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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"Colwellia, an obligate psychrofilic member, has a special position within all hydrocarbonoclastic bacteria due to unique metabolic features and its role in global carbon and nutrient cycling in cold marine environments (Methé et al., 2005). Crude oil is a complex mixture of thousands of different hydrocarbon compounds (Boehm et al. 2007, Boehm et al. 2008). The variation in the solubility and volatility of different components of crude oil made it attractive to search for a biological indicator of hydrocarbon presence, in particular a biological indicator that could be detected with appropriate real time assays used on the ESP. "
[Show abstract][Hide abstract]ABSTRACT: We are exploring the ability of the Environmental Sample Processor (ESP), a "molecular laboratory in a can", to detect real- or near-real time biological responses to alterations in the chemical and physical conditions from offshore activities. Here, we propose to use specific micro-organisms as target indicators of these responses in cold environment. To that purpose, an experimental setup with addition of oil loads in seawater at 4°C was run for 9 days and a selection of hydrocarbon-related microbial DNA assays were performed using extraction and analytical protocols similar to those used by the ESP. We found an early increase (1 day) of Oleispira antartica and DWH Oceanospiralles 16S rRNA gene copies at the highest oil loading (0.1%) and generally a dose-time response relationship for these two assays. The response time for Colvellia was late and did not follow the expected oil dose treatment. This species was however very abundant in subsurface seawater collected at an offshore North Sea site. The largest effect of the ubiquitous Alcanivorax sp. members was measured between 3 and 9 days of oil incubation and was most pronounced at the highest crude oil loading. Our study shows dynamics and time response which resemble that reported by recent literature, hence confirming the utility of the chosen approach for monitoring hydrocarbons following accidental leaks and spill. Using these targets further for the current and future generation ESP's will provide O&G operators and environmental managers an unprecedented, innovative and powerful tool to track oil in seawater and follow up the effects of offshore activities on the marine environment.
"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). "
[Show abstract][Hide abstract]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.
"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 Boehm et al. ( , 2007) produced an extensive database of the concentrations of TPAH in mussel samples collected from 1989 to 2005 from oiled and unoiled shorelines including sites of past human activity (e.g., mines, canneries) in PWS.Figure 5 shows the arithmetic means of TPAH water concentrations derived from analyses of mussel tissues from oiled and unoiled shorelines using the conversion of Neff and Burns (1996). The profile of exposure concentrations inFig. "
[Show abstract][Hide abstract]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