Introduction

As oil spreads through the marine environment and undergoes the changes described in Part II, concerns are raised by the general public, scientists, and regulators about possible effects on biological resources. These concerns may be most obvious when they relate to important subsistence and commercially valuable resources such as salmon or herring, but they extend as well to a variety of wildlife. In the days and weeks following an oil spill, speculations and hyperbole abound. Documenting whether there are actual effects, how long they last, and whether the effects are due to the oil spill or something else requires rigorous science. The chapters in this section describe how science was brought to bear on assessing potential injury to natural resources and what was learned in the process, both about the effects of the Exxon Valdez spill and about the challenges of conducting scientific investigations in a harsh and variable environment with much at stake.

We begin with two chapters that provide essential background on several analytical and design issues that reappear in subsequent chapters. In Chapter 9, James Oris and Aaron Roberts provide a cautionary review of the use of biomarkers – biochemical and molecular responses of organisms to chemicals and other stressors in the environment – as indicators of exposure. They focus on cytochrome P450 1A (CYP1A), which was used to assay exposure of several species to aromatic hydrocarbons from fossil fuels following the Exxon Valdez spill. Because CYP1A can be mobilized in response to a wide array of hydrocarbons, elevated concentrations do not provide unambiguous evidence of exposure to a specific hydrocarbon source, nor do they link exposure to potential injuries, so they must be interpreted with care.

Introduction

Coastal shorelines teem with life. The intersection of the land with the sea, combined with tidal fluctuations and coastal currents, creates an array of habitats that supports an amazing diversity of plants and animals – limpets, starfish, anemones, crabs, rockweed, eelgrass, snails, tubeworms, and the like – that live on the surface and in the sediments of the intertidal zone. When floating oil from a marine oil spill strikes a shoreline, the potential effects on these organisms (the shoreline biota) may be severe. Even species that are not directly affected by spill may suffer its effects if the shoreline prey on which they feed are diminished. Understanding how a spill affects the shoreline biota is therefore important to assessing the potential effects on the broader shoreline and coastal ecosystems.

During the Exxon Valdez spill, oil first spread over shorelines in Prince William Sound (PWS) and later extended outside of PWS to the Kenai Peninsula, Kodiak Island, and Alaska Peninsula (see Map 1, p. v). The effects of the spill and the need to respond rapidly were of enormous concern, particularly within PWS, where oil quantities and potential toxicity were greatest. In this chapter, we discuss three major programs undertaken to assess the effects of the Exxon Valdez oil spill on shoreline biota in PWS, including studies to determine the effects of intensive cleanup efforts.

Introduction

The chapters in the previous section provide a detailed picture of how studies were designed and conducted, what they assumed, what they found, and what was learned in the process. Putting it all together to assess the real effects of the oil spill and ecologically significant, long-term consequences requires a broader, more synthetic approach. This is the topic of Chapter 16. Mark Harwell, John Gentile, and Keith Parker develop the conceptual framework and operational models for formalized ecological risk assessments, in which all plausible pathways of exposure to oil hydrocarbons are evaluated to determine the likelihood of exposure and its potential consequences. Using the rich lode of data and insights developed in the studies reviewed in the rest of the book, they apply the approach to two species: harlequin ducks and sea otters. Because this risk-assessment framework was not available when the Exxon Valdez spill occurred in 1989, the analyses were not conducted until much later. If applied in the early phases of a spill, however, the risk-assessment approach can help to direct studies to the exposure pathways posing the greatest potential risk.

Introduction

Petroleum spills and other sources of hydrocarbon contamination represent risks for society. Regardless of whether oil is stranded on a shoreline, spilled from a pipeline, or leaked from underground storage tanks, the same basic physical and chemical principles characterize exposure levels of contaminants. The purpose of this chapter is to explain and illustrate these principles. In particular, we use these principles to explain the apparent paradox of how oil residues persist at some shorelines of Prince William Sound (PWS) as isolated subsurface patches, but yet pose little if any exposure risk to the local ecology. We resolve this apparent paradox using well-established scientific and engineering tools.

One of the biggest challenges of any study of a contaminated site is identifying the most important questions and the most important observations and data needed to answer these questions. This challenge is discussed in this chapter in both a general way and for the PWS study in particular. One of the key lessons learned from this study was the need for experts in multiphase flow in contaminated sediments to be a central part of the team addressing these questions. Our goal is to convey a coherent understanding and perspective that brings all of the observations and measurements by various environmental experts of different scientific disciplines into a consistent explanation.

