Manatee, pelican deaths suggest serious problems for Indian River Lagoon
March 21, 2013|By Kevin Spear, Orlando Sentinel
The mysterious deaths of dozens of manatees and hundreds of pelicans may be an indication that the ailing Indian River Lagoon, among the state’s most magnificent waterways, is headed for one of the more epic collapses of a Florida ecosystem in years.
The 156-mile-long lagoon, one of the richest marine environments in North America, has suffered extensive blooms of microscopic algae in recent years that have in turn triggered mass die-offs of seagrass, the submerged plants that shelter many aquatic species and are a primary source of food for manatees
Scientists feared something bad would happen as a result, and beginning last summer manatees began perishing in areas with the worst seagrass losses, mainly in Brevard County, though no cause of death has been determined.
“The loss of manatees has been less than we’ve seen with red tide and from cold stress in recent years. But to me, this is scarier,” said Katie Tripp, science director of the Save the Manatee Club.
“With cold stress, we know it’s going to warm up, and with red tide we know pretty much what to expect. But it’s been a long time since we’ve had manatees dying off in large numbers for reasons that aren’t known,” Tripp said.
Coinciding with the unexplained deaths of 80 manatees as of Thursday is the rising toll of brown pelicans, whose deaths also have no explanation. State officials said that, as of Thursday, nearly 230 pelican carcasses have been recovered or reported this year.
Dan Wolf, a state Fish and Wildlife Conservation Commission biologist, said he and other investigators think the pelican and manatee deaths are related, even though there are perplexing differences.
“Manatees eat plants, and pelicans eat fish. The only thing they share is water,” Wolf said.
Wolf said that whatever is afflicting the pelicans kills a bird during a span of weeks and leaves its victims emaciated and plagued with parasites. By contrast, the manatees appear to sicken and die quickly — and, as far as investigators know, display no warning symptoms.
“We’ve seen signs of acute shock and drowning,” said Martine deWit, an FWC veterinarian.
State investigators think that the loss of seagrass has forced manatees to forage on a type of red-colored algae in the Indian River known as gracilaria. Necropsies of manatees have found their stomachs filled with it.
“It looks like they ingest this stuff, and once it gets into their system, it causes an issue with their intestines, and there actually seems to be a reaction in the small intestine,” said Andy Garrett, an FWC marine-mammal biologist.
Gracilaria isn’t thought to be toxic. So the challenge for investigators is to determine whether there is an unknown toxin at work. But even if investigators determine what is killing the manatees and pelicans, there may not be much that can be done to prevent further deaths, deWit said.
The same holds for the health of the Indian River overall. State water managers now fear that “nutrient” pollution tied to street runoff, lawn fertilizers and sewage is driving the lagoon’s ecosystem. That pollution, which is essentially plant food, has been absorbed through the years by seagrasses or by gracilaria and other large species of algae.
But cold snaps in 2010 and 2011 killed much of that large algae, which decomposed and released the nutrient pollution back into the water, where it triggered an explosive growth of single-cell, microscopic algae in three sections of the lagoon. Those blooms of microscopic algae then blocked sunlight from reaching the surviving seagrass, killing off more than 30,000 acres of the plants.
“We are in a crisis mode,” said Troy Rice, director of the Indian River Lagoon National Estuary Program.
The question now is whether the lagoon is transforming from a system where seagrasses and large algae absorb nutrient pollution to a system in which microscopic algae are in control. Charles Jacoby, a St. Johns River Water Management District scientist, said there are many examples of ecosystems making that “flip.”
“When they flip, they flip pretty radically,” he said. “Sometimes it takes a lot of effort to flip them back.”
What’s happening to the coastal waterway, which extends from New Smyrna Beach south to Jupiter and is a major manatee habitat, has been drawing much attention, including from dolphin biologists.
“Because of what’s going on with manatees, we’re on alert,” said Megan Stolen, a scientist at Hubbs-SeaWorld Research Institute, which documented a mini-spike of five dolphin deaths in February, up from the month’s average of 2.3 deaths.
Leesa Souto, executive director of the Marine Resources Council, which advocates lagoon restoration, hopes recent events finally trigger a critical mass of public and government concern.
“Maybe now that there are pelicans falling out of the sky, then maybe the public will start rallying on behalf of the system,” Souto said. “I’m hearing from people here in Melbourne that, ‘Oh, we saw another dead manatee.’ And these are children.”
Tripp, the Save the Manatee Club scientist, said the lagoon’s plight underscores the vulnerability of manatees, which have been under consideration for reclassification from “endangered” to the less-dire category of “threatened.”
Chuck Underwood, a U.S. Fish and Wildlife Service spokesman, said agency biologists are asking questions about the lagoon’s deterioration, including what it may mean for manatee conservation.
“The answer is, we are not sure,” Underwood said.
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