Gulf’s Complexity and Resilience Seen in Studies of Oil Spill

[GLT]

Gulf’s Complexity and Resilience Seen in Studies of Oil Spill
Erik S. Lesser/European Pressphoto Agency


In the year since the wellhead beneath the Deepwater Horizon rig began
spewing rust-colored crude into the northern Gulf of Mexico,
scientists have been working frantically to figure out what
environmental harm really came of the largest oil spill in American
history.

What has emerged in studies so far is not a final tally of damage, but
a new window on the complexities of the gulf, and the vulnerabilities
and capacities of biological systems in the face of environmental
insults.

There is no doubt that gulf water, wildlife and wetlands sustained
injury when, beginning on April 20 last year, some 4.9 million barrels
of oil and 1.84 million gallons of dispersants poured into the waters
off Louisiana. But the ecosystem was not passive in the face of this
assault. The gulf, which experiences a natural seepage of millions of
gallons of oil a year, had the innate capacity to digest some of crude
and the methane gas mixed with it. Almost as soon as the well was
capped, the deep became cleaner to the eye. By the same token, dozens
of miles of marsh still remain blackened by heavy oil, government
crews are still grooming away tar balls that wash up ceaselessly on
beaches and traces of the dispersants are still found floating in the
currents.

Biologists are nervously monitoring as yet unexplained dolphin
strandings this year, trying to come up with a realistic count of
birds and mammals killed during the spill and working to understand
what happens when the gulf floor is covered with the remains of oil-
eating bacteria. “It is really kind of hard to get a grasp of the big
picture, and it is not for a lack of trying,” said Christopher Reddy,
a senior scientist at the Woods Hole Oceanographic Institution who
studies long-term consequences of oil spills. “Hundreds of scientists
are working day and night trying to carve out a piece of that giant
puzzle, but it is an entire region and it is complicated.”

How the regional ecosystem has responded, its strengths and
weaknesses, will keep scientists busy analyzing data for years and
help them in understanding the effects of environmental disasters.

An Army in Hot Pursuit

After an oil spill, the government is responsible for toting up the
ecological damages in something called a Natural Resource Damage
Assessment. The document, which requires battalions of researchers,
makes the case for damages that the companies responsible for the
spill should pay to restore the ecosystem to its pre-spill health. The
companies hire their own teams of assessors, who might paint a very
different picture. The two sides settle or go to court.

At of the end of January, the government said its scientists alone had
taken 35,000 images, walked more than 4,000 miles of shoreline and
culled more than 40,000 samples of water, sediment and tissue.

The scientists are also testing how to estimate what they can’t count
precisely, like animal deaths. One group of evaluators is scattering
bird carcasses offshore and measuring how many sink and how many wash
ashore. Those numbers will be used to calculate how many birds may
have died in addition to the ones that were found and counted.

For all this effort, it will take time for some of the consequences to
manifest themselves. It was three years after the Exxon Valdez spill
in Prince William Sound in Alaska, for example, that the herring
fishery suddenly collapsed.

During the Deepwater Horizon disaster, as the slick was spreading, the
federal Fish and Wildlife Service moved about 28,000 eggs from
turtles’ nests on at-risk beaches in Alabama to the coast of Florida.
While 51 percent of the eggs hatched — roughly consistent with normal
survival rates— it will be another two decades or so before the
hatchlings that survive come back to Florida as adults to lay eggs.
Only then will anyone know how successful the rescue effort really
was.

Many of the results that have been gained so far, by government or
private industry, are not yet public; they are awaiting rigorous
review before eventual release. Moreover, in some key cases,
scientists must keep their findings confidential because of continuing
legal actions.

“We have a real responsibility to make sure that we come out of this
process with as much compensation as is appropriate for the damages,”
said Bob Haddad, chief of the assessment and restoration division of
the National Oceanic and Atmospheric Administration, which is taking
the lead in coordinating the damage assessment. “I don’t want to get
tripped on issues like inadmissibility of evidence.”

