Distribution and speciation of iron in the northeast subarctic Pacific

Date

2009-11-09T22:05:46Z

Authors

Chong, Marina

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Abstract

The marine chemistry of dissolved iron (Fe) was examined in two studies conducted off the coast of British Columbia in the northeast Pacific. Dissolved (<0.4 µm) Fe was measured along inshore-offshore transects across the continental shelf in Queen Charlotte Sound. A benthic layer of high Fe, enriched due to exchange with shelf sediments, was found to extend across the shelf-slope break into offshore waters. Advection of these shelf waters may be a significant source of Fe to the nearby Fe-poor region of the northeast Pacific. In this Fe-limited gyre, little is known about the chemical speciation and bioavailability of Fe. The fractionation of dissolved Fe into inorganic and organically bound species along Line P was established by competitive ligand equilibration coupled with cathodic stripping voltammetry (CLE-CSV), and the results confirm the presence of biogenic Fe-binding ligands at concentrations in excess of dissolved Fe with conditional stability constants between 8.3 x 1010 and 5.6 x 1012 for the Fe-ligand complexes. The temporal and spatial variations observed are consistent with either a biological source of the ligands or an atmospheric source where greatest deposition occurs during the summer when stratification of the upper water column is most pronounced.

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Keywords

Seawater, iron content, British Columbia, Queen Charlotte Sound, Chemical oceanography, Pacific Ocean

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