Oil in the Sea

Nonpoint pollution, not oil spills, is the largest source, and reducing it will require coordinated efforts on a number of fronts.

“When it rains, it pours”—or so a motorist caught in a sudden storm might think while sliding into another vehicle. It is not merely the reduced visibility and the frenetic behavior of drivers in the rain that foster such mishaps; the streets also are slicker just after the rain begins to fall. Why? Because the oil and grease that are dripped, spewed, or otherwise inadvertently deposited by motor vehicles onto roadways are among the first materials to be lifted off by the rain, thereby literally lubricating the surface. Nor do matters end with making life miserable for motorists. The oil and grease washed off roads will most likely run into storm sewers and be discharged into the nearest body of water. From there, the oily materials often are carried to the sea, where they can cause a host of environmental problems.

These events on a rainy day in the city illustrate an important but often overlooked route by which petroleum finds its way into coastal waters. Shutting down this and other routes presents a pressing challenge. True, the nation is doing a better job than ever of keeping oil out of the marine environment. But much work remains. We need to better understand the various pathways by which oil gets into the environment, how it behaves when it gets there, what effects it has on living organisms, and, perhaps most important, what steps can be taken to further reduce the amount of petroleum that enters the nation’s and the world’s oceans.

Sources and problems

Approximately 75 million gallons of petroleum find their way into North America’s oceans each year, according to Oil in the Sea III: Inputs, Fates, and Effects, a report issued in 2002 by the National Research Council (NRC). About 62 percent of the total—roughly 47 million gallons per year—derives naturally from seepages out of the ocean floor. The rest comes from human activities.

Contrary to common belief, the bulk of human-related inputs is not due to large-scale spills and accidents that occur during the transport of crude oil or petroleum products. Indeed, these types of releases account for only about 10 percent of the oil that reaches the sea as a result of human activity. The other 90 percent comes in the form of chronic low-level releases associated with the extraction and consumption of petroleum. Within this category, the biggest problem is nonpoint source pollution. Rivers and streams that receive runoff from a variety of land-based activities deliver roughly 16 million gallons of oil to North American coastal waters each year, more than half of the total anthropogenic load. The loads are most obvious in watersheds that drain heavily populated areas. Other sources of oil that turns up in the marine environment include jettisoned aircraft fuel, marine recreational vehicles, and operational discharges, such as cargo washings and releases from petroleum extraction.

There is at least some good news. Less oil is now entering the oceans as compared to the levels found in a previous NRC report issued in 1985. Some of this change may be attributable to differences between methodologies used in the two reports, but some decreases are due to improved regulations regarding how oil is produced and shipped. Spills from vessels in North American waters from 1990 through 1999 were down by nearly two-thirds compared to the prior decade. There also has been a dramatic decline in the amount of oil released into the environment during exploration for and production of petroleum and natural gas. Still, the recent NRC report concludes that despite such progress, the damage from oil in the marine environment is considerably more pervasive and longer-term than was previously understood.

Oil in the sea, whether from catastrophic spills or chronic releases, poses a range of environmental problems. Major spills receive considerable public attention because of the obvious attendant environmental damage, including oil-coated shorelines and dead or moribund wildlife, especially among seabirds and marine mammals. The largest oil spill in U.S. waters occurred on March 24, 1989, when the tanker Exxon Valdez, en route from Valdez, Alaska, to Los Angeles, California, ran aground on Bligh Reef in Prince William Sound, Alaska. Within six hours of the grounding, the ship spilled approximately 10.9 million gallons of crude oil, which would eventually affect more than 1,100 miles of coastline. Large numbers of animals were killed directly, including an estimated 900 bald eagles, 250,000 seabirds, 2,800 sea otters, and 300 harbor seals.

Oil pollution also can have more subtle biological effects, caused by the toxicity of many of the compounds contained in petroleum or by the toxicity of compounds that form as the petroleum degrades over time. These effects may be of short duration and limited impact, or they may span long periods and affect entire populations or communities of organisms, depending on the timing and duration of the spill and the numbers and types of organisms exposed to the oil.