Oil and Water Do Mix

Still, there has been some independent scientific work done in the
gulf, and it has produced some good news. Because the spill occurred
at very high pressure a mile beneath the ocean’s surface, some of the
oil was reduced to tiny droplets that remained suspended thousands of
feet deep in a fine mist.

Terry C. Hazen, who leads the ecology department at Lawrence Berkeley
National Laboratory, took 170 samples from around the Deepwater
Horizon between July 27 and Aug. 26 last year, just weeks after the
wellhead was capped.

Dr. Hazen was looking to track the fate of the underwater oil as it
spread and instead found it to be entirely gone. “We can detect down
to 2 parts per billion,” he said, “but nothing was there.”

His work was financed by a grant his lab won from BP, the owner of the
well, long before the spill, and it was not in any way reviewed or
influenced by the company, he said.

The results showed that the oil had not just been diluted with water
but that it had largely been eaten by naturally occurring bacteria.
Researchers worried early on that such bacteria might not exist
thousands of feet down or that the process of digestion might be
particularly slow because of colder temperatures at these depths. But
Dr. Hazen’s group found bacteria that specialized in oil eating in
frigid temperatures.

Another byproduct of the spill was roughly 200,000 metric tons of
methane gas. In June 2010 there was as much as 100,000 times as much
methane dissolved gas in the gulf as normal. Scientists worried that
it could remain dissolved in the water column, depleting oxygen
levels, for years.

But by fall, researchers from the University of California, Santa
Barbara, and Texas A&M took water samples from 207 sites near the
spill and found that methane proportions were back to normal.

John Kessler, an oceanographer at Texas A&M, said: “It appeared that
the methane would be present in the gulf for years to come. Instead,
methane respiration rates increased to levels higher than have ever
been recorded.”

In other words, bacteria ate it. Other scientists, however, are not
convinced. Samantha B. Joye, a professor of marine science at the
University of Georgia, said her team found elevated methane levels at
exactly the time Dr. Kessler’s team did not.

Further, at a recent meeting of the American Association for the
Advancement of Science, Dr. Joye said that the digestion of the oil
and methane had not been entirely benign. Her team took sediment
samples in a roughly 35-square-mile area at several different times,
most recently in December, and found the muddy gulf floor covered with
a blanket of dead bacteria, much of it oily and sticky. At every one
of the sites she sampled, she said, bottom-dwelling invertebrates —
worms, starfish, even coral — were dead.

“These are keystone species to the ecosystem,” she said, “and we don’t
know what will happen without them.”

Her findings have been substantiated in part by Charles Fisher, a
biologist at Pennsylvania State University, who has documented dead
fan corals seven miles from the wellhead, probably killed by oil
plumes in the deep sea, Dr. Fisher said. “Fan corals live for
hundreds, perhaps hundreds of thousands of years,” he said. “The odds
that something beside the oil from the spill killed them are
vanishingly small.”

Dispersants in Diaspora

The fate of some 1.84 million gallons of dispersant poured into the
gulf to get the oil to break into smaller pieces and thus degrade more
quickly is less definitive than what happened to the oil and methane.
Some 770,000 gallons were applied to the wellhead itself.

Dispersants have toxic elements, and at the time critics of the
application saw it as a gigantic unregulated experiment.

The Environmental Protection Agency has now done extensive testing on
the most commonly used dispersant, Corexit 9500, mixed with Louisiana
crude and found it to be no more or less toxic to marine life than
eight other alternative dispersants or than the oil alone. The E.P.A.
administrator, Lisa P. Jackson, said that not only was the toxicity of
the dispersants evaluated, so was their effectiveness. “The chemicals
helped break up the oil,” Ms. Jackson said in a recent interview. “It
was the right decision to use them.”

