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 * The Problem **

A “dead zone” is defined as a large area of the world's oceans that has a decreased oxygen concentration, also known as hypoxia, and is therefore unable to support life. Dead zones usually occur near inhabited coastlines, where aquatic life is most concentrated. They can be found all around the world, with one of the largest located along the northern shore of the Gulf of Mexico.


 * What Causes the Dead Zone **

Dead zones are generated when chemical nutrients in the water such as nitrogen and phosphorus rise above normal levels. This spike in nutrients often leads to the rapid growth of certain forms of algae, a phenomenon known as an algal bloom. Although the algae produce oxygen by photosynthesis during the daytime, they undergo cellular respiration at night and deplete the surrounding waters of oxygen. When the algae die, they sink into the deeper waters and begin to decompose, which is a process that significantly depletes the oxygen in the water, creating conditions that can no longer support aquatic life.


 * The Gulf of Mexico Dead Zone **

The dead zone in the Gulf of Mexico measures roughly 8,000 square miles, originating near the mouth of the Mississippi River, where much of the nutrients causing the dead zone come from. The Mississippi River Basin drains most of the water runoff in the central portion of the United States, from Pennsylvania to Montana. Most of the nitrogen and phosphorous chemicals enter the river through the runoff of fertilizers used on farms, soil erosion, animal wastes and sewage.


 * Consequences **

Although the algal blooms are a natural phenomenon, they have been significantly increased by the abundant concentration of nutrients in the water as result of increased farming practices in the Midwest. According to an article from BBC news, “In 2007, the level of algae-boosting nutrients entering the Gulf of Mexico represented a 300 percent increase over levels of a half century before, when dead zones were an infrequent occurrence”. Along with effects from the weather, such as flooding which can greatly increase the nutrient runoff from the Mississippi, a scientist from Louisiana State University stated that an increase in intensive farming, which generally employs nitrogen-rich fertilizers, was a main factor responsible for the current size of the dead zone in the Gulf.

High concentrations of these nutrients and algal blooms have been shown to reduce biomass and biodiversity in the waters surrounding the dead zones. This low oxygen, hypoxic water supports much fewer organisms, and causes marine life to either flee the area or face their death. Organisms that remain in low oxygen areas tend to have reproductive problems due to hypoxia, resulting in decreased size of reproductive organs, low egg counts and a lack of spawning.

Consequently, this presents a threat to the $2.8 billion dollar fishing industry that operates in the northern Gulf, along the Texas and Louisiana coastlines. Fisherman have stated a significant decrease in the amount of brown shrimp caught in these waters over the last decade, which may be a direct result of the hypoxic waters.


 * What can be done **

It is possible to effectively reverse the growing patterns of the dead zone in the Gulf of Mexico by controlling the amount of nitrogen and phosphorous that empty into the Gulf from the Mississippi River Basin.

The crop that may have the most significant affect on nutrient runoff is corn, which loses more nitrogen per acre than most other crops. The country has been recently pushing to boost bio fuels from 12 billion gallons this year to 36 billion gallons by 2022, with 15 billion gallons expected to come from corn ethanol. If the U.S. meets its corn ethanol goal, then nitrogen amounts in the Mississippi River would increase by up to 15 percent, which will greatly exacerbate hypoxia in the Gulf. One solution to this problem is to use more cellulose bio fuel crops that require less nitrogen, however this type of ethanol production may not reach commercial scale anytime soon.

One of the main solutions is for the agribusinesses in the Midwest to make a commitment to reduce and manage their nutrient and sewage runoff, as well as regulating animal wastes. This may come in the form of government incentives that persuade farmers to conserve. Industries must also practice limiting their disposal of nutrients and chemicals from manufacturing facilities, as well as monitor septic and sewage systems to reduce the discharge of nutrients into the groundwater. Steps such as these have led to successful reversal of dead zones in the Great Lakes.


 * Sources: **

Feldman, Stacy. "Corn Ethanol Boom Driving 'Dead Zone' Expansion, Federal Scientists Say." //Inside Climate News//. N.p., 08 09 2010. Web. 13 Sep 2011. <http://insideclimatenews.org/news/20100908/corn-ethanol-boom-driving-dead-zone-expansion-federal-scientists-say>.

<span style="font-family: Calibri,sans-serif;">Dodds, Walter K. "Nutrients and the “dead zone”: the link between nutrient ratios and dissolved oxygen in the northern Gulf of Mexico." (2006): n. pag. Web. 13 Sep 2011. <http://www.esajournals.org.libproxy.rpi.edu/doi/full/10.1890/1540-9295%282006%29004%5B0211%3ANATDZT%5D2.0.CO%3B2#h1>.

<span style="font-family: Calibri,sans-serif;">"Dead zone (ecology)." Web. <http://en.wikipedia.org/wiki/Dead_zone_%28ecology%29>.

<span style="font-family: Calibri,sans-serif;">Bruckner, Monica. "The Gulf of Mexico Dead Zone." //Microbial Life//. N.p., n.d. Web. 13 Sep 2011. <http://serc.carleton.edu/microbelife/topics/deadzone/>.

<span style="font-family: Calibri,sans-serif;">Silverman, Jacob. "Should we be worried about the dead zone in the Gulf of Mexico?." //How Stuff Works//. N.p., n.d. Web. 13 Sep 2011. <http://science.howstuffworks.com/environmental/earth/oceanography/dead-zone.htm>.

<span style="font-family: Calibri,sans-serif;">"Gulf dead zone to be biggest ever." //BBC News// n. pag. Web. 13 Sep 2011. <http://news.bbc.co.uk/2/hi/science/nature/6904249.stm>.

<span style="font-family: Calibri,sans-serif;">"How Does the Dead Zone Affect Gulf Shrimp Catches?." //Exploring Earth//. N.p., n.d. Web. 13 Sep 2011. <http://www.classzone.com/books/earth_science/terc/content/investigations/es2206/es2206page08.cfm>.