Introduction

When an environmental accident such as an oil spill occurs, several things happen. There can be immediate efforts to contain the damage to natural ecosystems or human structures or livelihoods. Steps can be taken to provide relief to the people or environments most immediately affected. If the accident is sufficiently large, media accounts can fuel responses by the broader public. For damages resulting from human-caused accidents, claims and counter-claims of the magnitude and extent of the accident and its consequences will be made and then amplified, often followed (in the United States, at least) by litigation. All of these consequences require knowledge of what really happened – where did the oil go, what natural resources or services were affected, and how persistent were these effects? As the chapters in this book amply demonstrate, the need for careful, rigorous, and objective science is paramount.

Just because there is a need for careful, rigorous, and objective science, however, does not mean that it is easily attainable. Because of demands for immediate action and the heightened emotions following an environmental accident, attempts to document the ecological effects and subsequent recovery run the risk of being hastily developed and inadequately designed. This can foster never-ending arguments about conclusions. Such accidents occur against a complex and dynamically varying environmental background, so they cannot be treated as traditional experiments to be analyzed with straightforward statistical procedures that are planned in advance. There is only a single replicate of the “treatment” (i.e., the accident), there are no pre-established controls, and a welter of other factors with varying degrees of intercorrelation confounds attempts to attribute observed changes to the environmental accident. After all, the real world is messy! Designing field studies and analyses that are quantitative, objective, and scientifically rigorous under such circumstances is difficult – yet it is essential.

Introduction

When the Exxon Valdez oil spill occurred in 1989, there was no accepted framework for conducting ecological risk assessments. The primary guidance for assessing effects from oil spills was Oil in the Sea (National Research Council, 1985), which emphasized individual species but provided little information on communities or ecosystem processes. More importantly, it did not provide a systematic, risk-based methodology for assessing relationships between exposures to oil and their effects. The United States Environmental Protection Agency's (EPA) risk-assessment framework had been developed specifically for determining human cancer risks from chemical exposures (National Research Council, 1983). Assessing ecological risks, however, presents significant additional challenges: diverse ecological systems are subjected to multiple natural and anthropogenic stressors, each potentially causing many different effects on many different ecological attributes. Consequently, EPA developed a new framework and guidance designed for conducting ecological risk assessments (ERAs) (US Environmental Protection Agency, 1992, 1998), but this did not occur until several years after the Exxon Valdez oil spill.

Another decade passed before we applied this ERA framework to evaluate the ecological significance of any remaining effects of the Exxon Valdez spill. Now, 20 years after the ERA framework was developed, the process has matured considerably into an integrated environmental-assessment framework (Cormier and Suter, 2008). The integrated framework no longer simply assesses exposures and effects, but now provides a more comprehensive approach to thinking about ecological incidents. This expanded construct focuses on identifying the system attributes that matter ecologically or societally and provides a means to assess both immediate and long-term effects on those important attributes. It also places spill risks in the context of other natural and anthropogenic stressors and incorporates a process to account for uncertainty. It ultimately provides a means to characterize recovery in light of natural variability over time.

Introduction

When oil is spilled into a marine environment, it immediately begins to undergo changes in its form and constituents as it is moved by wind, waves, and currents to other places. If the spill occurs close to land, some of the oil will be deposited on shorelines. Over time, much of the deposited oil is removed by cleanup efforts, bioremediation, or natural processes. Some of the oil may end up beneath the shoreline surface, particularly in locations sheltered from natural weathering. Understanding what happens to spilled oil and the forces affecting its fate is an essential prerequisite to assessing its potential effects on valued natural and cultural resources. That is the focus of the chapters in this section.

In Chapter 3, Paul Boehm, Jerry Neff, and David Page describe the physical and chemical factors that affect oil in water and how these factors came into play in the Exxon Valdez spill. As the oil changes and undergoes weathering over time, it is essential to sample the composition of the oil. This requires careful attention to sampling design. In the Exxon Valdez spill, intensive sampling of the water column showed that perhaps one quarter of the spilled oil evaporated from the water’s surface within a few days, and concentrations of polycyclic aromatic hydrocarbons (PAH) had returned to background levels within a few months.

Introduction

The Exxon Valdez oil spill generated enormous public and scientific attention on sea otters (Enhydra lutris). Photos of oil-covered sea otters hauled out on beaches or collected in boats frequently appeared in the media and in government reports, making it one of the most notable “poster species” of this spill (Batten, 1990). Rice et al. (2007, p. 450) commented, that “Perhaps our most persistent collective memory of the oil spill is the dead and dying sea otters.” A major report, Legacy of an Oil Spill 20 Years after Exxon Valdez, featured sea otters on the cover and used this species as the predominant case study (Exxon Valdez Oil Spill Trustee Council, 2009).

Attention to sea otters was fueled by their charismatic nature and appearance, combined with the fact that no mammal suffered greater spill-related mortality. Given the large number of otters that died (or were not born) as an immediate or long-term result of the spill, the significance of this species in terms of natural resource damage assessment and public relations was enormous. It was argued, for example, that each otter killed in the spill was “worth” at least $80 000, the minimal cost to Exxon for each otter that was captured, cleaned, and rehabilitated (Estes, 1991).

