Second Gulf of Mexico dead zone stretches from Louisiana to Alabama

NEW ORLEANS, 1 February 2012 (AP) – A new study finds that Louisiana’s second Gulf of Mexico dead zone stretches at least from the Chandeleur Sound off Louisiana to Alabama’s Dauphin Island — and could be bigger. John Lopez, executive director of the Lake Pontchartrain Basin Foundation, said Wednesday that the foundation was able to check only as far as the Mississippi-Alabama state line in 2011, but officials hope to get other states to extend the reach of studies that will start later in February. In 2010, the foundation checked a 1,050-square-mile area in the Chandeleur Sound and found that it held too little oxygen to support life. The area found last July was 250 square miles. “This is four times larger than the region found in 2010, because a much larger area was surveyed,” Lopez wrote in a news release. A wider look is likely to find a still bigger area, possibly extending into the area off the Florida Panhandle, he said in an interview. Monthly checks at two waterbottom sites off of Alabama, 12 and 25 miles out in the Gulf, also have found low oxygen levels “with some regularity” during the summer, said Ron Kiene, a marine sciences professor at the University of South Alabama and a faculty member at Dauphin Island Sea Lab. Another half-dozen stations closer to shore occasionally show hypoxia, he said. He said he’d like to get more data from across the region to see if such areas are patchy or more extensive. Ocean currents and geology make hypoxia unlikely off of Florida, said Lisa E. Osterman, a scientist with the U.S. Geological Survey in St. Petersburg, Fla. […] Oxygen gets into the ocean from the air, mixed in by winds, waves and currents. Fresh water is lighter than salt water, and river water carries in nutrients that feed the growth of tiny plants and animals that fall to the sea floor when they die. If the water is so calm that water stays layered, the decomposition of that plankton uses up oxygen in the saltier layer and the cap of lighter water gets all the oxygen. Osterman agreed that lack of ocean currents is a big factor. “That whole Mississippi Sound area is kind of cut off from the general circulation,” she said. “It is very isolated in that little area.” The Mississippi Sound also has a history of hypoxia, she said: Studies using sediment cores have found evidence of previous low-oxygen episodes within the last 50 years. “It’s not like, ‘Wow, this is something that never happened before,'” she said. In 2010, scientists thought that opening a Mississippi River diversion — part of an attempt to keep oil from the BP spill out of state waters — might have caused the hypoxia found that year near the Chandeleurs. Although the Bonnet Carre Spillway poured fresh water and nutrients into Lake Pontchartrain after it was opened during last spring’s record floods, Lopez said he didn’t think it had a big role in last year’s dead zone. […]