Endangered Species Handbook

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Aquatic Ecosystems

Oil Spills

     The interdependence of mangroves, sea grass and coral reefs can result in the decline of all three ecosystems when oil spills occur.  After a 1986 oil spill on the Panamanian Caribbean coast, even minute effects could be measured because the mangrove ecology of this particular area had been studied in detail by scientists from the Smithsonian Institution since the 1970s.  First the spill killed expanses of sea grasses and their root systems, along with 150 acres of mangrove trees and their roots in a thin strip along the coast (Luoma 1993).  Following this, the waves were able to loosen and suspend the bottom sediments, and these mixed with oil particles which sank to the sea floor; each rainy season, the oil was stirred up and re-suspended (Luoma 1993).  This annual flushing of the oil contaminated the entire ecosystem and gradually killed the coral reef (Luoma 1993).  Up to 96 percent of corals on heavily polluted reefs died, and even at depths of 12 meters, 45 percent of corals perished; many of the surviving corals suffered toxic effects, being left with bleached and diseased patches (Wells and Hanna 1992).  Effects on fish populations were more gradual, taking three or four years before stocks showed sharp declines as a result of destruction of their eggs.  The Smithsonian’s Tropical Research Institute prepared a report on the effects of this spill, concluding that full recovery of the ecosystem might take as long as a century (Luoma 1993). 
     The worst oil spill in US history occurred on March 24, 1989 in Prince William Sound, Alaska, when the Exxon Valdez, an oil tanker fully loaded with crude oil from the Alaskan Oil Pipeline, foundered on a reef just miles from the port of Valdez.  This southern coast teemed with wildlife.  Fifty pairs of Bald Eagles nested within the Sound, and 2,500 more lived within the archipelago that extends 900 miles to the southwest.   Millions of sea birds and waterfowl in vast colonies nested along the coasts, among them the very rare harlequin duck (Histrionicus histrionicus), which had a large breeding population.  More than 20 million shore birds and other arctic species pass through the Sound while on migration, and in all, 219 bird species have been recorded in Prince William Sound (Browne 1989).  The Exxon spill occurred only two weeks before spring migration.
     Sea otters (Enhydris lutris) numbered at least 10,000 in Prince William Sound, the largest concentration in the world.  Thousands of harbor seals used the islands for feeding and calving. Gray whales fed and migrated through the area, and killer whales had resident pods.  Commercial fishermen caught vast catches of salmon, herring and other food fish.  The coastline, one of the world's most spectacular, is lined with federal, state and native Alaskan protected lands.  Kenai Fjords and Katmai National Parks, Kodiak National Wildlife Refuge and thousands of acres of state and native lands had, until the spill, preserved a magnificent environment almost intact.  Rocky beaches alternated with marshes and sheer cliffs studded with sea bird nests.
     The Exxon Valdez spilled more than 11 million gallons of crude oil.  Almost no action to clean the spill took place for days, due to a lack of preparation on the part of the Exxon Corporation and state authorities, and a lack of agreement about whether to burn off the oil, which the state refused to allow, or to spread chemical dispersants that were feared to cause wildlife mortality.  This delay allowed the heavy oil to sink to 90-foot depths and spread hundreds of miles along the coast.  By April 10, it covered 3,000 square miles, having spread throughout the region's inlets and coves and southwest 500 miles to Kodiak Island, the haven for the massive Kodiak bear (Ursus arctos middendorffi).  The amount of shoreline oiled equaled the distance from Boston to the Chesapeake Bay (Mitchell 1999).  Surface oil was 18 inches thick, coating sea birds that landed in it with a lethal film.  Many died and sank in open water.  By the time the spill ceased spreading, it was found to have fouled 1,500 miles of shorelines and covered 10,000 square miles, an area the size of Vermont (Schneider 1994a).
     When cleaning finally began days later, it consisted of high-pressure hosing and wiping rocks.  This did not remove the tons of oil that sank deep into the sand, marshes and offshore shellfish beds.  Only 15 percent of the oil was recovered through vacuum tubes and booms, while the sunken oil remained a decade later, preventing oxygen in mudflats and wetlands from entering with microorganisms that would break down the oil (Mitchell 1999).   The rest has been dispersed by a decade of surf and ocean currents washing it away and has evaporated from the surface.  
