Ocean Dead Zones

The ocean is an important part of our ecosystem. It produces most of the oxygen we breathe. It’s also very important for our economy, providing food for many people around the globe.

That’s why ocean dead zones are a serious threat to everyone.

What are ocean dead zones?

An ocean dead zone is an area of the ocean that does not have enough oxygen to support life. Another word for an ocean dead zone is hypoxia. (Research from Ocean Service)

The ocean becomes hypoxic when oxygen levels dip below two milliliters of oxygen per liter of water.
In a dead zone, all marine life either dies or leaves the area. Basically, the area becomes deserted and completely empty of life.
Ocean dead zones can occur naturally. But often, human activity causes these dead zones.
Farmers let too many nutrients from growing crops in groundwater and farm runoff gets into rivers. These nutrients cause too many algae to grow. Eventually, the algae die and decompose, using up the oxygen that other life forms need to survive.

There are dead zones in many parts of the United States. The largest of these is in the northern Gulf of Mexico. Dead zones can also occur in other large bodies of water, such as the Great Lakes.

Ocean Dead Zones: Facts

Ocean dead zones have always existed. But in the 1970s, scientists first began to notice that these dead zones were becoming more widespread. In fact, the number of dead zones in the world has doubled each decade.

As of 2008, there were more than 400 dead zones worldwide.
The largest dead zone in the world is in the Arabian Sea. It takes up more than 63,700 square miles in the Gulf of Oman.
The second-largest dead zone is the Gulf of Mexico, which takes up about 3,275 square miles.
Many dead zones only occur during a specific season of the year. For example, most of the dead zones in the Gulf of Mexico only occur between the months of May and September. This is mostly the result of the use of fertilizers in the American Midwest, which causes nutrients to run off into the Mississippi River.

Ocean Dead Zones Caused by Animal Agriculture

Raising animals for meat is a huge business in the US. Animal agriculture produces large amounts of fertilizer. In order to produce enough corn to feed all this livestock, farmers need to use a lot of fertilizer. Farm waste can end up as runoff into local rivers.

That runoff packs a punch of life-giving nitrogen and phosphorus. The same nutrients that help the corn to grow also feed algae in the ocean. The algae bloom, which covers the surface of the water and blocks sunlight from reaching the fish and plants below. Once the blooms die, they sink to the bottom of the ocean and their process of decomposition uses the oxygen in the water. Eventually, they use up all the oxygen in an area. Then, fish and other marine life can no longer live there.

The Midwest is a prime location for large farms. Unfortunately, the fertilizer and animal waste from Midwestern agriculture ends up in the Mississippi River. The river flows to the Gulf of Mexico, which is why there is currently such a large dead zone in that area.

How to Prevent Dead Zones in the Ocean

There are some things we can do to prevent dead zones in the ocean, or at least to keep them from getting bigger.

Managing the amount of fertilizer we use in meat production is one way to do this. If farmers use exactly the amount of fertilizer they need, and no more than that, this can limit harmful runoff.
Planting cover crops also help to keep nutrients in the soil instead of running off into waterways.
Plant trees and shrubs near bodies of water, so they can filter away some of the nutrients before they get into the groundwater.
Conservation tillage is another farming practice that can prevent dead zones. Farmers can reduce soil erosion by limiting how often they till some of their fields. As the soil becomes more compacted, there will be less runoff.

Ocean Dead Zones Solutions

Section 404 of the Environmental Protection Agency’s Clean Water Act addresses the problem of water pollution in the United States. This law helps us to make progress in solving the problem of ocean dead zones. (Research from: Sailors for the Sea)

It’s also important to work with farmers. Scientists can educate farmers to plant cover crops and manage their fertilizer use better.

Another important practice is restoring floodplains around the Mississippi River. A floodplain is a flat area around a river that protects from flooding and provides a habitat for marine life. Floodplains also stop runoff before it gets to the ocean.

Ocean dead zones are a growing problem in the Gulf of Mexico and all over the world. But with thoughtful, sustainable agriculture practices, we can bring life back to these areas of our oceans again.