More than 60 million gallons of oil enter the oceans every year, but it's not reported on the news. That's because this oil seeps from oil-bearing rock layers into the ocean as part of a natural process. When tankers running aground spill oil, that's news, and currently these accidents deposit about 37 million gallons of oil into the ocean every year. The largest amount of oil entering the ocean through human activity is the 363 million gallons that come from industrial waste and automobiles. When people pour their used motor oil into the ground or into a septic system, it eventually seeps into the groundwater. Coupled with industrial waste discharged into rivers, oil becomes part of the run-off from waterways that empty into the ocean. All of this oil affects ocean ecosystems.
When an oil spill occurs in the ocean, the oil may spread across miles of open water and up onto beaches, littering them with tar balls. The intertidal zones-coastal areas that are the habitat for fish, birds, and other wildlife-are often the most vulnerable. Animals may perish when the oil slicks their fur or downy feathers, decreasing the surface area so they are no longer insulated from the cold water. Or the animals may ingest the oil, then become sick or unable to reproduce properly.
When an oil spill occurs along a coastline, it affects the human population as well as wildlife. Emergency equipment and personnel must be rushed to the scene. The responsible party must be identified to determine who will pay for the cleanup. Usually the cleanup is a group effort by oil companies, government agencies, local groups, and volunteers. People rescue and clean birds and animals and painstakingly scrub the oil from the rocky shores with brushes and detergent. Coming in by sea and by air, crews skim the spreading oil from the water's surface. Oil that cannot be skimmed is emulsified-that is, droplets of oil are scattered into tiny particles that will then float away and disperse out to sea.
Sometimes microscopic helpers are put to work. Genetic engineers have developed oil-eating bacteria that can be used to ingest the oil, to clean up long after the crews and volunteers have left. The experience gained from several well-publicized oil spills has ushered in an era of greater understanding and international cooperation with regard to containing spills and avoiding environmental disasters that affect our global ocean. One bright spot of news is that ecologists revisiting oil spill sites have found marine population recovery better than they had predicted.
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