[CINC] Oceanus Magazine: Article on SB Oil Seeps

Mon May 18 11:25:37 PDT 2009

http://www.whoi.edu/oceanus/viewArticle.do?id=57272&sectionid=1021

  While Oil Gently Seeps from the Seafloor

    Oil naturally leaking into the ocean offers a 'laboratory' to study
    accidential spills

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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)
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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)
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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)
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UCSB's Dave Valentine, left, and WHOI's Chris Reddy. (Photo by Julia 
Vraspir)
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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.
	Related Multimedia

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» View Slideshow 
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	Related Links

» Natural Petroleum Seeps Release Equivalent of 8 to 80 /Exxon Valdez/ 
Oil Spills <http://www.whoi.edu/page.do?pid=7545&tid=282&cid=57286&ct=162>
Media Release

» Chris Reddy's Lab <http://www.whoi.edu/hpb/Site.do?id=621>

» Dave Valentine's Lab 
<http://www.coastalresearchcenter.ucsb.edu/cmi/Valentine.html>

» Mixing Oil and Water <http://www.whoi.edu/oceanus/viewArticle.do?id=2493>
from /Oceanus/ magazine

» Study Reveals Microbes Dine of Thousands of Compounds in Oil 
<http://www.whoi.edu/page.do?pid=9779&tid=282&cid=51366&ct=162>
Media Release

» Weathering and the Fallout Plume of Heavy Oil from Strong Petroleum 
Seeps Near Coal Oil Point, CA 
<http://pubs.acs.org/doi/abs/10.1021/es802586g>
from /Environmental Science & Technology/ (subscription required)

Christopher Reddy
Director
Coastal Ocean Institute
Woods Hole Oceanographic Institution

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.

When the /M/V Cosco Busan/ 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.

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?

"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.
*
An oil spill every day *
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.

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.

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.

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.

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.

*Following an oily trail *
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.

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. 

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.

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.

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.

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.

With UCSB graduate student George Wardlaw as lead author and three other 
co-authors, we reported our findings in the October 2008 issue of 
/Environmental Science & Technology/.

Then it was on to the next steps---tracking how much oil at the surface 
sank back into the mud atop the seafloor.
*
The fallout from the seeps *
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 /Atlantis/, the 
mother ship for the research submarine /Alvin/. The two usually work in 
the deep ocean, but this time /Alvin/ dove to only a fraction of its 
4,500-meter depth capacity, allegedly setting a record for its 
shallowest science dive ever.

We used /Alvin/ to observe spectacular shows of oil and gas seeping and 
bubbling up from cracks at the ocean bottom. And one evening after 
/Alvin/ surfaced for the night, I, Dave, and Chris Farwell, a UCSB 
undergraduate student at the time (and my cabin mate aboard /Atlantis/) 
began collecting samples of sediments starting 2.2 nautical miles (4 
kilometers) downstream of the oil seeps.

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 /Atlantis /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 /Alvin/ group was preparing the submarine for another dive.

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.)

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.

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.

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 /Environmental Science & Technology. /

*Munching microbes*
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.

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.

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 /Exxon Valdez/ accident. But our study 
by no means is a direct comparison on the overall fate and impacts of 
the /Exxon Valdez/ spill and the Santa Barbara seeps.

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 /Exxon Valdez/ spills.

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.

/
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./

-- 
Shauna Bingham 
Volunteer and Outreach Coordinator
NOAA Channel Islands National Marine Sanctuary
3600 S. Harbor Blvd. #111
Oxnard, CA 93035
Shauna.Bingham at noaa.gov
(805) 382-6149 ext. 102
Fax (805) 382-9791
http://channelislands.noaa.gov

´¯`·.¸¸..><((((º>·´¯`·.¸¸..><((((º>·´¯`·.¸¸..><((((º>·´¯`·.¸¸..

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