Assessment of hydrocarbon exposure in the waters of Prince William Sound after the Exxon Valdez oil spill: 1989–2005

Exponent, Inc., Maynard, MA 01754, United States.
Marine Pollution Bulletin (Impact Factor: 2.99). 04/2007; 54(3):339-56. DOI: 10.1016/j.marpolbul.2006.11.025
Source: PubMed


The synthesis of all reported TPAH concentrations measured in water samples and those estimated from caged and indigenous, intertidal mussels from Exxon and government studies provides an effective means to assess acute and long-term exposure of and ecological risk to offshore and nearshore water-column organisms. Measured TPAH concentrations in more than 2000 water samples and estimated water TPAH concentrations based on PAH concentrations in more than 2700 mussel samples were incorporated into this synthesis. Concentrations of PAH in the upper water column at scattered locations in the spill zone were elevated in the first few weeks after the spill to levels that probably were high enough to cause harm to some individual marine organisms; however, only nine (9) of the 1288 water samples taken along the spill path in PWS in 1989 contained more than 10 ppb TPAH, the State of Alaska's water-quality standard for total aromatic hydrocarbons. TPAH concentrations in shallow water adjacent to oiled shorelines were elevated, but, by the time herring spawned along the shore several weeks after the spill, and when herring larvae and juvenile pink salmon were abundant in coastal waters 2 to 3 months after the spill, average concentrations in the water column were less than 0.5 ppb, lower than concentrations known to cause harm to sensitive early life stages of these species. Water column concentrations of TPAH resulting from the spill returned to background levels by 1990, ranging from 0.001 to 0.1 ppb TPAH. On a larger, population-level and ecologically significant scale, TPAH levels in the water column declined rapidly in the spill area and, after the first few weeks, were not high enough to cause population-level harm to even sensitive early life stages of marine organisms, including herring and salmon. TPAH concentrations measured in spill-zone water samples in 2005 do not indicate any detectable release into the water column of buried oil residues known to still exist at several locations in PWS. The findings from this synthesis are consistent with those from other spills and with other measures of exposure determined in other Exxon Valdez related studies.

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Available from: Jerry M Neff, Apr 27, 2015
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    • "Very little oil is dissolved in the water column and what oil does enter the dissolved phase is thought to be rapidly degraded. For instance, following the Exxon Valdez oil spill, total polycyclic aromatic hydrocarbon (PAH) concentrations in the water column were found to be equal to background within a year of the spill (Boehm et al., 2007; Payne et al., 2008) whereas oil buried in sediments can still be found (Short et al., 2007). Dispersants are frequently applied to break up oil slicks and to prevent impacts on coastlines, air breathing marine animals and benthic resources (National Research Council (NRC), 2005). "
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    ABSTRACT: Dispersants are commonly used to mitigate the impact of oil spills, however, the ecological cost associated with their use is uncertain. The toxicity of weathered oil, dispersed weathered oil, and the hydrocarbon-based dispersant Slickgone NS(®), to the diatom Phaeodactylum tricornutum has been examined using standardized toxicity tests. The assumption that most toxicity occurs via narcosis was tested by measuring membrane damage in diatoms after exposure to one of the petroleum products. The mode of toxic action was determined using microarray-based gene expression profiling in diatoms after exposure to one of the petroleum products. The diatoms were found to be much more sensitive to dispersants than to the water accommodated fraction (WAF), and more sensitive to the chemically enhanced WAF (CEWAF) than to either the WAF itself or the dispersants. Exposure to dispersants and CEWAF caused membrane damage, while exposure to WAF did not. The gene expression profiles resulting from exposure to all three petroleum mixtures were highly similar, suggesting a similar mode of action for these compounds. The observed toxicity bore no relationship to PAH concentrations in the water column or to total petroleum hydrocarbon (TPH), suggesting that an undescribed component of the oil was causing toxicity. Taken together, these results suggest that the use of dispersants to clean up oil spills will dramatically increase the oil toxicity to diatoms, and may have implications for ecological processes such as the timing of blooms necessary for recruitment.
    Full-text · Article · Aug 2012 · Aquatic toxicology (Amsterdam, Netherlands)
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    • "Direct water-column sampling was discontinued several years after the EVOS because TPAH concentrations were at background or below method detection limits. Boehm et al. (2004, 2007 "
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    ABSTRACT: This paper updates previous reviews of the 1993 stock decline of Pacific herring (Clupea pallasi) in Prince William Sound, Alaska, and focuses on hypotheses about subsequent poor recovery. Recent age structured assessment modeling with covariate analysis indicates that the population dynamics of the sound’s herring are influenced by oceanic factors, nutrition, and, most substantially, hatchery releases of juvenile pink salmon. For the 1993 decline, poor nutrition remains the most probable cause with disease a secondary response. Concerning poor recovery, we examined 16 potential factors and found three to be causal: oceanic factors, poor nutrition, and hatchery releases of juvenile pink salmon. Absences of strong year classes at both Sitka and Prince William Sound after 1993 indicate the action of large-scale ocean processes. Beyond regional-scale environmental factors, two factors specific to the sound influence the population dynamics of herring and are likely impeding recovery. First, pink salmon fry releases have increased to about 600 million annually and may disrupt feeding in young herring, which require adequate nutrition for growth and overwintering survival. Juvenile pink salmon and age-1 herring co-occur in nearshore areas of bays in late spring and summer, and available data on dietary overlap indicates potential competition between the age-1 juvenile herring and juvenile pink salmon. Field studies demonstrate that juvenile herring reduce food intake substantially in the presence of juvenile pink salmon. Second, overwintering humpback whales may consume potentially large amounts of adult herring, but further studies must confirm to what extent whale predation reduces herring biomass.
    Full-text · Article · Mar 2012 · Reviews in Fish Biology and Fisheries
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    • "This site contains a large otter pit-digging area in the low tide zone. Boehm et al. (2007b) found more than 110 otter-dug pits at this site (DI067A-W) between about À0.5 and +1.3 m tidal elevation at DI067A-W in 2006. The continuously moist sand/gravel sediments in the lower intertidal zone at this site are ideal habitat for the large clams that sea otters prefer (Neff et al., 2010), explaining the abundance of otter foraging pits. "
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    ABSTRACT: Twenty years after the Exxon Valdez oil spill, scattered patches of subsurface oil residues (SSOR) can still be found in intertidal sediments at a small number of shoreline locations in Prince William Sound, Alaska. Some scientists hypothesize that sea otters continue to be exposed to SSOR by direct contact when otters dig pits in search of clams. This hypothesis is examined through site-specific examinations where SSOR and otter-dug pits co-occur. Surveys documented the exact sediment characteristics and locations on the shore at the only three subdivisions where both SSOR and otter pits were found after 2000. Shoreline characteristics and tidal heights where SSOR have persisted are not suitable habitat for sea otters to dig pits during foraging. There is clear separation between areas containing SSOR and otter foraging pits. The evidence allows us to reject the hypothesis that sea otters encounter and are being exposed by direct contact to SSOR.
    Full-text · Article · Dec 2010 · Marine Pollution Bulletin
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