The Dead Zone: Hypoxia In The Gulf Of Mexico

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The dead zone is an area when hypoxia happens in a large body of water. Hypoxia is a term referring to the reduced level of oxygen in water. The Gulf of Mexico has the second largest manmade dead zone to be recorded as of today. This zone has been primarily affected by the agriculture waste mixing with the waters of the Mississippi River. The areas of the dead zone lack marine life, hence the name “dead zone” and is constantly growing in size every year. Not all dead zones are caused by pollution. The largest dead zone in the world, the lower portion of the Black Sea, occurs naturally. Oxygenated water is only found in the upper portion of the sea, where the Black Sea's waters mix with the Mediterranean Sea that flows through the shallow Bosporus …show more content…
Hypoxic zones can occur naturally; recently more occurrence of these zones is happening from human activity. Hypoxia in terms of the northern Gulf of Mexico is defined as the concentration of oxygen being less than 2mg/L. This approximation is based on the observational data that fish and shrimp of that area are normally present on the sea floor. What causes hypoxia? It is caused by nutrient pollution, also know eutrophication. The leading cause of hypoxia in the gulf include: freshwater discharge, eutrophication, decomposition of biomass by bacteria on the ocean floor, and depletion of oxygen due to …show more content…
In the northern Gulf of Mexico, eutrophication initiates a massive growth of phytoplankton on the water’s surface. Nitrogen and Phosphorus cause enormous phytoplankton blooms, which results in larger zooplankton populations that feed on the phytoplankton. The size of this plankton population is well beyond the natural capacity of predators or consumers to graze it down to a balanced level. Phytoplankton have a relatively short life span, and after dying sink down to the bottom waters where they await decomposition by bacteria. Large amounts of dead phytoplankton and zooplankton waste then accumulate on the bottom of the seabed. The decomposition of this matter depletes the oxygen in the area faster than it can be replace. Eutrophication occurs naturally as part of the process of succession in many freshwater systems. The key difference in the case of hypoxic areas like the Gulf of Mexico Dead Zone is that excess nutrient inputs from human activities cause the eutrophication to be much more rapid and extensive than the normal process. Different regions of the world emit different levels of these nutrients. In developed countries, such as the United States and nations in the European Union, heavy use of animal manure and commercial fertilizers in agriculture are the main contributors to
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