Effects of oil on wildlife and habitat
Contents
Introduction
The U.S. Fish and Wildlife Service is the federal agency responsible for many of the nation’s fish and wildlife resources and one of the primary trustees for fish, wildlife and habitat at oil spills. The Service is actively involved in response efforts related to the Deepwater Horizon oil spill that occurred in the Gulf of Mexico (Gulf of Mexico large marine ecosystem) (Gulf of Mexico large marine ecosystem)on April 20, 2010. Many species of wildlife, including some that are threatened or endangered, live along the Gulf Coast and could be impacted by the spill.
Oil spills affect wildlife and their habitats in many ways. The severity of the injury depends on the type and quantity of oil spilled, the season and weather, the type of shoreline, and the type of waves and tidal energy in the area of the spill.
Oilcan be categorized into five groups, ranging from very light to very heavy oils. Most oil has a density less than water, so it floats. Oil tends to spread into a thin layer on the water surface as a sheen. Once in the water, oil undergoes weathering, a process that describes the physical, chemical, and biological changes that occur when oil interacts with the environment.
Weathering (Natural oil degradation processes)reduces the more toxic elements in oil products over time as exposure to air, sunlight, wave and tidal action, and certain microscopic organisms degrade and disperse oil. Weathering rates depend onfactors such as type of oil, weather, temperature, and the type of shoreline and bottom that occur in the spill area.
Types of Oil
Although there are different types of oil, the oil involved in the Deepwater Horizon spill is classified as light crude. Light crude is moderately volatile and can leave a residue of up to one third of the amount spilled after several days. It leaves a film on intertidal resources and has the potential to cause long-term contamination.
In general, oil is a mixture of chemicals, all of which may have different effects on marine animals and the combination may be even more hazardous. In addition, some of the chemicals and methods used to clean up oil spills may also have effects on marine animals.Toxicityor harmful effects are dependent upon:
- the mixture and types of chemicals that make up the oil or are used to clean up the oil,
- the amount of exposure (dose for internal exposures or time for external exposures),
- the route of exposure (inhaled, ingested, absorbed, or external), and
- the biomedical risk factors of the animal (age, sex, reproductive stage, and health status). Forturtles,this will include differing impacts and vulnerabilities at the different life stages such as eggs, post-hatchlings, juveniles and adults. For cetaceans this will include neonates, calves, juveniles and adults.
Impacts to Wildlife and Habitat
Oil causes harm to wildlife through physical contact, ingestion, inhalation and absorption. Floating oil can contaminate plankton, which includes algae, fish eggs, and the larvae of various invertebrates. Fish feeding on these organisms can subsequently become contaminated through ingestion of contaminated prey or by direct toxic effects of oil. Larger animals in the food chain, including humans, can consume contaminated organisms as they feed on these fish.
Whales, dolphins, manatees and sea turtles are air breathers and all must come to the surface frequently to take a breath of air. In a large oil spill, these animals may be exposed to volatile chemicals during inhalation.Cetaceans, manatees and sea turtles may be exposed to chemicals in oil (or used to treat oil spills like dispersants) in two ways: internally (eating or swallowing oil, consuming prey containing oil based chemicals, or inhaling of volatile oil related compounds) and externally (swimming in oil or dispersants, or oil or dispersants on skin and body).Additionally sea turtles may experience oiling impacts on nesting beaches and eggs through chemical exposures resulting in decreased survival to hatching and developmental defects in hatchlings.
Inhalation of volatile organics from oil or dispersants may result in respiratory irritation, inflammation, emphysema, or pneumonia.Ingestion of oil or dispersants may result in gastrointestinal inflammation, ulcers, bleeding, diarrhea, and maldigestion.Absorption of inhaled and ingested chemicals may damage organs such as the liver or kidney, result in anemia and immune suppression, or lead to reproductive failure or death.
Although oil causes immediate effects throughout the entire spill area, it is the external effects of oil on larger wildlife species that are often immediately apparent.Depending on the size of a particular spill, marine animals could be exposed to these chemicals for a fairly long time.Long-term effects, however, are less understood, but oil ingestion has been shown to cause suppression to the immune system, organ damage, skin irritation and ulceration, and behavioral changes. Damage to the immune system can lead to secondary infections that cause death and behavioral changes may affect an animal’s ability to find food or avoid predators. Long-term consequences can include impaired reproduction potentially impacting population levels.
