This year is the largest the “dead zone” in the Gulf of Mexico has ever been since monitoring began 32 years ago, according to the National Oceanic and Atmospheric Administration (NOAA). The zone is the size of New Jersey and is oxygen depleted, making it uninhabitable to marine life. A dead zone this large is also dangerous to the economy, with the fisheries in the Gulf, valued at $1 billion, at risk.
Dead zones like the one in the Gulf are caused by human activity from agriculture and raising livestock. Excess nutrients run off the land and eventually reach the coast. Marine regions rely on such nutrients, like nitrogen and phosphorus, to stimulate growth, but too much is deadly. Microscopic algae, or phytoplankton, feed on the abundance of nutrients and reproduce rapidly, causing an explosion in population—an algal bloom. The phytoplankton eventually die, and their decomposition depletes the water of oxygen, leaving it with less than two milligrams of dissolved oxygen per liter. The result is hypoxia (reduced oxygen levels), which causes “dead zones”—areas where the reduction of oxygen causes marine life to suffocate and die, leaving these areas to be described by NOAA as “biological deserts.”
Nitrogen and phosphorus are the main nutrients that crops need to grow. Though these nutrients are critical for life, their over-application, or their use in fields that are being improperly managed, poses a threat to water quality. Nitrogen, phosphorus, and other nutrients are found in manure and chemical fertilizers that eventually wash off corn and soy fields into local water systems, which they pollute. There is no infrastructure in place to stop the nutrient pollution from journeying downstream. The United States Geological Survey (USGS) reports that in 2016 alone, more than 1 million metric tons of nitrogen pollution flowed into the Gulf of Mexico.
The fishing industry is heavily impacted by fertilizer pollution, which is estimated by NOAA to cause $82 million in losses every year for the restaurant, seafood, and tourism industries. The Environmental Protection Agency says that water pollution from excess nitrogen and phosphorus is “one of America’s most widespread, costly, and challenging environmental problems.”
There are ways to reduce fertilizer pollution, including aquatic buffers, drainage ditches, cover crops, better manure management, and flood plains. Aquatic buffers are plants, such as trees and shrubs, that are placed between the farmland and waterways to filter out excess nitrogen and phosphorous before it reaches the water. Drainage ditches can also be used to prevent nutrients from getting into our waterways. Cover crops are planted after a cash crop season has ended so that the land is not left bare. This protects the soil from erosion and absorbs excess nutrients. Better manure management improves over current methods, in which manure is sprayed over fields and poured into lagoons. More sustainable methods have been introduced, such as turning the manure into biofuel. Last but not least, floodplains help filter and remove nutrients from water.
Author: Erin Brown
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- "Stopping the Cycle of Dead Zones in the Gulf of Mexico and Beyond," The Nature Conservancy
- "What is a dead zone?" National Oceanic and Atmospheric Administration (NOAA)
- "New Jersey-Size 'Dead Zone' Is Largest Ever in Gulf of Mexico," National Geographic
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- "Harmful algal blooms: Advances in early warnings & forecasts for fishermen and fishing communities," National Oceanic and Atmospheric Administration (NOAA)
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