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.
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.