Species of Concern
Birds
Oil Impacts on Birds
Even a small amount of oil can kill a bird. Birds such as brown pelicans are likely to be exposed to oil as they float on the water’s surface.When a bird gets oiled, the oil sticks to its feathers, causing them to mat and separate. This affects the bird’s waterproofing capabilities, and the bird cannot stay afloat or regulate its temperature, becoming susceptible to hypothermia in the right conditions. Oiled birds can also lose the ability to fly, dive for food or float on the water which could lead to drowning.Many oil-soaked birds that lose their buoyancy and can no longer swim often beach themselves and hide on shore in an attempt to escape the cold water. These vulnerable birds panic when approached and can become injured when trying to flee humans.
Instinctively, the bird tries to get the oil off its feathers by cleaning itself (preening) and may ingest and inhale oil when doing so. While ingestion can kill animals immediately, more often it results in lung, liver, and kidney damage which can lead to death.Since the bird’s natural instinct is to focus on preening, that behavior overrides all other natural behaviors such as feeding and evading predators. This causes the bird to be vulnerable to such things as severe weight loss, anemia, and dehydration.Scavengers such as bald eagles and gulls are also exposed to oil by feeding on carcasses of contaminated fish and wildlife.
Bird eggs may also be damaged if an oiled adult sits on the nest.
Managing Oil Impacts on Birds
Many people want to help when they see the birds that have been impacted by the Deepwater Horizon oil spill. While this instinct is positive, the involvement of untrained people can actually do more harm than good. Untrained people can injure birds that they are trying to rescue or even harm themselves doing so. Rescuing, treating, and cleaning birds require proper facilities, equipment, and trained staff. Oiled animals should be approached, handled, treated, and cleaned by individuals with proper training and access to facilities. So what can you do to help?
If you see or find a bird affected by the oil, please call the Wildlife Reporting Hotline at 866-557-1401. A dispatcher is available 24 hours a day, seven days a week. When calling, please include the location of the distressed wildlife, including geographic information with nearby physical landmarks such as a marina, condominium, or beach name, and GPS coordinates if possible. The reporting party’s contact information and originating zip code will also be requested. All calls are returned to the reporting party to confirm that the information has been received and to assure prompt follow-up action will take place.
Once a call is received and it is determined to be within the Deepwater Horizon oil spill response area, a wildlife response team is notified. A team equipped with appropriate personal protective equipment (PPE) is dispatched from staging areas that are based on the location of the animal, the previous day’s response activities, and anticipated movement of oil. Given the dynamic nature of the situation, the weather, and the location of the distressed animal, response time can vary.
Once the bird is located by the response team, it is placed carefully in an animal carrier or kenneltype container. The bird is then taken to one of four area rehabilitation centers staffed by employees of the Tri-State Bird Rescue & Research Center, the International Bird Rescue Research Center, and other paraprofessionals and volunteers, all of whom are trained in wildlife rehabilitation. The rehabilitation centers are located in Ft. Jackson, Louisiana; Gulfport, Mississippi; Theodore, Alabama; and Pensacola, Florida.
Upon arrival at an oiled wildlife rehabilitation center, oil-contaminated birds receive the specialized treatment they need to get back on the road to recovery. Each bird is examined, provided with life-saving IV and oral fluids, and fitted with a temporary leg band so its progress can be monitored throughout the rehabilitation process. It is critical that the debilitated bird is medically stabilized prior to undergoing washing and examined by a wildlife veterinarian experienced in treating oiled wildlife. A small blood sample is used to evaluate the bird’s status to ensure it is strong enough to be washed. Teams of experienced oiled wildlife responders wash the birds in tubs of very warm water and a mild detergent. Once the soap is rinsed from the bird’s feathers, the bird is placed in a specialized drying pen to allow it a chance to preen as it dries.
