Factors determining the long-term persistence of Exxon Valdez oil in gravel beaches

ABSTRACT A substantial amount of the crude oil which spilled from the tanker Exxon Valdez on March 24, 1989, was deposited on beaches in Prince William Sound. Major beach cleanup activities began in May and continued throughout the summer of 1989. Additional cleanup activities occurred during the summer of 1990. A study was conducted in 1989 to document the short-term impact to biota of hot water wash treatments. Additional field surveys were conducted in the summer of 1990 to evaluate recovery of littoral habitats from the effects of oiling and shoreline treatment. Stratified-random sampling was used to assess epibiota and infauna at 27 sites, representing several habitats and degrees of disturbance. Preliminary data evaluations indicate that treatment methodologies applied in 1989 had varied effects on intertidal assemblages. Some treated rocky beaches were stripped of flora and fauna at mid- and upper intertidal elevations and showed relatively little colonization by mid summer 1990. On other oiled rocky beaches that received less severe or no treatment, the majority of the community dominants remained in place and significant recolonization was underway. Protected sand and gravel beaches subjected to hydraulic treatments displayed greatly altered beach morphology. Finer sands and gravels were flushed from upper intertidal elevations, often burying the lower beach in several centimeters of sediment, resulting in major reductions in infauna in 1990. Oiled but untreated sand and gravel beaches had a rich and varied infauna. The effects of 1989 shoreline treatment activities on intertidal flora and fauna were significant and widespread and will greatly complicate assessment of the long-term impacts of the oil itself.

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Factors Controlling Initial Deposition and Long-Term Fate of Spilled Oil on Gravel Beaches

International Oil Spill Conference Proceedings ◽

10.7901/2169-3358-1991-1-453 ◽

1991 ◽

Vol 1991 (1) ◽

pp. 453-460 ◽

Cited By ~ 11

Author(s):

Miles O. Hayes ◽

Jacqueline Michel ◽

David C. Noe

Keyword(s):

Deep Penetration ◽

Polar Regions ◽

Exxon Valdez ◽

Oil Accumulation ◽

Local Conditions ◽

Gravel Beaches ◽

Initial Deposition ◽

Spilled Oil ◽

Gravel Beach

ABSTRACT Several major oil spills of record (including the 1974 Metula spill, the 1978 Amoco Cadiz spill, and the 1989 Exxon Valdez spill) occurred along shorelines with abundant gravel beaches. Observations of these spills help in understanding factors controlling the initial deposition and long-term fate of spilled oil in such locations. Gravel beaches are most common on rocky, glaciated coasts (Holocene and/or Pleistocene). For example, leading-edge coastlines in subpolar to polar regions, of which the Alaska coast is a prime example, may have gravel beach deposits along more than 50 percent of their length. Spilled oil coming onshore in such gravel areas is likely to remain for a long time (up to decades), because of the potential for deep penetration and burial of the oil in the coarse sediments. The detailed, three-dimensional configuration of gravel beach deposits is affected by the internal characteristics of the waves shaping the beach (reflective or dissipative). Reflective waves typically produce steep, coarse, cuspate berms, which allow for deep penetration and burial in the beach face/berm areas. Dissipative waves typically build intertidal swash bars that may move landward and bury oil deposits, such as asphalt pavements. It would be useful for future contingency mapping projects to include this distinction on maps of gravel beaches. The formation of armoring (structural strengthening) of a gravel beach surface impedes erosion and sediment transport. Therefore, such beaches are likely to retain buried oil longer than those without armoring. Gravel beaches, because they are commonly located along plate margins, are usually subject to tectonic readjustment. The Exxon Valdez spill occurred along a shoreline out of equilibrium as a result of the 1964 earthquake. Uplift and downwarp is on the order of 1 to 3 meters throughout most of the area of the spill. Almost every coastal location affected by the spill is undergoing readjustment, causing many site-specific interpretive problems related to burial, penetration, and hydraulic flushing. For example, in many areas, a thin gravel veneer of armor overlies uplifted rock platforms and/or fine-grained bay bottom, or downwarped soil horizons, which served as either zones of oil accumulation or pathways of hydraulic flushing, depending on local conditions.

