There's good and bad news for those who believe adding iron to the oceans will create enough plankton to drag CO2 to a watery grave and thereby save the planet from global warming.
First the good news: a controversial experiment to seed the waters of the Scotia Sea, east of Argentina with six tonnes of iron sulphate over 300sq km, has definitively been given the green light by German authorities.
The experiment, which is called Lohafex, was put on hold earlier this month as the Germans investigated whether the iron fertilisation research broke environmental standards or international law in force.
The conclusion was that it did neither and so the iron has been dumped and researchers will monitor the site for 40 days aboard the German polar research ship RV Polarstern.
The plankton community biomass is expected to increase substantially about two weeks following fertilisation, and the fate of the organic matter produced will be investigated in detail, said the Alfred Wegener Institute for Polar and Marine Research.
The decision to proceed with Lohafex by the Germans did not sit well with environmental pressure groups, which are concerned about the long-term impacts of such experiments.
Yesterday the World Wildlife Foundation issued a statement saying it was now "doubting Germany's commitment to global agreements on the environment".
"The German government's decision is appalling," said Stephan Lutter, international marine policy officer of WWF Germany, adding that the government has chosen to forego its international obligations and instead undermine and ignore agreements it was party to last year.
The bad news for ocean fertilisation proponents may mean the whole controversy could peter out in the not too distant future because a separate study on iron in the oceans and its affect on CO2 produced non-too-encouraging results.
Researchers tested iron-rich water off the volcanic Crozet Islands in the Southern Ocean and found that though increased iron supply may directly have enhanced carbon export to the deep ocean the area only two-to-three times richer in carbon - less than previously thought.
"[However] our estimate of carbon sequestration for a given iron supply still falls 15-50 times short of some geo-engineering estimates," lead author of the research Professor Raymond Pollard, of the National Oceanography Centre, Southampton told the BBC.
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