An evaluation of marine bird population trends following the Exxon Valdez oil spill, Prince William Sound, Alaska

We examined post-spill trends (1989-1998) of marine bird populations in Prince William Sound (PWS) following the Exxon Valdez oil spill (EVOS) to evaluate recovery of injured taxa. Two criteria were employed. First, we examined population trends of injured taxa only in the oiled area of PWS using regression models. Second, we examined population trends of injured taxa in the oiled area relative to the unoiled area using homogeneity of the slopes tests. We considered a population recovering if there was a positive trend using either criteria. We considered a population not recovering if there was no trend using either criteria or a negative trend in the oiled area. A significant negative trend in the oiled area relative to the unoiled area was considered a continuing and increasing effect. Most taxa for which injury was previously demonstrated were not recovering and some taxa showed evidence of increasing effects nine years after the oil spill. Four taxa (loons Gavia spp, Harlequin Duck Histrionicus histrionicus, Bufflehead Bucephala spp, and North-western Crow Corvus caurinus) showed weak to very weak evidence of recovery. None of these taxa showed positive trends in both winter and summer. Nine taxa (grebes Podiceps spp, cormorants Phalacrocorax spp, Black Oystercatcher Haematopus bachmani, Mew Gull Larus canus, Glaucous-winged Gull Larus glaucescens, terns Sterna spp, murres Uria spp, Pigeon Guillemot Cepphus columba, and murrelets Brachyramphus spp) showed no evidence of recovery during summer or winter. Four taxa (scoters Melanitta spp, mergansers Mergus spp, goldeneyes Bucephala spp, and Black-legged Kittiwaka Rissa tridactyla) showed evidence of continuing, increasing effects. We showed evidence of slow recovery, lack of recovery, and divergent population trends in many taxa which utilize shoreline and nearshore habitats where oil is likely to persist. Potential lingering spill effects and natural variability appear to be acting in concert in delaying recovery of many PWS bird populations.     

Oil persistence on beaches in Prince William Sound - a review of SCAT surveys conducted from 1989 to 2002

In 2002, 13 years after the Exxon Valdez oil spill (EVOS), 39 selected sites in Prince William Sound (PWS) were re-surveyed following established shoreline cleanup assessment team (SCAT) field observation procedures to document surface and sub-surface oiling conditions in shoreline sediments and to compare results with those from previous Shoreline Cleanup Assessment Team (SCAT) surveys and other surveys in PWS. The selected sites are locations where EVOS oil persisted in 1992, at the time the Federal and State On-Scene Coordinators determined that the cleanup was complete and that further cleanup activities would provide no net environmental benefit. These sites had been included in a 2001 NOAA survey of shoreline oiling conditions and account for 88% of the sub-surface oil residues (SSO) oil documented by that study. The 2002 field survey found isolated occurrences of residual EVOS surface oil residues (SO) in the form of weathered asphalt pavement at 15 of the 39 sites. This residual SO typically consisted of asphalt in mixed sand/gravel substrate, located within a wave shadow effect created by boulders or bedrock in the upper intertidal to supratidal zone. Residual SO, expressed as a continuous oil cover, was less than 200 m(2) within the approximately 111,120 m(2) surveyed. A total of 1182 pits were dug at locations where SSO residues were present in 1992. Six of the 39 sites and 815 (68%) of the pits contained no residual SSO. Eighty-three percent of pits with SSO residues were found primarily in middle to upper intertidal locations. SSO residues commonly occurred in a discontinuous approximately 3 cm thick band 5-10 cm below the boulder/cobble or pebble/gravel veneer. The SO and SSO occurrences in the 2002 survey closely match the locations where they were found in 1992 and earlier surveys; however, in 2002 residual SSO patches are more discontinuous and thinner than they were in the earlier surveys. These sites are biased toward SSO persistence; those that have SSO residues represent less than 0.5% of the originally oiled shorelines in PWS. Despite evidence of continued oil weathering, both at the surface and in the sub-surface, it is clear that the natural cleaning processes at these particular locations are slow. The slow weathering rates are a consequence of the oil residue being incorporated in finer sediments (fine sand, silt, mix) and isolated from active weathering processes as boulders and outcrops, shallow bedrock asperities, or boulder-armoring create wave shadows and limit effective physical action on shorelines.     

