Red tide probably has been around almost as long as the oceans themselves.
Some scholars believe that Moses’ biblical plague was the first recorded red tide bloom, and legend tells that American Indian tribes went out the night before harvesting shellfish and stirred up the seawater to see if it glowed with phosphorescent toxic algae. If it did, the mussels weren’t safe to eat.
Every summer, portions of the Atlantic Ocean turn a deep reddish-orange and a poisonous microscopic algae called Alexandrium washes toward the Maine coast. It poisons shellfish, then sickens, and even kills, the people and wildlife that eat tainted clams, mussels or oysters. Reports of Alexandrium have just begun to be received this week.
“It’s about as bad as it gets anywhere right around here, and nobody knows why,” said David Townsend, a University of Maine professor who studies phytoplankton.
For the past 50 years, Maine has had a first-alert system, a network of coastal volunteers who test the water and work with the Department of Marine Resources to protect the public. Since the program began, Maine has never recorded a death from red tide, a testament to volunteers’ vigilance, said Jay McGowan of the DMR.
More than 20 types of phytoplankton are found along Maine’s coast, but the volunteers are watching only for four that are known to be harmful.
Alexandrium, Dinophysis, Prorocentrum and Pseudonitzschia can cause illness and even death, said Sarah Gladu, head of the phytoplankton monitoring program, who is employed by both Maine Sea Grant and the University of Maine Cooperative Extension.
Viewed through a microscope, Alexandrium is round and golden brown and it moves through the water with a corkscrew motion. Each tiny organism has an appendage to help it swim, and the means to produce a deadly poison. Swimmers, and even fish, can’t absorb enough toxin to harm them. But the toxin can build up in high concentrations in the flesh of filter-feeding oysters, clams and, particularly, mussels.
When a person eats enough tainted shellfish, the toxin causes a disease known as paralytic shellfish poisoning. In serious cases of PSP, a person’s diaphragm, the muscle that allows us to breathe, is paralyzed and the victim can survive only with the aid of a respirator.
Both Dinophysis and Prorocentrum have been blamed for diarrhetic shellfish poisoning, a violent and immediate type of food poisoning. Pseudonitzschia causes amnesic shellfish poisoning – a strange disease that killed a handful of people and permanently destroyed the short-term memory of nearly 100 others who ate mussels during a late ’90s bloom off Prince Edward Island.
Though illnesses are rare, Maine is constantly on the watch.
“Basically, it comes down to public health,” Gladu said.
Alexandrium – Maine’s biggest threat – typically starts appearing near outer islands and peninsulas by the end of June. If the conditions are right, it can move into the bays and start ruining shellfish beds just a few days later.
“They can bloom up really fast,” McGowan said.The pattern changes every year. Last summer, no blooms moved inland. This year is late because of the cold ocean water. “The devil’s in the details, and the details keep changing,” McGowan said.
Townsend is trying to solve the mystery.
Last year, he completed a five-year joint research project with scientists from throughout New England who investigated a theory that Alexandrium lives far offshore, and comes inland on the same currents that bring Maine its weather.
More than 2,000 water samples later, they have proved the theory.
“We did more cruises and more sample stations than had ever been done before,” Townsend said.
The project also showed that Alexandrium blooms only when the sunlight and nutrient levels are in the right balance, explaining why some areas see blooms year after year, while others seem immune.
But years of research are necessary before scientists can predict red tide blooms with anything approaching the precision of weather forecasts.
“We need to have this first-alert system … though we are developing new tools, [red tide] continues to surprise us,” Gladu said.
Every day, Jane Disney takes a group of students out to test the waters around Mount Desert Island. The biology teacher from Bar Harbor is one of 50 volunteers statewide who make up the state’s first-alert system.
“By hook or by crook, we have somebody out there,” she said.
On a recent morning, the crew from the Mount Desert Island Water Quality Coalition, which Disney and her students founded, was peering at water droplets under microscopes.
Students counted the organisms and recorded their findings on data sheets bound for the DMR.
The state started sampling statewide in 1975, in response to a large phytoplankton bloom in the western Gulf of Maine three years earlier. But with tight budgets in recent years, the volunteer effort – the only such program in the United States – has become critical, Gladu said.
“Right now, I think the state of Maine is a model for the whole world,” Disney said.
Disney and her fellow volunteers send their data to the DMR, where biologists determine whether a bloom is occurring.
“Just because you see some of these toxic cells on a microscope slide doesn’t mean you have a public health problem,” McGowan said. “These diatoms are out there most of the time.”
But a high concentration of the organisms indicates a bloom, and shellfish samples are taken.
To test for Alexandrium, biologists grind up shellfish, extract the poison, then inject it into mice to see how long they survive. A dead mouse typically means an emergency closure of local clam flats. To test for the other toxins, the shellfish samples are sent to a federal lab.
Two years ago, Disney’s students saw Alexandrium in their samples, and, soon, all the clam flats on MDI were closed.
Doing “real science” with real results attracts volunteers, This summer, middle school, high school and college students are participating, along with a local retiree. Disney jokes about shoving her students out of the way to look at a rare organism in their microscopes.
“You could spend a lifetime on this, and every day, the ocean reveals something new,” she said.
Maine?s Toxic Blooms
Phytoplankton monitoring volunteers are on the lookout for four types of diatoms, or microscopic algae, that make toxins. The toxins are harmless to swimmers and fish, but are concentrated in the flesh of most shellfish, where they can be poisonous when eaten by birds and people.
Alexandrium: Causes paralytic shellfish poisoning, an illness that often kills by paralyzing the diaphragm and causing the victim to suffocate. Alexandrium lives in the open ocean and comes in to shore during the summer. It?s common in Maine, and people have been hospitalized, but no deaths from eating tainted shellfish have ever been recorded.
Dinophysis: Causes diuretic shellfish poisoning, with immediate symptoms like food poisoning, but there have never been any verified cases in Maine. Though the phytoplankton is common here, the toxin that it produces has only been found in very low, harmless, levels in Maine shellfish.
Prorocentrum: Causes diuretic shellfish poisoning. Until recently, scientists didn?t know it lived in Maine waters. Blooms here have been patchy, and no illnesses have been verified.
Pseudonitzcia: Causes amnesiac shellfish poisoning, which can be fatal. The name comes from a complete loss of short-term memory suffered by victims. The organism has been found here in Maine, and DMR has twice closed clam flats in Washington County as a precaution. However, tests have never found the toxin that causes ASP in either shellfish or the pseudonitzcia itself. Scientists hypothesize that something in the environment triggers the organism to become toxic, but don?t agree on the cause.