Of course, oil spills need not be large to be hazardous to marine life. Even a small spill in an ecologically sensitive area can result in damage to individual organisms or entire populations. A spill’s influence also depends on the type and amount of toxins present in the petroleum product released. For instance, the fuel oil leaked when the tanker Prestige broke apart off the northwest coast of Spain in 2002 was initially more toxic than the crude oil spilled from the Exxon Valdez.

One major problem with all spills, no matter their size or type, is that the oil can remain in the environment for a long time. Several lines of evidence point to continued exposure of marine organisms to oil spilled by the Exxon Valdez. Substantial subsurface oil beneath coarse beaches in the spill area was found in the summer of 2001. The oil was still toxic and appeared to be chemically unchanged since its release more than a decade earlier. Some researchers predict that oil beneath mussel beds in the region affected by the spill may not decline to background levels for at least another two decades. In another instance, scientists studying salt marshes in Massachusetts that had been covered by fuel oil spilled from the barge Florida 30 years ago recently reported that oil is still present in sediments at depths of 6 to 28 centimeters. Moreover, the concentrations of oil found in the sediments are similar to those observed shortly after the spill. The researchers, from the Woods Hole Oceanographic Institution, predict that the compounds may remain there indefinitely, while crabs and other intertidal organisms continue to burrow through the oil-contaminated layer.

Prescribed remedies

Reducing the threat of oil in the oceans will require blocking the routes by which oil enters the environment. Focusing on inputs from spills and nonpoint sources, two of the major anthropogenic contributors, will show the range of actions needed.

Reducing spills. Worldwide, large spills resulting from tanker accidents are down considerably from the totals reported by the NRC in 1985—they have decreased to 17 million gallons annually from 140 million gallons annually. This gain was achieved even as the size of the global tanker fleet increased by 900 vessels, to a total of 7,270 in 1999. Progress was made through the implementation of numerous regulations and by technological advances in vessel construction, including the increased use of double-hull tankers, the use of new construction materials, and improvements in vessel design. Spills larger than 50,000 gallons now represent less than 1 percent of total spills by number but are responsible for more than 80 percent of the total spill volume. It is important to note, however, that more than half of all tanker spills now occur in North American waters. Although the number and size of spills in these waters have been reduced considerably during the past two decades, with total volume falling to 2.5 million gallons per year, they remain the dominant domestic source of oil input to the marine environment from petroleum transportation activities, as they are globally.

More must be done to prevent potentially large spills from aging pipelines and abandoned coastal facilities, such as in Louisiana.

Prevention, in the form of stricter regulations for tankers, has obviously not prevented all large spills, as the Prestige spill so dramatically illustrated. Irreparably damaged by a storm, the ship spilled nearly 3 million gallons of fuel oil, which spread over 125 miles of coastline in one of Spain’s leading areas of commercial fishing and shellfishing. But out of this calamity may come improved policies. The spill has highlighted concerns about older, single-hull ships (the Prestige was 26 years old) that are due to be phased out by 2015, and about what Europe should do to keep these ships safe and inspected in the meantime. Under a proposal made by the European Commission in December 2002, which the European Union (EU) is expected to adopt, single-hull oil tankers will not be allowed to carry heavy grades of oil in EU waters. Prohibited grades will include heavy fuel oil, heavy crude oil, waste oils, bitumen, and tar. Questions also have been raised about single-hull ships that are bypassing EU ports in order to avoid tough new EU-mandated inspection rules adopted in 1999 after the Erika oil spill polluted 250 miles of French shoreline. The EU regulations before the passage of the latest restrictions on transport in EU waters required port authorities to check at least 25 percent of all ships coming into dock, starting with older, single-hull vessels, with priority going to ships flying flags of convenience or registered in countries with lax safety, labor, or tax rules.

The potential for a large tanker spill, however, is still significant, especially in regions without stringent safety procedures and maritime inspection practices. Furthermore, tanker traffic is expected to grow over the coming decades, as the centers of oil production continue to migrate toward the Middle East, Russia, and former Soviet states. U.S. agencies should expand their efforts to work with ship owners, domestically and internationally, through the International Maritime Organization, to enforce and build on the international regulatory standards that have contributed to the recent decline in oil spills and operational discharges.