Results from a sixteen year study on the effects of oiling from the Exxon Valdez on adult pink salmon returns

For sixteen years following the 1989 Exxon Valdez oil spill adult returns of pink salmon in Prince William Sound, Alaska were monitored to assess spill effects on survival. No evidence of spill effects was detected for either intertidal or whole-stream spawning fish. From 1989 through 2004 mean densities for oiled and reference streams tracked each other, illustrating similar responses of oiled and reference stream adult populations to naturally changing oceanographic and climactic conditions. Hatchery fish strayed into the study streams, but similar incursions occurred in oiled and reference streams, and their presence was compensated for to eliminate their influence on determining the success of the returning natural populations. These results, showing no detectable effects of oiling on pink salmon spawning populations, are supported by published field studies on pink salmon incubation success in oiled streams.     

Induction of DNA strand breaks in the mussel (Mytilus trossulus) and clam (Protothaca staminea) following chronic field exposure to polycyclic aromatic hydrocarbons from the Exxon Valdez spill

In 2002, 13 years after the Exxon Valdez spill, mussels and clams were examined for lingering oil exposure and damage. Known oil patches were sampled at four locations, and compared to nearby reference areas (same bay), and were also compared to "hot reference" sites to verify the methods used (Cordova harbor and fresh diesel spill at Port Chalmers). Passive samplers deployed for a month at the sites, along with tissue samples, confirmed that the oiled sites were oiled (fingerprinting back to Exxon Valdez oil) and that reference sites were clean. The highest PAH loads were detected in sub-surface interstitial waters at oiled sites. Exposure at the surface was generally low level, and probably intermittent. DNA damage was assessed in blood cells using sensitive comet analyses. DNA strand breakage was detected in both mussels and clams, with the highest level of damage detected at "hot reference" sites of Cordova harbor and Port Chalmers. Bioavailability and DNA damage at the oiled sties was low, indicating there has been substantial progress in recovery from the spill 13 years before, yet low level bioavailability and damage were still detectable.     

Cytochrome P4501A biomarker indication of the timeline of chronic exposure of Barrow's goldeneyes to residual Exxon Valdez oil

We examined hepatic EROD activity, as an indicator of CYP1A induction, in Barrow’s goldeneyes captured in areas oiled during the 1989 Exxon Valdez spill and those from nearby unoiled areas. We found that average EROD activity differed between areas during 2005, although the magnitude of the difference was reduced relative to a previous study from 1996/1997, and we found that areas did not differ by 2009. Similarly, we found that the proportion of individuals captured from oiled areas with elevated EROD activity (?2 times unoiled average) declined from 41% in winter 1996/1997 to 10% in 2005 and 15% in 2009. This work adds to a body of literature describing the timelines over which vertebrates were exposed to residual Exxon Valdez oil and indicates that, for Barrow’s goldeneyes in Prince William Sound, exposure persisted for many years with evidence of substantially reduced exposure by 2 decades after the spill.     

A hierarchical approach measures the aerial extent and concentration levels of PAH-contaminated shoreline sediments at historic industrial sites in Prince William Sound, Alaska

