Michael L. Sowby

Standardization of the Preparation and Quantitation of Water-accommodated Fractions of Petroleum for Toxicity Testing

Abstract Oil spill response can be highly affected by the perceived costs and benefits of a particular countermeasure. Responders’ perceptions of these can be influenced by the way in which scientific data are collected and presented. To date, a large amount of information has been generated on the aquatic toxicity of oil, dispersants and dispersed oil. Unfortunately, much of these data are not comparable because of differing toxicological and analytical methods used, as well as frequent lack of analytical verification of exposures. Recently, a group of federal, state, academic and industry representatives from North America and Europe have been working toward standardizing both biological and analytical methods used to produce acute toxicity estimates of complex mixtures such as oil, dispersants and dispersed oil. This standardization provides guidelines for future investigations to be conducted in a sufficiently rigourous manner that both inter- and intra-laboratory datasets will be comparable, thus providing a more coherent and robust database from which to derive response guidance.

Influence of dispersants on the bioavailability and trophic transfer of petroleum hydrocarbons to larval topsmelt (Atherinops affinis)

Use of chemical dispersants as oil spill clean-up agents may alter the normal behavior of petroleum hydrocarbons (PH) by increasing their functional water solubility, resulting in increased bioavailability and altered interactions between dispersant, oil, and biological membranes. The objective of this research was to determine the impact of dispersing agents on PH bioavailability and trophic transfer to larval fish from primary levels of a marine food chain. Uptake, bioaccumulation, depuration, and metabolic transformation of a model PH, [14C]naphthalene, were measured and compared for Prudhoe Bay crude oil (PBCO) dispersed with Corexit 9527(R) (DO) and undispersed preparations of the water-accommodated fraction (WAF) of PBCO. The model food chain consisted of a primary producer, Isochrysis galbana; and a primary consumer, the rotifer, Brachionus plicatilis; and larval topsmelt, Atherinops affinis. Direct aqueous (AQ) exposure was compared with combined aqueous and dietary (AQ&D) exposure. Dispersants altered the uptake and depuration processes of naphthalene, independent of aqueous concentrations, in primary trophic species of a marine food chain. The amount of naphthalene taken up by topsmelt was initially significantly (P < or = 0.05) enhanced in the presence of dispersant, reaching a maximum more quickly than undispersed samples. Dispersion treatment significantly increased naphthalene dispension in topsmelt (P < or = 0.05) from both AQ and AQ&D exposures. No significant change in naphthalene uptake by fish was observed with the addition of contaminated food for either WAF or DO medium; however, both uptake and depuration rate constants varied significantly with route of exposure consistent with greater naphthalene turnover. The majority (> or = 72%) of naphthalene-derived radioactivity from fish tissue following all exposures was in the parent form, with smaller quantities of alpha- and beta-naphthols, alpha- and beta-naphthyl sulfates, and an unidentified derivative.

Characterization of the metabolic actions of crude versus dispersed oil in salmon smolts via NMR-based metabolomics.

With maritime transport of crude oil from Alaska to California, there is significant potential for a catastrophic spill which could impact migrating salmon. Therefore, this study compared the lethal and sublethal metabolic actions of the water-accommodated fraction (WAF) and the chemically enhanced WAF (CEWAF, via Corexit 9500) of Prudhoe Bay crude oil in smolts of Chinook salmon (Onchorhyncus tshawytscha). After 96-h exposure to the CEWAF, the resulting LC50 was some 20 times higher (i.e., less toxic) than that of the WAF. Muscle and liver samples from surviving fish were collected and low-molecular weight metabolites were analyzed using one-dimensional (1)H and projections of two-dimensional (1)H J-resolved NMR. Principal component analysis (PCA), employed to analyze NMR spectra and identify most variance from the samples, revealed age-related metabolic changes in the fish within the replicated studies, but few consistent metabolic effects from the treatments. However, ANOVA results demonstrated that the dose-response metabolite patterns are both metabolite- and organ-dependent. In general, exposure to either WAF or CEWAF resulted in an increase of amino acids (i.e., valine, glutamine and glutamate) and a decrease of both organic osmolytes (i.e., glycerophosphorylcholine) and energetic substrates (i.e., succinate). The simultaneous increase of formate and decrease of glycerophosphorylcholine in the liver, or the decrease of glycerophosphorylcholine in muscle, may serve as sensitive sublethal biomarkers for WAF or CEWAF exposures, respectively. In conclusion, dispersant treatment significantly decreased the lethal potency of crude oil to salmon smolts, and the NMR-based metabolomics approach provided a sensitive means to characterize the sublethal metabolic actions.

