New Orleans, La. – Scientists from the National Oceanic and Atmospheric Administration and the Environmental Protection Agency say lower levels are probably caused by microbes eating the oil. Testing at 33-hundred to 43-hundred feet showed a 20 percent decline in oxygen levels. NOAA spokesman Steve Murawski says it's not a major concern.
"To date the decrease in oxygen has not been significant enough to cause hypoxia at depth - that is, the dead zone - - nor is it likely to going forward."
Marine life can't survive in areas deprived of oxygen. Dead zones form in the summer in shallow Gulf waters that receive agricultural runoff from the Mississippi River. NOAA continues looking for undersea oil and studying its impact on the Gulf.
For NPR News, I'm Eileen Fleming in New Orleans.