Source: Press Herald [edited]
<http://www.pressherald.com/news/state/031023whales.shtml>
Sea poison: Natural toxin is found in dead whales
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Poison in microscopic algae may have killed as many as 21 large
whales that were found floating off the New England coast in July
2003. Domoic acid, a natural toxin that had never been known to kill
marine mammals in the Atlantic Ocean, was found in samples
taken from some of the dead humpbacks and other whales. More
tests are under way to confirm the suspicion that the whales died
after eating plankton or fish containing the poison.
Researchers working with the National Marine Fisheries Service
disclosed the preliminary findings Wednesday at a meeting of the
U.S. Marine Mammal Commission in Newport, R.I.
Although scientists immediately suspected food poisoning as a
culprit, finding domoic acid was a surprise. The toxin has killed sea
lions and other animals off the West Coast, but had never been
connected to marine mammal deaths on the East Coast.
The findings also underscore the risk to humans from harmful algal
blooms that can poison the ocean food chain. Scientists first
identified domoic acid in 1988, when 4 Canadians died and many
more were sickened from eating Prince Edward Island mussels
that had filtered the toxic plankton out of the water. Some of those
who survived suffered permanent memory loss.
"It attacks the brain," said Mark Wells, an associate professor at
the University of Maine's School of Marine Sciences. "It causes
nerve cells to fire continuously and die."
Officials in Canada and Maine now monitor for domoic acid and
other waterborne toxins, and there have been no more fatal
poisonings of people.
Domoic acid has never been found in dangerous levels along the
Maine coast, where it could taint clams or mussels, said Amy
Fitzpatrick of the Maine Department of Resources. The dead
whales were found about 200 miles southeast of Portland
[Maine, USA] and do not suggest any increased threat along the
coast, she said.
Federal and state officials also said the findings do not necessarily
mean that domoic acid was a factor in the deaths of at least 9
whales and dozens of seals that were found along the Maine coast
in September and early October [2003]. Samples from some of
those animals are still being tested for domoic acid as well as other
potential culprits. Although both clusters of marine mammal deaths
were highly unusual, they may well be unrelated, said Teri Frady, a
spokeswoman for the National Marine Fisheries Service's
Northeast Science Center. "I would resist linking this particular
event to the (dead animals found) in Maine," she said.
Domoic acid is not related to the toxin in red tide, a more common
and notorious algal bloom that forced the state to ban mussel and
clam harvesting this fall. Eating shellfish severely contaminated by
the red tide toxin can cause paralysis and death. Parts of the
Maine coast remain off-limits to mussel harvesting and clam
digging, although the contamination levels are gradually dropping
and some parts of the coast have been reopened.
Toxic red tide algae were blamed for a similar cluster of whale
deaths in 1987 off Cape Cod, and quickly became the prime
suspect when the whales were found around Georges Bank in July
[2003]. Most of the whales were humpbacks, which feed on
plankton as well as small fish. There also was a fin whale and a
pilot whale. They showed no signs of a viral infection or injury.
Samples of tissue and waste products taken from the whales have
not tested positive for significant exposure to the toxin in red tide.
The finding of domoic acid, however, suggests it was a more
unusual form of food poisoning.
Reports of harmful or toxic algal blooms have increased around the
world in recent years. Last year [2002], for example, almost 100
whales and dolphins beached in southern California, apparently
because of domoic acid poisoning.
Some have linked the algal blooms to such factors as global
warming, increased pollution and ship traffic that carries organisms
around the globe. David Townsend, director of the University of
Maine's School of Marine Sciences, said pollution may be a factor
in some cases of algal blooms. But the organism producing domoic
acid lives in pristine waters, scientists said.
Townsend said the more significant reason for the increasing
reports is that scientists have only recently begun studying the
toxins. "The more you look, the more you see," he said.
Domoic acid, for example, was identified only after the deaths in
Canada in 1988. It likely existed for millions of years, however, and
has since been found around the world, Wells said.
The findings reported on Wednesday were significant because
scientists had never before documented domoic acid killing whales
in the North Atlantic, Wells said. But, he said, that doesn't mean it
never happened. "There are all sorts of unexplained marine
mammal deaths," he said. "It's possible these toxic events have
been happening."
[Byline: John Richardson]