Cleaned birds are generally moved into outdoor aviaries equipped with pools to allow the birds an opportunity to preen, swim, and exercise. The birds are monitored closely to make sure the stress of captivity is minimized as well as to ensure that their health continues to improve. In accordance with U.S. Fish & Wildlife Service (USFWS) protocols, prior to release the bird’s behavior, body weight, blood values, and waterproofing are evaluated.
A rehabilitated bird is released to an area that has been approved by state and federal wildlife conservation agencies and where the risk of becoming re-oiled has been minimized. Before release, the bird is fitted with a numbered USFWS stainless steel leg band to allow identification if the bird is recaptured or recovered in the future. Releases are usually made early in the day and during fair weather so the bird can adjust to its natural habitat during daylight hours.
Previous oiled bird rehabilitation efforts indicate that rehabilitated birds released into suitable habitat can successfully return to the wild. The USFWS and partner agencies have determined suitable, non-oiled habitat for released birds currently exists on the Gulf Coast of Texas and are exploring additional options as conditions allow.
This important work is only accomplished through collaboration, cooperation, and partnerships that create a seamless sequence: first, a private citizen makes the initial call about a distressed animal; second, rescue teams and rehabilitators respond and rehabilitate the wildlife; and third, federal agencies and their partners return the bird to the wild. Often it is the U.S. Coast Guard, accompanied by a veterinarian, that transports the rehabilitated wildlife to the release site.
Through careful evaluation of each bird during the rehabilitation process, every effort is made to reduce the effects of oil on birds. Strict release criteria are in place to ensure that birds released back into the wild will survive. Due to the migratory nature of most bird species potentially impacted by the spill and the limitations of monitoring technology for such light-weight flighted creatures, it is difficult to monitor individual birds after release. Bird conservation partners are developing specialized plans to conduct postrelease studies to help determine the survival rate of oiled birds following the Deepwater Horizon oil spill incident.
Mammals
Research on dolphins in human care has shown that the animals avoid oil on the surface of the water, however observations of wild dolphins have ocumented the animals swimming in, feeding in and socializing in oiled water during previous oil spills in theGulf of Mexico (Gulf of Mexico large marine ecosystem) (Gulf of Mexico large marine ecosystem).
Cetaceans and manatees have no fur which can be oiled and do not depend on fur for insulation. Therefore they are not susceptible to the insulation effects (hypothermia) that often puts haired marine mammals (such as fur seals or sea otters) at risk. However, oil and other chemicals on skin and body may result in skin and eye irritation, burns to mucous membranes of eyes and mouth, and increased susceptibility to infection. For large whales, oil can foul the baleen they use to filter-feed, thereby potentially decreasing their ability to eat.
Terrestrial mammals are also at risk of oil spills in the open ocean. Scavengers, such as raccoons and skunks, arealso exposed to oil by feeding on carcasses of contaminated fish and wildlife.
Sea Turtles
General Sea Turtle Facts
Each summer on the beaches of the Gulf Coast, a unique natural event takes place: one of the largest living reptile species—the sea turtle—leaves the water during the night to crawl ashore to lay her eggs in a sandy nest. After about an hour digging with her rear flippers, she deposits her clutch of eggs, covers them with sand, and then returns to the sea. About two months later hatchlings are born and emerge to scramble to the waters of the Gulf of Mexico. We have much to learn about this primitive animal, which serves as an indicator of the overall health of our oceans (Ocean).
All sea turtles are listed as either threatened or endangered under the Endangered Species Act. Five of the seven species ply Gulf of Mexico waters: loggerhead, green, hawksbill, Kemp’s ridley, and leatherback turtles. Their history—sea turtles have existed for more than 100 million years—and their travels throughout the world’s oceans add to their intrigue. Sea turtles play a major role in two ecosystems—the ocean community and the beach community.
Oil Spills and Sea Turtles
TheDeepwater Horizon oil spill has affected sea turtles, which are already sensitive to human impacts. Several aspects of sea turtles put them at risk including the lack of avoidance behavior of oiled waters and indiscriminate feeding in convergence zones.The life history of sea turtles places them at heightened risk due to the intersection of their behavior with areas where oil collects. Sea turtle habitats include fine-grained sand beaches for nesting, seagrass beds and coral reefs for foraging, and open water convergence zones. Since oil often collects in these habitats after a spill and is difficult to access and remove, there is an increased potential for sea turtles to encounter oil.
