Prior exposure to weathered oil influences foraging of an ecologically important saltmarsh resident fish

Estuarine ecosystem balance typically relies on strong food web interconnectedness dependent on a relatively low number of resident taxa, presenting a potential ecological vulnerability to extreme ecosystem disturbances. Following the Deepwater Horizon (DwH) oil spill disaster of the northern Gulf of Mexico (USA), numerous ecotoxicological studies showed severe species-level impacts of oil exposure on estuarine fish and invertebrates, yet post-spill surveys found little evidence for severe impacts to coastal populations, communities, or food webs. The acknowledgement that several confounding factors may have limited researchers’ abilities to detect negative ecosystem-level impacts following the DwH spill drives the need for direct testing of weathered oil exposure effects on estuarine residents with high trophic connectivity. Here, we describe an experiment that examined the influence of previous exposure to four weathered oil concentrations (control: 0.0 L oil m−2; low: 0.1 L oil m−2; moderate: 0.5–1 L oil m−2; high: 3.0 L oil m−2) on foraging rates of the ecologically important Gulf killifish (Fundulus grandis). Following exposure in oiled saltmarsh mesocosms, killifish were allowed to forage on grass shrimp (Palaeomonetes pugio) for up to 21 h. We found that previous exposure to the high oil treatment reduced killifish foraging rate by ~37% on average, compared with no oil control treatment. Previous exposure to the moderate oil treatment showed highly variable foraging rate responses, while low exposure treatment was similar to unexposed responses. Declining foraging rate responses to previous high weathered oil exposure suggests potential oil spill influence on energy transfer between saltmarsh and off-marsh systems. Additionally, foraging rate variability at the moderate level highlights the large degree of intraspecific variability for this sublethal response and indicates this concentration represents a potential threshold of oil exposure influence on killifish foraging. We also found that consumption of gravid vs non-gravid shrimp was not independent of prior oil exposure concentration, as high oil exposure treatment killifish consumed ~3× more gravid shrimp than expected. Our study findings highlight the sublethal effects of prior oil exposure on foraging abilities of ecologically valuable Gulf killifish at realistic oil exposure levels, suggesting that important trophic transfers of energy to off-marsh systems may have been impacted, at least in the short-term, by shoreline oiling at highly localized scales. This study provides support for further experimental testing of oil exposure effects on sublethal behavioral impacts of ecologically important estuarine species, due to the likelihood that some ecological ramifications of DwH on saltmarshes likely went undetected.

EVOS and the Prince William Sound Long Term Environmental Monitoring Program

ABSTRACT Following the 1989 Exxon Valdez oil spill (EVOS), the Prince William Sound Regional Citizens' Advisory Council began the Long-Term Environmental Monitoring Program (LTEMP) in 1993 to track oil hydrocarbon chemistry of recovering sediments and mussel tissues along the path of the spill in Prince William Sound (PWS) and across the Northern Gulf of Alaska (NGOA) region. The program also samples sites near the Alyeska Marine Terminal (AMT) within Port Valdez, primarily to monitor tanker operations and the resulting treatment and discharge of oil-contaminated tanker ballast water. Over the last 28 years, the program has documented EVOS oil's disappearance at the spill-impacted sites (albeit buried oil still exists at a few unique sheltered locations in PWS). Within the Port, a few tanker- and diesel-spill incidents have been documented over the years, but all were minor and with recovery times of < 1 yr. Of highest concern has been the permitted chronic release of weathered oil from tankers' ballast-water that is treated and discharged at the Alyeska Marine Terminal (AMT). In earlier years (1980s–90s), with discharge volumes reaching 17–18 MGD, up to a barrel of finely dispersed weathered oil would be released into the fjord daily. Over the last two decades, total petrogenic inputs (TPAH43) into the Port have declined as measured in the monitored mussels and sediments. This trend reflects a combination of decreased Alaska North Slope (ANS) oil production and thus, less tanker traffic, plus less ballast from the transition to double-hulled tankers with segregated ballast tanks, and improved treatment-facility efficiency in removing PAH. From the 2018 collections, mussel-tissue hydrocarbon concentrations from all eleven LTEMP stations (within Port Valdez as well as PWS and NGOA regions) were below method detection limits and similar to laboratory blanks (TPAH43 < 44 ng/g dry wt.). At these low background levels, elevated TPAH values from a minor 2020 spill incident at the Terminal were easily detected at all three Port Valdez stations.