Introduction

Many microorganisms have evolved the ability to feed on naturally occurring petroleum hydrocarbons, which they use as sources of carbon and energy to make new microbial cells. Most of the tens of thousands of chemical compounds that make up crude oil can be attacked by bacterial populations indigenous to marine ecosystems. A consortium of different bacterial species rather than any single species acts together to break hydrocarbons down into carbon dioxide, water, and inactive residues. Even toxic oil residues, including highly toxic polycyclic aromatic hydrocarbons (PAH), can be detoxified. Microorganisms do not accumulate hydrocarbons as they consume and degrade them, so they are not a conduit for transferring hydrocarbons into the food web. In fact, microorganisms grown on hydrocarbons can be a potential source of protein for animal and human food (Shennan, 1984).

For many years before the Exxon Valdez oil spill, the US Environmental Protection Agency (EPA), the National Oceanic and Atmospheric Administration (NOAA), and other governmental agencies had supported research on microbial degradation of oil in marine environments – biodegradation – and on ways to enhance and accelerate it – bioremediation. These studies showed that, while in many cases biodegradation can mitigate toxic impacts of spilled oil without causing ecological harm, environmental conditions for it to happen rapidly are not always ideal (Atlas, 1995). If water carrying sufficient amounts of oxygen and nutrients cannot reach the oil, rates of biodegradation will be severely limited: oil incorporated into, or on, sediment above the tidal zone, oil buried in low-permeability sediments (Chapter 7), and thick oil layers and tarballs that are not intimately in contact with flowing water are especially resistant to biodegradation.

Shortly after midnight on March 24, 1989, the Tanker/Vessel Exxon Valdez, fully loaded with its cargo of Alaska North Slope crude oil, grounded on Bligh Reef in Prince William Sound, Alaska. Eight of its 11 cargo tanks ruptured, releasing some 11 million gallons (40million liters) of oil – about 20% of its cargo – into the icy waters of the Sound. The floating oil rapidly spread, pushed by strong coastal currents. Three days later, a severe winter storm moved in, widening and accelerating the spread of oil and thwarting attempts at containment. As the floating oil reached shorelines, it began coating beaches and intertidal algae and animals with layers of thick, black oil. Over 200 000 seabirds may have died. Commercial fisheries were closed. The spill eventually extended down the Kenai and Alaska peninsulas to beyond Kodiak Island, roughly the distance between Boston and Washington, District of Columbia.

It would be hard to imagine a worse place for an oil spill. Prince William Sound is widely regarded as pristine, and the remoteness and climate of the region present formidable challenges to mobilizing spill responses and cleanup. It supports large populations of charismatic wildlife: sea otters, seabirds, whales, bears, and seals. Tourism, cruises, recreation, and sport fishing are significant activities, and there are economically important commercial fisheries. Alaska Natives also rely heavily on the area for subsistence harvesting.

Introduction

Following the Exxon Valdez oil spill in 1989, concern quickly arose about potential effects on Pacific herring (Clupea pallasii). As the most abundant forage fish in Prince William Sound (PWS), Pacific herring is a keystone species, consuming zooplankton and providing high-quality prey for birds, marine mammals, and other fish (Spies, 2007). Pacific herring are also commercially important, supporting five fisheries in PWS: two spring fisheries for roe (eggs as food), two spring fisheries for eggs on kelp (a delicacy), and a fall “fish” fishery for bait and food. The four spring fisheries are the first opportunity to conduct commercial fishing after the winter. These five fisheries provided landings (i.e., landed catches) worth about $12 million in the year before the spill (Brady et al., 1991a). And Pacific herring are an important subsistence food for people living in the area.

Herring life history is complex (Fig. 13.1; Blaxter, 1985; Hay, 1985; McQuinn, 1997), and multiple factors – such as ocean conditions, prey availability, predation, and competition – structure herring population dynamics in PWS and the Gulf of Alaska (GOA). Establishing whether and how the spill affected herring required separating spill-related injuries from changes caused by the complex of other factors affecting herring. Moreover, little information about several aspects of herring life history and population dynamics in PWS was available at the time of the spill. Thus, although the overall goal of scientific investigations of herring was to assess the effects of the oil spill, it was also necessary to undertake basic research to fill in the information gaps necessary to assess the spill’s effects.