     The toll on wildlife was immediate. Sea birds began washing up on the shore coated with thick oil, some still alive.  Sea otters struggled ashore as well, trying to clean their coats while lying on oiled rocks.  Crews employed by Exxon picked up dead birds and sea mammals, and by May 12, ABC News reported that 20 tons of dead animals had been collected along 550 miles of soiled beach, of which only two miles had been cleaned.  Actual numbers of sea bird mortalities will never be known, but some biologists have estimated that up to 500,000 birds died.  Species most affected were common and yellow-billed loons, horned grebes, Pacific cormorants, black-winged and white-winged scoters, common murres, pigeon guillemots and the threatened marbled murrelets (Brachyramphus marmoratus).  The entire population of common murres in the Barren Islands in Prince William Sound apparently died (Senner 1989), and 40 percent of the region's murres died (Mitchell 1999).  Oiled birds and sea otters were brought to special rescue centers, where survival tended to be low.
     Sea otters incurred very high mortality and suffered for long periods before they died. Their extremely fine fur collected oil as they swam about the surface, unable to avoid the oil like seals and sea birds who submerged or flew away from the spill.  At least 980 carcasses were recovered, but judging from counts carried out during the next few years, almost half the Sound's sea otters died during the spill or from its effects (Schneider 1994).  People scouring the beaches for oiled animals often heard the otters before they saw them.  The crude oil's toxic chemicals literally destroyed their livers and other internal organs within hours, causing such pain that they screamed as they died.  Some were found dead with mouths wide open as if still screaming.  An ABC news program filmed several of the otter pups that were rescued, doll-like balls of fluff who spent hours screeching for their dead mothers.  Having no thick layer of body fat to keep them warm, sea otters rely on their dense, layered fur which they constantly groom so that it remains waterproof, with a layer of air to insulate against the cold.  When they swam into oil, the otters groomed furiously but succeeded only in distributing oil over their bodies and into their gullets (Wheelwright 1994).  Their clumped fur let icy water in, and the crude oil burned their stomachs, sometimes causing acute emphysema, with air bubbles bulging out under the skin of the otter's throat in a grisly necklace (Wheelwright 1994).  Many succumbed to hypothermia and sank.  When the dead otters were autopsied, a majority of females had near-term fetuses the size of plump rabbits; the western Sound where the oil spill occurred was a "female" area, and they outnumbered males in the otter morgue two to one, with more than 60 percent pregnant (Wheelwright 1994). 
     Of the several hundred sea otters brought to rescue centers, fewer lived than died, and only a tiny percentage of the total oiled animals were rescued.  Most of the surviving pregnant females aborted or had stillborn cubs.  Carolyn McCollum was one of the hundreds of volunteers who came from all parts of the country, and even from foreign countries, to help care for oiled animals.  In an article for Wildlife Conservation, she described seeing these otters snuggling with towels, bunching them up for a pillow or using them to groom their faces.  These intelligent animals have been documented as tool users:  they use rocks as shell-openers when hand-held or as hard surfaces upon which they bang open shells.  Carolyn McCollum (McCollum 1990) took care of one female so ill she was unable to eat, wheezing with emphysema: "I could tell from her abdominal breathing that she was in great pain; her sad eyes followed my movements lethargically and I wished there was something more I could do.  About 10:00 p.m. she fell asleep; as I felt her chest to make sure she was still breathing, she pressed my hand to her body with her short forearm and I let her hold it there.  Ill and weak, the otters at the center behaved like small babies . . .I held my patient's paw until 4:15 the next morning when she stopped breathing.  As the vet came to take her to be autopsied . . . I shuddered to think how many more animals would go through the same ordeal.”
