Gulf Oil Spill: Scientists Develop New Model for Deep-water Oil Spills

On the second anniversary of the Deepwater Horizon blowout, a panel of researchers is offering a new model for understanding what happened in the disaster, how to think of such events in the future, and why existing tools were inadequate to fully predict what lay ahead.

The May issue of the journal BioScience published findings by the members of the University of California, Santa Barbara's, National Center for Ecological Analysis and Synthesis (NCEAS) Gulf Oil Spill Ecotox Working Group.

Many of the co-authors received rapid response grants and other funding from the National Science Foundation (NSF) to conduct research in the Gulf of Mexico after the spill.

"The paper offers important new thoughts on how we might respond to future environmental disasters of this magnitude," said David Garrison, a program director in NSF's Division of Ocean Sciences, which, along with NSF's Divisions of Environmental Biology (DEB), Earth Sciences and others funds Gulf oil spill research.

"This synthesis sheds new light on the nature of spills and the potential, generally unappreciated, of subsurface ecological effects," adds Henry Gholz, program director in DEB.

The old model assumed that oil would "simply float up to the surface and accumulate there and along the coastline," said article co-author Sean Anderson of California State University Channel Islands.

"That model works well for pipeline breaks and tanker ruptures, but it is inadequate for this novel type of deep blowout."

The 2010 Deepwater Horizon spill in the Gulf of Mexico was unlike any other spill science and society had encountered.

The well blowout occurred at unprecedented depths and released enormous quantities of oil--an estimated 4.9 million barrels, or 206 million gallons.

Marine and wildlife habitats suffered major damage which, the co-authors say, continues to happen today, out of sight.  Local economies and livelihoods suffered as well.

According to the paper's authors--ecotoxicologists, oceanographers and ecologists who convened under the auspices of NCEAS while the spill was active--the response to clean up and contain the oil followed a certain framework.

That framework assumed the oil's behavior would mimic the more familiar shallow water and surface spills, despite the fact that the dynamics, fate and effect of deep-water oil on ecosystems are not well understood.

"As the Deepwater Horizon spill unfolded, you would hear folks saying things like 'we all know what happens when oil and water mix; the oil floats,'" said Anderson.

"But that wasn't the whole story. And that oversimplification initially sent us down an incorrect path with assumptions and actions that were not the best possible use of our time and effort."

As they synthesized existing knowledge to anticipate the potential ecotoxicological effects of the spill and highlighted major gaps in scientific understanding, the scientists created the first complete conceptual model for understanding both the Deepwater Horizon spill and analogous disasters in the future.

The new model accounts for how deep-water oil spills unfold and where the resulting ecological effects accrue.

It also emphasizes that the vast majority of the oil is retained at depth--rapidly emulsified and dispersed due to the physics of the pressurized oil jetting from the tip of the wellbore--and, among other response actions, calls into question the efficacy of dispersants.

"We have generally hailed the use of [chemical] dispersants as helpful, but are basing this on the fact that we seemed to have kept oil from getting to the surface," said co-author Gary Cherr of the University of California, Davis, Bodega Marine Lab.

"The truth is that much of this oil probably was staying at depth independent of the amount of surfactants we dumped into the ocean."

"And we dumped a lot of dispersants into the ocean, all told approximately one-third the global supply."

Co-author Ron Tjeerdema, an environmental toxicologist at UC-Davis, concurs.

"The problem is that we must address the downside of such compounds, particularly in light of the fact that the upside probably was not as great as it seemed at the time," he said.

Armed with a new foundation for research and policy implications, the scientists are calling for further investigation on the long-term effects of deep-water oil spills like that of the Deepwater Horizon.

"We now have a sense that the bulk of the effects were probably in the mid-water and deep ocean," said the paper's lead author, Charles "Pete" Peterson of the University of North Carolina at Chapel Hill.

"We need an integrated collaboration among deep-water explorers, modelers, ecotoxicologists, microbial ecologists and others. All working together in unprecedented ways.

"We need a whole new type of marine ecology."