Effects of Oil Spills on Marine Life

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 worst oil spill in U.S. history -- although the 2010 BP leak in the Gulf of Mexico could prove to be even worse.
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. But here are some ways an oil spill can impact marine life, including seabirds, pinnipeds and sea turtles.
Hypothermia


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 to 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 effect 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 in the can effect ocean habitat, both offshore and onshore.
Before an oil spill reaches shore, the oil can poison plankton and other pelagic marine life.
On shore, 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.
Effects of petroleum crude on marine bio-system – Spilled oil poses serious threats to fresh water and marine environments, affecting surface resources and a wide range of subsurface organisms that are linked in a complex food chain that includes human food resources. Spilled oil can harm the environment in several ways, including the physical damages that directly impact wildlife and their habitats (such as coating birds or mammals with a layer of oil), and the toxicity of the oil itself, which can poison exposed organisms. The severity of an oil spill’s impact depends on a variety of factors, including the physical properties of the oil, whether petroleum-based oils or non petroleum-based oils, and the natural actions of the receiving waters on the oil.

The biological effects of oil include:
(a) Hazards to man through eating contaminated seafoods,
(b) Decrease of fisheries resources or damage to wild life such as sea birds and marine mammals,
(c) Decrease of aesthetic values due to unsighty slicks or oiled beaches,
(d) Modification of marine ecosystems by elimination of species with an initial decrease in diversity and productivity and
(e) Modification of habitats, delaying or preventing re-colonization.
When an oil spill occurs, many factors determine whether the spill will cause heavy, long lasting biological damage, comparatively little or no damage or some intermediate degree of damage. Thus for instance, if a spill occurs in a small confined area so that the oil is unable to escape, damage will be greater for a given volume and type of oil spilled than if the same volume was released in a relatively open area.
In the open sea the possible impact on biota can be on phytoplankton, zooplankton, benthos, fishery, birds, mammals, etc. whereas in coastal waters the impacts will also be on inter-tidal fauna, aquaculture, seaweeds and mangroves.