Scientists Discover Connecticut-Sized Dead Zone Smaller Than Expected

Each year, the Gulf of Mexico's dead zone appears as oxygen is leeched from the water. The large swathe of dead ocean can stretch for miles, affecting fish populations and, consequently, fisheries in the area. Now, scientists have found that this year's dead zone measures 5,840 square miles, making it about the size of Connecticut.

A dead zone occurs when hypoxic conditions happen over a stretch of water. Hypoxia is fueled by nutrient runoff that stimulates an overgrowth of algae. While this algae produces oxygen while alive, it eventually dies. As it sinks, it decomposes and consumes most of the oxygen in the water. This causes there to be little to no oxygen near the ocean floor.

Although the size of the dead zone is relatively impressive, it's nothing compared to what was predicted. Wet spring conditions in the Mississippi watershed caused nutrients to flood into the river which then transported to the ocean. These nutrients, in turn, were expected to spark an algal bloom which would lead to hypoxic conditions across a huge stretch of ocean. Yet the hypoxic conditions didn't spread like the researchers expected. Instead, nature's wind-mixing events and winds forced the mass of low oxygen water toward the east. This caused the dead zone to be far less severe than initially expected.

Although the dead zone was smaller than expected, it's still large compared to the 2012 Gulf of Mexico dead zone. Drought scoured the region at the time, causing the fourth smallest dead zone on record; it measured just 2,889 square miles, which made it slightly larger than Delaware. The largest dead zone, in contrast, was in 2002. That's when a massive 8,481 square miles were affected.

Whether large or small, though, the dead zone can cost commercial and recreational fisheries millions of dollars over years. Reducing the amount of nutrients being used in agricultural practices, therefore, is crucial to improving the Gulf ecosystem.

"For those who depend upon and enjoy the abundant natural resources of the Gulf of Mexico, it is imperative that we intensify our efforts to reduce nutrient pollution before the ecosystem degrades any further," said Robert Magnien, director of NOAA's Center of Sponsored Coastal Ocean Research, in a news release.

For more information about this year's dead zone, check out the Gulf Hypoxia web site.