Directions: Read the following passages and choose the best answers to the questions.

   The Indian River Lagoon has been suffering recently because of microscopic algae blooms, which have caused mass die-offs of seagrass, which shelters aquatic species and is the primary food for manatees. The Orlando Sentinel’s Kevin Spear reports manatees began dying in the areas that had the worst seagrass loss last year, but no cause of death has officially been determined.
   His report said 80 manatees have been found dead thus far Brown pelicans also have died in the area, but scientists have not been able to come up with an explanation for their deaths. So far, more than 200 pelican carcasses have been found. Spear reported.
   "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 algae, 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.
   Wolf said that when the manatees die, it appears to happen quickly, but the pelicans are plagued with parasites for weeks before they perish. The question now is whether the lagoon is transforming from a system where seagrasses and large algae absorb nutrient pollution to a system in which microscopic algae are in control.

What does the writer infer about the manatees?