Manatees eat plants, and pelicans eat fish. The only thing they share is water," Dan Wolf, a state Fish and Wildlife Conservation Commission biologist, told Spear. Investigators believe that manatees are eating gracilaria, a red-colored alga, because of the seagrass shortage and because the dead manatees' stomachs are full of it. Gracilaria isn't known to be toxic, but scientists are trying to find whether some type of toxin is at work.