Record Breaking Midwest Rainfall Results In 8,000 Mile ‘Dead Zone’ In Gulf of Mexico

Source: National Geographic/Sarah Gibbens

Photo: NASA/Wikimedia Commons 

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Just off the coast of Louisiana and Texas where the Mississippi River empties, the ocean is dying. The cyclical event known as the dead zone occurs every year, but scientists predict that this year’s could be one of the largest in recorded history.

Annual spring rains wash the nutrients used in fertilizers and sewage into the Mississippi. That fresh water, less dense than ocean water, sits on top of the ocean, preventing oxygen from mixing through the water column. Eventually those freshwater nutrients can spur a burst of algal growth, which consumes oxygen as the plants decompose.

The resulting patch of low-oxygen waters leads to a condition called hypoxia, where animals in the area suffocate and die. Scientists estimate that this year the dead zone in the Gulf of Mexico will spread for just over or just under8,000 square miles across the continental shelf situated off the coast.

Choking an ecosystem

“When the oxygen is below two parts per million, any shrimp, crabs, and fish that can swim away, will swim away,” says Louisiana State University ocean ecologist Nancy Rabalais. “The animals in the sediment [that can’t swim away] can be close to annihilated.”

Animals like shrimp will often search for more oxygen in shallower waters closer to the shore. Shrimp subjected to hypoxic waters are smaller, their growth stunted by pollution.

One study published in 2017 noted how the dead zone affects Gulf Coast shrimpers by driving down the price of shrimp and reducing profit for local businesses.

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Photo: NASA/Wikimedia Commons

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