Oil spills are sometimes caused by natural fissures in the Earth's surface, where crude, unrefined oil escapes into the surrounding water but these spills are relatively minor compared to the vast, damaging spills caused by the artificial release of massive oil pockets by Man.
Crude oil is water repellent, it floats, it smothers. The ocean can deal with an amazing amount of waste products -it has an ecosystem designed to cope with rotting vegetation, mud and silt washed in from estuaries, bodies and it copes with our waste products because the chemistry is well balanced and there are enough microbial organisms which break down many potentially harmful products into bio-degradable or usable ones.
However, a massive oil spill has devestating effects on oceanic ecology.
Oil floats so it covers the surface of the water, preventing sunlight from penetrating to lower layers. It is also affected by sunlight itself and is converted into harmful gases and solids which combine to create a toxic environment for marine life. Sunlight is required by microbial life called phytoplankton which are minute plant forms and these feed a huge number of larger organisms including some turtles, fish and invertebrates. Zooplankton are often associated with phytoplankton and these in turn feed the largest organisms of the sea - the whales and other large oceanic creatures. ALgae such as the seaweeds require sunlight to grow and these will die if the surface of the water is covered with oil. Many blue-green and red seaweeds provide shelter, food and the prey for oceanic creatures and if they are unableto grow, sea life suffers. These seaweeds are biologically designed to grow at depths where they use different wavelengths of light which penetrate deeper into the water. With oil on the surface, little light reaches them, they die and their death rings the death knell for the animals which rely on them.
With little light reaching the water, phytoplankot die and the zoo plankton die resulting in barren waters with little food for other larger organisms. These organisms often form the base of oceanic food chains so the knock-on effect is felt right the way up to the predators like sharks and orcas.
Oil also covers animals which rely on the sea for their food. They have to go into the water to find food and become covered in oil. This reduces the ability of their feathers, skin or fur, to resist water and they become waterlogged, cannot swim or take off and they eventually starve. Preening to remove the oil results in the animal taking in harmful toxins and these also affect their life cycle, feeding ability and kills them.
The sea can and does recover but it cannot cope with oil spills as well as the other environmental pressure which are put upon the ocean such as the discharge of raw sewage, untreated factory pollutants and chemicals which are dumped into the oceans on a regular basis. When there are oil spills it tips the balance of the oceans away from that of being able to sustain and retain life. They cannot clean up at the rate the oil is discharged and the resulting effect is devastation and barren seas.
Ecologists have long been concerned about the ecological welfare of our oceans - even the once pristine Arctic and Antarctic Oceans are starting to show signs of pollutants entering their waters from elsewhere in the globe. Given the chance, we can have a balance of clean seas, well able to deal with our waste but oil spills are one pollutant too many and we must clean up or pay the consequences.