Effects

An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially marine areas, due to human activity, and is a form of pollution.
 

The oil penetrates into the structure of the plumage of birds and animals, reducing its insulating ability, thus making the birds more vulnerable to temperature fluctuations and much less buoyant in the water.
 

It also impairs or disables birds' flight abilities to forage and escape from predators. As they attempt to preen, birds typically ingest oil that covers their feathers, causing kidney damage, altered liver function, and digestive tract irritation. This and the limited foraging ability quickly causes dehydration and metabolic imbalances. Hormonal balance alteration including changes in luteinizing protein can also result in some birds exposed to petroleum. 

Very light oils (jet fuel, gasoline) are highly volatile and evaporate quickly. Very light oils are one of the most acutely toxic oils and generally affect aquatic life (fish, invertebrates, and plants) that live in the upper water column.
 
Heavy oil can cause severe long-term contamination of intertidal areas and sediments. Heavy oils have severe impacts on waterfowl and fur-bearing marine mammals.Very heavy oils can float, mix, sink, or hang in the water. These oils can become oil drops and mix in the water, or accumulate on the bottom, or mix with sediment and then sink.

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 that feed on these organisms can subsequently become contaminated. Larger animals in the food chain, including bigger fish, birds, terrestrial mammals, and even humans may then consume contaminated organisms.

Mmmm Tasty Right?

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, including salmon, are highly sensitive to oil toxins.

Polycyclic aromatic hydrocarbons (PAHs) are cancer-causing chemicals found in crude oil that can accumulate in the food chain, absorbed by fish and shellfish. During the ongoing testing of seafood in the Gulf of Mexico by federal and state authorities, PAHs are of primary concern.

But crude oil also contains heavy metals such as lead, mercury and cadmium that can accumulate in the food chain as well, though at a slower pace than PAHs, and are toxic to the brain and nervous system. It's too early for government officials to conclude that eating Gulf seafood that is contaminated poses no future risks.

“So you could imagine if a large fish feasted on several hundred small fish and each of those small fish have eaten a certain number of microorganisms which had a little of contaminant, there’s a possibility, certainly, that you could go over the current measurements.”(Jacobson, 2010)

"Oil Wave"