Oil Spill in Gulf Could Cause ‘Dead Zone’, Further Hitting Sea Life

Published on
by
Financial Times

Oil Spill in Gulf Could Cause ‘Dead Zone’, Further Hitting Sea Life

by
Sheila McNulty

Dead zone: This image from NOAA shows the dead zone in the Gulf of Mexico. (NOAA)

High concentrations of methane gas - in some cases approaching 1m
times the normal level - have been found around the BP oil spill,
raising fears it could create an oxygen-depleted “dead zone” where
marine life cannot survive.

Dead zones are areas in the water where algae blooms as it feeds on
nutrients in high concentrations of foreign matter, such as  methane, in
this case, or, more typically, the components of farmland fertiliser
runoff into the water. The algae gorge, reproduce quickly and then, in
turn, are eaten by bacteria in a process that depletes the immediate
area of oxygen. Fish and other sea life cannot survive in these zones,
leading scientists to call them “dead”. 

That the spill could cause a dead zone in the Gulf would be yet
another negative for the environment, already
suffering
from the destruction of marine nurseries and bird nesting
grounds in the wetlands and projections of negative impacts on sea life
along the Gulf Coast. The knock-on effect would be a pocket of the Gulf
where fishermen would find no fish or other sea creatures to harvest.

The site where large concentrations of methane has been found is in a
six-mile radius around the spill, where John Kessler, assistant
professor in the Department of Oceanography at Texas A&M University,
has just returned from a 10-day
research trip
.

From a previous trip last year to the same area, he has identified
the rise in methane to the Deepwater Horizon accident. Methane is a key
component of natural gas, such as ethane and propane, and it accounts
for 40 per cent of the weight of material emanating from BP’s leaking
well.

Last year the concentrations of these gases were at normal levels of
one to two parts per million. This year, the concentration of methane
dissolved in the seawater is 100,000 times more and, in some places,
approaching 1m times more, he said.

While methane may be toxic to various marine organisms, one of the
focuses of Kessler’s research is investigating if the high concentration
of methane could lead to a feeding frenzy by marine microorganizations
that feed on this hydrocarbon, depleting the oxygen in the area and
creating a dead zone.

“There are some drawdowns in oxygen,” Kessler said. “It’s
significant; we notice it. It’s there.”

But whether it will increase enough to cause a dead zone remains to
be seen, he said, with significant factors being how high the
concentrations of methane will get and how long they will remain at
these enhanced levels.

With BP siphoning increasing amounts of hydrocarbons to the surface,
there are hopes the amount gushing into the Gulf is on a decline. That
said, the leak is expected to continue until the UK company can complete
at least one of the two relief wells it is drilling to intersect the
leaking well and plug it up. BP is hoping that will be in late July or
August.

The National Oceanic and Atmospheric Administration, the US
Environmental Protection Agency and the White House Office of Science
and Technology Policy said in its first peer reviewed, analytical
summary report about subsea monitoring that “dissolved oxygen levels
remained above immediate levels of concern.” But it added, “There is a
need to monitor dissolved oxygen levels over time.”

The Gulf of Mexico already is home to one of the world’s biggest dead
zones - averaging about 17,000 square kilometres, the size of Lake
Ontario, over the past five years, according to the Louisiana
Universities Marine Consortium.

But researchers do not know if the site of the spill - more than 100
miles from shore - will link up with the one they have been watching
over the years. That long-studied dead zone is close to shore, in
shallower water, where the Mississippi River drains, over-enriching the
waters with nutrients that lead to an abundance of algae that consumes
all the oxygen in the water so that it can no longer support marine
life.

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