Red tide poisons food of sea cows
Ray Lopez Braindead Killfile the Pest
AID=/20070422/NEWS/704220314
Red tide poisons food of sea cows
Even after noxious algae dies off, toxins left in sea grasses can kill
manatees.
By KATE SPINNER
kate.s...@heraldtribune.com
When 27 manatees died from red tide poisons near the Caloosahatchee River
in March and April, there were no signs of a red tide bloom.
But toxins from an earlier bloom settled into sea grass beds near Fort
Myers, and the grasses stayed poisonous for weeks. As the weather warmed,
manatees migrated out of their river wintering grounds and ate the deadly
grass.
Because scientists are just beginning to realize that red tide can render
sea grass toxic weeks after a bloom passes, few solutions have been
proposed to make spring migration for manatees less deadly.
"It's really a dangerous time now," said Jan Landsberg, a marine
scientist at Florida Wildlife Research Institute.
Manatees frequently perish when a red tide bloom creeps into Charlotte
Harbor's estuaries during their spring migration, but it's unusual for so
many to die in the absence of a bloom, said Leanne Flewelling, a
scientist with the Florida Fish and Wildlife Conservation Commission.
The last time that sort of event happened was in 2002, when 30 manatees
died between March 10 and April 30, weeks after an intense February bloom
had dissipated.
The only possible culprit in both cases was tainted sea grass, because
the red tide bloom had gone away.
"When there's an actual bloom present, then there's all different routes
of exposure," Flewelling said.
With the help of researchers such as Flewelling, scientists have begun to
realize that sea grasses can remain poisonous to marine life for weeks,
even months, after red tide has passed.
Flewelling's tests showed that sea grasses near the mouth of the
Caloosahatchee retained lethal amounts of toxin for weeks, at least into
early April.
The manatees died over a three-week period, starting on March 14.
Necropsies show the animals probably died quickly, said Ken Arison, a
biologist with the state's marine mammal pathology lab.
The persistence of toxins in sea grass adds complexity to a question that
already confounds scientists -- how to keep red tide away from manatees.
Landsberg introduced a proposal to push salt-loving red tide algae out of
the Caloosahatchee River with water from Lake Okeechobee last summer at a
conference on harmful algae.
But in drought years, the lake has little water to spare. And if grasses
stay toxic for weeks, a flush might not do much good.
The Caloosahatchee is one of the most popular winter refuges for manatees
in the state. More than 400 at a time have been counted near the warm
outfall of a power plant on the river east of Fort Myers.
It is also a river vulnerable to extreme fluctuations in salinity. When
red tide is present near shore in the dry season, the toxic algae can
start to proliferate in the river.
Red tide algae usually thrive in oceanic waters, not rivers and bays.
The algae naturally produce deadly chemicals called brevetoxins. Fish are
usually the first victims of a bloom, but the poisons go on to kill
birds, dolphins and manatees.
Red tide is such a unique threat to the approximately 1,000 manatees in
Southwest Florida that a state report last year predicted their numbers
would drop 80 percent in three generations. The same report recommended
reclassifying the manatee from endangered to threatened, because they are
faring better in other parts of the state where red tide is rare.
Federal scientists also reported last month that manatees no longer meet
the criteria for a federally endangered species.
It could be years before the animal is downlisted federally and months
before it is officially reclassified in the state.
In a seeming contrast to the reports, a record 417 manatees died in
Florida waters last year, about 50 due to red tide exposure in the summer
and fall.
Scientists have long suspected that the manatees die from red tide by
consuming the toxins. Years ago, however, they thought manatees got
exposed by eating sea squirts, which often inhabit grassy areas and
accumulate toxins similar to shellfish. Flewelling said her research is
showing that the chemicals either cling to the grasses or become absorbed
by them. Sea squirts could still be a factor, she said.
Flewelling and Landsberg said research is concentrating on how manatees
get exposed to red tide and why they end up dying. Once scientists grasp
the problem, more research might be directed at keeping the animals out
of harm's way.
Patrick Rose, executive director of Save the Manatee Club, said there are
a couple commonsense solutions.
Wildlife officials could more aggressively locate animals in distress and
rehabilitate them to keep them from dying.
He also said that reducing pollution from fertilizers, septic tanks and
sewers could help keep red tide at bay.
Some scientists say nutrient pollution is contributing to long-lasting
blooms that stretch into the dry season.
"There's getting to be more and more evidence that man-induced pollution
might be actually making red tide worse," Rose said. "If that is the
case, they could go to work on reducing pollution levels in the
Caloosahatchee and other water bodies."
catt...@yahoo.com
Ray Lopez Braindead Killfile the Pest wrote:
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> Red tide poisons food of sea cows
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