Tons of Iron in the Southern Ocean

An American oceanographer, John Martin, also turned his attention to the paradox of nutrient salts abundance /phytoplankton scarcity. It should be pointed out that this enigma is not endemic to the Southern Ocean, but is also found in the Equatorial and Arctic Pacific.

His hypothesis was based on the iron deficiency of the water. At the beginning, this was merely an intuition, but of course based on scientific publications. Nevertheless, the hypothesis caused quite a stir; for, while cautiously advancing this new idea, the Director of Moss Landing Marine Laboratories (south of San Francisco) was suggesting that a deliberate iron-enrichment of the Antarctic Ocean (therefore a manipulation of the chemical components of the ocean) could not only stimulate artificial flowering of the microscopic algae but also - after the fashion of the vegetation that consumes the CO2 in the surrounding air - bring about a reduction of the carbon dioxide level in the atmosphere. He was claiming that 300,000 tons of iron would be enough to remove two billion tons of CO2 from the atmosphere.

A deliberate iron-enrichment of the Antarctic Ocean (therefore a manipulation of the chemical components of the ocean) could not only stimulate artificial flowering of the microscopic algae but also bring about a reduction of the carbon dioxide level in the atmosphere.

John Martin's theory was so spectacular that the American Press seized upon the subject (1) closely followed by the scientists who were getting together in 1991; the latter recommended their governments to consider the impact of iron on marine productivity as a field of research and not as a political expedient for neglecting the need to reduce the carbon dioxide emissions of their respective industries.

Once home again, the oceanographers went back to work. They came up with two solutions: either to remain at the observation and research level (to go and look for, in the areas where this paradox was present, anomalies that could provide elements of a response or even to follow and locate these same areas by satellite), or to apply practised laboratory methodology to oceanography, that is to say to disturb the system in order to analyse the reactions: in other words, to go and throw not inconsiderable quantities of iron into the ocean in order to observe the effects of this artificial fertilisation on the phytoplankton.
It was this second route that was taken by John Martin's colleagues, the latter having died in June 1983 without having been able to validate his hypothesis. Three months later, 450 kilograms of iron were dispersed over an area of 65km² 500 kilometres to the south of the Galapagos Islands.
Even though they were not very striking, the results showed nevertheless that, thanks to this shock treatment, the microscopic algae made more effective use of the luminous energy and saw a fourfold multiplication of their carbon production.
But the experiment was less satisfactory in terms of chemical reaction; on the one hand, CO2 was not reduced in the manner foreseen in John Martin's calculations, and on the other, there was no significant reduction in the concentration of nutrient salts.

The operation was renewed two years later under the name of IronEx II. This time, success was at the end of the road; after having injected iron into the Equatorial Pacific for a week, the algae grew in such a manner that they significantly reduced the nitrate concentration of the water and absorbed 30% of carbon dioxide initially present. Although the complete results of this latest experiment are not yet available, the hypothesis of the ocean's iron deficiency had been brilliantly confirmed.

 

(1) See the article by Curt Suplee "How To Save The World : Give Oceans An Iron Shot", International Herald Tribune, Tuesday 15 October 1996.