The Reasons Behind Florida´s Manatee Die-Off: So far this year, 769 manatees have turned up dead in the waters of the Sunshine state

The Baffling Reasons Behind Florida’s Super Sad Manatee Die-Off

So far this year, 769 manatees have turned up dead in the waters of the Sunshine state.

November 5, 2013

The Reasons Behind Florida's Manatee Die-Off
A manatee swims in Crystal River, Florida. (Photo: Nina Leen/Getty)

For manatees in Florida, January 1, 2014 can’t come soon enough—2013 has been, quite simply, the year from hell for the docile and endangered marine mammals.

With two months left to go this year, 769 manatees have turned up dead in rivers and estuaries on both sides of the Sunshine state—an average of two per day. The grisly toll already tops figures for as long as these deaths have been counted, and is nearly 2012’s.

There have been two hotspots of death: Lee County, in southwestern Florida, where some 300 manatees have died in 2013, and the Indian River Lagoon system, on the east coast near Cape Canaveral, where nearly 250 animals have perished.

In earlier years, motorboats were frequent culprits. Today, though, it’s something much more insidious: The Lee County deaths have been mostly due to severe “red tide” conditions earlier this year, while those in the Indian River Lagoon deaths were caused by a sudden, acute, and unidentified illness that’s baffling scientists.

“It’s still a mystery in terms of a definitive cause of death, and it’s very frustrating,” said Patrick Rose, an aquatic biologist and Executive Director of Save The Manatee Club.

Necropsies revealed intestinal tracks “with a lot of evidence of inflammation and very watery content, and evidence of being very irritated, with bloody materials in it,” Rose says. He adds that so far, researchers have not been able to identify any lethal bacteria in the manatees, but are now looking at other pathogens and toxic materials.

The deaths may be mysterious, but less so is that the Indian River Lagoon is in deep ecological distress. Many of Florida’s estuaries are still recovering from a devastating cold snap in 2010 that contributed to the deaths of 766 manatees (the previous record).

But the lagoon has also witnessed parching droughts, which vastly reduce freshwater runoff and raise salinity, followed by near-record rainfall, especially this year. This both lowers salinity and washes high levels of pollutants and nutrients into the lagoon, spawning massive algal blooms. The algae consumes oxygen in the water, robbing other species that need it to survive.

High-salinity water and concentrated nutrients are shifted around by winds, spreading the devastation further. Parts of the lagoon are “becoming hyper-saline, more salty than seawater,” Rose says, leading to radical changes in the composition of native species, including 47,000 acres of sea grass wiped out by different microbial blooms, (plus 46 dolphins and 3,000 pelicans). When all that plant matter died and decayed, it released even more nutrients into the system “and created a vicious cycle,” Rose says.

The search for answers to the Indian River mystery was hampered last May when Governor Rick Scott vetoed $2 million in funding to study the lagoon’s physics, chemistry, and biology. “I do blame the governor and legislature for being much too lax on water quality and growth management laws that are being removed,” Rose says.

Save the Manatee is working with government and academic researchers on identifying the cause of death in the lagoon this year, but the mystery remains unsolved. Fortunately, manatee deaths in Lee County and the Indian River fell sharply after peaking between February and April, and are currently occurring less frequently.

But that could change at any moment, Rose warns. Severe red tides could return, and whatever was killing the Indian River manatees could too. For one thing, many more manatees inhabit the lagoon in winter than in summer, so the death toll might start to climb as we head into 2014.

There are some bright spots on the horizon, though. Brevard County is finding better ways to control over-nutrification of the lagoon by creating more barriers between homes and farms and the water, as well as ordinances limiting use of lawn fertilizer.

It’s not just elected officials with the power to help fix the problem, Rose says.

John Q. Public can “contact the Governor, even if they don’t live in Florida, and tell him he needs to be much more aggressive in protecting these waters and these animals.”

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