Karin Zeitvogel Yahoo News 16 Mar 10;
WASHINGTON (AFP) – Adding iron to the world's oceans to capture carbon and fight global warming could do more harm than good, as the mineral appears to boost the growth of a plankton that produces a deadly neurotoxin, a study published Monday shows.
Researchers led by Charles Trick of the University of Western Ontario in Canada found that fertilizing the ocean with iron can boost the growth of Pseudo-nitzschia, a phytoplankton that produces a component of the neurotoxin, domoic acid.
Humans who eat shellfish or crab that have ingested Pseudo-nitzschia could get amnesic shellfish poisoning (ASP), severe cases of which can cause neurological symptoms, including permanent, short-term memory loss, which gives the intoxication its name.
Amnesic shellfish poisoning can also be fatal.
For the study, which was published in the Proceedings of the National Academy of Sciences, the researchers examined water samples taken from open-ocean tracts in the sub-Arctic North Pacific Ocean where iron-fertilization experiments were conducted.
They found that the population of Pseudo-nitzschia had doubled compared to controls, that adding iron to the water appeared to increase the amount of domoic acid produced by individual phytoplankton, and that the natural release of the toxin boosted further growth of the potentially harmful plankton.
Previous iron-enrichment experiments have focused on studying how adding iron to the sea affects carbon cycling, but have overlooked the potential ecological impacts of geo-engineering-designed fertilizations, the study, which was published in the Proceedings of the National Academy of Sciences, says.
Earlier studies by other teams have shown that iron fertilization produced no measurable quantities of domoic acid, and that some coastal Pseudo-nitzschia produced only low concentrations of the toxin.
Iron fertilization is still mainly in the experimental phases, with about "12 experiment-sized iron fertilizations" already undertaken, mainly in the Pacific Ocean, Trick told AFP.
The findings of the study he led raise "serious concern over the net benefit and sustainability of large-scale iron fertilizations."
Scientists in the 1990s began fortifying small areas of the ocean where the sea water is rich in nutrients but low in plankton, to see if adding iron to the water would stimulate the growth of phytoplankton and boost carbon capture.
Adding iron resulted in rapid growth of the phytoplankton, which, in the process of photosynthesis, uses energy from sunlight to fix inorganic carbon in surrounding surface waters to produce organic carbon.
Some of the organic carbon ends up deep in the ocean, effectively removing carbon from the surface waters, while surface-water carbon is replenished by taking carbon dioxide from the atmosphere.
Iron fertilization, like other forms is geo-engineering is "purposely changing the system and may have unintended consequences," said Scott Doney, a senior scientist at Woods Hole Oceanographic Institution in Massachusetts, commenting to AFP on the findings.
"You have to weigh how the changes affect higher animals, how it affects fish and mammals," said Doney, who did not take part in the study.
"You have to know what are the trade-offs between how much carbon you actually store and how big an effect you have on the environment," he said.
Toxic troubles for climate 'fix'
Richard Black, BBC News 17 Mar 10;
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."
