Chemically and Geographically Distinct Solid-Phase Iron Pools in the Southern Ocean

Abstract

Swimming in Iron Pools Because iron is essential for marine phytoplankton growth, its availability limits the primary productivity of the oceans. Iron is typically bioavailable only when present in a dissolved state; however, a large fraction of the total iron in the oceans exists as tiny solid-phase particles ranging in size from a few nanometers to a few micrometers. von der Heyden et al. (p. 1199 ) used high-resolution x-ray microscopy and spectroscopy to characterize the distribution of iron particles along two transects of the Southern Ocean. Analysis of a number of individual particles reveals strong variation in iron oxidation state, particle mineralogy, and substitution of aluminum for iron—all of which control the solubility, and hence bioavailability, of iron.