The toxicological impacts of oil and chemically dispersed oil: UV mediated phototoxicity and implications for environmental effects, statutory testing and response strategies

Tracking and Assessing Oil Spill Toxicity to Aquatic Organisms: A Novel Approach

An in situ exposure and effects bioassay system was developed for assessing the toxicity of oil spills to aquatic organisms. The assessment tool combines components of 2 previously developed systems, the sediment ecotoxicity assessment ring (SEA Ring) and the drifting particle simulator. The integrated drifting exposure and effects assessment ring (DEEAR) is comprised of a Global Positioning System (GPS) float, a drifter drogue, the SEA Ring, and the Cyclops-7 fluorescent sensor. Polyethylene passive sampling devices (PED) were mounted for an additional means to characterize water quality conditions and exposures. The DEEAR is optimized for evaluating oil exposure and toxicity in the shallow surface mixing layer of marine waters. A short-term preliminary test was conducted in San Diego, California, USA, to verify the operation of the GPS tracking, the iridium communications, and the integrated SEA Ring exposure system. Further, a proof-of-concept demonstration was conducted offshore in the Santa Barbara Channel, where natural oil seeps produce surface slicks and sheens. Two DEEAR units were deployed for 24 h-one within the oil slick and one in an area outside observable slicks. An aerial drone provided tracking of the surface oil and optimal sites for deployment. The DEEAR proof-of-concept demonstrated integrated real-time tracking and characterization of oil exposures by grab samples, PED, and fluorescent sensors. Oil exposures were directly linked to toxic responses in fish and mysids. This novel integrated system shows promise for use in a variety of aquatic sites to more accurately determine in situ oil exposure and toxicity. Environ Toxicol Chem 2021;40:1452-1462. © 2021 SETAC.

Photoenhanced Toxicity of Petroleum to Aquatic Invertebrates and Fish

Photoenhanced toxicity is a distinct mechanism of petroleum toxicity that is mediated by the interaction of solar radiation with specific polycyclic aromatic compounds in oil. Phototoxicity is observed as a twofold to greater than 1000-fold increase in chemical toxicity to aquatic organisms that also have been exposed to light sources containing sufficient quantity and quality of ultraviolet radiation (UV). When tested under natural sunlight or laboratory sources of UV, fresh, and weathered middle distillates, crudes and heavy oils can exhibit photoenhanced toxicity. These same products do not exhibit phototoxicity in standard test protocols because of low UV irradiance in laboratory lighting. Fresh, estuarine, and marine waters have been shown to have sufficient solar radiation exposure to elicit photoenhanced toxicity, and a diversity of aquatic invertebrate and fish species can exhibit photoenhanced toxicity when exposed to combinations of oil and UV. Risks of photoenhanced toxicity will be greatest to early life stages of aquatic organisms that are translucent to UV and that inhabit the photic zone of the water column and intertidal areas exposed to oil.

Unraveling the interactive effects of climate change and oil contamination on laboratory-simulated estuarine benthic communities

There is growing concern that modifications to the global environment such as ocean acidification and increased ultraviolet radiation may interact with anthropogenic pollutants to adversely affect the future marine environment. Despite this, little is known about the nature of the potential risks posed by such interactions. Here, we performed a multifactorial microcosm experiment to assess the impact of ocean acidification, ultraviolet B (UV-B) radiation and oil hydrocarbon contamination on sediment chemistry, the microbial community (composition and function) and biochemical marker response of selected indicator species. We found that increased ocean acidification and oil contamination in the absence of UV-B will significantly alter bacterial composition by, among other things, greatly reducing the relative abundance of Desulfobacterales, known to be important oil hydrocarbon degraders. Along with changes in bacterial composition, we identified concomitant shifts in the composition of oil hydrocarbons in the sediment and an increase in oxidative stress effects on our indicator species. Interestingly, our study identifies UV-B as a critical component in the interaction between these factors, as its presence alleviates harmful effects caused by the combination of reduced pH and oil pollution. The model system used here shows that the interactive effect of reduced pH and oil contamination can adversely affect the structure and functioning of sediment benthic communities, with the potential to exacerbate the toxicity of oil hydrocarbons in marine ecosystems.

Issues and challenges with oil toxicity data and implications for their use in decision making: a quantitative review

Aquatic toxicity considerations are part of the net environmental benefit analysis and approval decision process on the use of dispersants in the event of an offshore oil spill. Substantial information is available on the acute toxicity of physically and chemically dispersed oil to a diverse subset of aquatic species generated under controlled laboratory conditions. However, most information has been generated following standard laboratory practices, which do not realistically represent oil spill conditions in the field. The goal of the present quantitative review is to evaluate the use of standard toxicity testing data to help inform decisions regarding dispersant use, recognizing some key issues with current practices, specifically, reporting toxicity metrics (nominal vs measured), exposure duration (standard durations vs short-term exposures), and exposure concentrations (constant vs spiked). Analytical chemistry data also were used to demonstrate the role of oil loading on acute toxicity and the influence of dispersants on chemical partitioning. The analyses presented here strongly suggest that decisions should be made, at a minimum, based on measured aqueous exposure concentrations and, ideally, using data from short-term exposure durations under spiked exposure concentrations. Available data sets are used to demonstrate how species sensitivity distribution curves can provide useful insights to the decision-making process on dispersant use. Finally, recommendations are provided, including the adoption of oil spill-appropriate toxicity testing practices.

Do UK coastal and estuarine water samples pose a phototoxic threat?

Many studies have investigated phototoxicity under controlled laboratory conditions, however, few have actually demonstrated it occurring in environmental samples. Here we report on the potential for UK marine coastal waters to demonstrate phototoxicity when tested using the oyster embryo (Crassostrea gigas) bioassay in the presence UV light. Subsurface water, sea surface microlayer samples and subsurface water samples that had been extracted through solid phase extraction (SPE) columns were analysed. Results demonstrated that the majority of samples failed to display any phototoxic potential. However, those collected from Belfast Lough did display an increase in toxicity when bioassays were performed in the presence of UV light when compared to identical samples assayed in the absence of UV light. Analysis of water samples at this location identified known phototoxic PAHs, pyrene and fluoranthene. These findings suggest the need to consider the potential UV light has when determining the toxicity of environmental samples.

Oil spill treatment products approval: the UK approach and potential application to the Gulf region

The environmental threat from oil spills remains significant across the globe and particularly in regions of high oil production and transport such as the Gulf. The ultimate damage caused can be limited by mitigation actions that responders deploy. The responsible and appropriate use of oil spill treatment products (e.g. dispersants, sorbents etc.) can offer response options that can result in substantial net environmental benefit. However, the approval and choice of what products to use needs careful consideration. The United Kingdom has had in place a statutory approval scheme for oil spill treatment products for 30 years. It is based on measures of efficiency and environmental acceptability. Two toxicity tests form an integral part of the assessment, the Sea test and the Rocky Shore test, and work on the premise that approved products will not make the situation significantly worse when added to spilled oil. This paper outlines the UK approach and how its rationale might be applied to the approval of products specific for the Gulf region. Issues such as species choice, higher temperatures and salinity and regional environmental conditions are considered.