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"Sea Snot" Explosion Caused by Gulf Oil Spill?
Christine Dell'Amore National Geographic News
Published September 23, 2010
The Gulf of Mexico oil spill sparked an explosion of sticky clumps of organic matter that scientists
call sea snot, according to ongoing research.
The boom likely precipitated a sea-snot "blizzard" in Gulf waters, researchers say. And as the
clumps sank, they may have temporarily wiped out the base of the food chain in the spill region by
scouring all small life from the water column.
In the weeks after the April 20 Deepwater Horizon oil rig explosion, scientists surveying the surface near
the drill site spotted relatively huge particles—several centimeters across—of sea snot.
These particularly slimy flakes of "marine snow" are made up of tiny dead and living organic matter,
according to Uta Passow, a biological oceanographer at the University of California, Santa Barbara.
Tiny plants in the ocean called phytoplankton produce a mucus-like substance when stressed, and it's
possible that exposure to the Deepwater Horizon oil caused them to pump out more of the sticky stuff
than usual.
This abundance of "mucus" made the naturally occurring marine-snow particles—usually about a few
millimeters wide—even stickier.
"Everything they collide with in their path they collect and take with them," said project leader Passow,
who's currently tracking marine snow aboard the research vessel Oceanus.
Sea Snot Spurred Marine "Snowfall"?
Based on surface observations and oily layers of dead plankton found on the seafloor, the researchers
believe the sticky particles may have plummeted to the bottom of the ocean in a marine-snow "blizzard"
around the Deepwater Horizon site in May. Passow cautioned, though, that no one actually witnessed the
snowstorm.
In the lab Passow and colleagues are working to reproduce the marine-snow conditions that might have
spawned the "huge, slimy" event, she said.
One simulation found that month-old marine snow would have sunk to the seafloor relatively fast—
sinking hundreds of yards a day, compared with an average marine-snow sinking rate of 115 feet (35
meters) a day.
It's unknown why the material would have sunk so fast, Passow said. But it's possible the oil killed so
many of the ocean's tiny floating organisms that the snow became abnormally heavy and so fell quicker
than usual.
That heft may also explain why Passow and colleagues are finding so much new sea snot in the seafloor
traps that they check every 36 hours—though nothing approaching the levels collected during the May
snowstorm.
Recent observations by the team—including Vernon Asper and Arne Diercks of the University of
Southern Mississippi—show no evidence of unusually voluminous sea snot at the surface nearly five
months later, Passow noted.
The sea snot explosion, it seems, has come and gone, though its effects may linger. The sea snot blizzard
"probably will have a long-term impact," Passow said—though exactly how the blizzard will affect the
Gulf is anyone's guess.
Sea Snot May Have Created Deadly Void
The possible long-term impact of the blizzard stems in part from its potential to starve or poison marine
creatures.
By sinking en masse, the marine snow may have deprived fish larvae of a crucial food source—the
phytoplankton itself. When fish larvae hatch, they have less than a day to find sustenance or they'll starve,
Passow noted.
On the Gulf seafloor, the sticky "snowstorm" may have killed bottom dwellers.
In addition to being perhaps suffocatingly large, the blizzard may have been toxic. Scientists have found
tiny black dots in sediment traps near the BP spill site that—if confirmed as oil from the Gulf spill—
suggest tarballs got swept up in the snowstorm.
Normally, dead organisms settling on the seafloor are free meal deliveries for animals living at depth.
"But when it's oil-soaked particles, I suspect the bottom-dwelling organisms might not be so happy,"
marine-snow expert Alice Alldredge said.
Likewise, if tarballs were indeed caught up in the marine snow, their toxicity may be killing off various
life-forms that hitchhike along with pockets of marine snow—each drifting pocket is usually a "hot spot
of activity," project leader Passow said.
In any case, the true toll of the blizzard may remain a mystery in the short term.
Since many fish species mature slowly, for example, it will take a few years to determine whether the oily
snowstorm caused a lost generation of certain species, said Alldredge, of the University of California,
Santa Barbara, who was not involved in the research.
Likewise, the Gulf, in general, may take a while to fully recover. "Humans tend to want things to be fixed
right away," she said, "and nature takes a little longer."
Sea Snot May Yield Giant Blobs of Mucus?
The addition of oil may cause the sea snot to coalesce into giant blobs called marine mucilage, which can
grow more than a hundred miles (160 kilometers) long, according to Roberto Danovaro, director of the
marine-science department at Italy's Polytechnic University of Marche.
Phytoplankton produce more mucus when there's more carbon and less nitrogen and phosphorus
available—"exactly the case created by the oil spill," Danovaro said. An oil particle is mostly hydrogen
and carbon.
In fact, because both the oil and the algae-generated mucus are gel-like, the apparently oily Gulf marine
snow may be especially prone to forming marine-mucilage blobs, UCSB's Alldredge noted.
Such blobs are relatively common in oceans in spring and summer, and they move with the currents like
"a submarine going up and down the water column," the Polytechnic University of Marche's Danovaro
said.
In rare cases, and if seas are consistently calm, mucilages can become very large and persist for months,
allowing disease-causing bacteria to accumulate within the blobs. It's unknown whether that will happen
in the Gulf, Danovaro said.
Even so, project leader Passow added, anything can happen. After all, she hadn't expected to find
evidence of a marine-snow blizzard in the first place.
"We are getting new things that are surprising to us," she said, "and learning a lot every day."