Dissolved hydrocarbons induced mortality for both species, but these hydrocarbons disappeared very quickly from the water column, regardless of the oil type. The amphipods were sensitive to both types of oil while the chironomids were only sensitive to diluted bitumens. The presence of a natural sediment seems to provide a protective role against dissolved hydrocarbons. The antioxidant enzymes measured (CAT, SOD and GPx) do not appear to be relevant biomarkers for the exposure of these organisms to diluted bitumen.

Automated morphometrics on microscopy images of Atlantic cod larvae using Mask R-CNN and classical machine vision techniques

Measurements of morphometrical parameters on i.e., fish larvae are useful for assessing the quality and condition of the specimen in environmental research or optimal growth in the cultivation industry. Manually acquiring morphometrical parameters from microscopy images can be time consuming and tedious, this can be a limiting factor when acquiring samples for an experiment. Mask R-CNN, an instance segmentation neural network architecture, has been implemented for finding outlines on parts of interest on fish larvae (Atlantic cod, Gadus morhua). Using classical machine vision techniques on the outlines makes it is possible to acquire morphometrics such as area, diameter, length, and height. The combination of these techniques is providing accurate-, consistent-, and high-volume information on the morphometrics of small organisms, making it possible to sample more data for morphometric analysis.•Capabilities to automatically analyse a set of microscopy images in approximately 2-3 seconds per image, with results that have a high degree of accuracy when compared to morphometrics acquired manually by an expert.•Can be implemented on other species of ichthyoplankton or zooplankton and has successfully been tested on ballan wrasse, zebrafish, lumpsucker and calanoid copepods.

Exposure to low environmental copper concentrations does not affect survival and development in Atlantic cod (Gadus morhua) early life stages

In this study we investigated potential impacts of Cu exposure at low, environmentally relevant, concentrations on early live stages of Atlantic cod (Gadus morhua). Cod embryos and larvae were exposed to 0.5 μg/L (low), 2 μg/L (medium), and 6 μg/L (high) Cu from 4 to 17 days post fertilisation (dpf). Hatching success, mortality, oxygen consumption, biometric traits, and malformations were determined. A dynamic energy budget (DEB) model was applied to identify potential impacts on bioenergetics. A positive correlation was found between Cu exposure concentrations and Cu body burden in eggs, but not in larvae. The tested concentrations did not increase mortality in neither embryos nor larvae, or larvae deformations. Further, the DEB model did not indicate effects of the tested Cu concentrations.