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<h1>While Oil Gently Seeps from the Seafloor </h1>
<h2>Oil naturally leaking into the ocean offers a 'laboratory' to
study accidential spills</h2>
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This illustration shows the route traveled by oil leaving the
subseafloor reservoir as it travels through the water column to the
surface and ultimately sinks and falls out in a plume shape onto the
seafloor where it
remains in the sediment. (Illustration by Jack Cook, Woods Hole
Oceanographic Institution)</td>
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Oil and methane bubble to the ocean's surface from natural seeps off
Coal Oil Point, near Santa Barbara, California. (Photo courtesy of Dave
Valentine, UCSB)</td>
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Two-dimensional
gas chromatograms show how many compounds were in the oil at the ocean
surface (top) and how few compounds remain in
the sediments (bottom) after parts of the oil dissolved into the water,
evaporated into the air, or were degraded by microbes. (Chromatogram by
Bob Nelson, Woods Hole Oceanographic Institution)</td>
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UCSB's Dave Valentine, left, and WHOI's Chris Reddy. (Photo by Julia
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Researchers
found that the total petroleum hydrogen (TPH) content in sampling
locations (dots) was highest in sediments closest to the seeps and
gradually diminished over distance as it was dispersed by currents—much
the way smoke trails away in the wind.
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<p class="caption">» <a
href="http://www.whoi.edu/page.do?pid=7545&tid=282&cid=57286&ct=162"
class="caption">Natural Petroleum Seeps Release Equivalent of 8 to 80 <em>Exxon
Valdez</em> Oil Spills</a><br>
Media Release<br>
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<p class="caption">» <a
href="http://www.whoi.edu/hpb/Site.do?id=621" class="caption">Chris
Reddy's Lab</a><br>
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<p class="caption">» <a
href="http://www.coastalresearchcenter.ucsb.edu/cmi/Valentine.html"
class="caption">Dave Valentine's Lab</a><br>
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<p class="caption">» <a
href="http://www.whoi.edu/oceanus/viewArticle.do?id=2493"
class="caption">Mixing Oil and Water </a><br>
from <em>Oceanus</em> magazine<br>
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<p class="caption">» <a
href="http://www.whoi.edu/page.do?pid=9779&tid=282&cid=51366&ct=162"
class="caption">Study Reveals Microbes Dine of Thousands of Compounds
in Oil</a><br>
Media Release<br>
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<p class="caption">» <a
href="http://pubs.acs.org/doi/abs/10.1021/es802586g" class="caption">Weathering
and the Fallout Plume of Heavy Oil from Strong Petroleum Seeps Near
Coal Oil Point, CA</a><br>
from <em>Environmental Science & Technology</em> (subscription
required)<br>
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<p class="name-aff">Christopher Reddy<br>
Director<br>
Coastal Ocean Institute<br>
Woods Hole Oceanographic Institution</p>
<br>
I
investigate what happens to oil spilled into the ocean—with an eye
toward finding better ways to “engineer” cleanups. But the brass ring
has always hung out of my reach. When oil hits the water, chemical
changes start occurring fast. It’s not like I can predict where or when
an accidental spill is going to occur, so I usually can’t get to spills
fast enough. I literally and figuratively miss the boat. <br>
<br>
When the <em>M/V Cosco Busan</em> struck the San
Francisco-Oakland Bay Bridge in November 2007 and spilled 58,000
gallons of heavy fuel oil, for example, I had to mobilize
singlehandedly to get plane tickets, transport scientific gear, outline
a plan to take samples, and arrange for a boat. <br>
<br>
In the immediate aftermath of an oil spill, rapid response teams have
their hands full with their primary mission of preventing more spillage
and mitigating the damage. They aren’t in the business of sampling and
studying oil. It took me a week to get on the scene, and during those
precious seven days, nature already had moved the oil and changed its
chemical composition. What happened to the oil in those seven days?<br>
<br>
“Oil,” you see, is actually a motley stew made up of thousands of
different compounds—each with distinctive chemical structures that give
them distinct properties. When oil spills into the ocean, some
compounds evaporate, while others break down in sunlight, or dissolve
in seawater, or get eaten by microbes, or sink and stick to sediments.
By the time I arrived, I had missed half the action. I could not
explain what happened and why with much certainty. <br>
<strong><br>
An oil spill every day </strong><br>
But I got a break in January 2005. I was aboard a 20-foot motorboat a
mile offshore from the campus of the University of California at Santa
Barbara (UCSB) with my colleague, Dave Valentine, a UCSB marine
geochemist. The water was calm and flat—dampened by a widespread,
iridescent film of oil on the surface. Big oil patties floated about.
