The Dead Zone
The Gulf of Mexico is plagued by high levels of nutrients each year. These nutrients trigger large blooms of algae, peaking in the summer. When the algae blooms die, they fall to the bottom and bacteria decompose the algae. This decomposition process consumes most or all of the oxygen in a significant area near the shoreline. Without oxygen, all aquatic life in the area flees or dies. The result is a large area with little or no aquatic life. Watch this video to learn more:
(Courtesy of NASA Mississippi Dead Zone)
The size of the dead zone has trended upward over the last several decades, as shown on the chart below. The increasing levels of nutrients (nitrogen and phosphorus) have triggered larger algae blooms, leading to larger areas of depleted oxygen. The biggest dead zone in 2002 was approximately the size of New Jersey. The 2013 dead zone was above the five-year average, larger than the state of Connecticut. Read more in the official press release about the 2013 measurements.
(Courtesy of LUMCON)
The solution to the problem is reducing the nutrient inputs that start the cycle leading to low oxygen. The Gulf of Mexico Watershed Nutrient Task Force developed a plan to reduce the dead zone in 2008. The plan set a goal to reduce nutrients by 45%, which would reduce the dead zone to 1,930 square miles. EPA then issued an “Urgent Call to Action” report in 2008 2009 describing the need for reduced nutrient levels. Unfortunately, from 1980 to 2009, nitrogen levels did not significantly decline. In the area upstream from Clinton, Iowa (including much of Minnesota and parts of Wisconsin), nitrogen levels actually increased by 76 percent. In Minnesota, the 2012 State of the River Report found that nitrates increased 47% in the metropolitan reach of the Mississippi River from 1976 to 2005. A 2013 report on nitrogen in water produced by the Minnesota Pollution control agency found increasing trends in many parts of the state. Only with major nutrient reductions from upstream states will the Gulf of Mexico be able to maintain aquatic life.
The Hypoxia Task Force determined in 2013 that it did not expect to meet the 2015 goal for reducing the dead zone. The Mississippi River Collaborative submitted comments requesting adoption of numeric criteria and pointing out how existing voluntary programs have failed to reduce the dead zone. The Collaborative also identified how “Nutrient Reduction Strategies” under development do not ensure water quality improvements.