Northern Gulf of Mexico

 Northern Gulf of Mexico Hypoxic Zone

             The northern Gulf of Mexico hypoxic zone spans from Louisiana to Texas. Hypoxia is a condition in which dissolved oxygen levels in the water are too low to sustain life. The hypoxic zone is created by the excessive amounts of nitrogen and phosphorous runoff that is dumped into the gulf from the Mississippi. The following discussion of this ecosystem will explore the general ecology of the area, anthropogenic interactions and effects on this area, and possible courses of action regarding the future of the ecosystem.

            The northern Gulf of Mexico ecosystem is located off the coasts of Louisiana, Texas, and Florida. This area is home to many different kinds of marine life, including at least 54 demersal fish species. (Sulak et al, 2007) These fish are drawn to this ecosystem by coral reefs that help tie the entire ecology of the area together. This ecosystem spans from the open ocean or pelagic zone down to the lower abyssal layers of the sea floor. The corals that occur in this ecosystem form large thickets and unlike many other species of corals, they are located in deep waters. (Sulak et al, 2007) Deep water corals serve in the northern Gulf provide their ecosystem with similar functions as their counter parts in shallower waters. Most notably is that they add to the biodiversity of the ecosystem. Fishes and other marine organisms of all sizes all benefit from the existence of the corals. Small fish can hide in them, larger fishes are attracted by the small fish, plankton feed off the organic particles that surround the corals, and starfish and crabs use the corals as their habitats. The reason that these corals exist in deep waters is due to the carbonate rock substrate. (Sulak et al, 2007) The carbonate substrate also allows other organisms such as sponges, anemones, and various other bottom dwelling species to take hold. Prior to the large amounts of agricultural runoff that currently affect the area, the corals in this ecosystem were the foundations of live. Now they are a death trap for slow moving species. The nitrogen and phosphorous runoff from the Mississippi river bring low levels of dissolved water and create a “Dead Zone.”  (Marder, 2011)

            The “Dead Zone” is likely to have appeared as early as the beginning of this century when fertilizers with phosphorous and nitrates began to be used by farmers. It became more severe closer to the 1950s when fertilizer runoff from the Mississippi increased threefold. (Mississippi River Gulf of Mexico Watershed Nutrient Task Force, 2008) Waters can be considered hypoxic when the dissolved oxygen content drops to below 2mg/l. (Rabalais, Turner, Wiseman, Jr., 2002) This dissolved oxygen level is the lowest possible that can sustain life. Hypoxia has its greatest effects on animals that live closer to the ocean floor in benthic areas. Hypoxic conditions generally occur from late February to early October, but they are most continuous and severe during June, July, and August. (Duffy, 2008) The fertilizer sediments bring about a phenomenon called eutrophication, which is an overloading of nutrients. (USGS, 2011) The excessive amounts of nutrients give rise to algal blooms. When these algal blooms die, the sink to the benthic zone of the ocean and decompose. The decomposition of the algae robs the water of oxygen. Animals such as fish, shrimp, and crabs that can move quickly can escape the waters with insufficient oxygen levels. Animals that cannot move quickly enough, such as starfish, sponges, and anemones, perish in the oxygen deficient water.

(Wendee, 2011)

           The sources of pollution that contribute to the dead zone are vast. The Mississippi River begins as a small outlet stream stemming from Lake Itasca in Northern Minnesota. It then travels 2,350 miles south to the Gulf of Mexico. The Mississippi drains the entire Mississippi River Basin, which includes 31 states and cover 1,245,000 square miles. (Mississippi River Gulf of Mexico Watershed Nutrient Task Force, 2008) This means that the Mississippi carries the entire basin’s fertilizer runoff. A few states such as Minnesota and Wisconsin are aware of this fact and have put restrictions in place to limit the amount of nitrogen and phosphorous runoff into their rivers. (Gannett, 2012) However, not all of the states that contribute to the nutrient runoff are receptive to such restrictions. Farmers and political leaders in the state of Iowa oppose nutrient runoff regulations. Corn is a regularly grown crop in Iowa and the demand for corn is ever-increasing. A high demand for corn leads to higher yields and therefore more fertilizer use.

