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Abstract

Primary productivity in large areas of the Southern Ocean is limited by the availability of a key micronutrient—iron (Fe). Recently it has been suggested that marine animals could play an important role in recycling Fe through their diet and subsequent defecation, however there is no information on the relative bioavailability of faecal Fe for uptake. The bioavailability of Fe in seawater is controlled by a number of complex interactions. The physical separation between the dissolved ( 0.2 μm) fractions is one common measure used to determine element bioavailability. Here, the size fractionation of Fe from 3 whale faecal samples in 4 different size classes ( 60 μm) was investigated, along with the leaching of particulate Fe over time. Although the total particulate fraction (> 0.2 μm, 5026–22,526 nmol L−1) dominated the total Fe pool, the concentrations of dissolved Fe in whale faecal samples (186–754 nmol L−1) were three order of magnitude higher than published Southern Ocean surface seawater concentrations. Furthermore, results from the leaching experiment suggest that Fe is continually leached from faecal particles over an initial 12-hour period, thus increasing the concentration of bioavailable Fe in surface seawater. Although the concentrations measured here are some of the highest reported in the literature, the true supply of Fe back to surface seawater will be controlled by processes such as organic complexation, scavenging and sinking by particles, remineralisation, and vertical transport, not measured in this study.

Item Type:	Article
Authors/Creators:	Ratnarajah, L and Lannuzel, D and Townsend, AT and Meiners, KM and Nicol, S and Friedlaender, AS and Bowie, AR
Keywords:	iron, baleen whales, faecal material, physical speciation, solubility, dissolved iron, particulate iron, Southern Ocean, biological recycling
Journal or Publication Title:	Marine Chemistry
Publisher:	Elsevier Science Bv
ISSN:	0304-4203
DOI / ID Number:	10.1016/j.marchem.2017.05.004
Copyright Information:	Copyright 2017 Elsevier B.V.
Related URLs:	Google Scholar: Lannuzel, D UTAS Profile: Lannuzel, D Google Scholar: Townsend, AT UTAS Profile: Townsend, AT UTAS Profile: Nicol, S Google Scholar: Bowie, AR UTAS Profile: Bowie, AR
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