Tankers are not the only potential source of large spills. There also is concern about aging oil pipelines and other coastal facilities. The aging of the infrastructure in fields in the central and western Gulf of Mexico and in some areas of Alaska is especially disconcerting, because these facilities often lie near sensitive coastal areas. Many pipelines in coastal Louisiana that should be buried no longer are. Numerous wellheads and other facilities within the estuaries are being abandoned, as one company takes over facilities from another. As the resources become depleted, the cost of extraction exceeds the profit to be gained from sale of the product, and owners file bankruptcy and abandon holdings. Federal agencies should work with state environmental agencies and industry to evaluate the threat posed by aging pipelines and abandoned facilities, and to take steps to minimize the potential for spills.

Reducing nonpoint source inputs. Regulations developed under the Clean Water Act of 1972 have significantly reduced the number and amount of pollutants coming from the end of a pipe, and the Toxics Release Inventory tracks many of the pollutants that are released. But the more diffuse sources, such as urban runoff, atmospheric deposition, and watershed drainage, are not regulated or even monitored adequately. Unfortunately, nonpoint source runoff is difficult to measure and sparsely sampled; as a result, estimates have a high degree of uncertainty. Clearly, new federal, state, and local partnerships are needed to monitor runoff and to keep better track of how much petroleum and other pollutants industry and consumers are releasing.

Such a call for increased monitoring will undoubtedly elicit groans from managers and other people responsible for water quality, yet few people would argue that existing efforts are adequate for the overall task. Even the better-funded federal efforts are insufficient. The National Stream Quality Accounting Network, the national network operated by the U.S. Geological Survey to monitor water quality in streams, has increasingly fewer stations, particularly along the coast, as budgets are tightened and tightened again. Additional funding is necessary to invigorate this program. Coastal stations that have been shut down need to be restored, and new stations along the coast and at critical inland locations need to be added. The network also must expand monitoring to include total hydrocarbons (instead of merely “oil and grease,” as is now the case), as well as a particular class of compounds called polynuclear aromatic hydrocarbons (PAHs). Growing evidence indicates that even at very low concentrations, PAHs carried in crude oil or refined products can have adverse effects on biota. This suggests that PAHs released from chronic sources may be of greater concern than previously recognized, and that in some instances the effects of petroleum spills may last longer than expected.

There also is a great need for expanded basic research. The most significant unanswered questions remain those regarding the effects on ecosystems of long-term, chronic, low-level exposures resulting from petroleum discharges and spills caused by development activities. Federal agencies, especially the Environmental Protection Agency (EPA), the U.S. Geological Survey, and the National Oceanic and Atmospheric Administration, should work with academia and industry to develop and implement a major research effort to more fully understand and evaluate the risk posed to organisms and the marine environment by the chronic release of petroleum, especially the cumulative effects of chronic releases and multiple types of hydrocarbons.

Apace with advances in monitoring and research, positive steps can be taken to implement proven methods for reducing nonpoint source discharges of oil into the environment. Remember, for example, the motorist brought low by slick pavement. The oil and grease that wash off highways during rain storms usually bypass sewage treatment plants in storm water overflow systems that pump the rain and any materials caught up in the flow directly to the closest body of water. In many urban settings, this source can be a significant contribution of petroleum to the ocean. As the population of coastal regions increases, urban runoff will become more polluted because of the expansion in the numbers of cars, asphalt-covered highways and parking lots, municipal wastewater loads, and the use and improper disposal of petroleum products. Collection and treatment of storm water overflows is necessary to control these inputs. Improved landscape management and urban management, increasing use of fuel-efficient vehicles, and public education can all contribute to lessening petroleum runoff.

