A fish swims in the oily waters of the Gulf of Mexico off the coast of Grand Isle, La. Wednesday, June 9, 2010. Scientists have discovered two low-oxygen pockets off the Alabama coast. AP Photo / Charlie Riedel

By Ben Raines
Published: Wednesday, June 09, 2010, 5:12 PM Scientists measured two areas of low oxygen off the Alabama coast Tuesday, finding levels below the threshold that marine creatures need to survive. The first low-oxygen pocket was found on the bottom in about 60 feet of water 12 miles off the coast due south of the mouth of Mobile Bay. The second was in about 100 feet of water 25 miles off the coast. The low-oxygen layer was about 9 feet thick in each location. Scientists traveled a north-south line during the sampling, so there was no indication as to how wide the areas were. Scientists said the unusual presence of low-oxygen areas off the coast raises the possibility that the number of oil-eating microbes has swelled because of the millions of gallons of oil in the Gulf. Water samples collected during the most recent cruise will be analyzed to determine whether oil and oil-consuming microbes were present along the seafloor, said Monty Graham, a University of South Alabama researcher working out of the Dauphin Island Sea Lab. There is growing concern among scientists that plumes of oil suspended underwater in the Gulf may cause long-term damage to the marine ecosystem. “I think it adds to the weight of evidence coming from the other people working on those offshore plumes of oil,” said George Crozier, director of the Sea Lab. Oxygen levels have declined steadily since a May 28 sampling effort, Graham said. Levels were between 4 and 6 milligrams per liter at the research sites on May 28. By June 2, they had declined to 3 milligrams per liter or less. Tuesday, researchers measured 1.7 milligrams per liter. Scientists consider 2 milligrams per liter the threshold for survival. “Below 2 milligrams per liter, creatures are stressed. Fish will leave an area looking for more oxygen,” Graham said. Creatures that can’t move — barnacles, oysters, mussels and burrowing animals such as the marine worms — will simply die. …

Low-oxygen pockets found off Alabama coast, raising new fears for sea life