Researchers are baffled by the cause of a year-long spike in deaths among manatees, dolphins and pelicans in the shallow lagoons and brackish streams of inland Florida.

Along 50 miles of northern estuary waters off Brevard County and the Kennedy space complex, about 280 manatees have died in the last 12 months, 109 of them under mysterious circumstances, according to a report by The New York Times. As the manatee deaths peaked this spring, hundreds of pelicans began dying along the same stretch of water, followed this summer by scores of bottlenose dolphins.

While the exact cause remains unknown, researchers and state officials fear the worst — the collapse of the natural balance that sustains more than 4,300 species of wildlife in the estuary’s northern reaches.

“We may have reached a tipping point,” said Troy Rice, who directs the Indian River Lagoon National Estuary Program, a federal, state and local government partnership at the St. Johns River Water Management District, told the Times.

The leading candidates, he says rapid population growth and pollution generated by coastal Florida’s explosive development.

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