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Long-Term Ecosystem Response to the Exxon Valdez Oil Spill

Science ◽

10.1126/science.1084282 ◽

2003 ◽

Vol 302 (5653) ◽

pp. 2082-2086 ◽

Cited By ~ 843

Author(s):

C. H. Peterson

Keyword(s):

Oil Spill ◽

Ecosystem Response ◽

Exxon Valdez ◽

Exxon Valdez Oil Spill

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A 10-Year Study of Shoreline Conditions in the Exxon Valdez Spill Zone, Prince William Sound, Alaska

International Oil Spill Conference Proceedings ◽

10.7901/2169-3358-2001-1-559 ◽

2001 ◽

Vol 2001 (1) ◽

pp. 559-567 ◽

Cited By ~ 1

Author(s):

Edward S. Gilfillan ◽

David S. Page ◽

Keith R. Parker ◽

Jerry M. Neff ◽

Paul D. Boehm

Keyword(s):

Oil Spill ◽

Individual Species ◽

Prince William Sound ◽

Exxon Valdez ◽

Worst Case ◽

Intertidal Community ◽

Infaunal Community ◽

Long Term Study ◽

Natural Factors

ABSTRACT A shoreline ecology program was performed in Prince William Sound (PWS), Alaska in 1990 and 1991 (1 and 2 years after the Exxon Valdez oil spill, EVOS) to assess the fate and effects of the oil in the intertidal zone. Major components of the study were repeated in 1998 and 1999. This update included a sediment-sampling program at formerly oiled “worst-case” boulder/cobble (B/C) sites and randomly chosen unoiled B/C reference sites. The samples were analyzed for petroleum hydrocarbons and benthic infaunal community characteristics. This paper focuses on the results of the benthic infaunal community analysis. Analysis of Covariance (ANCOVA) was used to analyze the 1990–1999 infaunal species composition data. Very little effect of oiling was detected in either the analysis of community structure parameters or in individual species abundances. Oiling effects were detected at some sites in 1990 and 1991, but not in 1998 and 1999. Nearly all the change in intertidal community parameters between 1990 and 1999 was attributed to natural interannual variation. The composition of the intertidal community of B/C shores changed over time because of natural factors not related to the spill. A core group of species was found in each of the 4 years. This group of species represented between 9 to 30% of all species identified. Two other groups of species did not co-occur. One group was present in 1990 and 1991, but not in 1998 and 1999; the other group was present in 1998 and 1999, but not in 1990 and 1991. The progressive change in the animal community observed between 1990 and 1999 is very likely related to long-term climatic changes occurring in the study area and not the oil spill. This long-term study demonstrates the importance of study designs that allow separation of oiling effects from natural factors that can affect biological communities.

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Long-Term Biological Damage: What is Known, and How Should that Influence Decisions on Response, Assessment, and Restoration?

International Oil Spill Conference Proceedings ◽

10.7901/2169-3358-2001-1-399 ◽

2001 ◽

Vol 2001 (1) ◽

pp. 399-403 ◽

Cited By ~ 1

Author(s):

Mark G. Carls ◽

Ron Heintz ◽

Adam Moles ◽

Stanley D. Rice ◽

Jeffrey W. Short

Keyword(s):

Oil Spill ◽

Polyaromatic Hydrocarbons ◽

Environmental Cost ◽

Life Stages ◽

Prevention Measures ◽

Long Term Effects ◽

Short Term ◽

Exxon Valdez ◽

Damage Scenarios

ABSTRACT Immediate damage from an oil spill is usually obvious (oiled birds, oiled shoreline), but long-term damage to either fauna or habitat is more subtle, difficult to measure, difficult to evaluate, and hence often controversial. The question is, are too many of response decisions such as dispersant use or shoreline cleanup based on short-term acute toxicity models? Have long-term damage scenarios been discounted because of the inherent difficulty in deriving definitive answers? Experience with the Exxon Valdez oil spill is shedding new light on the potential for long-term damage. Government-funded studies demonstrated that oil persists in certain habitats for extended periods of time, such as the intertidal reaches of salmon streams, in soft sediments underlying mussel beds, and on cobble beaches armored with large boulders. Observation of long-term persistence of oil in some habitats is not new, but an increasing number of studies indicate that fauna may be chronically and significantly exposed to oil in these habitats. The toxic components in oil responsible for much of the long-term effects are believed to be the larger 3- and 4-ring polyaromatic hydrocarbons (PAHs) that can induce cellular and genetic effects rather than the narcotic monoaromatic hydrocarbons (MAHs) responsible for acute mortalities. Observation of long-term persistence of Exxon Valdez oil, coupled with adverse effects on sensitive life stages, leads to the conclusion that strategies based on minimizing acute mortalities immediately following a spill probably do not provide adequate protection against long-term damage. When making environmental decisions in response to a spill (prevention measures or restoration measures), more weight should probably be given to long-term issues rather than discounting their significance. Total environmental cost is the sum of short-term damage and long-term damage, and long term-damage to habitats and sensitive life stages probably needs more consideration even though it is very difficult to evaluate and compare to the relatively obvious acute issues.

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