            The future of this ecosystem depends on multiple factors. Corn has been and will continue to be a major crop in the United States, therefore the need for nitrogen and phosphorous fertilizers are going to persist. This is an ugly truth for the people that depend upon the health of the northern Gulf. Shrimp fishermen that maintain their livelihood are suffering the consequences of high use of fertilizers. There are many people that contribute to the pollution of the Mississippi River, and none of them are affected by how much they pollute the water. When shrimp fishermen want to go out and harvest shrimp and the areas that are normally full of shrimp are now hypoxic, then they will not be able to catch shrimp and lose substantial amounts of money. The human population will continue to grow for some time, meaning the demand for corn will continue to grow as well. For Midwestern corn farmers, this means higher yields during growing seasons are necessary, so fertilizer inputs need to be increased. For the northern Gulf ecosystem and the shrimp farmers, this could result in awful consequences. The hypoxic zone varies in size each summer for a combination of reasons including fertilizer runoff as well as precipitation rates. (WSA, 2006) In years that precipitation is low, the fertilizer runoff decreases and that leads to a smaller hypoxic zone. (Slivka, 2012) Since rainfall cannot be controlled, other techniques to lessen the hypoxic zone need to be utilized.  

            Reducing the amount of nitrogen and phosphorous runoff that enters the northern Gulf of Mexico is a challenging task, but it is not impossible. The keys to achieving this goal are the distribution of information and cooperation amongst polluters of the Mississippi River. In order to bring attention to any sort of issue, the proper information must be presented to the proper audience. In this case, people and industries that pollute the Mississippi River need to be made aware of the consequences of their actions. Some polluters may already know how they are impacting others that depend on the health of the northern Gulf yet output must be continued otherwise they will lose profits and begin to struggle. The best option is to put in place a system of pollution credits, not unlike the carbon trading system that is going to be implemented in California. A cap needs to placed on the total amount of nitrogen and phosphorous runoff that can enter the Mississippi. This cap can be determined by the main polluters of the states in the Mississippi Basin and the lawmakers of those states in conjunction with northern Gulf fisherman, research organizations such as the Louisiana Universities Marine Consortium (LUMCON), and the lawmakers of the affected states. Another option is to push for a shift in farming practices. Farmers in the Mississippi Basin have many choices in advanced farming technology and methods that can reduce dependency on fertilizers and the cut down on runoff. Drip irrigation, organic farming, and properly timed fertilizer applications are all methods that are effective.

            Prior to the overloading of nutrients in the northern gulf ecosystem, hypoxia was not a problem. Without the occurrence of hypoxia, marine organisms did not have to flee for their lives from the suffocating waters or perish because they could not escape.  The northern Gulf of Mexico ecosystem feels the pressure of anthropogenic pollution daily; the runoff from the Mississippi River will never cease. The hypoxic zone that exists there is in no way a damning sentence that humans have placed on the ecosystem. The effects of the dead zone can be diminished if the area is properly managed. This coastal ecosystem can thrive and continue to be a home to many marine creatures as well as serve the coastal communities that depend on it.

 Works Cited

Duffy, J. Emmett. “Gulf of Mexico Large Marine Ecosystem.” Encyclopedia of Earth

            Online. Encyclopedia of Earth, 28 Dec. 2010. Online.

Gannett, Perry Beeman. “What is Hypoxia?” The News Star, 24 Nov. 2012. Online.

Marder, Jenny. “Farm Runoff in Mississippi River Floodwater Fuels Dead Zone in Gulf.”

            Public Broadcasting Service, 18 May 2011. Online.

Mississippi River Gulf of Mexico Watershed Nutrient Task Force. “The Mississippi-

            Atchafalaya River Basin (MARB).” Environmental Protection Agency, 2008.

            Online.

Nicole, Wendee. "Dead Zone." Adventures in Climate Change, The Wendee Nicole Report,
            7 July 2011. Online.

Rabalais, Nancy N., Turner, R. Eugene., and Wiseman Jr., William J. Gulf of Mexico          

            Hypoxia, a.k.a “The Dead Zone.” Annual Review of Ecology and Systematics 33           

            (2002): 235-63. Online. 

Slivka, Kelly. “Big Drought Makes for a Small Dead Zone.” New York Times, Green

            Blog. 2 August 2012. Online.

Sulak, Kenneth J., et al. Demersal Fishes Associated with Lophelia Pertusa Coral and       

            Associated Biotopes on the Continental Slope, Northern Gulf of Mexico. Bulletin

            of Marine Science 81.1 (2007): 61-92. Online. 

United States Geological Survey. “Eutrophication.” Toxic Substances Hydrology

            Program], 27 Dec. 2011. Online. < http://toxics.usgs.gov/definitions/eutrophication.html>

Wadeable Streams Assessment. “Nitrogen and Phosphorous Pollution in the     

          Mississippi River Basin: Findings of the Wadeable Streams Assessment.”             

          Environmental Protection Agency, 2006. Online.