Manatees are herbivores, feeding on a large variety of submerged, emergent, and floating plants. They can eat up to 10% of their body weight in vegetation daily. Seagrass beds are important feeding sites. Many of these coastal and estuarine feeding areas are particularly vulenerable to destruction by prolonged salinity changes, dredge and fill activities, surface water run-off from nearby construction sites or agricultural lands and herbicide spraying.
Grass Bed Maps for St. John's River, Duval Co. 1997