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St. Johns River salinity dip after rains; manatee deaths rise as births increase, scientist says
Summary
A St. Johns River status report cited higher salinities during a dry stretch, recent heavy rains lowering salinity, early high temperatures raising algae‑bloom risk, and an uptick in manatee deaths this month driven in part by perinatal deaths amid improving population condition; one watercraft strike death was reported.
Dr. Pinta delivered a St. Johns River status report to the Waterways Commission May 15, saying recent heavy rains reduced salinity after an extended dry period, raising the risk for algae blooms as hot weather begins earlier than usual.
Dr. Pinta told commissioners salinity had been fairly high during a recent dry month but that three to nine inches of rain in the region last week diluted the salt and raised river water levels roughly two feet above typical levels in some downtown locations. He said high temperatures (around 90 degrees) combined with recent rainfall create conditions favorable to algal growth; the most recent Department of Environmental Protection sampling from April showed mixed algae but no toxins detected.
On manatees, Dr. Pinta reported an increase in reported deaths: three in the previous month and nine so far in the current month. He said a number of the deaths were perinatal (newborn) mortalities and that the uptick partly reflects improving body condition among the population following earlier starvation events — animals are reproducing again and peri‑natal mortality can increase when births resume.
He noted one watercraft-related manatee death this year, reported in the Mayport Naval Air Station turning basin, the first such strike of the year. An April aerial survey counted about 46 manatees in the St. Johns River proper; Pinta said next month’s flight typically shows higher numbers and that the animals are “back in town.”
Commissioners had no additional questions beyond clarifying earlier remarks. Dr. Pinta recommended continued monitoring for algae toxins as the warm season progresses and flagged manatee mortality events for follow-up by wildlife authorities.
