What About Spilled Oil That Doesn't Reach Shore?

Scientists studying 'natural' oil spills fear for a sea floor about to be overwhelmed by detritus from the BP spill in the Gulf of Mexico.
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As the oily goo from the massive spill in the Gulf of Mexico begins to come ashore, the immediate concern is for the devastating effects it will have on the shore birds and sea life in the coastal regions. But what of the long-term effects on the ocean itself?

David Valentine, a biologist with the University of California, Santa Barbara, worries as much about the effects of the hundreds of thousands of gallons of crude settling on the sea floor, where much of the gushing oil is likely to settle.

While the obvious immediate danger is to the coastal areas — and oil has already started to wash up on island beaches at the Breton National Wildlife Refuge and other areas off the Mississippi and Louisiana coasts — Valentine said there should be equal concern for the shallow shelf waters and, ultimately, the deep-sea floor.

Valentine has been studying oil deposits in the Santa Barbara Channel off the California coast for more than 10 years, focusing on the organisms that eat petroleum and tars that seep naturally out of the channel floor. More than 100 barrels (or 4,200 gallons) of oil a day ooze from seeps just 2 miles offshore, and much of it ends up on Santa Barbara's beaches. It's been described as a "permanent natural oil spill."

Valentine and his co-investigator, Chris Reddy of Woods Hole Oceanographic Institute in Massachusetts, two years ago reported the discovery of microscopic creatures that eat oil on the sea floor.

"It takes a special organism to live a half mile deep in the earth and eat oil for a living," Valentine said. "It's actually a whole consortium of organisms — some that are eating the oil and producing intermediate products, and then those intermediate products are converted by another group to natural gas."

This illustration shows the route traveled by oil leaving the sub-seafloor reservoir as it travels through the water column to the surface and ultimately falls back to the seafloor. The oil remaining after weathering falls in a plume shape onto the seafloor where it remains in the sediment. Click to enlarge. (Jack Cook, Woods Hole Oceanographic Institution)

This illustration shows the route traveled by oil leaving the sub-seafloor reservoir as it travels through the water column to the surface and ultimately falls back to the seafloor. The oil remaining after weathering falls in a plume shape onto the seafloor where it remains in the sediment. Click to enlarge. (Jack Cook, Woods Hole Oceanographic Institution)

Also, because the deep ocean is an anaerobic environment, and very cold, the breakdown process is much slower than would happen with, for example, bioremediation, where organisms that eat oil are sprayed on slicks to break them down naturally. (Take a look at a look at the work of environmental microbiologist Terry Hazen here.)

But the spill in the Gulf of Mexico is on a scale that overwhelms the organisms that would typically digest it, Valentine explained.

"It's really a matter of amount, of how much ends up depositing on the sea floor. You've got micro-organisms that are capable of consuming components of the oil, but they are finicky. They're not a magic bullet by any sense, and they act on their own time frame."

In the case of the Gulf spill, there's too much oil, and it's happened too fast.

"It's just overwhelming the capacity of biology to deal with it. The longer the oil stays afloat, the better off it's going to be," Valentine said.

In addition to the oil's impact, he worries about the potential effects of the surfactant — essentially a detergent — that is being sprayed on the slicks and pumped into the Gulf to break up the oil. Because the surfactant's chemical makeup is a proprietary mixture, its exact makeup is not known, and Valentine worries how those chemicals will affect coastal wildlife and sea life over time.

One result of using dispersants is that thicker blobs of oil may be created extending under the surface, making tracking the oil far more difficult.

"It's going to be a very interesting fallout pattern that comes from that. We need to know where. The beach is the place you really don't want it. The next place you don't want it is the shallow shelf. The place most people don't care about is the deep water. I care about the organisms there that are likely to be impacted."

The deep ocean is home to a rich assortment of organisms and creatures, including mussels, snails, crabs, shrimp, fish and large sea worms. Many live around deep-sea vents where extremes of temperature and pressure create difficult environments. How those colonies of life would be affected by blankets of thick crude is unknown.

"It certainly has the potential to impact the critters of the deep ocean. It may not have a big economic impact, but it will affect the ecosystems," Valentine said.

Oil is made up of thousands of different hydrocarbons that can break down by the action of light, bacteria or oxygen into chemicals such as aldehydes, ketones or sulfur compounds. They can also become acids, and many are potentially toxic, Valentine said.

Valentine also studies methane hydrates, a solid ice that forms when methane contacts cold water under the intense pressure of the deep ocean. Methane hydrates are the reason that British Petroleum engineers encountered problems over the weekend while placing a collection tower over the ruptured pipeline. Methane hydrates are stable at low temperatures and high pressure, as at the ocean floor, but they coagulate — kind of like cholesterol in your veins — and in this case they simply clogged up the top of the containment structure, Valentine explained.

As soon as BP put the tower in place, the hole at the top of the tower became plugged, casting doubt on whether that proposed fix is viable. Meanwhile, the oil continues to spew out of the ruptured pipeline at a rate of about 5,000 barrels, or about 210,000 gallons, per day. At between 150 and 180 degrees Fahrenheit, it's like a blistering Jacuzzi jet shooting into the open ocean, Valentine said.

Until someone figures out how to harness it, the devastation will continue, Valentine said.

"The reality is it could certainly go for months or even years."

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