Florida's governor and legislature are finally taking an active interest in the demise of the Indian River Lagoon, which runs for 156 miles along the state's Atlantic coast. The lagoon, once prided for hosting more species of marine life than any other estuary in the U.S., is now better known for its toxic algal blooms and mass animal die-offs.

In just the past year, 68 dolphins, 112 manatees, and hundreds of pelicans have turned up dead along the lagoon's shores.

“The Indian River Lagoon has become a toilet,” said Brian Lapointe, a marine environmental scientist from the Harbor Branch Oceanographic Institute at Florida Atlantic University.

The lagoon’s continuing collapse has prompted impassioned pleas from citizens desperate to halt the catastrophe and save the embattled ecosystem; scientists are racing to find out what's killing the lagoon's treasured birds and marine mammals. Earlier this year, the federal government declared the manatee and dolphin die-offs an "Unusual Mortality Events" and sent federal funds and investigators to the region.

Now, with the clamor from Florida residents reaching a crescendo, the state government is ramping up its efforts too.

Last week, Florida’s state senate convened a special day-long hearing to discuss immediate methods for slowing what can only be described as an environmental train wreck caused by, among other things, a collusion of unfortunate weather and decades of pollution from an inland, freshwater lake and septic tanks in the north. Yesterday, Florida’s governor announced a $90 million investment in infrastructure modifications that would help divert polluted water from inland Lake Okeechobee away from the lagoon.

The lagoon's troubles extend along much of its length.

In the central and southern lagoon, around St. Lucie County, fresh water discharges from Lake Okeechobee have spawned algal blooms that are staining the water a toxic, Technicolor green and triggering warnings to avoid the water.

The northern lagoon, which includes the Mosquito Lagoon and Banana River, is where most of the mysterious animal die-offs have happened. And there's no sign it's letting up.__ __“We’ve starting to get a lot of calves,” Megan Stolen, a research biologist at Hubbs-SeaWorld Research Institute, said on Thursday. “We had two more today.”

Stolen has been responding to and retrieving the dead dolphins. She and her colleagues are examining the carcasses and looking for clues to what’s killed them – a task that is more difficult when calves are dying. The little dolphins are smaller, and their mothers don’t want to let them go.

“Their moms are still pushing them around,” Stolen said. “We don’t interfere with that, we let them do their thing.”

No one knows why the animals in the northern lagoon are dying. The dolphins and pelicans appear to be starving, but the manatees look healthy except for being dead.

Some suspect the manatees are being poisoned by an unusual food source: Gracilaria, a seaweed they don’t normally eat, but which has replaced the seagrasses the animals naturally ingest. Some of the manatee carcasses recovered had Gracilaria in their digestive systems.

retrieved from the Indian River Lagoon. Photo: Brian Lapointe/HBOI

In May, Lapointe retrieved a handful of Gracilaria from an area in the Banana River that has been a hotspot for manatee deaths. He took the plant, a form of macroalgae, to his colleague Peter Moeller, an organic chemist with NOAA's National Ocean Service, who specializes in finding and identifying mysterious toxins.

Moeller ground up the Gracilaria and tested the mush for signs of toxic activity. He found that the extract killed mammalian cells growing in dishes – a sign that something deadly might be lurking in the plant. Eventually, Moeller identified three “bands” of cell-killing compounds. Now, he and Lapointe think they are looking at several toxic glycosides – a type of chemical compound in which a sugar is bonded to a chemical group that becomes active when that bond is broken.

Glycosides are common in plants. Some of them, with sugars bonded to cyanide groups, are toxic. Others have friendlier active groups that behave as anti-inflammatories, antioxidants, or sweeteners.

Moeller and Lapointe don’t yet know which kind – or kinds – of glycoside they’re dealing with, but hope to figure that out soon. Even then, more work will needed to link the Gracilaria to the manatee deaths – including finding evidence for the toxins in the dead manatees. In the meantime, Lapointe has retrieved more samples of the algae and the team is looking to see whether the seaweed is still toxic.

“A lot of these toxins, they’re not always present in these algae. They’re largely a function of environmental conditions,” Lapointe said.

Those environmental conditions include things like nutrient levels in the water. Nitrogen leaking into the northern lagoon from the region’s 237,000 septic tanks have disrupted the normal balance of the estuary, Lapointe said at the Florida senate hearing. In the north, without many inlets to keep the water moving and the lagoon flushed, “what happens in the northern Indian River Lagoon, stays in the northern Indian River Lagoon,” Lapointe said.

There, he said, more than 2 million pounds of nitrogen make their way into the lagoon each year.

Some of the solutions mentioned at the state senate hearing include replacing septic tanks with sewer systems, limiting fertilizer use, and diverting nutrient-rich, polluted water from Lake Okeechobee to the south, toward the Everglades – instead of west through the Caloosahatchee River or eastward into the lagoon.

Though sending the polluted water from Okeechobee south is among the more popular ideas, it's an imperfect solution. In the 1980s and 1990s, fertilizer-saturated, nitrogen-rich water flowing south toward the Florida Keys contributed to a cascade that killed or damaged most of the corals growing in the Florida Keys National Marine Sanctuary.

“Jamaica used to be the poster child for what not to do to coral reefs, but we have surpassed Jamaica,” Lapointe said. “We can’t send more water and nitrogen back down the Florida Bay, the Florida Keys, without further exacerbating what is already a disaster.“