A baby cooter on the bank of Dunns Creek, off the St. Johns River.
© Will Dickey / The Florida Times-Union
A baby cooter on the bank of Dunns Creek, off the St. Johns River.
Freshwater turtles are dying throughout the St. Johns River watershed and baffling state wildlife scientists concerned about the die-off in at least three counties.

Our Florida Times-Union news partner reports the Florida Fish and Wildlife Conservation Commission (FWC) is investigating the death of multiple species of freshwater turtles discovered in various bodies of water in Putnam, Orange and Seminole counties.

"These types of turtles are pretty resilient," said St. Johns Riverkeeper Lisa Rinaman said Wednesday. "So it was quite alarming to us."

The advocacy group was among the first to notify the commission about the turtle die-off.

Rinaman said the issue could be one of water quality.

Reports and surveys indicate at least 100 dead and dying turtles have been discovered along the massive watershed for the 310-mile long St. Johns River. The commission also has received scattered reports of dead turtles in other regions of the state including Trout Lake near Eustis in Lake county.

So far, the die-off is primarily affecting Florida softshell turtles, which is one of the most common freshwater turtle species in Florida. But some river cooters also were found dead, according to commission, which has been monitoring the situation since early this year after receiving initial reports about dead turtles.

Important to a healthy, functioning ecosystem, freshwater turtles are considered an indicator species of water quality/stream health.

"It definitely is a red flag," Rinaman said of the die-off. "We want to figure out what's going on for the sake of the turtles but also make sure there is not a larger human health issue to be concerned about."

Rinaman said on May 16 members of the group's Headwaters Advisory Council discovered a significant number of dead and dying turtles near the Tosohatchee Wildlife Management Area at the river's headwaters in Orange County.

Other dead turtles were found in Crescent Lake in Putnam/Flagler County, as well as the Puzzle Lake in Seminole County and Lake Poinsett in Brevard County, she said.

"We have not seen anything like this in the past," said Carli Segelson, a Fish and Wildlife Commission spokeswoman.

Rinaman said the animals found by her group showed no obvious injuries or signs of illness such as lesions.

"It was more like they were having trouble breathing. They were lethargic. They would crawl out and just kind of gave up and couldn't go any where," she said.

Rinaman said the dead turtles they've seen are in areas near sites where sewage sludge is allowed to be spread as fertilizer.

"Our concern was this high level of sewage sludge that's being applied on adjacent lands there in the headwaters. In particular, some of the areas where they are seeing a high number of turtle deaths," she said.

Rinaman also said there's no indication as yet from the Fish and Wildlife Commission's investigation that there might be any connection between the turtle deaths and the sewage sludge.

But some microcystis — a type of bacteria that includes harmful algal blooms — has been detected in the areas of the headwaters, she said.

"So it could be a bacteria. It could be something that's resulting from toxic algae, but they're still investigating," Rinaman said.

Commission biologists and veterinarians have collected samples for necropsy and diagnostics. However, the cause of the die-off remains unknown.