The dead zone that has been persisting in the Gulf for over a month now, is most likely due to the BP oil spill, say experts.
Oil spills can deplete oxygen in water by providing a source of food to microbes that grow on oil and consume oxygen in the process.
Although the long-term effects are unknown, researchers say that animals that could, have swum away.
"It's over a regional scale. It wouldn't surprise me if there were a band of low oxygen over that entire area between the Mississippi River and Apalachicola, Florida," Discovery News quoted Monty Graham of the Dauphin Island Sea Lab, who is tracking the zone, as saying.
"The low oxygen was pushing up very close to the shore," he added.
Like sea stars, plankton can't escape the oxygen-depleted waters.
"In the bottom layer, all the plankton were a white colour," said Graham.
"The others were nice and pink-looking. The ones that were white at the bottom would indicate that they were probably dead for a while," he added.
The low oxygen levels have persisted past the time of the seasonal freshwater surge into the Gulf; the zone is larger than would be expected from river-borne nutrients; and the low-oxygen waters seem to be arriving via a tongue of cold water that has pushed up from offshore carrying elevated levels of methane, Graham said.
This suggests that the oxygen depletion has occurred because of the spill.
The good news is that the shallow waters turn over relatively quickly, so once the spill is stopped, oxygen levels should rise.
In deeper waters, where researchers have measured decreased oxygen levels, it might be a different story. (ANI)