Effects of Oil Spills on Marine Life

USA - Deepwater Horizon Disaster - Rescue Team Cleans Oil from Pelican
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Many people became familiar with the disastrous effects of oil spills in 1989 after the Exxon Valdez incident in Prince William Sound, Alaska. That spill is considered the most infamous oil spill in U.S. history -- although the 2010 BP leak in the Gulf of Mexico proved to be even worse, surpassing Exxon Valdez in scale.

Overall, the effects of an oil spill depend on a variety of factors, including the weather and other environmental conditions, the composition of the oil and how close it gets to shore. Here are some ways an oil spill can negatively impact marine life, including seabirds, pinnipeds, and sea turtles.


Oil, a product that we often use to keep warm, can cause hypothermia in marine animals. As oil mixes with water, it forms a substance called "mousse," which sticks to feathers and fur.

A bird's feathers are filled with air spaces that act as insulation and keeps the bird warm. When a bird gets coated with oil, the feathers lose their insulating ability and the bird could die of hypothermia.

Similarly, oil coats a pinniped's fur. When this happens, the fur gets matted with oil and loses its natural ability to insulate the animal's body, and it can die of hypothermia. Young animals like seal pups are particularly vulnerable.

Poisoning and Internal Damage

Animals can be poisoned or suffer internal damage from ingesting oil. Effects include ulcers and damage to red blood cells, kidneys, liver and to the immune system. Oil vapors can injure the eyes and lungs, and can be particularly hazardous while new oil is still coming to the surface and vapors are evaporating. If vapors are severe enough, marine mammals may become "sleepy" and drown.

Oil can also cause effects 'up' the food chain, such as when an organism higher on the food chain eat a number of oil-infected animals. For example, reproduction in bald eagles decreased after the eagles ate animals infected by oil after the Exxon Valdez spill. 

Increased Predation

Oil can weigh down feathers and fur, making it difficult for birds and pinnipeds to escape from predators. If they are covered with enough oil, birds or pinnipeds may actually drown.

Decreased Reproduction

Oil spills can affect the eggs of marine life such as fish and sea turtles, both when the spill happens and later on. Fisheries were impacted years after the Exxon Valdez spill due to the destruction of herring and salmon eggs when the spill occurred.

Oil can also cause disruption of reproductive hormones and behavioral changes that lead to reduced reproduction rates or affect the care of young.

Fouling of Habitat

Oil spills can affect ocean habitat, both offshore and onshore. Before an oil spill reaches the shore, the oil can poison plankton and other pelagic marine life.​

Onshore, it can cover rocks, marine algae, and marine invertebrates. The Exxon Valdez spill coated 1,300 miles of coastline, initiating a massive cleanup effort.

Once the cleanup of surface areas has occurred, oil that has seeped into the ground can hurt marine life for decades. For example, oil can drip into the ground, causing issues for burrowing animals such as crabs.

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Your Citation
Kennedy, Jennifer. "Effects of Oil Spills on Marine Life." ThoughtCo, Sep. 2, 2021, thoughtco.com/effects-of-oil-spills-on-marine-life-2291548. Kennedy, Jennifer. (2021, September 2). Effects of Oil Spills on Marine Life. Retrieved from https://www.thoughtco.com/effects-of-oil-spills-on-marine-life-2291548 Kennedy, Jennifer. "Effects of Oil Spills on Marine Life." ThoughtCo. https://www.thoughtco.com/effects-of-oil-spills-on-marine-life-2291548 (accessed June 5, 2023).