U.S. Florida: Manatee die-off in polluted Indian River Lagoon begins anew

Craig Pittman, Tampa Bay Times 13 Jul 16;

The manatees are dying again.

Between 2012 to 2015, state officials said 158 manatees died in Florida's Indian River Lagoon, once known as the most diverse ecosystem in America. They weren't alone — pelicans and dolphins died by the score in the polluted lagoon too.

The manatee die-off sputtered out last summer. But now, according to St. Petersburg's Florida Fish and Wildlife Research Institute, it has begun anew.

Since May nine new victims have been discovered. The most recent was found on July 4. All came from the Melbourne area.

Because manatees are an endangered species, whenever one is found dead in Florida, it's brought to the FWRI's laboratory to determine its cause of death. Examinations there are overseen by Dr. Martine de Wit.

The deaths do not appear to be connected to the toxic blue-green algae bloom afflicting the state's Atlantic coast and Lake Okeechobee, she said Wednesday. So far, no manatees deaths have ever been tied to that species of algae, she said, although the state continues to monitor it.

But this wave of manatee deaths may be indirectly tied to two other, different algae blooms, apparently fed by pollution in the lagoon, she said.

The Indian River Lagoon has had algae blooms before, but none of them were like the one that hit in 2011. Experts called the explosion of the greenish Resultor species a "superbloom" because it covered nearly 131,000 acres and lasted from early spring to late fall.

Then came the "brown tide" algae bloom of 2012, which tinted the water a chocolate brown. The algae, Aureoumbra lagunensis, have been a recurring headache for Texas. Why it suddenly showed up in Florida is another mystery.

A large algae blooms shades out sunlight needed by sea grass. By the time the "brown tide" algae bloom was done, the lagoon had lost more than half its sea grass, essential to nurturing fish and other marine species — including manatees.

With much of the seagrass gone, the manatees turned to eating a red sea weed called gracilaria. That's what was found in the guts of the dead ones, de Wit said. One theory is that the change in diet, prompted by the algae bloom's impact, is what killed them.

"The loss of seagrass led to them eating something else that caused them a gut upset," she explained.

Normally the stomach contents of a dead manatee are fairly dry, she said, but what was in these stomachs was "like a Slurpee."

So far, she said, there is no discernible pattern to the 167 manatees killed by whatever is in the lagoon — the victims are calves and adults, males and females.

That's out of the 1,500 or so manatees that normally swim around the Canaveral area.

"The majority of the manatees were apparently able to deal with the different vegetation," she said.

The only good thing, she said, is that so far the pelican and dolphin die-offs haven't started back up yet too.