Oil can affect turtles or their habitats in many ways. Ingested oil may cause harm to their internal organs. Oil covering their bodies may interfere with breathing because they inhale large volumes of air to dive. Oil can get into cavities such as the eyes, nostrils, or mouth. Turtles can be physically impaired or overwhelmed by tar patties, causing hatchlings to become easy prey.
Oil also diminishes turtles’ food sources. Even if turtles avoid contact with oil slicks, eating and ingesting contaminated food will harm them.
Because it is occurring in the middle of hatching season, the oil spill may effect future population levels and reproduction.
Coral Reefs
General Coral Reef Facts
Healthy coral reefs are among the most biologically diverse and economically valuable ecosystems on earth, providing valuable and vital ecosystem services (Ecosystem Services (collection)). Coral ecosystems are a source of food for millions; protect coastlines from storms and erosion; provide habitat, spawning and nursery grounds for economically important fish species; provide jobs and income to local economies from fishing, recreation, and tourism; are a source of new medicines, and are hotspots of marine biodiversity. They also are of great cultural importance in many regions around the world, particularly Polynesia.
Based on current estimates, shallow water coral reefs occupy approximately 284,300 square kilometers
(110,000 square miles) of the sea floor. If all of the world's shallow water coral reefs were placed side-by-side, they would occupy an area a bit larger than the state of Texas.The total area of coral reefs represents less than 0.015 percent of the ocean. Yet coral reefs harbor more than one quarter of the ocean's biodiversity. No other ecosystem occupies such a limited area with more life forms. Reefs are often compared to rainforests, which are the only other ecosystem that can boast anywhere near the amount of biodiversity found on a reef. Coral reefs are sometimes called rainforests of the seas.
Oil Spills and Coral Reefs
NOAA has produced two summary documents on corals and oil spills:
- Oil Spills in Coral Reefs: Planning & Response Consideration (PDF - 90 pages, 9.87 MB)
- Toxicity of Oil to Reef-Building Corals: A Spill Response Perspective (PDF - 95 pages, 325 KB)
Impacts of oil spills to coral reefs are difficult to predict because each spill presents a unique set of physical, chemical, and biological conditions. How corals are exposed to oil - and the composition of the oil at the time of impact - bears directly on how serious the impact will be. In 2005, NOAA conducted its Safe Sanctuaries 2005 exercise (PDF - 2 pages, 283 KB), designed to test emergency response to a simulated oil spill in the Florida Keys.
There are three primary modes of exposure for coral reefs in oil spills:
- Direct oil contact is possible when surface oil is deposited on intertidal corals that live near the surface of the water and become exposed with the tides.
- Rough seas and a light, soluble oil can combine to mix the oil into the water below the surface, where it can impact corals. Corals are exposed to less oil beneath the water surface, but the lighter oil components that mix easily are often the most toxic.
- Subsurface oiling can occur when heavy oils weather, or mix with sediment material. This increases the density of the oil to the point where it may actually sink, potentially smothering corals.
Oil Spill Response Strategies for Coral Reefs
Booms (Florida Keys National Marine Sanctuary) are sometimes used to control the movement of oil at the water surface. This should be done carefully in coral reef areas, as boom anchors can physically impact corals, especially when booms are moved around by waves.
Dispersants (Florida Keys National Marine Sanctuary)act like detergents, breaking an oil slick into droplets that mix into the water column, where they dilute and eventually biodegrade. Dispersants work best on light oils, and are less effective on oil that has been extensively weathered or in areas of low water movement. Dispersants offer a trade-off of oil effects in the water versus at the shoreline. The use of dispersants over shallow submerged reefs is generally not recommended, but the potential impacts to the reef should be weighed against impacts that might occur to birds, mammals, turtles, and sensitive shoreline resources (such as mangroves) where it is extremely difficult to clean the oil.
