A researcher has isolated at least three varieties of toxins on microscopic algae sticking to a type of seaweed called gracilaria, the same seaweed found in the bellies of dead manatees in Brevard County. The seaweed also is eaten by fish that are eaten by dolphins and pelicans.
A researcher working with Harbor Branch Oceanographic Institute has discovered several toxins that could be killing manatees, dolphins and pelicans in the northern Indian River Lagoon.
Peter Moeller, a research chemist at the National Ocean Service in Charleston, S.C., has isolated at least three varieties of toxins on microscopic algae sticking to a type of seaweed called gracilaria, the same seaweed found in the bellies of dead manatees in Brevard County. The seaweed also is eaten by fish that are eaten by dolphins and pelicans.
In the past year, 111 manatees, 51 dolphins and about 300 pelicans in Brevard County have died from unknown causes.
Researchers don’t know, however, what type of microalgae on the seaweed is producing the toxins.
“That’s the next step,” said Brian Lapointe, a research professor at Fort Pierce-based Harbor Branch, a division of Florida Atlantic University. “We have to identify the organism producing the toxins. … Then we’ll look at tissues (from dead manatees, dolphins and pelicans) to see if the organism is there, too, so we can make the link.”
Lapointe said he collected six seaweed samples May 29 in the lagoon near Cocoa Beach, “one of the hot spots for manatee deaths,” and sent them to Moeller.
“Normally, gracilaria isn’t toxic,” Lapointe said. “In fact, it’s widely consumed by humans in various parts of the world. But I sent it to Peter to look at what’s growing on the gracilaria, not at the seaweed itself. Peter’s one of the best toxin sleuths around. Sure enough, he turned it around pretty quickly.”
Lapointe said Moeller found three “bands” of toxins that killed mammal cells, adding there “could be several more organisms producing toxins.”
Researchers have suspected toxins were responsible for the manatee deaths because the animals appeared to be healthy but drowned due to toxic shock-like symptoms, Thomas R. “Tom” Reinert, a research administrator with the Florida Fish and Wildlife Conservation Commission, told members of the Indian River Lagoon National Estuary Program Advisory Board at their spring meeting in Vero Beach.
Manatees’ normal diet consists primarily of seagrass, but the widespread disappearance of seagrass in the northern lagoon has forced the animal to eat seaweed, especially gracilaria.
“With the manatees, there’s a direct link to the toxins,” Lapointe said.
The dead pelicans and dolphins, on the other hand, have been emaciated and parasite-ridden — apparently not victims of toxic shock, except that dolphins and pelicans eat fish that eat gracilaria.
Brian Lapointe: “So we could be looking at the same toxins,” Lapointe said, “killing in different ways.”
Lapointe said the toxins also pose a threat to humans.
“You would definitely not want to ingest the gracilaria that contains these toxins,” he said. “As for physical contact (from swimming or wading in the seaweed), we do not yet know the solubility of the toxin, but there is reason for concern.”
Typically, algae blooms thrive when there’s plenty of phosphorus in the water, Lapointe said. But when the phosphorus runs low, algae can begin producing toxins to out-compete other organisms.
“Basically, they’re fighting for the phosphorus,” Lapointe said.
STOP THE BLOOMS
The goal, Lapointe said, is to stop algae blooms from starting in the first place. Lapointe’s research so far suggests the excessive amounts of nutrients — including phosphorus and nitrogen — that feed the blooms come from several sources, including fertilizer runoff, septic tanks, sewer plants and reclaimed water.
“This is when we could really use those LOBOs,” Lapointe said, referring to Land/Ocean Biogeochemical Observatories, remote-controlled sensors that measure temperature, depth, salinity, turbidity, and the amount of chlorophyll and dissolved nitrogen and phosphorous in the water.
This spring, the Florida Legislature approved, but Gov. Rick Scott vetoed, a $2 million grant to help Harbor Branch set up a lagoon-wide “observatory” using LOBO devices.
Moeller, who could not be reached Monday, is funded by the National Oceanic and Atmospheric Administration. Lapointe said he plans to apply for a grant through the National Science Foundation to ramp up Harbor Branch’s research into lagoon toxins.
“Right now we have limited funds for this kind of focused yet major research effort,” he said. “To do this work at the level it needs to be is quite expensive.”