     Long-term damage to Prince William Sound started to become apparent by 1994.  Marine ecological systems had suffered serious effects.  Some species of water birds, especially harlequin ducks, ceased to reproduce in the Sound (Schneider 1994a).  Although salmon catches initially rose in 1990 and 1991, as did herring in 1991 and 1992, the catches later plummeted (Schneider 1994a). In the spring of 1994, Alaska officials closed the Sound's herring fishery because there were too few fish.  The herring, which are the keystone species in Prince William Sound, fed on by sea birds, mammals and humans alike, died from disease which manifested in skin lesions, perhaps caused by sub-lethal effects of oil (Mitchell 1999).  By 1999, herring had still not recovered, and a population estimated at 120,000 tons prior to the spill fell to 40,000 tons (Mitchell 1999).  The oil remaining in the water has apparently affected a variety of wildlife, preventing the recovery of virtually every species except the Bald Eagle (Mitchell 1999).  Populations of sea otters, harbor seals, killer whales, pink salmon, herring and many sea birds have not recovered.  Harbor seals plummeted from 2,000 to only 900 in the Sound.  For seals and other fish-eating marine mammals, there are apparently not enough fish to eat, and recovery of fish populations seems to have been slowed by the remaining oil, which kills young fish even at very low concentrations (Mitchell 1999).  Fishermen were awarded $5 billion for their losses by a US District Court in 1994, when a jury decided that the captain of the Exxon Valdez had acted recklessly (Schneider 1994b), but they have yet to be paid by Exxon (Mitchell 1999).  This company, now merged with Mobil Oil Company, continues to earn approximately $8 billion per year, yet it refuses to settle this claim, and fishermen now earn only half their pre-spill income.
     The spectacular Steller's eider (Polysticta stelleri) was once an abundant bird of Alaskan and Russian arctic waters.  These striking waterfowl formerly nested on the Alaskan Peninsula and the Yukon Delta to the Canadian border, but in recent years they have disappeared from Alaska except the western Arctic coastal plain.  Worldwide, their population has declined 50 percent, and they have been listed on the Endangered Species Act as threatened.  The oil from the Exxon Valdez and other spills may have spread throughout the region in miniscule amounts that gradually became lethal to these birds.  Other oil spills have occurred in Alaska since 1989, including 100,000 gallons spilled in 1997.  Some oil tankers have illegally dumped or spilled oil and oily ballast. 
     Some good came from this massive oil spill.  The state of Alaska purchased 650,000 acres of land within the archipelago for wildlife protection with $900 million from the Exxon settlement.  Old-growth forests, providing key habitat for threatened species, have been deeded by native corporations for permanent protection from logging in conservation easements, and 61 trout and salmon spawning streams will be purchased (Mitchell 1999).  A fund of $140 million, which began in 1994 from Exxon payments, will be available for spending on research, monitoring, fisheries applications and habitat protection (Mitchell 1999).  The corporation that monitors the movements of oil tankers through Prince William Sound has adopted new procedures and equipment for fighting future spills, but only three of 28 tankers that use the Sound have double hulls (Mitchell 1999).  Double hulls, or an inner hull protected by an outer one, greatly reduce leakage in a collision.  It is estimated that 60 percent or less of its oil would have spilled had the Exxon Valdez been equipped with double hulls (Mitchell 1999).
     Other oil spills around the world have involved heavy wildlife mortality as well.  Jackass or African penguins (Spheniscus demersus) once numbered more than 1 million birds in colonies along the coasts of South Africa and Namibia, but their numbers have been in decline for decades.  They have declined to 180,000 birds ‒ a result of multiple oil spills, destruction of breeding habitat for extraction of guano, food shortages as a result of overfishing by commercial purse seiners, feral cats on their nesting grounds and disturbance by humans causing them to abandon nests (BI 2000).  In June 1994, a large spill near Cape Town killed thousands of these penguins (Associated Press 1994).  The species was classified as near-threatened by BirdLife International in 1994 (Collar et al. 1994), and it has suffered population declines ever since.  In Threatened Birds of the World, BirdLife International classifies the species as vulnerable, a more threatened category that indicates serious decline. 
In the summer of 2000, a large oil spill occurred within feet of their prime breeding ground off Cape Town.  Professional bird rescue organizations, experts and volunteers from around the world converged on the area within a few days.  This was the most massive bird rescue in history and saved the lives of over 38,500 adult penguins by placing all adults that could be caught in a giant warehouse and holding area in Cape Town (Associated Press 2000a).  Oiled birds were cleaned and fed, while oil-free birds were held to prevent them from becoming oiled in the spill.  Most were caught on land attending to chicks and incubating eggs, as this was the height of the breeding season.  More than 19,000 birds were shipped 500 miles up the coast and released (Associated Press 2000a).  By the time they returned to Cape Town, a swim that was monitored on the Internet, the spill had been cleaned up.  The rescuers claimed the unprecedented survival rate of 90 percent.  The unfortunate casualties were abandoned chicks and eggs.  In spite of the large numbers of birds saved, the entire generation of young were lost, and an unknown number of oiled adult birds died at sea.
