Underwater oil plumes could create new 'dead zone' in Gulf
by Staff Writers
New Orleans, Louisiana (AFP) May 17, 2010
Giant plumes of oil floating deep in the Gulf of Mexico could create a
new 'dead zone' of oxygen-depleted waters unfit for marine life and
wreak environmental damage that will take generations to overcome,
scientists warned Monday.
"Normally, in a shallow spill, everything pretty much shoots up to the
surface and the impacts are primarily to surface organisms like
turtles, dolphins, and birds," said Paul Montagna, a marine ecologist
at the Harte Research Institute for Gulf of Mexico Studies.
But the oil which has been gushing out of the wreckage of the BP-leased
Deepwater Horizon since April 22 is traveling up through chilly, dark
waters 5,000 feet below the surface.
"Under this really cold, high pressure environment the oil is getting
dispersed through the water column," Montagna said in a telephone
"What that means is that basically life in the entire water column is
now being exposed."
Adding to the toxic soup are more than 580,000 gallons of chemical
dispersants applied to the surface of the slick and also directly into
the subsea stream of crude gushing out of a ruptured pipe.
Those dispersants are being used to help keep the oil away from
sensitive shorelines by breaking it up into smaller clumps, some of
which will be consumed by microbes and some of which will eventually
sink to the ocean floor.
The problem is that those microbes end up consuming oxygen in the
process and there is an enormous amount of oil that needs to be
consumed, said Chris D'Elia, dean of the School of Coast &
Environment at Louisiana State University.
"The toxicity alone or the bod (the biological oxygen demand) problem
alone are substantial issues," D'Elia told AFP.
"When you start adding the two together, God only knows what's going
The Gulf already suffers from a massive 'dead zone' which forms every
spring when agricultural runoff carried out to sea by the Mississippi
River causes algae to bloom and suck up the oxygen in shallower waters.
Mobile marine life like fish, shrimp and dolphins usually migrate east
of the dead zone, which happens to be the area most directly affected
by the oil slick.
"Clearly you'd expect a huge die off in the water column as well as in
the (affected) sediments," said Wilma Subra, a chemist and consultant
who works with the Louisiana Environmental Action Network.
Another major concern is that the subsea oil and dispersants can be
carried by currents in an entirely different direction that where the
wind and waves send the surface slick, creating a "much larger area of
impact," Subra said.
BP has managed to stem the flow of oil by about 1,000 barrels a day
using a mile-long tube inserted into the mouth of the ruptured pipe
which is funneling the crude up to a waiting ship.
BP estimates that about 5,000 barrels of oil a day are currently
gushing out of the pipe, but independent experts have said that the
amount could be as much as ten times higher.
"Even when the leak is stopped completely, there's still going to be
that large sheen, there's still going to be that large (level of)
dispersant in the water column and in the sediment," Subra told AFP.
"The environmental impact will go on from those sources for a very,
very long time and the results of those impacts will last for
Researchers with the National Institute for Undersea Science and
Technology discovered evidence of huge undersea plumes of oil - one
reportedly 15 to 20 miles long and four or five miles wide - which were
already beginning to deplete the oxygen in nearby water by as much as
Jane Lubchenco, who heads the National Oceanic and Atmospheric
Administration, cautioned that it was "premature" to conclude that the
plumes were caused by the use of chemical dispersants.
"As we have emphasized, dispersants are not a silver bullet," she said
in a statement.
"They are used to move us towards the lesser of two environmental
outcomes. Until the flow of oil is stemmed, we must take every
responsible action to reduce the impact of the oil."