Submerged Aquatic Vegetation (SAV)

The St. Johns River’s delicate tidal balance of salt and freshwater has historically enabled healthy underwater grasses to thrive, providing critical habitat for fresh and saltwater species that have attracted sportsmen and eco tourists from near and far.

Now our thriving estuary and fishing economy are at risk. Due to overuse of our aquifer, dredging and increasing saltwater intrusion, the river’s underwater grasses are disappearing, the cypress forest wetlands are stressed, and fish habitat is vanishing within the St. Johns River estuary from Welaka to Palatka to Jacksonville.

The loss of our river’s submerged grasses also increases the threat of toxic blue green algae and flood risk throughout the lower St. Johns.

SAVe our River's Grasses

In May 2023, St. Johns Riverkeeper launched its SAVe our River’s Grasses Expedition seeking answers and solutions to the disappearing SAV of the St. Johns.

Most of the Eelgrass Has Disappeared in the Lower St. Johns River

The St. Johns River Estuary is in Trouble

An unprecedented amount of submersed aquatic vegetation (SAV) has been lost from just south of Jacksonville through Palatka and Lake George. The dramatic decline occurred in 2017 following Hurricane Irma and subsequent storms. Because of decreased water quality conditions, causing loss of light to the bottom, eelgrass and other plants have not been able to recover.

Why is Eelgrass Important?

  • Underwater grasses are needed for baby fish to hide and grow.
  • This estuary provides fish and shellfish for the St. Johns and Ocklawaha rivers.
  • Grasses are vital to fishing and commercial shell fishing industries.
  • Submerged vegetation is essential for manatee survival.

What Scientists Conclude

  • 99% of submersed aquatic vegetation has been lost
  • Approximately 90% of the plants are eelgrass.
  • The primary reason is light not reaching plants on the bottom.
  • Saltwater intrusion has also contributed.
  • Increased runoff of dark water and nutrients promote algal growth which shades eelgrass.
  • Grasses are not recovering after 2017 Hurricane Irma and other storms. The few remaining submersed plants are not growing.

Potential Solutions

  • A cooperative effort by agencies and non-governmental organizations.
  • Reduction of fertilizers, septic tanks, sewage disposal, and saltwater intrusion along the entire river.
  • Breaching the Rodman/Kirkpatrick Dam would provide more than 150 million additional gallons a day of clearer, freshwater to the entire St. Johns River.
  • Maintaining natural buffers along the shorelines.

“What would restoring the Ocklawaha do for this environment and do for these grasses?”

“The clearer water would provide a lot more light for the grasses, plus it would provide connectivity between the Ocklawaha and the St. Johns rivers so manatees could move up the Ocklawaha River to Silver Springs… Fishes could migrate, they would use the grass beds as nursery habitat for hiding and growing when they’re small.”

Robert Virnstein

Seagrass Scientist