A field study was conducted in 2003 to estimate the areal distribution and concentrations of polycyclic aromatic hydrocarbons (PAH) in intertidal sediments at sites of past human and industrial activity (HA sites) in Prince William Sound (PWS), Alaska, the site of the 1989 Exxon Valdez oil spill. More than 50 HA sites, primarily in western PWS, were identified through analysis of historic records and prior field studies, and nine sites were selected for detailed surveys. The areal assessment process consisted of seven steps: (1) identify site from historic records and field surveys; (2) locate visual evidence of surface oil/tar at a site; (3) prepare a site map and lay out a sampling grid over the entire site with 10-m grid spacing; (4) excavate pits to 50 cm depth on the grid; (5) perform a field colorimetric test to estimate total PAH (TPAH) in sediments from the wall of each pit and record the results in the ranges <1 ppm; 1-10 ppm; >10 ppm TPAH; (6) expand grid size if necessary if elevated PAH levels are detected colorimetrically; (7) select 20 samples from each site for same-day shipboard PAH analysis by immunoassay (SDI RaPID PAH) and, based on these results, select sediment samples from each site for full PAH analysis in the laboratory to identify PAH sources. A total of 416 pits were dug at the nine sites. Nine acres of sediments with TPAH >2500 ppb dry wt. were mapped at the nine sites. TPAH concentrations obtained by immunochemical analysis of 181 samples from the nine sites ranged from 20 to 1,320,000 ppb (wet wt.). The contaminants are mixtures of petroleum products (2-3 ring PAH) and combustion products (4-6 ring PAH) unrelated to the 1989 Exxon Valdez oil spill. Mussels and clams collected at these sites have elevated levels of PAH that are compositionally similar to the PAH in the sediments. These findings indicate that at least a portion of the sediment PAH is bioavailable. The PAH sources at these historic industrial sites are chronic. They include relict fuel oil tanks and works located above and within the intertidal zone, with contamination at some locations extending into nearshore sub-tidal sediments. This study shows how a hierarchical approach can be used to quickly and successfully map, quantify, and subsequently, identify sources of PAH in shoreline sediments.     

Relationship Between Oil Exposure and Reproductive Parameters in Fish Collected Following the Exxon Valdez Oil Spill

Following the Exxon Valdez oil spill (EVOS) in 1989, the effect of oil exposure on reproductive parameters was investigated in wild populations of female dolly varden, yellowfin sole, and pollock. Exposure to oil was the highest in the first year of sampling and decreased in the subsequent years of sampling. Both positive and negative correlations between reproductive parameters and indices of exposure were detected in varying degrees for all three species. Reproductive parameters were not measured in the first year of sampling. For those parameters found to be significantly correlated to oil exposure, an exponential regression function was used to project reproductive parameters of fish sampled in the first year of the spill. A higher proportion of dolly varden sampled in 1989 were projected to have depressed plasma estradiol-17β compared to the fish sampled in 1990.     

Biomarker responses in pelagic and benthic fish over 1 year following the Hebei Spirit oil spill (Taean, Korea)

After the Hebei Spirit oil spill incident (7th December, 2007) in the west coast of Korea, contamination of biliary PAH metabolite and hepatic biomarkers in a pelagic and a benthic fish was monitored for 1 year. Concentrations of 16 PAHs and alkylated PAHs in fish muscle were highest (22.0 ng/g d.w. for 16 PAHs and 284 ng/g d.w. for alkylated PAHs) at 5 days after the spill and then decreased rapidly to background levels at 11 months after the spill. Fish from the oiled site had elevated biliary PAH metabolite concentrations immediately after the spill; these declined steadily in both species, but were still above reference site concentrations 2 months after the spill. Oiled-site fish showed hepatic CYP 1A induction whose trend closely followed those of biliary PAH metabolite concentrations, implying continuous exposure to PAHs. Brain acetylcholinesterase activity was not related to oil exposure.     

Using tolerance intervals to assess recovery of mussel beds impacted by the Exxon Valdez oil spill

Polycyclic aromatic hydrocarbons (PAH) have been measured in mussel tissues in early spring and summer since 1993 throughout Prince William Sound (PWS) and the Gulf of Alaska (GOA). Season-specific thresholds were established at reference sites to identify ‘above background’ total PAH levels. Thresholds were estimated using one-sided 99% tolerance limits. Thresholds were similar across reference sites but differed by an order of magnitude across seasons. Trends in total PAH since 1998 were assessed for sites impacted by the 1989 Exxon Valdez oil spill or the Alyeska Marine Terminal. Summer samples exhibited no trends; early spring samples declined. In early spring, all sites were judged ‘recovered’ by 2004; in summer, one site in western Prince William Sound and two in the western GOA exceeded thresholds by 11 ng/g dry weight or less. Robust estimation methods prevented bias from observations affected by unknown releases or laboratory errors.     

