What bay do manatees frequent?
The open waters are inhabited by fishes, molluscs and crustaceans living on sea grasses or who prey on each other. The shallowness of the lagoon makes it suitable habitat for diving birds such as anhinga, cormorants and diving ducks. The bay also provides habitat for juvenile sea animals that have left the shelter of the mangrove belts.  Manatees frequent the quiet waters of the bay. The bay has a year-round population of double-crested cormorants. Winter residents include northern gannets, American white pelicans and common loons. The bay also has a resident population of common bottlenose dolphins.Biscayne Bay is a shallow lagoon with little vertical density or salinity gradient due to its lack of depth. Instead of a vertical gradient, the bay shows a horizontal density gradient, with fresh water entering from the drainage canals on the west side and seawater entering through gaps in the keys and through the safety valve section of shoals. Bay salinity reaches a peak in June. Changes in the salinity pattern of the bay have had negative effects on formerly abundant species such as red drum. Biscayne Bay and Florida Bay are major nurseries for red grouper and gray snapper. The bottom of the lagoon hosts sponges and soft corals in places where grasses cannot not grow. Three primary species of seagrass are found in the park: turtlegrass, shoal grass and manatee grass. The endangered Johnson's seagrass is also found in small quantities in the bay, which is at the southern end of the grass's range. Roughly 75 percent of the central bay floor is covered by grasses. Scarring of seagrass beds by vessel groundings or propellers is a significant problem. About 200 such incidents are documented each year, with full re-growth requiring up to 15 years. The bay is also affected by commercial shrimp trawling, which is permitted in park waters.  The passage of roller-frame trawl nets does not harm grasses, but damages soft corals and sponges.
Biscayne Bay