Effect of long term natural weathering on oil composition: study of the 41-years-old Amoco Cadiz and 20-years-old Erika oil spills

On 16 March 1978, the oil tanker the Amoco Cadiz, transporting 223,000 tons of crude oil and 4,000 tons of bunker fuel oil, suffered a failure of her steering mechanism and ran aground on Portsall Rocks, on the Breton coast. The entire cargo spilled out as the breakers split the vessel in two, progressively polluting 360 km of French shoreline from Brest to Saint Brieuc. This was the largest oil spill caused by a tanker grounding ever recorded in the world. The consequences of this accident were significant, and it caused the French Government to revise its oil response plan (the Polmar Plan), to acquire equipment stocks (Polmar stockpiles), to impose traffic lanes in the Channel and to create Cedre. On 12 December 1999, the tanker Erika broke up and sank off the coast of Brittany (France) leading to the spill of 20,000 tons of a heavy fuel oil. 400 km of the French Atlantic coastline were polluted. Because of the characteristics of the oil (a very heavy fuel oil with a high content of light cracking oil) and the severe weather conditions (a centennial storm with spring tides) when the oil came on shore, the Erika spill was one of the most severe accidental releases of oil along the French coastlines. All types of habitat were concerned, and pollution reached the supratidal zone affecting terrestrial vegetation and lichens. In 2019, respectively 41 years and 20 years after these major oil spills affecting the French shoreline, a sampling round was conducted at two sites recorded to present some residual traces of oil. Samples of weathered oil were collected, extracted with methylene chloride and then purified through an alumina-silica microcolumn. SARA fractionation and GC-MS analyses were performed in order to assess respectively the total degradation of the weathered oil (amount of saturates, aromatics and polar fraction) and the specific degradation of nalkanes from n-C9 to n-C40, biomarkers (such as terpanes, hopanes and steranes) and PAHs (parents and alkylated derivatives).

Determination of Oil Spill Chemical Concentrations in Nearshore Matrices

ABSTRACT Marine oil spill incidents create concerns about human health risks, particularly in nearshore locations such as beaches used for recreation. To improve the timeliness of risk estimates during an oil spill, we need to expand modelling capacity for oil spill chemicals (OSCs) from predictions for chemical bulk measurements such as Total Petroleum Hydrocarbons (TPH) to predictions of individual concentrations of the more toxic Polycyclic Aromatic Hydrocarbons (PAH)s. The objective of this study is to establish a relationship for TPH and PAH nearshore sampling concentration values with the oil mass landing and TPH hindcast from a 3D Hydrodynamic Fate and Transport Model (3D-FTM) for a past oil spill. The overall goal is to use this information to expand current modeling capacities to predict concentration distributions for individual PAHs as a starting point for health risk assessment. During Phase I of this study, historic sampling data for various matrices (weathered oil, seawater and sediments) were used to evaluate PAH concentration distributions within time-space specific categories. The categories corresponded to samples collected prior to nearshore oiling, post nearshore oiling and at no time impacted by oil as predicted by historic oil spill trajectories. For matrices within each category, concentration frequency distributions and concentration patterns were generated for a subset of PAHs. Results show differences in PAH concentration patterns within each matrix and for each category. Concentration frequency distributions for most PAHs in each category were log-normally distributed. Phase II is ongoing. Here we analyze PAH and TPH concentrations measured from surface weathered oil slick samples collected at the time of the Deepwater Horizon (DWH) oil spill. Preliminary results show that concentrations for a subset of PAHs in weathered oil slicks correlate well with TPH concentrations (R2=0.76). We are collocating the historic environmental sampling data with the output from the Oil-Connectivity Modelling System (Oil-CMS). The relationship between measured and model predicted TPH is explored by comparing values for samples that coincide in time and space with the model's particles. A subsequent step is to use output of the oil-CMS in combination with the physical and chemical properties for each PAH to predict concentration distributions for individual PAHs. The overarching goal is to improve risk estimates and, therefore, better guide public health decision-making.

GC×GC-HRMS nontarget fingerprinting of organic micropollutants in urban freshwater sediments

Background Sediments are sinks for organic micropollutants, which are traditionally analysed by gas chromatography-mass spectrometry (GC-MS). Although GC-MS and GC-MS/MS (tandem MS) are preferred for target screening, they provide only limited chromatographic resolution for nontarget screening. In this study, a comprehensive two-dimensional GC-high-resolution MS method (GC×GC-HRMS) was developed for nontarget screening and source identification of organic micropollutants in sediments from an urban lake and channel in Copenhagen, Denmark. The GC×GC-HRMS data were processed by pixel-based chemometric analysis using baseline subtraction, alignment, normalisation, and scaling before principal component analysis (PCA) of the pre-processed GC×GC-HRMS base peak ion chromatograms (BPCs). The analysis was performed to identify organic micropollutants of high abundance and relevance in the urban sediments, to identify pollution sources. Tentative identifications were based on match factors and retention indices and tagged according to the level of identification confidence. Results The channel contained both significantly higher concentrations of micropollutants and a higher diversity of compounds compared to the lake. The PCA models were able to isolate distinct sources of chemicals such as a natural input (viz. a high relative abundance of mono-, di- and sesquiterpenes) and a weathered oil fingerprint (viz. alkanes, naphthenes and alkylated polycyclic aromatic hydrocarbons). A dilution effect of the weathered oil fingerprint was observed in lake samples that were close to the channel. Several benzothiazole-like structures were identified in lake samples close to a high-traffic road which could indicate a significant input from asphalt or tire wear particles. Conclusions Several chemical fingerprints of different sources were described in urban freshwater sediments in Copenhagen using a pixel-based chemometric approach of GC×GC-HRMS chromatograms. Various micropollutants of anthropogenic origin were identified. Tailored pre-processing and careful interpretation of the identification results is inevitable and still requires further research for an automated workflow.