Underwater 'Snowstorms': an Unexpected Consequence of Oil Spills

Exactly five years to the day, an explosion at the Deepwater Horizon oil rig leaked nearly five million barrels of oil into the Gulf of Mexico. Now, research looking into the long-term effects of this disaster have made an unexpected discovery. Oil may encourage the formation of an unusual fall of organic matter called "marine snow" - a revelation that could help find smaller oil leaks in the future.

"Marine snow is like dust bunnies in the house," Uta Passow, an oceanographer at the University of California in Santa Barbara, explained in a statement. "All the gunk and little pieces in the ocean stick together, and underwater it looks like a snow-storm. The little particles aren't heavy enough to sink, but marine snow is big enough to sink very fast, 100 meters or more per day. It's the only way in which material that grows on the surface, where there is light, goes to depth."

She added that "before Deepwater Horizon (DWH), we didn't even know that oil and marine snow had anything to do with each other."

Now, that has all changed. According to a study recently published in the journal Deep Sea Research II - Topical Studies in Oceanography, microbes and plankton found in the ocean have an unexpected interaction with oil, providing alternate ways for marine snow to develop.

Traditionally, marine snow occurs when organic matter from runoff and sedimentary shedding clump and grow heavy enough to sink to the bottom. There are many natural ways for this clumping to occur, but clumping around oil is rarely one of them. That, of course, changed after the BP oil spill disaster. (Scroll to read on...)

"The impact of the oil on the open ocean ecosystem when it's disbursed and diluted at the top of the water column is very different from the impacts it has when it sinks and accumulates on the seafloor," Passow said.

"It is widely believed among scientists that anywhere from 3 to 25 percent of the oil released during the spill was deposited on the seafloor as a result of marine snow sedimentation," she added. "However, this pathway was not considered in response strategies, nor was it included in the calculations for the DWH spill."

As a proof-of-concept, Passow and her colleagues used seawater containing particulates no greater than a millimeter in size and presented them with different natural and oil spill conditions.

"Even when spill oil was added to artificial seawater, marine snow formed," Passow said. "This suggests that the oil included microbes capable of creating marine snow."

And these results provide strong evidence that marine snow is an important factor involved in the dispersal of oil after a leak.

"We need to know where the oil is to learn how to keep the damage to a minimum for the whole ecosystem," Passow said, "and for that we need to understand all of the pathways involved."

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