Iron supply and demand in the upper ocean: Is extraterrestrial dust a significant source of bioavailable iron?

Interplanetary dust particles accrete on the Earth at a rate of ∼40 ktons yr −1 . Some 90% of this material evaporates in the atmosphere, producing a bioavailable iron flux of 3×10 −7 mol Fe m −2 yr −1 . This extraterrestrial Fe flux is 30–300% of the eolian flux of bioavailable iron transported from terrestrial sources in remote marine regions and ∼20% of the upwelled Fe flux in the Southern Ocean. Extraterrestrial Fe may play an important role in regulating the marine carbon cycle in these regions.