Abstract
Although many methods are available for removing or degrading oil stranded on shorelines, not all are effective, many are appropriate for only a few shoreline types and some are more damaging than no cleanup at all. The EXXON VALDEZ Oil Spill offered a unique opportunity to compare and contrast the short-term and long-term (years) effectiveness and effects of several shoreline cleanup methods including no response, high-temperature high-pressure washing, berm relocation and use of chemical shoreline cleaners. Much of the shoreline marine life survived the initial oiling but was destroyed by the pressure washing and has been slow to recover even though a lot of oil was removed. One shoreline cleaner produced few impacts on surviving marine life, but it was not used in the response. The results of bioremediation were controversial and unclear, even though it was approved and used extensively. Subsequent field research on bioremediation indicates that it is useless to add oil-degrading microbes to shoreline but under some circumstances, continuous application of nutrients (fertilizers) can accelerate oil degradation. The bottom line is that each cleanup method must be tailored to specific types of oils and shorelines and that care should be taken to protect marine life that survives the initial oil spill.
1.0 Introduction
Since the 1989 EXXON VALDEZ oil spill in Alaska, a "new wave" of field research has been conducted to evaluate both the effectiveness (oil-removal efficiency) and effects (biological injury) of shoreline oil spill cleanup methods. In addition, the overall benefits and impacts of past response strategies are being reviewed. As a result of this work, much of it still ongoing, response authorities are now much more selective and careful about methods used to treat shorelines. In addition, they are careful to answer the ultimate question, "How clean is clean enough?" This paper is a review of the status of shoreline oil spill cleanup methods, and cleanup research, with focus on benefits and effects on marine life.
2.0 How Bad is Oil on the Shoreline?
The public, policy-makers and the media generally assume that oil spilled in the marine environment is a very damaging and persistent substance and that it must be quickly and completely removed. On the water, it kills birds and mammals by smothering; if these animals remain coated or exposed for more than a few hours, the oil can also be toxic to them or their young (nesting bird and turtle eggs). On a resort beach, oiling will immediately cause lost uses and income to resort villages, even if the oiling is light or non-toxic. Fisheries may be closed for fear of contaminating sea food products, even if it does not do so. This public image of death and destruction from oil spills is not completely true and should not be the primary factor directing the response and shoreline cleanup.
2.1 The Fate and Toxicity of Oil
Oil is a highly-variable and complex natural substance (top, Figure 1). When released into theocean or coastal waters its properties and chemistry undergo important changes caused by exposure to various physical, chemical and biological processes (lower left, Figure 1). Among other things, these processes work to make oil more or less toxic (usually less) to marine life and marine ecosystems (lower right, Figure 1 ). By the time it reaches the shoreline, or has been stranded for many days, this "weathered" oil may damage shoreline marine life by smothering, but it's toxicity may decrease rapidly. Furthermore, it begins to experience additional processes (clay/oil interactions, biodegradation, etc.) that accelerate its degradation and destruction.Only in very heavy oiling (Saudi Arabia during the Gulf War Oil Spill) do shorelines not recover from an oil spill within a few years.
2.2 The Nature of Shoreline Marine Life and Its Recovery from Oil Spills
Most of the world's shorelines provide habitat for a great variety and abundance of marine life. Rocky shores, cobble beaches, marshes, mangroves, tide flats, and even sandy beaches and man-made structures jetties, groins) each have a unique, abundant and constantly changing assemblage of marine life that provide food and shelter for the entire coastal food web, including fisheries and seafood consumers. Shoreline organisms include thousands of species of fishes, crabs, barnacles, sea urchins, starfish, marine worms, clams, oysters, snails, limpets, chitons,sea weeds and kelps, sea grasses and micro-organisms (including oil-degrading bacteria!). These plants and animals live, feed, compete, prey and reproduce in loosely-knit biological communities. These shoreline resources and biological communities are threatened and can be severely damaged by the initial
