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Dead Zone in the Gulf of Mexico

Every summer, the dead zone—or hypoxic zone—in the Gulf of Mexico results in millions of acres of habitat potentially unavailable to fish and bottom species. Learn how we all play a role in contributing to the dead zone and what steps we can take to fix it.


Dead Zone

No, we’re not talking about a scary movie. But “dead zone” is the common term for what’s happening in the Gulf of Mexico, and it is a little frightening.

A dead zone—or hypoxic zone—is an area of low oxygen that can harm fish and marine life near the bottom of the sea. Yikes! And there are hundreds of dead zones in coastal waters around the world. The Gulf of Mexico’s dead zone is one of the largest.

What’s harming all that ocean life? Unfortunately, without meaning to, we all are. But wait, you probably don’t even live near the Gulf. So, how can you be responsible?

Think about the last meal you ate. Some of that food may have been grown right here, in the middle of the United States. Now, think about the hundreds of millions of people across the country and the billions around the world. They all need to eat too. To meet the demand for all that food, farmers rely on fertilizer, or nutrients, that help plants grow and increase crop output. We end up with more food on our tables and more food to sell to the rest of the world. 

But what does a farm in the middle of the country have to do with fish dying in the ocean? To answer that, we have to look at the Mississippi River. Think of the Mississippi River as a drainage system for your street, except it connects 31 U.S. states and even parts of Canada. That’s the Mississippi Watershed. When farmers apply fertilizer, the excess nutrients—such as nitrogen and phosphorus—can run off during a rainstorm or snowmelt and end up in waterways that feed the Mississippi River. 

And farms aren’t the only source of excess nutrients or nutrient pollution. Urban runoff, such as fertilizer from lawns and golf courses, and discharges from sewage treatment plants, also feed into the Mississippi.

These nutrients are ultimately funneled into the Gulf of Mexico, sometimes traveling more than a thousand miles downstream to start a chain of events in the Gulf that turns deadly. The nutrients cause plants known as algae to grow out of control, fueling large blooms that then sink, decompose, and consume oxygen in the water. This is hypoxia, when oxygen in the water is so low it can no longer sustain marine life in bottom or near bottom waters—literally, a dead zone. Fish and shrimp leave the area and anything that can't escape—like crabs, worms, and clams—dies.

And it happens every summer. The exact size of the Gulf dead zone varies each year. Scientists collect water samples across the Gulf to determine the size. The dead zone can be as large as the state of New Jersey. That means millions of acres of habitat potentially unavailable to fish and bottom species. If the amount of pollution entering the Gulf isn't reduced, the dead zone will continue to wreak havoc on the ecosystem and threaten some of the most productive fisheries in the world. 

And climate change is making the problem worse as warmer ocean water holds less oxygen. Now that’s scary! 

Fortunately, we have the opportunity to rewrite the ending to this story.

What are States doing to help reduce the size of the dead zone in the Gulf of Mexico?

A variety of innovative technologies and practices are being implemented across the Mississippi River watershed to reduce nutrient pollution, such as: technology that removes nutrients from wastewater, practices on the land to limit nutrients entering into waterways, and programs that help farmers implement conservation practices that protect water quality.

NOAA is also working with states to develop new runoff risk forecasting tools that help farmers determine when to use fertilizer, based on anticipated rainfall amounts.

There are even steps you can take at home, such as reducing excess runoff from areas around the house, planting trees and other native plants in your yard, applying slow release fertilizers and only when needed, and minimizing food waste.

Even though these efforts may take place far from the Gulf, they can still reduce the harmful impact of the dead zone!