Quantcast
Environmental News for a Healthier Planet and Life

Connecticut-Sized Dead Zone Found in Gulf of Mexico

Connecticut-Sized Dead Zone Found in Gulf of Mexico

Ocean Conservancy

By Alexis Baldera

Imagine if all of the animals throughout the entire state of Connecticut left or died. This is what happens every year in the Gulf of Mexico. The size of the dead zone varies—sometimes it’s as big as New Jersey or only the size of Rhode Island, but the problem always persists.

Researchers from the Louisiana Universities Marine Consortium just spent a week measuring dissolved oxygen concentrations off the coasts of Louisiana and Texas to determine how big the dead zone is this year. And they found that it is about 5,800 square miles, or roughly, the size of the state of Connecticut.

This area is called “the dead zone” because dissolved oxygen levels are too low to support life. Animals that can move out of the area, like fish and shrimp, will leave, and animals that can’t, like brittle stars and mussels, will become stressed and eventually die.

The dead zone forms every summer because nutrient-rich water from the Mississippi River basin flows into the Gulf and causes algal blooms. Nutrients, like nitrogen and phosphorus, are helpful when used to fertilize gardens and crops, but like most other things, the best rule for nutrients is moderation. While these nutrients are naturally occurring in the Gulf and all ecosystems, levels that are too high can cause problems.

In the Gulf of Mexico, the nutrient-rich waters, fueled by agricultural runoff fed down the Mississippi River, create explosive algae blooms. Photo credit: eutrophication'hypoxia/Flickr

The Mississippi River basin drains 41 percent of the contiguous U.S. and as water runs off fields, yards and pavement, it collects nutrients. These nutrients are carried to the Gulf where they “fertilize” coastal waters and cause algal blooms. As algae die, they sink to the seafloor where they are decomposed by bacteria, a process that uses oxygen.

During most times of the year, bottom waters and surface waters mix frequently, so oxygen levels are replenished regularly. However, during the summer there is an abundance of warm fresh water in the Gulf due to seasonal warming and freshwater river outflows. This water is less dense than the cold salty water near the bottom of the seafloor.

The densities are different enough that the two layers of water will become separated (think oil and water) and prevent mixing of the oxygen-poor bottom waters with the oxygen-rich surface waters. This is called stratification. When stratification occurs, low-oxygen waters are trapped at the bottom, and as more algae are decomposed, the oxygen levels continue to drop until they get low enough to cause a dead zone.

While the dead zone off the coast of Louisiana is the largest and most recognized example of coastal hypoxia in the Gulf, this problem is a Gulf-wide issue. The Ocean Conservancy has mapped the documented cases of low-oxygen areas in the extensive report, Gulf of Mexico: A Marine and Coastal Atlas.

What is the best way to reduce the size of the dead zone? Reduce the amount of nutrients that reach the Gulf.

The two best ways to do this are:

  1. Reduce nutrient inputs into coastal and upriver water bodies
  2. Increase the watershed’s capacity to retain excess nutrients

 

As consumers of agricultural goods, we can contribute to reducing nutrients by supporting farming practices that promote sustainable, responsible agriculture. For example, one practice called crop rotation can reduce fertilizer application by rotating plants like legumes that add nitrogen to the soil with plants like corn that take it up. And the practice of adding stream buffers to drainage ditches can capture nutrients before they enter waterways.

In our own yards, the best way to reduce excess nutrients is to use fertilizers carefully and slow storm water runoff by using techniques such as rain gardens.

Visit EcoWatch’s WATER page for more related news on this topic.

——–

Kevin Maillefer / Unsplash

By Lynne Peeples

Editor's note: This story is part of a nine-month investigation of drinking water contamination across the U.S. The series is supported by funding from the Park Foundation and Water Foundation. Read the launch story, "Thirsting for Solutions," here.

In late September 2020, officials in Wrangell, Alaska, warned residents who were elderly, pregnant or had health problems to avoid drinking the city's tap water — unless they could filter it on their own.

Read More Show Less

EcoWatch Daily Newsletter

Eat Just's cell-based chicken nugget is now served at Singapore restaurant 1880. Eat Just, Inc.

At a time of impending global food scarcity, cell-based meats and seafood have been heralded as the future of food.

Read More Show Less

Trending

New Zealand sea lions are an endangered species and one of the rarest species of sea lions in the world. Art Wolfe / Photodisc / Getty Images

One city in New Zealand knows what its priorities are.

Dunedin, the second largest city on New Zealand's South Island, has closed a popular road to protect a mother sea lion and her pup, The Guardian reported.

Read More Show Less

piyaset / iStock / Getty Images Plus

In an alarming new study, scientists found that climate change is already harming children's diets.

Read More Show Less
Wildfires within the Arctic Circle in Alaska on June 4, 2020. Contains modified Copernicus Sentinel data processed by Pierre Markuse. CC BY 2.0

By Jeff Masters, Ph.D.

Earth had its second-warmest year on record in 2020, just 0.02 degrees Celsius (0.04°F) behind the record set in 2016, and 0.98 degrees Celsius (1.76°F) above the 20th-century average, NOAA reported January 14.

Read More Show Less