In the case of marine oil spills, the first living receptors who come in contact with the oil spill are the marine life, including the various fish species. Apart from affecting the coastal fishing and fisheries, exposure to oil spills may have negative health effects on marine life.
The negative effects on marine life relate to the accumulation of persistent and bioaccumulative components of oil in the tissue and bodies of marine life (fish) with the potential to induce a variety of health and reproductive problems, as well as mass mortality events within marine life in general.
The problem is exacerbated for the higher organisms on the food chain (which consume other smaller organisms) and may seriously affect birds and marine mammals, as well as bigger fish. This is due to the gradual and additive accumulation of increased concentrations of oil pollutants through combined exposure to a polluted environment (i.e. polluted water) and polluted food (with higher pollutant concentrations than in ambient environment). The unavailability of food is another issue when mass mortality events occur.
Apart from direct contact and accumulation of oil spill pollutants, oxygen depletion may also occur due to the formation of oil slicks at the surface of the water. This may especially affect species of fish and marine life living in shallower waters. As for the marine life from deeper water, it may also be affected by deep oil spills such as the one due to well leaks at very high depth in the Gulf of Mexico (in conjunction with BP offshore drilling activities).
Those who consume contaminated food from the wildlife, may be at even higher risk of poisoning or developing negative effects due to exposure to higher pollutant concentrations than in the surrounding environment. Basically, any bird, mammal, amphibian, reptile and/or other wildlife from polluted areas may develop negative health effects due to:
Direct contact with oil spill pollution which, as in the case of humans, may enter animal bodies through ingestion, inhalation, skin absorption and/or injection (through cuts in the skin, for example). Potential deterioration of thermal insulation and damage to behavior and reproductive system are some specific examples of negative effects due to oil spill pollution exposure;
Indirect exposure through consumption of smaller organisms which were exposed to oil spill pollution themselves;
Lack of usual food - when mass mortality events occur, affecting large amounts of fish and exposed marine life (for example, in the case of a severe marine oil spill). This may have serious long-term ecological effects, ending up with the complete eradication of some species.