Dead zone off Louisiana coast slightly larger than last summer, but triple the size of the target set by a task force
Dead zone off Louisiana coast slightly larger than last summer, but triple the size of the target set by a task force
"Water containing so little dissolved oxygen that it can’t support marine life was found in an area stretching 6,474 square miles off the coast of Louisiana this summer.
At the size of Connecticut and Rhode Island combined, the dead zone is larger than last year’s 5,052 square miles and much larger than a national target, which was to reduce the annual size to just 1,900 square miles.
For decades, Louisiana Universities Marine Consortium’s Nancy Rabalais has done annual measurements of the dead zone size. A research cruise ran from Tuesday through Monday shows the dead zone extending from the mouth of the Mississippi River west to almost the state’s border with Texas.
“It’s a sick ecosystem. It’s still productive, but it’s ailing, and we need to do something about it,” Rabalais said.
The dead zone is defined as an area where the dissolved oxygen in the water measures 2 milligrams per liter, but this year, there were also large areas where the dissolved oxygen was 1 or even close to zero, Rabalais said. Healthy water in the Gulf of Mexico would measure about 4 or 5 milligrams per liter.
Dead zones occur when nutrients from agricultural land and cities run into the Mississippi River and then into the Gulf of Mexico. These nutrients, often included in fertilizers, feed small organisms that then use up oxygen as they die and decompose on the floor of the Gulf. Without any mixing of the upper freshwater layers from the Mississippi River and the lower saltier waters of the Gulf of Mexico, this lower layer of water can end up with such low oxygen levels that it can no longer support large amounts of marine life."
