The dead zone that grows and shrinks in the Gulf of Mexico, at the outlet of the Mississippi River, has long been on my radar. Hurricanes too, have long been on my agenda, for fear that global warming is increasing their intensity and frequency. However I never thought that I would report on both in the same article, especially in this way.
According to Nancy Rabalais, head of the Louisiana Universities Marine Consortium, the recent hurricane that swept through the Gulf of Mexico, Hurricane Dolly, managed to keep in check the growth of the dead zone.
“If it were not for Hurricane Dolly, the size of the Dead Zone would have been substantially larger,” she said in a news release sent from the consortium’s research vessel, the Pelica, as it returned from its annual mapping cruise, carrying Rabalais out at the same time each year to measure the area.
The current record for size of this particular dead zone is 8,006 square miles, recorded in 2001. Many experts feared that the level of flood runoff would bring so much fertilizer along the Mississippi and in to the Gulf that it would increase the lack of oxygen in the waters, and the size of the dead zone to a record of between 8,300 and 8,800 square miles.
A dead zone is formed when fertilizers and chemicals make their way to the ocean, feeding microscopic plants that reside at the surface, which in turn kills them. Falling to the bottom, they begin to decompose, using up the salt waters oxygen. Add to that the fact that, when the fresh water of the Mississippi mixes with the salt water of the Gulf, it creates layers, keeping oxygen trapped at the bottom.
The resulting deoxygenated water becomes impossible to live in for almost all forms of life.
But due to Hurricane Dolly’s fierce and forceful mixing of the waters, the spread has stopped, especially along the western and shoreward areas, Rabalais said.
Sadly, it may not last. Steven F. DiMarco, an associate professor in the oceanography department at Texas A&M who also studies the dead zone says that “I expect that pulse to be making its way out in a few weeks. It could extend this year’s hypoxic zone or dead zone further into the summer – maybe even in September.”