Have you ever heard of aquatic dead zones? They are areas of water near inhabited coastlines that through natural or human intervention have oxygen levels low enough that no aquatic life can live. Fish and other animals that wander into these areas die and there are no plants on the sea floor. Scientists first discovered dead zones in the 1970s. Since then, a recent study in 2008 confirmed four hundred and five dead zones worldwide. Most of these are around heavily populated areas. Dead zones, while in some cases natural phenomenon, are typically the result of water pollution. Reducing the dead zones is beneficial not only to the environment, but also to the fishing industry which depends on healthy water to produce healthy fish.
The largest dead zone currently is in the Gulf of Mexico. Covering an area about 27,000 miles square it is about the size of New Jersey. This area is a recurring dead zone and is caused by the runoff from the Mississippi River. Dead zones that are caused by pollution are usually created by chemicals rich in nitrogen. Examples include fertilizers and pesticides. When these chemicals are introduced into, for example, the Mississippi, they flow downriver and eventually end up in the Gulf. Once there, “single-celled, plant-like organisms” that live in the ocean began feeding on the nitrogen in tight packs. This is visible to the naked eye as “algae bloom”. Algae is notorious for depleting water of oxygen through their process of “cellular respiration” which is the same way the human body changes food into energy. Eventually the oxygen in the area the algae are blooming is used up and all the aquatic life in that area dies. Last year, in 2009, the dead zone in the Gulf of Mexico shrank due to weather conditions. While this ordinarily is a good thing, in this case the shrinking meant that instead of covering a large portion of the ocean floor, the dead zone area extended more vertically toward the surface of the ocean, putting a strain on the 2.8 billion dollar fishing industry.
“Low oxygen levels recorded along the Gulf Coast of North America have led to reproductive problems in fish involving decreased size of reproductive organs, low egg counts and lack of spawning.” These changes in the fish will have a large impact not only on the fishing industry, but also on the natural food chain in the Gulf. Combined with the recent problem of the BP oil spill and the Gulf of Mexico’s environmental ecosystem is in serious trouble.
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For more information on water pollution and conservation please visit http://www.centralbasin.org/
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