The air smelled like diesel fuel.<br>
<br>
By any definition, it was a classic oil spill. But we were the only
boat in the area—no Coast Guard, no oil booms, no throngs of cleanup
crews in white Tyvak suits, no helicopters, no media, and no shipwreck.<br>
<br>
Why? Because this oil spill was entirely natural. The oil had seeped
from reservoirs below the seafloor, leaked through cracks in the crust
about 150 feet (45 meters) under water. Lighter than seawater, the
escaped oil floated to the ocean surface. <br>
<br>
It was one of those days in your career that you never forget.
Adrenaline raced through my body, and my brain was in overload,
thinking about the research that could be done at this site. Nature was
offering an ongoing experiment that was impossible (not to mention
illegal) for me to perform. Off Santa Barbara, there’s an oil spill
every day, allowing us to take a close look at a process that
previously eluded our grasp.<br>
<br>
I vividly remember standing on the boat and calling my lab manager, Bob
Nelson, telling him to book a plane ticket and pack a long list of
gear. We returned days later to start investigating the fate of oil in
the coastal ocean, using this readily accessible natural laboratory. <br>
<br>
<strong>Following an oily trail </strong><br>
I had learned about natural oil seeps in graduate school, and I knew
that they account for about 50 percent of oil that ends up in the
coastal environment. That’s five times as much oil as is delivered by
accidental spills. <br>
<br>
The Santa Barbara seeps, for example emit 5,280 to 6,600 gallons
(nearly 20 to 25 tons) of oil per day, and natural seeps have been
active for hundreds to thousands of years. Local Native Americans used
the oil to waterproof their boats. But I just didn’t appreciate how
spectacular they were and what a powerful opportunity they provided to
study oil spills. <br>
<br>
In our initial research, Dave and his scuba-diving team collected
bubbles of oil that trail out in a line from a seafloor seep (we call
these “stringers”). We compared this oil with samples extracted from a
nearby offshore drill rig, which tapped into the same reservoir that
leaked oil out of the seafloor seeps. <br>
<br>
We analyzed the specimens using a technique called “comprehensive
two-dimensional gas chromatography (GC×GC).” The instrument reveals
distinct chemical “biomarkers” in the oil, which like genetic markers
allow us to track the oil’s source and lineage. It also lets us
identify and differentiate the thousands of compounds that oil is
composed of. <br>
<br>
To our surprise, we discovered for the first time that on the oil’s
journey up to the seafloor, approximately 1,000 compounds in the oil
were devoured by microbes living in the rocks beneath the sea floor.
Some ate the oil and created intermediate byproducts. These were
subsequently eaten by other microbes that likely converted the oil into
natural gas. <br>
<br>
We also compared the compounds in oil seeping out of the seafloor with
those in oil at the sea surface. We discovered that about 10 percent of
the remaining compounds in the oil evaporated within seconds or minutes
after it had floated to the surface. That was something we had never
been quick enough on the scene to measure before in accidental spills. <br>
<br>
With UCSB graduate student George Wardlaw as lead author and three
other co-authors, we reported our findings in the October 2008 issue of
<em>Environmental Science & Technology</em>. <br>
<br>
Then it was on to the next steps—tracking how much oil at the surface
sank back into the mud atop the seafloor. <br>
<strong><br>
The fallout from the seeps </strong><br>
In the summer of 2007, we brought in a boat quite a bit bigger than the
little motorboat we used in 2005—Woods Hole Oceanographic Institution's
(WHOI) 274-foot-long research vessel <em>Atlantis</em>, the mother
ship for the research submarine <em>Alvin</em>. The two usually work
in the deep ocean, but this time <em>Alvin</em> dove to only a
fraction of its 4,500-meter depth capacity, allegedly setting a record
for its shallowest science dive ever. <br>
<br>
We used <em>Alvin</em> to observe spectacular shows of oil and gas
seeping and bubbling up from cracks at the ocean bottom. And one
evening after <em>Alvin</em> surfaced for the night, I, Dave, and
Chris Farwell, a UCSB undergraduate student at the time (and my cabin
mate aboard <em>Atlantis</em>) began collecting samples of sediments
starting 2.2 nautical miles (4 kilometers) downstream of the oil seeps.<br>
<br>
We sampled 16 locations with various water depths over a 35-square-mile
(90-square-kilometer) grid, with an additional comparison sample
obtained from within the seep field itself. I tip my hat to Capt. A.D.
