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St. Johns River salinity edges up; manatee rescues reported, no deaths since last meeting
Summary
At the Feb. 13 Jacksonville Waterways Commission meeting, Dr. Jerry Pinto reported rising salinity and warm water temperatures, noted a mother-and-calf manatee rescue, and said algae test results show no toxins.
Dr. Jerry Pinto, representing Jacksonville University, told the Jacksonville Waterways Commission on Feb. 13 that salinity and water temperatures in the St. Johns River have risen since the commission's previous meeting and that recent sampling shows mixed algae with no detectable toxins.
Pinto said salinities measured last week and had increased “by a couple of points” as of the meeting. He reported ranges by location: Mayport about 26–32 parts per thousand, Dames Point about 18–26 parts per thousand, Jacksonville University sampling sites about 9–20 parts per thousand, downtown about 4–12 parts per thousand, and near the Buckman Bridge about 1 part per thousand. Water temperatures were unusually high for February, with Mayport near 59 °F, Jacksonville University near 66 °F and the Buckman Bridge at about 67 °F.
Pinto said there have been no manatee deaths to report since the last meeting but that the commission's area had seen rescues: a mother and calf were rescued from the Ortega River and transferred to SeaWorld to reduce the risk of cold stress. On algae, Pinto said the most recent sampling date he referenced was Feb. 14; results were mixed algae with no toxins detected, and some results from the newest sampling were still pending.
Commissioners asked technical questions. Commissioner Andrew Bridal asked when manatees usually migrate back to Duval County; Pinto said manatees typically begin returning when water temperatures reach about 68 °F and that “next month, basically — middle to end of next month” is the normal timing, while noting a warm February could bring them earlier. Councilman Ken Amaro asked about salinity thresholds for aquatic impacts; Pinto explained the estuary's transition zone near the Buckman Bridge is where freshwater grasses and species are most affected and said grasses begin to show stress when salinity reaches about 12 parts per thousand for more than two weeks.
Captain Jim Suber asked whether a reported carcass under a dock on Heckscher Drive had been identified; Pinto said that was the first he’d heard of it and that he had not received follow-up. Pinto closed by noting the estuary is highly tidally influenced and that salinities fluctuate with tides, sometimes felt up to Palatka and Lake George.
The commission did not take formal action on the status report; commissioners asked for continued updates and for staff to coordinate public outreach tied to boating- and manatee-season press activity in April.