Influence of Salinity on Petroleum Accommodation by Dispersants

Abstract The effect of receiving water salinity on the effectiveness of two oil dispersants, Corexits ® 9527 and 9500, was investigated using a recently implemented modified version of the Swirling Flask efficacy test. The dispersants were tested with ten different oils, representing a wide range of physical–chemical properties. Test salinities ranged from 0 to 35 ppt, with temperature held constant at 15°C. Results showed Corexit 9500 to be generally more effective on most of the dispersible oils at most salinities, but performance of both products was significantly affected by salinity. Both dispersants performed best at salinities above 25 ppt, with Corexit 9500 maintaining its effectiveness over a fairly wide range of salinities. Correlations between dispersant effectiveness and various oil physical/chemical properties were highly variable.

Influence of dispersants on the bioavailability and trophic transfer of petroleum hydrocarbons to primary levels of a marine food chain

Abstract Use of chemical dispersants as oil spill clean-up agents, alters normal behavior of petroleum hydrocarbons (PH) by increasing functional water solubility. The bioavailable fraction may be increased through higher PH concentrations in the water column and altered interactions between dispersant, oil, and biological membranes. The objective of this research was to determine the impact of dispersing agents on PH bioavailability and trophic transfer. Uptake, bioaccumulation, depuration, and metabolic transformation of a model PH, [ 14 C]naphthalene, were measured and compared for Prudhoe Bay crude oil (PBCO) dispersed with Corexit ® 9527 (DO) and undispersed preparations of the water-accommodated fraction (WAF) of PBCO. The model food chain consisted of Isochrysis galbana , a primary producer, and Brachionus plicatilis , a primary consumer. Direct aqueous (AQ) exposure was compared with combined aqueous and dietary (AQ and D) exposure. Results showed uptake of naphthalene by rotifers was not increased significantly ( P >0.05) in the presence of dispersant. A significant ( P 14 C] recovered in AQ and D exposures and remained associated with the organism during depuration. Characterization of WAF and DO media showed aqueous concentrations of naphthalene were not significantly different. This research has demonstrated that dispersants altered uptake and depuration processes of naphthalene, independent of concentration, in representative species of primary trophic levels of the marine food chain which may in turn modify bioavailability and bioaccumulation at higher trophic levels.

Metabolic responses produced by crude versus dispersed oil in Chinook salmon pre-smolts via NMR-based metabolomics

Crude oil spills from tankers remain a serious threat along coastal California. Resource managers require information on the acute toxicity of treated and untreated oil, and their sublethal effects on wildlife. This investigation compared the toxic actions of the water-accommodated fraction (WAF) and the chemically-enhanced WAF (CEWAF; Corexit 9500) of Prudhoe Bay crude oil in pre-smolt Chinook salmon (Oncorhynchus tshawytscha) via nuclear magnetic resonance (NMR)-based metabolomics. Metabolite profiles from muscle samples, after 96h exposures, were measured using 1D (1)H NMR and compared via principal component analysis. It was determined that both WAF and CEWAF produced similar profiles in which amino acids, lactate and ATP comprised the highest intensity signals. Overall, metabolic substrates and growth measurements did not show residual effects of short-term exposure on long-term development. In conclusion, the 96h LC(50)s indicate dispersant application significantly decreased hydrocarbon potency and identified metabolites may be bio-indicators of hydrocarbon stress from hydrocarbon exposure.