That doesn’t mean the dispersants were harmless, however. Elizabeth
Kujawinski, an associate scientist in chemistry at Woods Hole, was
able to track dispersants using highly sensitive tests. Dr. Kujawinski
found that while they have become diluted, they are “not entirely
biodegraded or decomposed.”

In other words, she said, they remain in the gulf, but in amounts that
the government does not consider dangerous.

“Toxicity looks at acute exposure — huge concentration, and then you
are done,” she said. “But in case of the Deepwater Horizon it was low
concentrations, but over a long period of time. We don’t know about
how this affects living creatures in the deep water that can’t move,
like corals.”

Death, Sudden and Otherwise

During the spill, the daily tallies of birds, turtles and sea mammals
found dead or alive and covered in oil were heartbreaking. They were
also just a beginning.

For every pelican or whale found beached or floating at sea, some much
larger number died. After the Exxon Valdez accident, 30,000 birds were
found, but 250,000 — eight times the number found — were eventually
estimated to have been killed by the oil. Each situation is different,
and scientists are trying to pin down the so-called death multipliers
for this spill.

Looking at annual carcass recovery rates for 14 groups of cetaceans —
the mammal group that includes whales and dolphins — a group of
biologists from the University of British Columbia recently said that
the multiplier for that group should be around 50. So although 115
cetaceans were found dead or stranded during the spill and in the
months immediately after, they might represent 5,000 actual deaths.

Melanie Driscoll, director of bird conservation in the gulf for the
National Audubon Society, said similar multipliers may need to be
applied to 8,000 birds so far discovered by the government, especially
in a category known as secretive marsh birds. “They already hide in
dark grasses naturally, so they were certainly missed,” Ms. Driscoll
said.

Some species may, however, have done better than it seemed at first.
Jim Franks, a fisheries professor from the University of Southern
Mississippi Gulf Coast, has been monitoring larvae of bluefin tuna.
While he says oil did affect some of their spawning grounds, it spared
some as well. Dr. Franks refuses to say what percentage of larvae
might have been killed, but it certainly was not a total wipeout, as
had been feared.

Plant life also suffered from the spill. Marshes in Bay Jimmy, south
of New Orleans, were hit particularly hard and remain coated in heavy
oil. Unknown amounts of pollution lay buried in the nearby sediments
as well. Federal monitors are watching these areas now to see if new
grasses come through the oiled ones this spring, or if it may be
necessary to burn off some of the old, oiled growth.

In addition, professors at the Northern Gulf Institute at Mississippi
State University and Jackson State University combined field
observation and satellite imagery to estimate injury to marsh areas
beyond those that were obviously still oiled. Their preliminary
findings indicate 2010 to be an anomalous year.

Looking at the normal marsh growing season from June to October 2010
and comparing it with 2009, a year with similar conditions besides the
oil spill, they found a significant spike in the amount of marsh that
was brown. It was up to 150 square miles, from about 25 to 30 square
miles. The part of the marsh that borders the open water is risk of
dying and being subsumed by the sea.

And there are the deaths yet to come. In February 59 dolphins were
founded stranded or dead on northern gulf beaches; 36 were premature
or stillborn babies. That was nine times the average number that were
found in the years 2002 through 2009. Dolphins began dying before the
oil spill; 56 were stranded in March 2010. But the spike in neonatal
dolphin deaths is new this year.

“Yes, their mothers were very likely in gestation during the spill,”
said Blair Mase, a marine mammal stranding coordinator with the
National Oceanic and Atmospheric Administration, “and exposure to
petroleum in mammals can cause decreased success in keeping young.”

But, Ms. Mase said, there could be other causes. For example, the
dolphins may be fighting a virus that appeared before the spill, but
is more dangerous because the exposure to oil has weakened the
dolphins’ immune systems.

As with so many of the effects of the spill, said Ms. Mase “right now
we cannot say for sure.”

http://www.nytimes.com/2011/04/12/science/12spill.html?_r=1&hp=&pagewanted=all