Gulf of Mexico ‘dead zone’ threatens to reach the size of Massachusetts

"Low oxygen conditions started to appear 50 years ago when agricultural practices intensified in the Midwest."

Image credit: Flickr

The infamous Gulf of Mexico ‘dead zone’ could swell this summer to a record 7,829 square miles, or roughly the size of the state of Massachusetts.

The hypoxic zone – or dead zone, an area of little or no oxygen that seriously threatens marine life – threatens to become the second largest in history. The previous record size was 8,776 square miles in 2017.

The Gulf of Mexico hypoxic zone occurs every year. According to the National Oceanic Atmospheric Administration, it is caused by “excess nutrient pollution from human activities, such as urbanization and agriculture, occurring throughout the Mississippi River watershed.” Heavy spring rains led to high river flows and flooding this year, contributing to this year’s dead zone.

Researchers from Louisiana State University predict that this year’s dead zone could be even larger than the NOAA predicted, closer to 8,717 square miles.

“This past May, discharge in the Mississippi and Atchafalaya rivers was about 67 percent above the long-term average between 1980 and 2018. USGS estimates that this larger-than-average river discharge carried 156,000 metric tons of nitrate and 25,300 metric tons of phosphorus into the Gulf of Mexico in May alone. These nitrate loads were about 18 percent above the long-term average, and phosphorus loads were about 49 percent above the long-term average,” said the NOAA.

High amounts of nitrogen and phosphorus in water stimulate the growth of phytoplankton or algae. After the phytoplankton dies and sinks to the bottom they decompose, a process that causes depletion of oxygen in the water. Marine life that can swim away will, but many animals stuck in the sediment that cannot swim away will die. The loss of life also deeply affects the commercial fishing industry operating in the area.

“Low oxygen conditions started to appear 50 years ago when agricultural practices intensified in the Midwest,” said Louisiana State University in a statement.

The Gulf of Mexico dead zone is among the world’s biggest. Unfortunately, it seems the dead zone is growing on average over time, with small fluctuations influenced by weather patterns.

“The bottom line is that we will never reach the dead zone reduction target of 1,900 square miles until more serious actions are taken to reduce the loss of Midwest fertilizers into the Mississippi River system,” said Don Scavia, an ecologist at the University of Michigan who worked with the NOAA on this year’s report.


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