While an out-of-control gusher deep in the Gulf of Mexico fouls beaches and chokes marshland habitat, another threat could be growing below the oil-slicked surface.
The nation’s worst oil spill could worsen and expand the oxygen-starved region of the Gulf labeled “the dead zone” for its inhospitability to marine life, suggests Michigan State University professor Nathaniel Ostrom. It could already be feeding microbes that thrive around natural undersea oil seeps, he says, tiny critters that break down the oil but also consume precious oxygen.
“At the moment, we are seeing some indication that the oil spill is enhancing hypoxia,” or oxygen depletion, Ostrom said. “It’s a good hint that we’re on the right track, and it’s just another insult to the ecosystem – people have been worried about the size of the hypoxic zone for many years.”
The dead zone is believed to stem from urban runoff and nitrogen-based fertilizers from farmland swept into the Gulf by the Mississippi River. Higher springtime flows carry a heavier surge each year, nourishing algae blooms that soon die and sink. Those decay and are eaten by bacteria that consume more oxygen, driving out marine life and killing that which can’t move, such as coral. The dead zone can grow to the size of a small state.
With the spill overlapping a section of the dead zone, the impact on that region is unknown.