     In the Siberian tundra, a delicate frozen ecosystem with a thin layer of soil covering permanently frozen ground, known as permafrost, is extremely vulnerable to damage from oil spills.  Oil exploitation over the past few decades has resulted in many spills that permanently scarred the land. The most recent, in the fall of 1994, spilled approximately 33 million gallons of oil, three times the total spilled in Alaska, polluting three major rivers.  Long-term effects will not be measured for years, but the immediate effects have been massive fish kills in the Kolva, Pechora and Usa Rivers of the northeast (Filipov 1994).
     Large oil spills, however dramatic, do not constitute the majority of oil spilled in oceans.  They may make up only about 12 percent (Wells and Hanna 1992).  Forty-five percent of the oil that is becoming pervasive in ocean ecosystems comes from the routine flushing of tanks and bilges of ships at sea, and one-third comes from regular leakages at land-based operations such as refineries (Wells and Hanna 1992).  Floating tar balls and dissolved light oil continue to cause mortality and ecological damage, destroying the waterproofing of birds' feathers and settling on coral reefs.  As marine biologist Dr. Sylvia Earle, former chief scientist of the National Oceanic and Atmospheric Administration (NOAA), noted in Sea Change: A Message of the Oceans (1995):  "Nets dragged through the sea anywhere are likely to come up clogged with tar balls, beaches in the most remote areas are fringed with an oily scum or lined with sticky gobs of oil; over the surface of much of the ocean a rainbow-hued film glistens with deadly beauty at one time or another."  Since 1970, 50 major spills the size of the Exxon Valdez's have happened worldwide (Mitchell 1999). 
     The ingestion of lethal oil compounds, whether within days or weeks after a spill or from residues remaining years afterward which enter the food chain, is the key cause of mortality for the millions of sea creatures that die in oil spills.  Research conducted by Dr. Daniel W. Anderson of the University of California at Davis revealed that only 12 to 15 percent of Brown Pelicans rescued in oil spills survived for two years (Kopytoff 1996).  The greater the amount of oil ingested, the higher the death rate.
     A remarkable discovery in the late 1990s has yet to be aggressively pursued as a means of cleaning up spilled oil.  A barber who watched the news of the Exxon Valdez spill noted that the sea otters died in large numbers as a result of the extreme absorbency of their fur and their ingestion of oil while grooming.  He began collecting human hair from his barbershop and testing it for absorption of oil.  It proved remarkable in its ability to suck up large amounts of oil when contained in mesh nylon bags, leaving almost no oil in the water.  He approached NOAA and showed them his findings.  They tested the process and confirmed his results.  Although this was widely publicized on television and in newspapers, little has apparently been done to place this very simple, low-tech process into real situations by encouraging oil tankers and land-based oil pollution teams to store large amounts of hair for this purpose.  NOAA tests determined that the oil absorbed by the hair could easily be recovered by squeezing the bags into holding tanks.
     In the wake of the Exxon Valdez spill, Congress enacted the Oil Pollution Act of 1990, which requires oil tankers operating in US waters to pay large penalties and carry massive insurance liability for spills. Civil penalties range up to $1,000 per barrel discharged.  Within a month of the passage of this law, 20 oil companies created two new organizations: the Marine Spill Response Corporation and the Marine Preservation Association (Earle 1995).  
     The need for such protection from catastrophic spillage has been apparent since the early 1970s when these supertankers began to ply the world's oceans loaded with 200,000 tons of crude oil, built so cheaply they had virtually no protection against splitting apart if they ran aground.  The dangers of these ships were dramatically portrayed in the 1974 book, Supership (Mostert 1974).  More than 25 years of oil spills later, stringent regulations still have not become the rule of the sea.  An international agreement requires all oil tankers built after July 1996 to have double hulls, but not all countries are complying. Congress put off the effective date of an amendment requiring replacement of single-hulled ships with environmentally sound double hulls to 2015, and even this date may be postponed.

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