Introduction

In the aftermath of an oil spill, the effects on the environment and wildlife are often painful to see. After the initial emotional impact come the questions: What wildlife and environments are at risk, and when will they recover? How can the oil be removed without causing further harm? Is it safe to eat the seafood or to be on the beaches? What will happen to the oil? Science can offer objectivity, rigor, and focus in addressing such questions, helping to separate fact from fiction, evidence from conjecture. A science-based approach defines potential spill effects and then formulates testable hypotheses, follows an unbiased study design, collects and analyzes data using rigorous methods, and interprets the results with a mind open to alternative explanations that evolve during the investigations. This is how good science is done.

Conducting science following the Exxon Valdez spill was not always easy, however. Along with everyone else, the first scientists on the scene were distraught over what they saw – shorelines awash with oil, oiled seabirds and sea otters (Enhydra lutris) struggling to survive, and fisheries closed for fear of contamination. It was challenging to come up with good, objective study designs. The remote location of the spill and the wide variation among places in the spill zone complicated data collection. Studies conducted at different times or of different durations produced different results, and relationships documented at different spatial scales did not always match. Study designs often seemed to be confounded by other factors or uncontrolled sources of variation at every turn, making it difficult to separate changes in the environment due to the oil spill from changes due to other, unrelated factors.

Introduction

Marine birds are among the most conspicuous elements of coastal ecosystems. Their variety, abundance, visibility, and behavior resonate with the public. They are also particularly vulnerable to oil spills. Most marine-bird species forage at or beneath the water’s surface, where they are at risk of exposure to floating oil. Additionally, many feed and nest along shorelines where floating oil can accumulate, and some form large breeding colonies that are susceptible to oil spills. Over 200 000 marine birds died as a direct consequence of the Exxon Valdez oil spill, and images of oiled birds dominated media coverage. Federal regulations requiring documentation of injuries to natural resources from oil spills (see Chapter 1) prompted multiple studies of marine birds, fueling debates about short- and long-term effects of the spill and subsequent recovery.

Determining how an oil spill (or any large environmental disturbance) affects marine birds is complicated by variation in the environment and in how birds respond to that environment. Coastal environments vary substantially from place to place and time to time. At high-latitude locations such as Prince William Sound (PWS), diurnal and monthly changes in tides; seasonal variations in storms, water temperatures, and productivity; and multiyear changes in ocean temperature and circulation such as El Niño events and the Pacific Decadal Oscillation can have dramatic effects. At any time, marine birds may be responding to a host of environmental factors over a range of scales, from the availability of suitable nesting sites along a small stretch of shoreline to the abundance of prey over a broad region or to variation in hemispheric-scale forces affecting the ocean. Because these influences do not disappear when an oil spill occurs, they and any associated environmental variations must be accounted for when assessing spill effects. Population changes attributed to an oil spill must be rigorously tested and documented, not just inferred.

Introduction

Every oil spill is different from the ones that preceded it. This is due in part to differences in the spill itself – the nature of the oil and the circumstances of the release – but it also stems from differences in the context of the spill – the setting, the resources at risk, and how people respond to the spill. All of these factors affect how science is brought to bear on investigating the spill and its consequences.

The two chapters in this section consider these factors in two ways. Chapter 1 (to which many of the authors contributed) introduces the environmental setting of the Exxon Valdez oil spill, what happened during the spill and to the oil that was released, the cleanup responses and the launch of scientific studies, and the regulatory and legal context of the spill responses and studies. Separate discussions consider: the characteristics of crude oil; the importance of assessing exposure of biota to the oil in gauging potential effects; the thorny issue of defining “impact,” “effect,” “injury,” and “recovery”; and the legal issues that followed from the spill.

In Chapter 2, Paul Boehm, Erich Gundlach, and David Page take a broader view. When oil is released in a marine environment, it immediately begins to undergo transformations resulting from a variety of physical and chemical processes. Although these changes are continuous, they can be separated into three overlapping phases that align with shifts in the focus of scientific studies over time. Recognizing these phases can help to plan which studies to conduct, and when. This, in turn, can facilitate an efficient and effective allocation of research efforts.

Introduction

For over 4000 years, humans have lived, fished, hunted, and developed industries in Prince William Sound (PWS). When Exxon Valdez oil spilled in 1989, hundreds of archaeological sites and artifacts were potentially at risk. Many were at least superficially known, but most were not. Archaeologists and other cultural resource experts had to move quickly to identify vulnerable sites and work with others engaged in the response to safeguard Alaska’s heritage from oil and incidental harm during cleanup. Exxon created the Exxon Valdez Cultural Resource Program (hereafter the “Program”) to address potential threats to archaeological sites and to comply with state and federal laws.

The 28 archaeologists contracted to Exxon in 1989 coordinated with archaeologists from governmental agencies and Alaska Native organizations to assess the integrity of sites, identify oil concerns, and protect sites from impacts during shoreline cleanup. The archaeological contractors and their agency counterparts were knowledgeable in all areas of cultural-resource management, laws, and the region’s pre- and postcontact history.