The federal government says as much as half of the oil spilled into the Gulf of Mexico from BP's well is still unaccounted for, and scientists are starting a giant search operation to try to figure out where that oil is and what it might be doing to sea life.
The National Oceanic and Atmospheric Administration has been taking water samples from the surface, but data from the measurements have been pretty hit-or-miss, NPR science correspondent Christopher Joyce says.
But one group of researchers in Sarasota, Fla., is taking the measurements one step further, by using "virtual shellfish" to quantify the amount of contaminants in the water.
The virtual shellfish is a passive, semi-permeable membrane device that attracts contaminants from the water for four weeks, says Dana Wetzel, a marine chemist at Mote Marine Laboratory who studies the effects of toxic chemicals on marine life. The device "will actually simulate what an organism like a fish or an oyster will be seeing as it lives in its environment."
"It's a possibility we could detect dispersants, but if you think about the amount of oil that was spilled in the environment versus the amount of dispersants that were used, the overwhelming signal you're going to get from an accumulation study or any sort of contaminant study is likely to be the spilled oil and not the dispersant," Wetzel says.
The device will provide scientists with a value that indicates how much contaminant -- in this case oil -- an animal is accumulating in a period of time. "But that doesn't tell us what that number translates to in what we call an acute or a sub-lethal effect," she says.
The long-term effects of contaminants on the animals are not known at this point, and Wetzel and her team hope their data will help them gain some insight.
"We could count dead bodies -- and that certainly is useful -- but it doesn't tell us what's going to happen to the reproductive fitness of this organism," Wetzel says. "Whether it's a clam, a tuna or a dolphin -- is the exposure to this oil at that level going to affect whether or not that animal can reproduce? Or will it affect whether or not its offspring can reproduce? That's something we really don't know."
The initial response to the Deepwater Horizon spill was to cap the well to stop the flow. Wetzel agrees that that is "absolutely the correct way to have gone," but now that the cap is on the well, "we need to move to the next phase, which is to assess both the acute damages and the long-term damages. But herein lies my concern: Now that the well has been capped, interest is going to wane, and perhaps the dedication that was there to do the science may not be there anymore."