by Christobel Rajesh

Created on: September 20, 2010   Last Updated: September 22, 2010

Dead zone or hypoxic zone is described as an area just above the sea floor where marine life is not supported due to lack of oxygen. Dead zone is a natural occurrence and can occur in all oceans at different seasons of the year. The main concern about dead zones is that, they make the marine life impossible due to anoxic conditions thereby affecting the commercial and recreational activities of a particular country. Gulf of Mexico is identified to be the second largest dead zone in the world. In 2009, the dead zone in Gulf of Mexico extended 3,000 square miles which is small but severe compared to other years.

There are three main reasons that cause dead zones in Gulf of Mexico. They are global warming, fertilizers and sewage disposal.   

GLOBAL WARMING
The changing environmental weather pattern due to global warming is one main reason which has been identified to cause dead zone. The climate has become very unpredictable and so no steps could be taken to reverse the condition of the dead zones. The change in wind and current patterns are found to cause the dead zone in Gulf of Mexico this year. Because of global warming, the atmospheric air is warm; the ocean water also gets warmer capacitating less dissolved oxygen. The ocean gets oxygen from the atmosphere and the plants that float on them. The ocean surface has more oxygen than deeper region and if the ocean surface is deprived of oxygen, the ocean floor at that area is prone to become a dead zone.
Warm climate makes the dead zones occur more frequently and more rain makes it worse. Pollutants (like carbon, nitrogen) released from the burning of fossil fuel (coal, petroleum and natural gas) goes up in to the atmosphere and come down as acid rain which decreases the oxygen content in water needed for marine animals and plants to live on.

FERTILIZERS
The use of fertilizers to enhance the growth and productivity of plants has become popular these days. These not only affect the health of human beings but also have become a causative agent for dead zones in the Gulf of Mexico. The fertilizers rich in nitrogen and phosphorus that are used for the agricultural purposes are drained in to the nearby rivers and finally reach the sea. The algae floating on the sea gets well nourished and flourished by the fertilizers, they are called as algal blooms. As they grow, multiply and die, sink to the bottom, decompose (which itself consumes more oxygen) and feed the oxygen depleting bacteria. This results in very

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