The Deepwater Horizon blowout, now into its fifth week, represents an unplanned environmental experiment on an enormous scale – one whose full impact on Gulf of Mexico ecosystems may not become clear for decades.
But scientists are scrambling to study the BP oil spill now, knowing that it is, in many ways, a unique event. Never before has a leak from such depths vented so much oil for so long. Scientists have many questions, from how the use of massive quantities of dispersants affects nature's ability to break down an oil to why oil plumes from deep-sea spills act in unexpected ways.
The information they gather could improve responses to future deep spills and provide a better sense of how they affect the ecology. Scientists, for example, know little about long-term effects that aren't severe enough to kill organisms, but can alter reproduction or behavior in fundamental ways, says Marshall Adams, a researcher with the environmental sciences division at the Oak Ridge National Laboratory in Oak Ridge, Tenn.
To the naked eye, "the oil can disappear, but we don't know the long-term effects on organisms and their population fitness," he says.
The open ocean is a particularly complex environment to understand, other researchers say. Research requires expensive ships, and many factors can affect the health of marine life at all levels of the water column, making it tough to single oil out from other stresses both human and natural.
But a concerted effort is afoot to use the BP oil spill as an opportunity to better understand deep water oil spills.
BP, which owns the exploratory well the Deepwater Horizon was working when the blowout occurred April 20, has offered $500 million over the next 10 years to underwrite research and monitoring efforts. Moreover, the National Science Foundation, which underwrites research by university-based scientists, has made quick-response grants available for gauging the spill's ecological effects.
For instance, scientists are trying to see if the wide use of chemical dispersants – more than 600,000 gallons so far – undercuts the ability of naturally occurring microbes to break down the oil.
On one hand, as dispersants break a slick into tiny oil droplets, more microbes get a chance to attack the oil, notes Qianxin Lin, a coastal ecologist at Louisiana State University in Baton Rouge. Microbes can attack oil droplet from every side. In a typical slick, they just nibble at the edges.
Yet dispersants also may also inhibit the chemicals microbes produce to gather and consume the oil, according to University of California at Santa Barbara researcher David Valentine. Armed with one of the rapid-response grants, he's heading to the Gulf to gauge the microbes' responses to dispersants.
Where does the oil go?
Scientists also want to know the amount of oil likely to come to rest on the sea bottom. On the surface, oil weathers, grows dense, and sinks. But in the BP oil spill, much of the oil never makes it to the surface.
Carefully controlled experiments a decade ago released small quantities of oil from a depth about half that of the Deepwater Horizon's Macondo well, and they revealed some surprises, notes Eric Adams, a scientist at the Massachusetts Institute of Technology who was involved in the work.
"One of the take-home messages was that most of the oil does not immediately reach the surface," he says, noting that this is also true of the oil in the BP oil spill.
Moreover, oil that did reach the surface arrived faster than models of oil behavior suggested, he says.
"We need a lot more research on plume dynamics," he says, referring to the mechanisms that prevent the oil from reaching the surface.
One factor is the sheer energy of oil leaving a wellhead. It is enough to begin breaking the oil into smaller blobs, and the behavior of oil varies according to the size of the blobs. Undersea currents also play a role in breaking down oil and disperses it over a wider area than the plume alone covers. Dispersants add yet another level of complexity to plume dynamics, Dr. Adams says.
All of these things could have an effect on deep-sea ecosystems. Within the past four years, Gulf research cruises conducted by the National Oceanic and Atmospheric Administration and the US Minerals Management Service have uncovered deep-ocean reefs, along with animals ranging from football-sized mussels to tube worms and shrimp.
"That's a good thing," says Lisa Levin, a marine ecologist at the Scripps Institution of Oceanography in La Jolla, Calif. Since "there's actually some baseline information" on these habitats, scientists can conducting before-and-after comparisons.
Food for many of these creatures drifts down from the surface – as would heavily weathered oil droplets. One research cruise a week ago found what could be oil spreading horizontally at depths of 2,300 and 4,200 feet.
But the full dimensions of what appears to be plumes remain unclear, as does the composition of the compounds present. The samples still need to be analyzed, according to Vernon Asper, one of the scientists who took part in the cruise.
Each unanswered question is a kaleidoscope for scores of others. Plankton and larvae move up and down the water column and make contact with oil droplets. Could that affect them directly, as well as fish that feed on them? Might dispersants, too, impact these ecosystems?
"It's clear that we still don't know about the effects and efficacy of dispersants," says Mark Greeley, another scientist at Oak Ridge and a participant in a 2005 National Research Council report on the subject.
Such work is crucial, environmentalists acknowledge, but should have come much sooner.
"It's a bad time to be starting the research when the oil's hitting the marshes," says Karla Raettig, the national campaign director for coastal Louisiana restoration at the National Wildlife Federation. "It needs to be done now for future impacts, but it should have been done previously" ahead of the permit process.