The Effects of Oil Spills on Marine Life

Oil spills can take an enormous ecological and economic toll. Even the smallest oil spills have severely negative effects on marine life. Usually, clean-up methods are chosen with a view to minimizing these negative effects, especially on any endangered species.

The most well-known and visible effect is the coating of the fur and feathers of the seals, otters and seabirds. This is what is most often shown on the news. Usually the camera will show a pelican or similar bird covered in oil, wings weighted down with heavy oil, unable to fly or swim properly, and making a futile attempt to preen itself. Wildlife rescue personnel will attempt to save as many animals as possible, by cleaning oil off of the fur and feathers with mild dish soap. Sadly, the survival rate of the rescued animals is quite low, as noted at The survival rate of the unrescued animals is very low indeed. They drown, or freeze, or die of chemo-pneumonia (a condition in which the lungs fill up with fluid as a result of some kinds of poisoning).

A less visible, but even more obvious, effect is on the lungs and gills of the marine life. The lighter the oil, the more toxic it is. As mentioned, there is the risk of chemo-pneumonia, from hydrocarbon poisoning. Various respiratory illnesses which might not be as immediately dangerous tend to show up over time. If it affects the human clean-up crew’s lungs, it may be presumed that it affects the lungs of the animals which live in the clean-up area.

In a large spill, there is an added hazard in the form of bacteria, which eat the oil. The fact that these microbes eat the oil is a good thing. However, as the bacteria reproduce and spread quickly, they use up the dissolved oxygen, producing a “dead zone”in the water, where the fish cannot breathe.  So, those whose gills were not destroyed by the toxins will suffocate for lack of oxygen in the water. The fish and other gilled animals can only use dissolved oxygen. The oxygen that makes up part of the water molecule is not breathable.

Oil that falls to the sea-bottom might be out of sight to the general public. This is part of what makes dispersant chemicals (substances which cause the oil to form little balls of “tar” and fall to the ground, instead of floating) a popular public-relations tool. However, it contaminates the habitat, feeding areas, and spawning grounds. The dispersants themselves pose their own risks to marine life, particularly fish and crustaceans (shellfish). However, because they cut down on the “coating” effect, they are believed to cause less damage to birds and wetlandsthan unaltered oil would do, according to

Sometimes, the clean-up organization believes that burning off the bulk of the floating oil is the safest way to clean up most of a spill.  This is especially true if most of the material can be contained within a circle of booms (floating barriers) out at sea, before it contaminates the shorelines or established spawning grounds. Any marine life caught in the burn-zone is at risk of being burned to death. This is risk applies especially to air-breathing animals such as turtles. In the case of large burn-offs, the smoke can kill nearby seabirds, as well.

Oil spills pose many hazards to the wildlife in the ocean. No matter which methods are chosen for containment and clean-up, the spill will have negative effects on the marine life.