Impacts of the Nakhodka heavy-oil spill on an intertidal ecosystem: an approach to impact evaluation using geographical information system

A major heavy-oil spill from the Russian tanker Nakhodka occurred in the Sea of Japan on 2 January 1997. We investigated the impacts of this spill on a rocky intertidal ecosystem along the southern coast of the Sea of Japan. We selected Imago-Ura Cove as our study site to observe temporal changes along the oiled shore, because minimal cleaning effort was made in this area. Field surveys were conducted every autumn and spring from 1997 to 2000. We measured coverage by macroalgae in 1 x 1-m(2) quadrats and counted the animals in 5 x 5-m(2) quadrats along the intertidal zone. Changes in the ecosystem caused by the oil spill were analyzed by applying a geographical information system (GIS) to the Sea of Japan for the first time. The GIS showed that following the accident there were heavily oiled areas in sheltered regions, but these decreased over the three years. It also showed that coverage by macroalgae and the number of animals increased, although some species of algae with microscopic sporophyte generations, and some populations of perennial shellfish, remained stable or decreased during the study period. GIS was able to trace temporal changes in intertidal communities resulting from the impacts of heavy oil on flora and fauna at a spatial scale of 10-100 m. GIS is thus a practical tool for visualizing, analyzing, and monitoring changes in an ecosystem polluted by oil, taking into account topographic differences along the coastline.     

PCB exposure in sea otters and harlequin ducks in relation to history of contamination by the Exxon Valdez oil spill

Exposure to contaminants other than petroleum hydrocarbons could confound interpretation of Exxon Valdez oil spill effects on biota at Prince William Sound, Alaska. Hence, we investigated polychlorinated biphenyls (PCBs) in blood of sea otters and harlequin ducks sampled during 1998. PCB concentrations characterized by lower chlorinated congeners were highest in sea otters from the unoiled area, whereas concentrations were similar among harlequin ducks from the oiled and unoiled area. Blood enzymes often elevated by xenobiotics were not related to PCB concentrations in sea otters. Only sea otters from the unoiled area had estimated risk from PCBs, and PCB composition or concentrations did not correspond to reported lower measures of population performance in sea otters or harlequin ducks from the oiled area. PCBs probably did not influence limited sea otter or harlequin duck recovery in the oiled area a decade after the spill.     

Effects of the 'Prestige' oil spill on macroalgal assemblages: large-scale comparison

An assessment of the effects of the 'Prestige' oil spill on intertidal, macroalgal assemblages was carried out comparing abundance data obtained before and after the spill. Four zones in the North and Northwest coast of Spain were sampled, one of them located at the immediate vicinity of the spill, the zone most heavily oiled. Macroalgal assemblages had similar structure between years. Neither critical decrease in abundance of the dominant macroalgae, nor increase in opportunistic species were found. Some differences in abundance were observed, but they did not show any pattern, being more likely the result of the natural variability of the assemblage. Extensive, but not intense fuel deposition on the shores and a limited use of aggressive cleanup methods are suggested as possible causes for the lack of the effects in these assemblages after the 'Prestige' oil spill.     

Impacts of the Jessica oil spill on sea lion (Zalophus wollebaeki) populations

Following the Jessica oil spill, a total of 79 oiled Galápagos sea lions (Zalophus wollebaeki) were recorded around the islands of San Cristóbal, Santa Fé, Isabela and Floreana. Almost half of these animals required washing and other treatment. One sea lion death and a high incidence of conjunctivitis and burns were detected during the period of the oil spill. Sea lion populations exhibited a tendency for decline in the first months following the spill at all three colonies monitored close to the grounding site on San Cristóbal. By comparison, declines of similar magnitude occurred at only one of six sea lion colonies monitored on islands more distant from the spill. However, no significant decreases in population numbers were detected for any colony in the year following the spill. Galápagos sea lion populations were partially recovering from the much more catastrophic impact of the 1997/98 El Ni?o.     

