Manatee deaths call attention to rising tide of toxic algal blooms

An explosive growth of microscopic ocean plants has been linked in recent weeks to the drowning of a record number of manatees in southwest Florida.

The culprit behind the deaths of more than 190 of the gentle, lumbering vegetarian marine mammals: Karenia brevis, or "Florida red tide."

Though the red tide organism is always present in the Gulf of Mexico, its dramatic proliferation can bring misery along the coast as it discolors waters, poisons fish and shellfish, and even causes breathing problems in beachgoers. Manatees have suffered excruciating drowning deaths as red tide's neurotoxins prevented the animals from lifting their heads above water to breathe.

The Florida red tide is just one type of harmful algal bloom -- part of a worldwide phenomenon that scientists say is growing in number and intensity around the world over the past 40 years. Scientists investigating the bloom boom are examining increased stormwater runoff, expanded ship traffic carrying microbes from one marine ecosystem to another and climate change. Others say natural factors like shifts in the Gulf Stream and changing weather patterns play roles.

There's agreement on two fronts: Harmful algal blooms are on the rise, and more needs to be done to warn people ahead of their occurrence.

Experts caution that part of the uptick is due to increased monitoring -- when more people started looking for harmful algal blooms, the more they found them.

"Most people believe it's not just the ability to detect [harmful blooms], there are true increases in frequency and severity of blooms," said Rob Magnien, director of the National Oceanic and Atmospheric Administration's Center for Sponsored Coastal Ocean Research and the chairman of a United Nations panel on harmful algal blooms.

A prime suspect are nutrients being washed into coastal waters, said William Sunda, a phytoplankton ecologist with NOAA's Center for Coastal Fisheries and Habitat Research in Beaufort, N.C.

"We're flooding the ocean with fertilizer," Sunda said.


Sunda and his colleagues at NOAA and North Carolina State University recently published a study in the peer-reviewed online journal PLOS ONE that says Karenia brevis becomes more toxic to deter predators as it runs out of phosphorous -- the nutrient, along with nitrogen, it needs to grow and reproduce.

Cells without access to phosphorous were two to seven times more toxic than those in solutions full of that nutrient.

"What was found in culture was exactly the same range of toxicity people were seeing out in the environment," said co-author Richard Wayne Litaker, a molecular biologist at NOAA.

While the study results might be viewed as an invitation to seed the ocean with more nutrients so algae don't run out and become more toxic, Sunda called that a deal with the devil. The cells will die and release their toxins eventually, so it would only serve to create a monster bloom that is even more lethal in the future.

'Unbelievably unpleasant'

Several dozen algae species -- a small fraction of the total microbes in the ocean -- are known to cause harm.

The toxic kind can cause fish to stop moving their gills and suffocate. Besides manatees, numerous animals have fallen victim to harmful algal blooms, including dolphins, whales, sea turtles, seals, sea lions and birds.

Not all harmful algal blooms are toxic. Others cause problems through sheer biomass, blanketing the ocean's surface until they block sunlight needed by plants below. Such blooms lead to swaths of dead, shriveled seagrass beds.

Or they use up all the dissolved oxygen in the water as they decay -- a condition called hypoxia -- smothering organisms that can't swim away.

"They can really devastate a system at the local scale," said Alina Corcoran, a research scientist at the Florida Fish and Wildlife Conservation Commission.

When one type of algae takes over, it can wreak havoc with the base of the food web by displacing better food sources. Zooplankton that eat algae sense the toxicity, so NOAA's Sunda said they are faced with a tough choice: "Either be poisoned or starve. Either way, they die."

That's a problem, he said, for the fish that eat the zooplankton, and so forth.

But it's not just marine animals that are affected. Toxic algal blooms also pose serious health risks to humans.

Perhaps the most well-known problem is shellfish poisoning. The shellfish don't die when they come in contact with the algae, but the toxin accumulates in their tissues.

"Sometimes, during the height of a red tide bloom, they are so toxic that just a few mussels or clams could be enough to kill a person," NOAA's Magnien said.

There is now extensive monitoring in and around U.S. shellfish beds, so regulators can stop harvesting until the bloom has dissipated and the shellfish no longer test positive for toxins.

But what might be less known -- at least to those who have never experienced red tide firsthand -- is algae cells get kicked into the air by sea spray, causing healthy people to cough and triggering asthma or more severe reactions in people with respiratory illnesses.

