Every summer in the Gulf of Mexico an area, sometimes as large as Massachusetts, becomes void of life due to severely depleted levels of oxygen in the Gulf’s water, a state known as hypoxia. This condition kills every oxygen-dependent sea creature within its 8,500 square mile zone. The dead zone varies in size, but it has been growing steadily since 1993. The dead zone is caused by excess nitrogen and phosphorous that is washed into the Gulf from the Mississippi River. These nutrients ignite huge algae and phytoplankton blooms. As the blooms die, they drop to the ocean floor and decompose, using up the oxygen of the deeper water. The stratification of the water that occurs during the summer in the Gulf prevents the deepest water from becoming reoxygenated. As a direct result, oxygen levels fall below 2 parts per million, a level that most marine life cannot survive, including all commercial fish, crab and shrimp species. The dead zone is now one of the largest hypoxic zones of water in the world.
The excess nutrients (nitrogen and phosphorus) result from human activities in the upstream Mississippi River watershed. The principal areas contributing nutrients to the Mississippi River, and ultimately to the Gulf, are streams draining the corn belt states, particularly Iowa, Illinois, Indiana, Ohio, and southern Minnesota.
Dead zones in the world’s oceans and seas that are starved for oxygen number some 150 throughout the world, according to a new report by the United Nations Environment Programme. Linked to an excess of nitrogen from agricultural fertilizers, vehicle fumes, factory emissions and wastes, dead zones do not have enough oxygen in the water for fish, oysters and other marine creatures to survive.
These dead zones are capable of recovering if proper sewage and agricultural run-off management is maintained, such as planting cover crops in the off-season to reduce the amount of run-off caused by rainfall on fallow fields. Unfortunately, worsening climate change and the increased use of fertilizers and reliance on factory farming is making it more difficult for nature to recover in these zones. In turn, rather than reduce the number of dead zones in the world, more are being created.
This puts wildlife and humans at even greater risk as coastal waters play an important role in the food chain. Fish and other marine life are dying because of the chemicals found in agricultural run-off, reducing the amount of seafood that commercial fisherman can haul in. Toxic algae blooms thrive on these chemicals, resulting in poisoned waters that are a threat to all life, including humans and pets. These algae blooms have only increased in recent years, resulting in waters that cannot be used for swimming or drinking.
The only way to reverse this trend is to reduce fertilizer use and factory farming to allow the slow recovery of these dead zones so they once again team with plants and wildlife and become sustainable ecosystems humans can properly manage and enjoy.
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