Interaction of oil and mineral fines on shorelines: review and assessment

The interaction of fine mineral particles with stranded oil in an aqueous medium reduces the adhesion of the oil to solid surfaces, such as sediments or bedrock. The net result is the formation of stable, micron-sized, oil droplets that disperse into the water column. In turn, the increase in surface area makes the oil more available for biodegradation. This interaction, referred to as oil–mineral aggregate (OMA) formation, can explain how oiled shorelines are cleaned naturally in the absence of wave action in very sheltered coastal environments. OMA formation also plays an important role in the efficacy of shoreline treatment techniques, such as physical mixing and sediment relocation that move oiled sediments into the zone of wave action to promote the interaction between oil and mineral fines. Successful application of these shoreline treatment options has been demonstrated at two spill events (the Tampa Bay response in Florida and the Sea Empress operation in Wales) and at a controlled oil spill experiment in the field (the 1997 Svalbard ITOSS program). Sediment relocation harnesses the hydraulic action of waves so that the processes of fine-particle interaction and physical abrasion usually occur in tandem on open coasts. There has been no evidence of significant detrimental side-effects of residual oil in pelagic or benthic environments associated with the use of these treatment options to enhance rates of dispersion and oil biodegradation.     

Persistence of 10-year old Exxon Valdez oil on Gulf of Alaska beaches: the importance of boulder-armoring

Oil stranded as a result of the 1989 Exxon Valdez spill has persisted for >10 years at study sites on Gulf of Alaska shores distant from the spill's origin. These sites were contaminated by "oil mousse", which persists in these settings due to armoring of underlying sediments and their included oil beneath boulders. The boulder-armored beaches that we resampled in 1999 showed continued contamination by subsurface oil, despite their exposure to moderate to high wave energies. Significant declines in surface oil cover occurred at all study sites. In contrast, mousse has persisted under boulders in amounts similar to what was present in 1994 and probably in 1989. Especially striking is the general lack of weathering of this subsurface oil over the last decade. Oil at five of the six armored-beach sites 10 years after the spill is compositionally similar to 11-day old Exxon Valdez oil. Analysis of movements in the boulder-armor that covers the study beaches reveals that only minor shifts have occurred since 1994, suggesting that over the last five, and probably over the last 10 years, boulder-armors have remained largely unmoved at the study sites. These findings emphasize the importance of particular geomorphic parameters in determining stranded oil persistence. Surface armoring, combined with stranding of oil mousse, results in the unexpectedly lengthy persistence of only lightly to moderately weathered oil within otherwise high-energy wave environments.     

Biomarker responses in caged rockfish (Sebastes schlegeli) from Masan Bay and Haegeumgang, South Korea

The purpose of this study was to compare enzymatic biomarker activities in fish caged at two sites, Masan Bay (contaminated) and Haeguemgang (reference). In the present study, ethoxyresorufin O-deethylase (EROD), brain acetyl cholinesterase (bAChE), muscle acetyl cholinesterase (mAChE) and butyryl cholinesterase (mBChE) in caged rockfish (Sebastes schlegeli) were measured 0, 1, 3, 7, 14, 21 and 30 days after caging. The level of CYP1A mRNA and Protein expression was induced higher in Masan Bay at 1, 3, 7, 14 and 30 days after caging. EROD activity in the caged fish was significantly higher in Masan Bay than in Haeguemgang 3 and 7 days after caging, but not at 14 and 30 days after caging. bAChE activity was significantly inhibited at 7 and 14 days after caging in Masan Bay. However, mBChE activity was not significantly inhibited during the experiment. Taken together, the data suggest that the caged fish were exposed, at least transiently, to CYP1A inducers and ChE inhibitors, which is consistent with our previous observations.     

Comparison of mussels and semi-permeable membrane devices as intertidal monitors of polycyclic aromatic hydrocarbons at oil spill sites

