Introduction

When crude oil or petroleum products are released during a marine oil spill, organisms living in the water or feeding at the surface are the first to be affected. Oil on water or mixed into the water column may injure aquatic species of all types. Understanding the potential for injury to organisms from exposure to oil requires fully studying physical and chemical effects and quickly communicating the results. The risks to the public from the consumption of fish or other species normally harvested from the water can also be serious. A comprehensive water-assessment program provides quantitative data to address multiple concerns.

The Exxon Valdez oil spill was, until recently, the most comprehensively sampled oil spill in history and remains the most exhaustively studied oil spill. In fact, the thoroughness of the data – and the disappearance of most oil slicks and sheens by the end of the summer of 1989 – enabled all commercial fisheries to be reopened in 1990, much earlier than had been anticipated. Techniques and protocols established during the Exxon Valdez spill have been used in subsequent spills, most notably in the 2010 Deepwater Horizon oil spill in the Gulf of Mexico.

Introduction and overview

Following a marine oil spill, it is important to know where the oil goes, how it changes chemically, how long the oil persists in various environmental compartments such as water or sediments, and what biological resources are affected. As an oil spill progresses over time, the behavior of the oil and the impacted areas and levels of risk to people and biological resources such as fish and wildlife change. Scientific studies provide the most benefit to cleanup efforts and the protection of people and biological resources in the area when they are coordinated and focused on the most pressing questions based on the phase of the oil spill. Over several decades, previous marine oil spills have shown a consistent pattern; understanding this pattern can help predict where the oil will go, how it changes chemically, where it will persist, and what living things are likely to be affected. Similarly, this predictability, coupled with specific observations at each spill, can help to provide a framework for designing and conducting studies that can address key questions at critical junctures in the evolution of the spill.

Water and air are the first environmental media affected during the early phase of any marine spill. Animal and plant life (or “biological resources”) can be affected immediately – as can humans involved in spill cleanup. The initial exposures to the chemicals in petroleum and the resulting effects can be acute, but short-lived. This is because once the spilled oil is no longer moving on or in the water, concentrations of harmful chemicals decrease rapidly owing to dilution, dispersion, and degradation (collectively known as “weathering”). Likewise, the evaporation of the volatile hydrocarbon components of fuels or crude oil immediately following a spill first increases, then decreases. By contrast, the effects on shoreline biological resources from oil that reaches land may persist. The last area potentially to be affected is bottom sediments, where oil can be transported before or after it reaches land (Chapter 4).

Introduction

The previous chapters have synthesized and evaluated the science that was brought to bear on the Exxon Valdez oil spill and its effects. Several overarching insights have emerged, including the importance of following a multidisciplinary, collaborative approach; of clearly defining one’s objectives to design rigorous studies and identify data requirements; of recognizing the value of natural processes in facilitating restoration or recovery from spill effects; of assessing and documenting exposure of organisms to harmful oil constituents from all sources; and of evaluating possible avenues of spill exposure and effects through risk assessment. These insights have been central to developing a science-based understanding of the environmental effects of the Exxon Valdez spill (see Box 17.1). In this chapter, I highlight these lessons and describe how they provide a foundation for dealing with future oil spills or other large environmental disruptions.

I also explore several challenges that emerged during the Exxon Valdez studies. The confounding effects of environmental factors other than oil, natural variability of the environment, the attendant uncertainty in scientific data, and contradictory interpretations and disagreements among scientists present challenges in any high-profile and contentious situation, as major environmental accidents are likely to be. These factors confuse those looking to science for clear answers and straightforward guidance about what to do, and they foster public perceptions of conflicts between industry scientists and government scientists that diminish the credibility and value of the science itself.

Introduction

Alaskan salmon are of major sport and commercial importance, figure importantly in the traditions and livelihood of native cultures, and support food webs for an array of carnivores and scavengers. Of the five Pacific salmon species, pink salmon (Oncorhynchus gorbuscha) are the most abundant in Prince William Sound (PWS). Annual harvests yield 20–70 million adult pink salmon, with a value that averaged over $29 million annually between 2001 and 2010 (Fig. 12.1). The subsistence and commercial importance of the pink-salmon fishery, combined with the overlap of the 1989 Exxon Valdez oil spill with the early life stages of the salmon, make understanding the effects of the spill both critical and challenging.

Following the spill, the commercial pink-salmon fishery was closed. In addition, an Oil Spill Health Task Force was organized to ensure the safety of subsistence foods. The Task Force used analytical data on hydrocarbons in pink salmon (and other subsistence foods) (Field et al., 1999) and determined that there were no Exxon Valdez polycyclic aromatic hydrocarbons (PAH) in sampled edible salmon tissues in 1989 and 1990.