Fragile ecology

The St. Johns River is an ancient intracoastal lagoon system. As sea levels dropped, barrier islands became an obstacle that prevented water from flowing east to the ocean. The water collected in the flat valley and slowly meandered northward, forming the St. Johns River.

For hundreds of years, the 310-mile-long St. Johns has been home to many plant species and marine animals — manatees, many types of fish, crabs, shrimp and other shellfish, river otters, waterfowl, and alligators and other reptiles. Wildlife is abundant in and around the St. Johns River. Alligators, largemouth bass, blue herons and bald eagles are just some of the animals that live in this river or its “neighborhood.”

Life in most waterways depends on the survival of underwater grasses. Underwater plants here, as in other waterways, serve as food for some animals and nurseries for others. The grasses are a vital part of the water world. In freshwater and salt water, the grasses provide food and habitat for fish, manatees and other wildlife. The plants also filter pollutants from the water and act as surfaces for organisms — snails, algae and insects — to hold on to. Submersed vegetation is also necessary because it adds dissolved oxygen to the water so aquatic animals can breathe. Its roots stabilize the river bottom and prevent erosion.

Without aquatic plants, the St. Johns River would not be as full of life as it is today. Poor water quality has a great impact on underwater grasses, and the loss of underwater vegetation deprives manatees and other wildlife of their primary food source and fish of their most important habitat.