Colburn, the <em>Atlantis </em>crew,
and shipboard technician Dave Sims for making this sampling effort so
seamless in shallow coastal waters in which they don’t typically work.
We finished as the sun was rising and the <em>Alvin</em> group was
preparing the submarine for another dive.<br>
<br>
After the cruise, under Dave’s (and occasionally my) direction, Chris
began a thorough study on these samples. He came to Woods Hole for a
week, staying with me and my wife Bryce and working in my lab. (To earn
his keep, I made him scrape wallpaper in our house.) <br>
<br>
Chris found plenty of oil in the samples to keep him busy. Once again,
biomarkers revealed by GC×GC showed that the oil in the sediments
matched the oil floating on the sea surface, the oil leaking out of the
seeps, and the oil extracted from the subseafloor reservoir. We could
say with confidence that the oil we found in the sediments came from
the oil reservoir and not from an accidental spill or runoff from land.<br>
<br>
In collaboration with Libe Washburn, a physical oceanographer at UCSB,
Dave and Chris estimated that oil on the surface stayed in the water
from about 10 hours to five days before settling back into the
sediments. Chris’s study revealed that the oil content was highest in
sediments closest to the seeps and gradually diminished over distance
as it was dispersed by currents—much the way smoke trails away in the
wind.<br>
<br>
At WHOI, Bob Nelson and Emily Peacock found that the composition of the
oil in the sediments had changed significantly from what we had found
floating in the ocean surface; only a few, very large chemical
compounds remained in the sediments. Our findings were published in the
May 2009 issue of <em>Environmental Science & Technology. </em><br>
<br>
<strong>Munching microbes</strong><br>
Nature had done an amazing job on the oil, but nature appears to have a
limit on its capacity to break down oil. Why this happens is one of my
keen research interests. We think the compounds in the sediments have
remained because their bulky structures make them hard to evaporate,
insoluble in water, and more difficult for microbes to digest. <br>
<br>
Microbes are astonishing and voracious little critters. They can eat
almost anything, but our research at the Santa Barbara oil seeps shows
they do it systematically: They select compounds whose size and shape
are the easiest for them to degrade. So they will chow down on a
simple, straight-chained alkane, but will avoid a hopane with twice as
many carbon and hydrogen atoms bonded in rings that offer difficult
access for enzymes. If they were at a buffet, they would devour the
pudding, soup, and rice first and eschew the chewy corned beef and
stale crusty bread. <br>
<br>
Another result of our study is that for the first time, we can quantify
the amount of oil residue that ends up in seafloor sediments after a
“natural” oil spill. To compare the amount the oil in the Santa Barbara
sediments with a figure people might understand, it's equivalent to 8
to 80 times the oil spilled in the <em>Exxon Valdez</em> accident. But
our study by no means is a direct comparison on the overall fate and
impacts of the <em>Exxon Valdez</em> spill and the Santa Barbara seeps.<br>
<br>
That estimate is as close as we could get, since we don’t know how
thick the layer of sediments is. But before this research, for all we
knew, it could have been the equivalent of 0.0001 or 10,000 <em>Exxon
Valdez</em> spills. <br>
<br>
Many people in the Santa Barbara region still believe that oil found in
the ocean and on nearby beaches comes from oil rigs, but our research
points the finger at the natural oil seep. At the same time, this
natural oil seep is teaching us many extraordinary lessons about how
oil responds in our ecosystem. And that offers better strategies for
people to respond to the oil they spill accidentally into our
ecosystems.<br>
<br>
<em><br>
This research was funded by the National Science Foundation, the U.S.
Minerals Management Service, the California Toxic Substance Research
and Training Program, the Department of Energy, the WHOI Coastal Ocean
Institute, and the Seaver Institute.</em><br>
<pre class="moz-signature" cols="72">--
Shauna Bingham
Volunteer and Outreach Coordinator
NOAA Channel Islands National Marine Sanctuary
3600 S. Harbor Blvd. #111
Oxnard, CA 93035
<a class="moz-txt-link-abbreviated" href="mailto:Shauna.Bingham@noaa.gov">Shauna.Bingham@noaa.gov</a>
(805) 382-6149 ext. 102
Fax (805) 382-9791
<a class="moz-txt-link-freetext" href="http://channelislands.noaa.gov">http://channelislands.noaa.gov</a>
´¯`·.¸¸..><((((º>·´¯`·.¸¸..><((((º>·´¯`·.¸¸..><((((º>·´¯`·.¸¸..
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