Induction of heat shock protein (hsp)60 in Isochrysis galbana exposed to sublethal preparations of dispersant and Prudhoe Bay crude oil

Abstract Adaptation to sublethal exposure to crude oil by phytoplankton is poorly understood. Use of chemical dispersants for oil spill remediation increases petroleum hydrocarbon concentrations in water, while exposing marine organisms to potentially toxic concentrations of dispersant. Heat shock proteins (hsps) have been found to serve as an adaptive and protective mechanism against environmental stresses. The objective of this project was to examine the induction of hsps in Isochrysis galbana, a golden-brown algae, following exposure to the water-accommodated fraction (WAF) of Prudhoe Bay crude oil (PBCO) and PBCO chemically dispersed with Corexit 9527® (dispersed oil: DO). Initial experiments using 35S-labeled amino acids and 2-dimensional electrophoresis with subsequent western blotting identified and confirmed hsp60, a member of the chaperonin family of stress proteins, as being efficiently induced by heat shock in this species. One-dimensional SDS PAGE and western blotting, with hsp60 antibodies and chemiluminesence detection, were used to quantitate hsp60 following exposure to a range of environmental temperatures and concentrations of WAF and DO preparations. I. galbana cultured in 22 parts per thousand (‰) salinity showed a statistically significant increase (p

ACUTE EFFECTS OF FRESH VERSUS WEATHERED OIL TO MARINE ORGANISMS: CALIFORNIA FINDINGS

ABSTRACT Early experiences with dispersants led to a widely accepted paradigm in the United States that chemically dispersing oil led to increased ecological damage. Since then, dispersant formulations have evolved significantly, leading many in the oil spill response community to revisit the question of whether or not dispersing oil can help achieve an overall net ecological benefit. Spill response must necessarily involve weighing the costs and benefits of both dispersant use and non-use to resources potentially at risk. The majority of comparative data on the toxicity of dispersed and undispersed oil in the literature to date is based on fresh oil. In most circumstances, however, mounting of dispersant operations requires hours to days, making the use of data based on fresh oil problematic. Laboratory-weathered oil has been used in the evaluation of dispersant effectiveness, but its use in toxicological investigations has been limited. Using standardized methods, the authors have compared the acute aqu...

Influence of dispersants on the bioavailability and trophic transfer of phenanthrene to algae and rotifers

Abstract Use of chemical dispersants as oil spill clean-up agents alters normal behavior of petroleum hydrocarbons (PH) by increasing functional water solubility. Different PHs may respond differently to dispersant based on their individual physical properties and altering the composition of the bioaccessible fraction of the oil. The objective of this research was to determine the impact of dispersing agents on the bioavailability and trophic transfer of phenanthrene, a model for a class of compounds in oil characterized by limited water solubility and the potential to bioaccumulate. Uptake, bioaccumulation, and depuration of [14C]phenanthrene, were compared for Prudhoe Bay crude oil (PBCO) dispersed with Corexit® 9527 (dispersed oil or DO) and undispersed preparations of the water-accommodated fraction (WAF) of PBCO. The model food chain consisted of Isochrysis galbana, a primary producer, and Brachionus plicatilis, a primary consumer. Direct aqueous (AQ) exposure was compared with combined aqueous and dietary (AQ&D) exposure. Results showed phenanthrene uptake by algae increased significantly (P 0.05) in phenanthrene uptake was observed in rotifers in DO, however, phenanthrene depuration significantly (P

Comparative toxicity of Corexit® 7664 to the early life stages of four marine species

The toxicity of the oil dispersing agent Corexit® 7664 was evaluated using the early life stages of four California marine species: the red abalone (Haliotis rufescens), the topsmelt (Atherinops affinis), a mysid (Holmesimysis costata), and the giant kelp (Macrocystis pyrifera). Spiked-exposure, continuous-flow toxicity tests of 48–96 h were performed in triplicate in closed test chambers. Dispersant concentrations were measured by UV spectrophotometry. In terms of median-effect concentration, the order of test sensitivity was Haliotis>Atherinops>Holmesimysis>Macrocystis. NOEC data also showed Haliotis tests to be the most sensitive, with Macrocystis tests having similar values, followed by Atherinops and Holmesimysis tests, respectively. Toxicity of Corexit® 7664 was compared to that of Corexit® 9527, and the latter was found to be more toxic to all four species; interspecific rankings were similar for the two agents.