Feds: Oil is lowering Gulf oxygen but not creating ‘dead zones’

Microbes eating subsurface oil in the Gulf of Mexico are reducing dissolved oxygen levels, but not enough to create new “dead zones” devoid of marine life, according to a federal report Tuesday.

The National Oceanic and Atmospheric Administration (NOAA) and two other agencies reported  “dissolved oxygen levels have dropped by about 20 percent from their long-term average in the Gulf of Mexico in areas where federal and independent scientists previously reported the presence of subsurface oil.”

“Scientists from agencies involved in the report attribute the lower dissolved oxygen levels to microbes using oxygen to consume the oil from the BP Deepwater Horizon oil spill,” states a summary of the report released by NOAA, the Environmental Protection Agency and the White House Office of Science and Technology Policy.

The dissolved oxygen levels measured within 60 miles of the ruptured well have stabilized above levels that would create oxygen-starved dead zones that cannot support most life, the agencies said.

“All the scientists working in the Gulf have been carefully watching dissolved oxygen levels because excess carbon in the system might lead to a dead zone. While we saw a decrease in oxygen, we are not seeing a continued downward trend over time,” said Steve Murawski, NOAA’s chief scientist for fisheries, in a prepared statement.

“None of the dissolved oxygen readings have approached the levels associated with a dead zone, and as the oil continues to diffuse and degrade, hypoxia becomes less of a threat,” he added.

Dead zones form each summer at shallower Gulf depths, the result of agricultural runoff that comes down the Mississippi River and other factors, but not in the several thousand feet of water where the agencies measured the oxygen levels linked to the subsurface oil.