Effects of Oil and Dispersants on Coral Reefs
Laboratory, field studies, and actual oil spill events often appear to show contradictory results for effects of oil and dispersants on coral reefs.
The old notion that coral reefs do not suffer acute toxicity effect from oil floating over them is probably incorrect. Direct contact with spilled oil can lead to coral death, but depends on coral species, growth form, life stage, and type/duration of oil exposure. Longer exposure to lower levels of oil may kill corals, as well as shorter exposure to higher concentrations. Death may not be immediate, but rather take place long after the exposure has ended.Instead of acute mortality, it is more likely that oil effects occur in sublethal forms, such as reduced photosynthesis, growth, or reproduction. Early developmental forms (like coral larvae) are particularly sensitive to toxic effects, and oil slicks can significantly reduce larval development and viability.
Coral communities may recover more rapidly from oil exposure alone than from mechanical damage. Recovery of coral reefs after oil exposure, however, may depend partly on the recovery of associated communities (e.g. nursery or foraging habitats, such as mangroves and seagrasses) that may be more seriously affected than the reef itself. Recovery time depends on the type and intensity of the disturbance and can range from several years to decades.
Past Oil Spills Impacts to Coral Reef Ecosystems
One extensively studied spill occurred at Bahia Las Minas, Panama in April, 1986. An estimated 60,000-100,000 barrels of medium weight crude oil spilled into the waters of the bay, causing widespread lethal and sub-lethal effects to coral reefs.
In contrast, in the Arabian (Persian) Gulf Spill in January 1991, the largest oil spill in history, an estimated 6.3 million barrels of oil were released. Given the magnitude of this release and the coral reef impacts noted at other tropical spills, there were dire expectations of severe impacts to reefs in Kuwait and Saudi Arabia. However, to date, the extent of coral reef damage directly attributable to the Gulf Spill has been remarkably minor.
Shellfish
Oil can be toxic to shellfish including bottom dwelling (lobsters, crabs, etc.) and intertidal (clams, oysters, etc.) species. The bottom dwelling species may be particularly vulnerable when oil becomes highly concentrated along the shoreline. Some can survive exposure, but may accumulate high levels of contaminants in their bodies that can be passed on to predators.
Fish
Fish can be impacted directly through uptake by the gills, ingestion of oil or oiled prey, effects on eggs and larval survival, or changes in the ecosystem that support the fish. Adult fish may experience reduced growth, enlarged livers, changes in heart and respiration rates, fin erosion, and reproductive impairment when exposed to oil. Oil has the potential to impact spawning success as eggs and larvae of many fish species are highly sensitive to oil toxins.
Plants
Marine algae and seaweed responds variably to oil, and oil spills may result in die-offs for some species. Algae may die or become more abundant in response to oil spills. Although oil can prevent the germination and growth of marine plants, most vegetation appears to recover after cleanup.
Habitat
Oil has the potential to persist in the environment long after a spill event and has been detected in sediment 30 years after a spill. On sandy beaches, oil can sink deep into the sediments. In tidal flats and salt marshes, oil may seep into the muddy bottoms. Effects of oil in these systems have the potential to have long-term impacts on fish and wildlife populations.
The Service responds to oil spills to minimize impacts to trust resources. The Service’s work continues long after a spill event occurs. Damage assessments of habitat and wildlife are conducted to find ways that will minimize long-term effects on new generations of wildlife.
Key Pointso
- Direct contact with of petroleum compounds or dispersants with skin may cause skin irritation, chemical burns, and infections.
- Inhalation of volatile petroleum compounds or dispersants may irritate or injure the respiratory tract which may lead to inflammation or pneumonia.
- Ingestion of petroleum compounds may cause injury to the gastrointestinal tract, which may affect the animals’ ability to absorb or digest foods.
- Absorption of petroleum compounds or dispersants may damage liver, kidney, and brain function as well as causing anemia and immune suppression.
- Long term chronic effects such as decreased survival and lowered reproductive success may occur.
- The Marine Mammal and Sea Turtle Stranding Networks have protocols and procedures in place for responding to live animals that are exposed to oil spills, and animals brought into rehabilitation facilities are provided veterinary care to remove oil and treat any related health effects.
