POLLUTION

Dead zones are areas of water where life is unable to survive due a process called  eutrophication. This is caused by excess nutrients in the water such as nitrogen and phosphorus. Normally, the nutrients are beneficial and help organisms such as cyanobacteria (algae) or phytoplankton grow. However, when there is an excess of nutrients in the water, it leads to an overgrowth of algae, also known as algae blooms. This huge overgrowth of algae not only blocks sunlight from underwater plants, but also consumes large amounts of oxygen. Eventually, algae will die but the issues do not end here. Hypoxia (lack of oxygen) events will follow algae blooms as algae and other organisms are decomposed by bacteria. This process also uses up much of the oxygen in the water. Overall, this process is extremely harmful to aquatic animals that may be living in the area as they are either forced to relocate or will die due to the extreme lack of oxygen in the water. Human activity is what usually causes the excess of nutrients (EPA).

Eutrophication has been increasing in recent years and is often linked to harmful agricultural practices and population growth. In more developed countries like the US,  excessive use of animal manure and synthetic fertilizers are the main causes for eutrophication. Eutrophication is often caused by agricultural centers upstream. When rain occurs it washes large amounts of nitrogen into waterways, this is known as runoff (EPA, National Geographic). 

Agricultural centers are not the only cause of Eutrophication. In less developed countries such as in parts of South America, Asia, and Africa, untreated sewage is the main cause of eutrophication. Sewage facilities will sometimes dump untreated wastewater into creeks and rivers not only causing the water to become unhealthy, but also adding a surplus of nutrients (EPA, National Geographic). 

One of the most prolific dead zones in the world is located right off of the United States in the Gulf of Mexico, spanning close to 7,000 square miles. This dead zone is a result of continuous runoff from the Mississippi river from things like urban centers, agricultural centers, and even discharge from sewage treatment plants. The Mississippi river is part of a huge watershed system that connects 31 different states and all of it flows out into the Gulf of Mexico. Animals such as fish and shrimp are forced to swim however, many animals such as clams and crabs are not able to leave quick enough and die. This dead zone is a cycle that happens every year in the summer and each year it varies in size (NOAA). 

It is estimated that the Gulf of Mexico dead zone costs over $82 million a year in lost revenue in sectors such as seafood and tourism. The Gulf is a major producer of seafood and accounts for 40% of the country’s production. States such as Lousisina heavily rely on the seafood industry as a means of economic output. Fishermen have to travel further and put in more time and money into catching fish as they escape further out into the ocean to avoid the dead zone. Overall, the seafood industry has been impacted fairly severely by the annual dead zone that occurs in the heart of the Gulf (The Nature Conservatory). 

Luckily, some things are being done to help mediate the harmful effects of nutrient runoff in the Gulf of Mexico. Along the Mississippi river, technology is being implemented that removes nutrients from the water to help limit the amount of nutrients that make it out to the Gulf. Additionally, some initiatives are in place to help farmers reduce their impact on water quality, such as the best times to use fertilizer based on rainfall predictions (NOAA). 
 

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