From CNN.com today:
Oil from the Deepwater Horizon spill may have settled to the bottom of the Gulf of Mexico further east than previously suspected and at levels toxic to marine life, researchers reported Monday.
Initial findings from a new survey of the Gulf conclude that dispersants may have sent the oil to the ocean floor, where it has turned up at the bottom of an undersea canyon within 40 miles of the Florida Panhandle. Plankton and other organisms showed a "strong toxic response" to the crude, according to researchers from the University of South Florida.
"The dispersant is moving the oil down out of the surface and into the deeper waters, where it can affect phytoplankton and other marine life," said John Paul, a marine microbiologist at USF.