Sunda said he could only stay at the beach for a few minutes when there was a bloom.

"You couldn't breathe the air," he said. "Nobody in their right mind will go to the beach. It is unbelievably unpleasant."

Barb Kirkpatrick, a public health researcher at Mote Marine Laboratory in Sarasota, Fla., has found that an hourlong walk on the beach during a bloom was enough to cause asthma symptoms for five days. She also found a bloom corresponded to an uptick in local emergency room visits related to gastrointestinal and respiratory complaints. She is currently analyzing data to determine whether the same pattern occurs statewide.

Early warnings

People can't control harmful algal blooms any more than they can control hurricanes or tornadoes. But if marine managers know where they are headed and when, it's possible to mitigate the impacts by providing early warnings to beachgoers and fishermen, Magnien said.

Right now, the primary way managers discover whether harmful algae is present at dangerous levels is by putting water samples under a microscope and counting cells. Florida officials analyze hundreds of water samples a week for more than 25 species of harmful algae. If a conservative threshold is met, shellfish beds are shut down.

These tests are combined with satellite images and wind and current models to create three-day forecasts.

In New England, NOAA is issuing seasonal forecasts, based on estimates of dormant algae in the sediment and other factors like water temperatures and runoff. The agency yesterday issued a "moderate" red tide forecast for this spring and summer along the Gulf of Maine, which may result in shellfish bed closures.

Blooms are patchy and highly dependent on winds and currents, so they can affect one beach for a couple of days while a nearby beach is fine.

During the 2005-2006 red tide along the southwest Florida coast that lasted for more than a year, Mote Marine Lab's Kirkpatrick launched a beach conditions report that now covers 36 beaches along the Gulf Coast.

Along with surf, swim and wind conditions, it provides daily updates on harmful blooms based on observations by lifeguards or park rangers. Among their criteria: the number of coughs they hear, the number of dead fish they count and water color.

While not as precise as counting cells, Kirkpatrick said, the system has been well-received by the public, which can check which beach to go to before leaving the house.

"Beachgoers don't really care how many critters are in the water," Kirkpatrick said. "They want to know, 'If I go to the beach, am I going to cough? Are there dead fish on the beach? I have a family member with asthma, are they going to get sick?'"

'Better, faster, cheaper' detection

Efforts are under way across the country to improve detection monitoring, so it can be done in real time directly from the ocean. For example, Gary Kirkpatrick, another researcher at Mote Marine Lab, built an optical sensor called the BrevBuster that measures Karenia brevis and beams the information back to shore via satellite.

A tool that could be used for a wider variety of algae is the environmental sample processor (ESP), a robotic genetics lab developed by the Monterey Bay Aquarium Research Institute. The machine collects water samples, extracts and sequences DNA, and transmits the results back to shore.

"That offers a promise for a better, faster, cheaper method to detect these cells and their toxins," Magnien said.

However, an ESP network, like a system of weather stations, is still a ways off, said Don Anderson, the director of the National Office for Harmful Algal Blooms at the Woods Hole Oceanographic Institution.

Anderson is deploying two ESPs this year as part of an effort to help transition the technology from an expensive research tool to a commercially viable product.

"It's very, very important that we prove the scientific value and the management value," he said.

ESP one of the more promising tools for getting ahead of harmful blooms, Anderson said.

Others are working on inexpensive, low-tech rapid detection kits for remote countries that lack sophisticated laboratories. The most widespread problem from toxic algae is ciguatera fish poisoning; people who eat infected fish experience a range of reactions from diarrhea or vomiting to neurological dysfunction and even death.

Magnien leads the Intergovernmental Panel on Harmful Algal Blooms. The U.N. panel is meeting next month in Paris -- many of these issues will be on its agenda, along with prioritizing research needs and sharing technology so no country has to reinvent the wheel.

While the United States has a lot to share about forecasting and detection technologies, it has a lot to learn from others, Magnien said. For example, some countries add clay to the water, which causes the algae to clump and sink, effectively clearing the water column. The United States is investigating how well it works and whether there are unintended consequences on the sea floor, he said.

"The Far East is way ahead of us in technology and techniques to protect aquaculture operations to protect from harmful algae," he said.

Want to read more stories like this?

