Algae "Techno-Fix" Found Toxic to Sea Life
Toxic troubles for climate 'fix'
BBCNews.com, March 16, 2010
Fertilising
the oceans with iron to absorb carbon dioxide could increase
concentrations of a chemical that can kill marine mammals, a study has
found.
Iron stimulates growth of marine algae that absorb CO2 from the air, and has been touted as a "climate fix".
Now researchers have shown that the algae increase production of a nerve poison that can kill mammals and birds.
Writing in Proceedings of the National Academy of Sciences, they say this raises "serious concern" over the idea.
The toxin - domoic acid - first came to notice in the late 1980s as the cause of amnesiac shellfish poisoning.
It is produced by algae of the genus Pseudonitzschia , with concentrations rising rapidly when the algae "bloom".
Now, its
presence in seawater often requires the suspension of shellfishing
operations, and is regularly implicated in deaths of animals such as
sealions.
Domoic
acid poisoning may also lie behind a 1961 incident in which flocks of
seabirds appeared to attack the Californian town of Capitola - an event
believed to have shaped Alfred Hitchcock's interpretation of Daphne du
Maurier's The Birds in his 1963 thriller.
Carbon focus
Over the last decade, about 10 research projects have investigated iron fertilisation, with mixed results.
But only
two of them measured domoic acid production, and only then as an
afterthought, explained William Cochlan from San Francisco State
University, a scientist on the new project.
"We had a
number of major aims in this work; but one of them was to ask 'do you
normally find the species of algae that produce domoic acid, are they
producing domoic acid, and will production be enhanced by iron?'," he
said.
In
studies conducted around Ocean Station Papa, a research platform moored
in the north-eastern Pacific Ocean, the answers to all three questions
turned out to be "yes".
Pseudonitzschia algae
were present naturally; they were producing domoic acid, and
experiments showed that production increased during fertilisation with
iron and copper.
Also, under iron-rich conditions, the Pseudonitzschia algae bloomed at a rate faster than other types.
The
levels of domoic acid in iron-enriched water samples were of the same
order as those known to cause poisoning in mammals in coastal waters.
Ailsa
Hall, deputy director of the Sea Mammal Research Institute at St
Andrews University in Scotland, said that domoic acid poisoning was
already becoming a regular occurrence in some parts of the world.
"Ever since 1998 we've seen regular episodes of mass mortality and seizures in sea lions on the US west coast," she said.
The toxin accumulates in animals such as fish that are themselves immune.
"We've
seen it in seals, pelicans and harbour porpoises; it does depend on how
much they eat, but if a sea lion or a pelican eats its way through a
school of contaminated anchovies, then that would be enough," Dr Hall
told BBC News.
Domoic
acid's effect on other species was unknown, she said, but it would be
reasonable to think it would also affect marine mammals such as whales.
Whether iron fertilisation ever will be deployed as a "climate fix" is unclear.
The last
major investigation - last year's Lohafex expedition - found that
despite depositing six tonnes of iron in the Southern Ocean, little
extra CO2 was drawn from the atmosphere.
Nevertheless, one company - Climos - aims eventually to deploy the technique on a commercial basis.
A Climos spokesman agreed that further research on domoic acid production was needed.
"Moving
forward, we need to understand exactly how deep-ocean phytoplankton
respond to iron, be it naturally or artificially supplied; whether and
in what situations domoic acid is produced, and how the ecosystem is or
is not already adapted to this," he said.
For
William Cochlan's team, the potential impact on sea life is something
that regulators and scientists must take into account when deciding
whether to allow further studies or deployment.
"We saw
some literature going around with claims like 'there is no indication
of toxicity to sea life' - well, if you don't measure it, of course
there's no indication, and we have to keep that kind of legalese out of
science," he said.
"If the end goal is to use it to fight climate warming, then we have to understand the consequences for marine life."
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