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\t\t\t\tby Agence France-Presse <\/p>\n
WASHINGTON—Adding iron to the world’s oceans to capture
\ncarbon and fight global warming could do more harm than good, as the mineral appears
\nto boost the growth of a plankton that produces a deadly neurotoxin, a study
\npublished on Monday shows.<\/p>\n
<\/p>\n
Researchers led
\nby Charles Trick of the University of Western Ontario in Canada found that
\nfertilizing the ocean with iron can boost the growth of Pseudo-nitzschia, a
\nphytoplankton that produces a component of the neurotoxin domoic acid.<\/p>\n
<\/p>\n
Humans who eat
\nshellfish or crab that have ingested Pseudo-nitzschia could get amnesic
\nshellfish poisoning, severe cases of which can cause neurological symptoms,
\nincluding permanent, short-term memory loss, which gives the intoxication its
\nname. Amnesic shellfish poisoning can also be fatal.<\/p>\n
<\/p>\n
For the study,
\nwhich was published in the Proceedings of the National Academy of Sciences, the
\nresearchers examined water samples taken from open-ocean tracts in the
\nsub-Arctic North Pacific Ocean where iron-fertilization experiments were
\nconducted.<\/p>\n
<\/p>\n
They found that
\nthe population of Pseudo-nitzschia had doubled compared to controls, that
\nadding iron to the water appeared to increase the amount of domoic acid
\nproduced by individual phytoplankton, and that the natural release of the toxin
\nboosted further growth of the potentially harmful plankton.<\/p>\n
<\/p>\n
Previous
\niron-enrichment experiments have focused on studying how adding iron to the sea
\naffects carbon cycling, but have overlooked the potential ecological impacts of
\ngeoengineering-designed fertilizations, the study found.<\/p>\n
<\/p>\n
Earlier studies
\nby other teams have shown that iron fertilization produced no measurable
\nquantities of domoic acid, and that some coastal Pseudo-nitzschia produced only
\nlow concentrations of the toxin.<\/p>\n
<\/p>\n
Iron
\nfertilization is still mainly in the experimental phases, with about “12 experiment-sized iron fertilizations”
\nalready undertaken, mainly in the Pacific Ocean, Trick told AFP.<\/p>\n
<\/p>\n
The findings of
\nthe study he led raise “serious concern over the net benefit and
\nsustainability of large-scale iron fertilizations.”<\/p>\n
<\/p>\n
Scientists in
\nthe 1990s began fortifying small areas of the ocean where the sea water is rich
\nin nutrients but low in plankton, to see if adding iron to the water would
\nstimulate the growth of phytoplankton and boost carbon capture.<\/p>\n
<\/p>\n
Adding iron resulted
\nin rapid growth of the phytoplankton, which, in the process of photosynthesis,
\nuses energy from sunlight to fix inorganic carbon in surrounding surface waters
\nto produce organic carbon.<\/p>\n
<\/p>\n
Some of the
\norganic carbon ends up deep in the ocean, effectively removing carbon from the
\nsurface waters, while surface-water carbon is replenished by taking carbon
\ndioxide from the atmosphere.<\/p>\n
<\/p>\n
Iron
\nfertilization, like other forms is geoengineering, is “purposely changing
\nthe system and may have unintended consequences,” said Scott Doney, a
\nsenior scientist at Woods Hole Oceanographic Institution in Massachusetts,
\ncommenting to AFP on the findings.<\/p>\n
<\/p>\n
“You have to weigh how the changes affect higher animals, how it
\naffects fish and mammals,” said Doney, who did not take part in the study.
\n“You have to know what are the trade-offs between how much carbon you
\nactually store and how big an effect you have on the environment.”<\/p>\n
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