Argument: Iron fertilization may require an impractical amount of iron
"Iron Fertilization Of Oceans: A Real Option For Carbon Dioxide Reduction?" Science Daily. 10 June 2007 - "Twelve oceanographic expeditions were carried out between 1993 and 2005 is the North Pacific, the Equatorial Pacific and the Southern Ocean to test the iron fertilization hypothesis. However, as pointed out by Hein de Baar, from the Netherlands Institut voor Onderzoek der Zee (NIOZ, Texel, The Netherlands), today after all those experiments we know that they are many losses and that this manipulation is not a real efficient way to capture and store CO2 into the deep ocean. Much more iron is needed that had originally been suggested for algae to bring down a certain amount of CO2 from the atmosphere."