Mississippi Dead Zone
By Kelly Poulos
The Gulf of Mexico dead zone is an area of oxygen-depleted waters at the outflow of the Mississippi River. In the case of the Gulf of Mexico, the dead zone is defined as being the portion of the water column with a dissolved oxygen concentration less than 2 milligrams per liter.
The record size of this hypoxic area is 8,776 square miles and it is caused largely by excess nutrient pollution into the Mississippi River.
The excess of nutrients, largely nitrogen and phosphorus from runoff fertilizers and treated sewage discharge from urban areas, encourages the growth of algae and development of algal blooms. When these algae die, they become a food source for bacteria, which consume dissolved oxygen as they decompose the algae, resulting in areas of the ocean with oxygen levels that are insufficient to support aquatic life, especially when there is strong stratification that prevents reoxygenation of the water column. As a result of this hypoxia, the microbial community in the water column shifts dramatically. This hypoxic zone can cover anywhere from 20%-50% of the Gulf of Mexico water column during the summer months and can persist through September.
A citation code consists of a hyperlinked reference within "ref" begin and end codes.
To repeat the citation for other statements, the reference needs to have a names: "<ref name=aa>”
The repeated citation works like this, with a back slash.
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