University of South Florida researchers have discovered that oil from BP's 205-million gallon spill is spreading along the floor of the gulf. They say the dispersant BP used broke it up into tiny droplets and it sank to the ocean floor and now it's threatening critical marine animals that are the building blocks of the ocean's food chain. Larry McKinney, head of Texas A&M's Harte research institute for Gulf of Mexico studies, spoke with CNN's American Morning Tuesday.