JACKSONVILLE, Fla. -- The big concern for the St. Johns River has traditionally been pollution -- either from industry or the nutrient runoff that causes the region's notorious toxic green algal blooms.
But for the first time in seven years, the annual State of the River Report addresses concerns about rising salinity levels.
Dr Radha Pyati, chair of the Chemistry Department at the University of North Florida and one of the report's authors, says the annual assessment aims to address all river concerns. This year, salinity was too big an issue to ignore.
"Over an approximately 20-year period, we've found salinity increasing in regions chiefly between the Fuller Warren Bridge and the areas south of Doctors Lake," she told First Coast News. The primary evidence of saltwater intrusion can be seen in diminishing underwater grass beds and shrinking hardwood swamps.
The cause of growing river salinity is twofold, she says: Sea level rise and "tidal forcing -- pressure from ocean tides that has been affected by deepening the river bed."
The river bed will be deepened even further with JaxPort's dredging project, which will carve the river bottom to a depth of 47 feet for 13 miles -- from the ocean to JaxPort's cruise ship terminal near Dames Point. But Jason Harrah, project manager for the US Army Corps of Engineers, says when it comes to river salinity, the dredging impact pales in comparison to "other impacting factors such as sea level rise and water withdrawal." Relative to those factors, and even cyclical drought, Harrah says, "Our project will have very little if any impact to the river upon the deepening completion."
Port spokesperson Nancy Rubin says the Port is confident in the Corps' scientific modeling and believes it has done its part to balance the needs of the environment and the local economy.
"It is a balance," says Rubin. "It is making sure that all those ingredients that go into a thriving community, a thriving region, are respected, are studied, are well cared for."
And salt water is just one on a list of threats, according to Pyati. "Salinity is high on the list," she says, "but I would also say nutrient [pollution], [low] dissolved oxygen [levels] and fecal coliform bacteria continue to remain very high priorities for the lower St. Johns River Basin."
Read the full report here.