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Hypoxia in the Gulf of Mexico and Around the World

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Introduction

During the summers the oxygen content atop the water normally has a salinity level consistent with “more than 8 milligrams per liter”; but when oxygen content drops down to “less than 2 milligrams per liter” the water is then known to be in hypoxic state (CENR, 2000; USGS, 2006). Hypoxia is the result of oxygen levels decreasing to the point where aquatic organisms can no longer survive in the water column. Organisms such as fish, shrimps, and crabs are capable to evacuate the area but the fauna that cannot move either become stress and/or die. Due to this, many call the hypoxia zone the “dead zone” (Overview, 2008; USGS, 2006).

Because of farm fertilizer, an excess quantity of nitrogen and phosphorus can be wash down becoming runoff into rivers. From this, marine algal blooms cause the water to turn green from the chlorophyll (Reed, 2011). Eutrophication then becomes a dilemma in the system causing either an increase of primary production or an expansion of algae. An enormous expansion of phytoplankton on the water’s surface is then established. At the same time the water column is also stratified, meaning things such as the temperature and salinity are not sync from top to bottom. The seasonal warm surface water has a low density forming a saltier layer above while the cooler and more dense water masses near the bottom layer is isolated from the top cutting off oxygen supply from the atmosphere (Overview, 2008).

History

Hypoxia is “rapidly increasing” throughout the world (Briggs, 2009). Areas in the United States included the Long Island Sound, Chesapeake Bay, and the Gulf of Mexico; off the coasts of Louisiana, Mississippi, and sometimes extending to the Texas shelf (EPA, 2003). The Gulf of Mexico is also ...

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...riggs, K., Watkins, J., Shivarudrappa, S., & Hartmann, V. (2009). Effects of Hypoxia on Sediment Properties in the Northern Gulf of Mexico. 9. Stennis Space Center, MS, USA.

Joyce, S. (2000). The Dead Zones: Oxygen-Starved Coastal Waters. Environmental Health Perspectives , 108 (3), 6.

Meade, R. H. (ed. 1995). Contaminants in the Mississippi River, 1987-1992. US Geological Survey Circular 1133, US Department of the Interior . Denver, CO, USA.

Overview. (2008). Retrieved October 2011, from Gulf hypoxia: www.gulfhypoxia.net/overview

Reed, C. (2011, June 20). Mississippi Floods to Raise the Dead Zone in the Gulf. Discovery News .

U.S. Geological Survey (USGS). (2006, March). Gulf of Mexico Dead Zone - The Last 150 Years. St. Petersburg, FL, USA.

United States Environmental Protection Agency (EPA). (2003). Hypoxia & Wetland Restoration. Washington, DC, USA.