Mysterious Manatee and Dolphin Deaths in Florida Confound Scientists

Once a lush and healthy estuary, the Indian River Lagoon is now an enigmatic death trap. Running along 40 percent of Florida’s Atlantic coast, the lagoon’s brackish waters harbor a mysterious killer that has claimed the lives of hundreds of manatees, pelicans, and dolphins.
Nobody knows why.
In April, NOAA declared the spate of manatee deaths an Unusual Mortality Event, a designation granted when marine mammal deaths or strandings are significantly higher than normal, demand immediate attention, and are the result of a common but unknown cause. Soon, the bottlenose dolphin die-off may be given the same designation.
“We have to hope we can find the answer, because until we do, we don’t know how we can help prevent it in the future,” said Jan Landsberg, a research scientist with the Florida Fish and Wildlife Conservation Commission.
Since last July, 51 dolphins, 111 manatees, and as many as 300 pelicans have perished in the lagoon. The deaths don’t follow an obvious pattern: Manatees are dying so quickly that some still have food in their mouths, while the dolphins and pelicans appear to be starving to death.
Mangrove islands in the Indian River Lagoon, a treasured estuary on Florida’s eastern shore. (South Florida Water Management District)
Investigators don’t know if the die-offs are the work of the same killer, or if by some coincidence, nature has produced three unrelated carcass piles at once. The only clear link so far is the lagoon, a treasured and frail ecosystem that’s home to more than 3,500 species of plants and animals.
Scientists searching for the killer are following a long, branching trail; the story begins years ago, when a prolonged drought and cold snap set the lagoon’s resources toppling like a string of dominoes. Now, a multi-year, $3.7 million protection initiative has been adopted in an attempt to put the brakes on the lagoon’s collapse, and prevent future crashes. But its success depends on scientists uncovering the culprit behind the ecological mayhem.
Imperiled Paradise
Designated an “estuary of national significance” by the EPA in 1990, the Indian River Lagoon system stretches for 156 miles along Florida’s eastern coast. Though less than 6 feet deep on average, the lagoon is stuffed with more species of marine life than any other estuary in the continental United States. Salt marshes, mangrove swamps, oyster reefs, fish nurseries, and one of the densest sea turtle nesting sites in the western hemisphere are some of the ecological stars studding the stretch of coastline. Estimates suggest the barrier island complex brings in more than $3.7 billion each year from citrus farming, fisheries, recreation, and employment.
But there’s a darker side to the Sunshine State’s eastern oasis. Surrounded by developments, the lagoon has, for decades, been the drainage pool for leaking septic tanks, polluted streams, and storm water rich with nutrients from fertilizers. It’s a wind-driven system, and without tides to push the water around and flush it out, segments stagnate and pollutants accumulate.
Running from Ponce de Leon Inlet in the north to Jupiter Inlet in Palm Beach county, the lagoon’s waters flow into canals and through locks, twisting and pooling into three main segments: The Indian River, the Mosquito Lagoon, and the Banana River.
In 2011, a blue-green algae superbloom turned the waters of the northern lagoon a sickly green color. (SJRWMD)
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