How Will the Gulf’s Dead Zone Impact the Oil Spill?

By AnimalTourism
Friday, April 30, 2010

The Gulf’s
Dead Zone is about 6,000 to 7,000 square miles, one of the biggest in the world, Microbial Life Educational Resources of Carleton College says. It’s caused by fertilizer run-off in the Mississippi overfeeding algae. Phytoplankton gobble up the algae–and all the oxygen. Scientists call the areas hypoxia–or low oxygen. They can’t support life. 
The oil spill so far is smaller, about 1,800 square miles. So far. 
Right now the dead zone is west of the Mississippi and the oil spill is east of it. The dead zone is mainly at the bottom, which is littered with phytoplankton carcasses. The oil is on top. 
But Nancy N. Rabalais, Ph.D., executive director of 
Louisiana Universities Marine Consortium thinks they’re likely to meet. 
"If the winds continue from the southeast as is common this time of year, then the surface manifestation may move to the west of the Mississippi River delta and become a surface feature of the Louisiana area of hypoxia," says 
Some seem to have fantasized that the oil burn off will end up cleaning up the dead zone. Not so, says Rabalais. "The burn would reduce the more volatile and toxic components,"

[in the oil] she says, but not burn off the algae. 
The algae isn’t going to slow the oil down, she says, but the oil may slow down the production of algae: 
"The movement of the oil would not be affected by where the area of low oxygen may be. Algal production if the oil were to come into the low oxygen would probably be reduced in productivity because of the proximity of the oil." 
The dead zone won’t necessarily have cleared out the wildlife; it’s too soon to tell, she says. While the dead zone is indeed dead to most sea life like plants and fish, birds and marine mammals pass through: "The area of low oxygen does not affect birds and marine mammals because they are air breathers and the marine mammals and turtles can reach the surface of the water for atmospheric air."

The impact she expects is the oil will calm that waters of the dead zone. There will be less oxygen transfer from surface air into surface waters. The waters will stratify. The oil would cut back on the production of phytoplankton at the surface. And the oil and dead zone could pinch in on organisms caught between the top and bottom. 
Perhaps the biggest impact is that the oil spill may decimate the wetlands–the wetlands the government had been building up in hopes of filtering water of fertilizers to short-circuit the dead zone. So much for that.

N.B. Not sure I really said all this, Nancy