Side-by-side comparisons of polycyclic aromatic hydrocarbon (PAH) concentrations in resident blue mussels (Mytilus trossulus) and in semi-permeable membrane devices (SPMDs) were made at four sites in Prince William Sound, Alaska. SPMDs were deployed for approximately 30 days on the surface of the beach sediment at three tidal elevations on each shore and in 0.5 m deep open pits in the middle intertidal zone. Total PAH (TPAH) concentrations in mussels and in SPMDs were correlated, but the PAH compositions were different. The lower molecular weight PAH were relatively more abundant in the SPMDs than in the mussels at oiled and HA sites. TPAH concentrations in SPMDs deployed in pits and mussels collected adjacent to those pits at oiled sites were higher than in SPMDs and mussels from non-pitted SPMD locations approximately 3-15 m from the pits. Pitting released buried oil making its PAH bioavailable. SPMDs deployed in the supratidal zone (+4.0 m tidal elevation) were exposed to atmospheric contaminants for a large fraction of the deployment time and accumulated primarily pyrogenic (combustion-sourced) PAH from the atmosphere. The SPMD strips supplied by the manufacturer contained significant amounts (approximately 125 ng/strip) of primarily alkylated 2-3 ring PAH. These blank levels make SPMDs unsuitable for shoreline assessments when environmental PAH concentrations are low. Consequently, where available, mussels are recommended for use in assessments of the bioavailability of buried oil residues sequestered in intertidal sediments following an oil spill. Mussels are the preferred monitoring tool when the assessments involve food-chain effects. At locations where the absence of mussels necessitates the use of SPMDs or other passive sampling devices, their limitations need to be carefully considered in the interpretation of results.     

Biomarker responses in caged rockfish (Sebastes schlegeli) from Masan Bay and Haegeumgang, South Korea

The purpose of this study was to compare enzymatic biomarker activities in fish caged at two sites, Masan Bay (contaminated) and Haeguemgang (reference). In the present study, ethoxyresorufin O-deethylase (EROD), brain acetyl cholinesterase (bAChE), muscle acetyl cholinesterase (mAChE) and butyryl cholinesterase (mBChE) in caged rockfish (Sebastes schlegeli) were measured 0, 1, 3, 7, 14, 21 and 30 days after caging. The level of CYP1A mRNA and Protein expression was induced higher in Masan Bay at 1, 3, 7, 14 and 30 days after caging. EROD activity in the caged fish was significantly higher in Masan Bay than in Haeguemgang 3 and 7 days after caging, but not at 14 and 30 days after caging. bAChE activity was significantly inhibited at 7 and 14 days after caging in Masan Bay. However, mBChE activity was not significantly inhibited during the experiment. Taken together, the data suggest that the caged fish were exposed, at least transiently, to CYP1A inducers and ChE inhibitors, which is consistent with our previous observations.     

Response of Spartina alterniflora Vegetation to Oiling and Burning of Applied Oil

A field study evaluated Spartina alterniflora sensitivity to oiling and to in situ burning of applied crude oil. Experimental plots (2.4 m × 2.4 m × 0.6 m) were constructed in the salt marsh for control, oiling (natural clean-up) and oiling/burning treatments. South Louisiana Crude was applied to oiling and oiling/burning treatment plots at 2 l m⁻² and the burn conducted. S. alterniflora responses (height, live stem density, carbon fixation and biomass) were measured for 50 weeks after the August burn. Oiling and oiling/burning had short-term detrimental effects on the salt marsh. One year after the late summer burn, S. alterniflora responses measured in the oiled and oiled/burned plots were not significantly different compared to control values. Results suggest that, under our experimental conditions, intervention may not be required for marsh recovery. However, if spill conditions require a rapid response to control contaminant spread or protect other sensitive resources, burning may be a clean-up operation to consider.     

Biomarker responses in caged rockfish (Sebastes schlegeli) from Masan Bay and Haegeumgang,South Korea

The purpose of this study was to compare enzymatic biomarker activities in fish caged at two sites, Masan Bay (contaminated) and Haeguemgang (reference). In the present study, ethoxyresorufin O-deethylase (EROD), brain acetyl cholinesterase (bAChE), muscle acetyl cholinesterase (mAChE) and butyryl cholinesterase (mBChE) in caged rockfish (Sebastes schlegeli) were measured 0, 1, 3, 7, 14, 21 and 30 days after caging. The level of CYP1A mRNA and Protein expression was induced higher in Masan Bay at 1, 3, 7, 14 and 30 days after caging. EROD activity in the caged fish was significantly higher in Masan Bay than in Haeguemgang 3 and 7 days after caging, but not at 14 and 30 days after caging. bAChE activity was significantly inhibited at 7 and 14 days after caging in Masan Bay. However, mBChE activity was not significantly inhibited during the experiment. Taken together, the data suggest that the caged fish were exposed, at least transiently, to CYP1A inducers and ChE inhibitors, which is consistent with our previous observations.