Agricultural run offs have resulted in the formation of hundreds of dead zones (also known as hypoxic zones) in the oceans and seas all over the world. One such dead zone is present in the Gulf of Mexico off the Louisiana and Texas Coast. This is the largest dead zone in the Western Hemisphere and was first observed by scientists in the 1980s.
Every year flooding of the Mississippi and Atchafalaya river basins results in the deposition of tons of fertilizers by these rivers into the Gulf of Mexico enlarging this dead zone. The nutrients especially nitrates present in the fertilizers allow microscopic organisms called phytoplankton to bloom. This phenomenon is also known as Algal Bloom. When these algae die they sink to the bottom of the ocean. They are decomposed by bacteria that use up the oxygen present in the water thereby hindering the survival of any other life forms in such waters. This results in the formation of a “Dead Zone” which is devoid of fishes, shrimps, or other marine life.
Although scientists had expected this zone to witness a record increase in size, experts believe that the zone is going to grow larger than expected. Scientists are now concentrating on reducing such zones. A multilevel government task force led by the U.S. Environmental Protection Agency is working to reduce the Gulf of Mexico dead zone to a five-year running average of less than 2,000 square miles (5,000 square kilometers).
via: msnbc