The power of public education can be seen in the Chesapeake Bay region. In small but effective ways, people living within the bay’s watershed are reminded daily of their consumptive uses of pollutants that enter the water. They see license plates that proclaim “Save the Bay” and storm water drain covers that say “Don’t Dump. Drains to Chesapeake Bay.” Education is a first step for a better-informed public that will recognize the need for less consumption, less pollution, and better conservation of resources. This knowledge should but does not always lead to legislation and funding for reducing pollutant loads, including oil reaching the sea.

Additional remedial actions should target the recreational watercraft that have grown so popular during the past two decades. Most of these craft, including jet skis and small boats with outboard motors, use two-stroke engines, which release up to 30 percent of their fuel directly into the water. Collectively, these watercraft contribute almost 1 million gallons of petroleum each year into North American waters. The bulk of their input is in the form of gasoline, which is thought to evaporate rapidly from the water surface. However, little is known about the actual fate of the discharge, or about its biological effects while in its volatile phase, which is highly toxic. In 1990, heightened awareness of this problem led the EPA to begin regulating the “nonroad engine” population, under the authority of the Clean Air Act. Questions remain regarding the amount of petroleum residing in the water column or along the surface for biologically significant lengths of time. The EPA should continue its phase-out efforts directed at two-stroke engines, and it should expand research, in conjunction with other relevant federal agencies, on the fate and effects of discharges from these older, inefficient motors.

To achieve maximal effectiveness, efforts to understand and minimize oil pollution should pay heed to worldwide needs. The United States and other developed countries have invested much in technologies to reduce the spillage of oil into the marine environment, as well as in the science that has increased knowledge of the effects of spilled oil, either acute or chronic. This knowledge should be transferred to people in other countries that are developing their petroleum reserves. It is imperative that the petroleum industry not simply comply with regulations in developing countries where they operate, but that they transfer the knowledge derived from extensive studies in U.S. waters to areas where their operations are expanding.

Shared responsibilities

Clearly, new partnerships are needed to monitor runoff and to keep better track of how much petroleum and other pollutants are being released.

It is tempting to blame the oil and shipping industries alone for spills such as those from the Exxon Valdez and the Prestige, but everyone who benefits from oil bears responsibility for the fraction that enters the sea. If companies have failed to build and buy double-hull tankers, it is in part because consumers do not wish to pay the increased fuel prices that would be needed to offset the extra cost. The push for improved methods of extracting, producing, and transporting oil must come from the general public, and this link reinforces the need for education.

The price of oil and natural gas is a major force in the world economy. As recently as the late 1990s, the average price of a barrel of crude oil was less than the cost of a takeout dinner. Yet a fluctuation of 20 or 30 percent in the price can influence automotive sales, travel decisions, interest rates, stock market trends, and the gross national products of industrialized nations. Perceived or real decreases in the availability of oil led to long lines for gasoline in the early 1970s and to the development and sale of fuel-efficient vehicles. Many observers argue that the low oil prices in recent years have helped put a glut of gas-guzzling vehicles on the highway. As the prices of a barrel of oil and a gallon of gasoline continue to rise in the face of social unrest in South America and the unrelenting hostilities in the Middle East, the value of this limited commodity may become more apparent.

The United States needs an energy policy that treats petroleum as a limited and treasured commodity that encourages conservation rather than waste, and that supports alternative energy development and use. The nation also should tighten controls on air and water pollution and should adequately fund environmental monitoring of water resources. Without these policy changes, U.S. citizens cannot expect wise and environmentally sound use of the nation’s or the world’s resources. And if U.S. citizens cannot reduce their overly consumptive use of petroleum to help in curbing its introduction to the diffuse but voluminous nonpoint source pollutant load, how can they expect citizens of developing countries to strive for less polluting and consumptive actions in the face of an improving economy derived from sales of petroleum?

“We’re all in this together,” as the saying goes, including the motorist who crashed on that oil-slicked road. There is just one global economy, one global ecosystem, and one global source of nonrenewable petroleum reserves.

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Cite this Article

Rabalais, Nancy. “Oil in the Sea.” Issues in Science and Technology 20, no. 1 (Fall 2003).

Vol. XX, No. 1, Fall 2003