Lower St. Johns River: Most of the Eelgrass has Disappeared

Seagrass expert Dr. Bob Virnstein shared at last week’s SJRWMD Board Meeting that more than 90% of submerged vegetation has been lost on the St. Johns River north of Lake George including Welaka, Palatka and Green Cove Springs. Most of the plants are eelgrass. He explained that due to unusually persistent dark water conditions, not enough light is reaching plants on the bottom. The dark water comes from multiple sources. Saltwater intrusion is also a factor with grass losses in Duval, Clay and St. Johns Counties.

Anglers participating in the recent Bassmaster Elite tournament on the St. Johns River near Palatka were astounded at the loss of grasses.  Bassmaster.com reported in February 2022, “The big talk this week at the 2020 AFTCO Bassmaster Elite at St. Johns River has been about the lack of eelgrass.” According the Bassmaster online article, Trevor Knight, the Northeast Region Fisheries Administrator for the Florida Fish and Wildlife Commission explained, “Juvenile bass depend on quality cover to act as a nursery so they can survive predation from birds and other predator fish.”

Eelgrass is necessary for fish and shellfish growth. This 100-mile lower St. Johns River estuary supports multi-million-dollar commercial crab, shrimp and sport fishing industries. Eelgrass also provides valuable food for manatees.

The dramatic decline occurred in 2017 following Hurricane Irma and wetter than normal subsequent years. Historically after major storm events, the grasses were able to bounce back after several years. Over four years later, however, the few small surviving plants are still not growing. There are multiple causes.

An extensive, coordinated effort by SJRWMD, other agencies, local governments and non-profit organizations is needed to pinpoint the causes and remedies. Dr. Virnstein notes that, “One implementable solution that would certainly help eelgrass recover is breaching the Rodman/Kirkpatrick Dam to restore the natural flow of more than 150 million gallons a day of additional clear spring-fed water to the St. Johns River, improving water clarity and sunlight penetration.”

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