[R-G] 'Slime highway' of BP oil suspected on Gulf floor
menecraj at shaw.ca
Tue Sep 14 08:30:32 MDT 2010
'Slime highway' of BP oil suspected on Gulf floor
Fluffy residue found at various sites both far from and near wellhead
msnbc.com staff and news service reports updated 9/13/2010
Samples taken from the seafloor near BP's blown-out wellhead indicate miles
of murky, oily residue sitting atop hard sediment. Moreover, inside that
residue are dead shrimp, zooplankton, worms and other invertebrates.
"I expected to find oil on the sea floor," Samantha Joye, a University of
Georgia marine sciences professor, said Monday morning in a ship-to-shore
telephone interview. "I did not expect to find this much. I didn't expect to
find layers two inches thick."
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scientists aboard the research vessel Oceanus suspect it's all from the BP
spill, but will have to wait until they return to shore this week to confirm
it's the same oil source.
"It has to be a recent event," Joye said. "There's still pieces of warm
If it is BP oil, it could undermine the federal government's estimate that
75 percent of the spill either evaporated, was cleaned up or was consumed by
What the scientists do already know is that the oil is not coming naturally
from below the surface.
"What we found today is not a natural seep," Joye wrote in her blog --
http://gulfblog.uga.edu/2010/09/focusing-in-on-oil/ -- on Sept. 5 when the
first surprise sediment was found.
"The near shore sediments contained grayish muddy clay and a thin layer of
orange-brown oil at the surface," she added. Oil seeping naturally would
create an oily stain throughout the sediment cores, but these samples only
had oil at the top.
"The oil obviously came from the top (down from the water column) not the
bottom (up from a deep reservoir)," Joye wrote.
'Slime highway' The researchers also have a name for it: a slime highway.
That's because they're confident much of the oil was trapped by mucus coming
from microbes that feast on oil in a natural process that helps break up the
contaminant. Those microbes are well documented, but not that their mucus
was sinking along with oil to the seafloor.
"The organisms that break down oil excrete mucus - copious amounts of
mucus," Joye told National Public Radio. "So it's kind of like a slime
highway from the surface to the bottom. Because eventually the slime gets
heavy and it sinks."
Another factor that could be trapping the oil was the earlier use of
chemical dispersants, which might have made the oil so small that it wasn't
buoyant enough to rise.
Joye wrote that the scientists call the substance "'oil aggregate snow' -
because it settled down the water column to the seafloor just like snow
falls from the sky to the ground."
"If you take a close look at the snow layer, oil aggregates are clearly
visible," she added. "Also visible are pteropod shells (which must have been
recently deposited because the shells dissolve rapidly) and remnants of
zooplankton (skeletons) and benthic infauna (dead worms and their tubes)."
The researchers took new samples on Monday and Sunday, and hope to take
several more, especially closer to the wellhead, before they return.
"It's weird the stuff we found last night," Joye said. "Some of it was
really dense and thick."
The samples have come from seafloors at depths ranging from 300 to 4,000
Since the well was capped on July 15, and after some 200 million gallons
flowed into the Gulf, there have been signs of resilience on the surface and
the shore. Sheens have disappeared, while some marshlands have shoots of
green. This seeming recovery is likely a result of massive amounts of
chemical dispersants, warm waters and a Gulf that is used to degrading
massive amounts of oil, scientists say.
Animal deaths also are far short of worst-case scenarios. But at the same
time, a massive invisible plume of oil has been found under the surface,
shifting scientists' concerns from what can be easily seen to what can't be.
For Ian MacDonald, a Florida State University biological oceanographer who
wasn't part of Joye's team, the latest findings confirm that government
assessments about how much oil remains - especially a report on the subject
by the National Oceanic and Atmospheric Administration in August - were too
The oil "did not disappear," he said. "It sank."
Some skeptics Not all scientists agree with this assessment.
Ed Overton, a Louisiana State University chemist who has analyzed the spill
for NOAA, doubted much oil was resting on the bottom. He said the heavier
components in oil - the asphalts - make up only about 1 percent of the oil
that was spilled.
And Roger Sassen, an organic geochemist at Texas A&M University who has
studied natural oil seeps, said so much oil seeps naturally into the Gulf
each year that it's hard to argue that the BP spill will make a significant
Nonetheless, the big questions now are exactly how much oil is at the bottom
and how many organisms are being exposed to it, said Robert Carney, an
oceanographer and deep-sea expert at Louisiana State University. The answers
to those questions could shed some light on the unseen damage to wildlife
from the oil spill.
"Deep-sea animals, in general, tend to produce fewer offspring than
shallower water animals, so if they are going to have a population impact,
it may be more sensitive in deep water," he said. "There is also some
evidence that deep-sea animals live longer than shallower water species, so
the impact may stay around longer."
At first, scientists, the media and the federal government focused their
attention on tracking rainbow sheens approaching land, tar balls hitting
beaches, measuring oil in marshes and scouting for oiled birds and sea
turtles. But a spate of recent studies increasingly points to the deep.
NOAA's Aug. 4 pronouncement that the oil was mostly gone also indicated that
some 53 million gallons remained in the Gulf. At the time, federal officials
said some of that could be on the sea floor, adding that the rest was mostly
broken down naturally or by the widespread use of chemical dispersants.
"As we get into weathered oil, there is more likelihood that it will get
into the sediment" on the seafloor, said Steve Murawski, chief scientist at
the National Marine Fisheries Service, a division of NOAA.
Getting a handle on where the oil is at extreme depths will not be easy.
Scientists will have to use expensive 1,000-pound devices that look like
moon landers. The spindly legged machines land on the bottom and shoot tubes
into the sea floor to collect 20-inch-long samples.
The terrain is exceedingly difficult. The area where the busted BP well sits
is on the continental slope, formed by millions of years of deposits from
the Mississippi River. It's a region of bumps and valleys, salt domes,
canyons and slopes.
Government scientists acknowledge they've not done enough to look for oil in
the obscure corners of the Gulf's bottom, but promise to do a better job.
Joye's latest discovery backs up the findings of a University of South
Florida crew that reported pulling up oily sediment in August.
The Associated Press contributed to this report.
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