Planktic foraminifera iodine/calcium ratios from plankton tows

Winkelbauer, Helge A.; Hoogakker, Babette A.; Chance, Rosie J.; Davis, Catherine V.; Anthony, Christopher J.; Bischoff, Juliane; Carpenter, Lucy J.; Chenery, Simon R.N.; Hamilton, Elliott M.; Holdship, Philip; Peck, Victoria L. ORCID: https://orcid.org/0000-0002-7948-6853; Poulton, Alex J.; Stinchcombe, Mark C.; Wishner, Karen F.. 2023 Planktic foraminifera iodine/calcium ratios from plankton tows. Frontiers in Marine Science, 10, 1095570. 11, pp. 10.3389/fmars.2023.1095570

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Text (Open Access Paper) © 2023 Winkelbauer, Hoogakker, Chance, Davis, Anthony, Bischoff, Carpenter, Chenery, Hamilton, Holdship, Peck, Poulton, Stinchcombe and Wishner. fmars-10-1095570.pdf - Published Version Available under License Creative Commons Attribution 4.0. Download (1MB) | Preview

Abstract/Summary

Planktic foraminifera test iodine to calcium ratios represent an emerging proxy method to assess subsurface seawater oxygenation states. Several core-top studies show lower planktic foraminifera I/Ca ratios in locations with oxygen depleted subsurface waters compared to well oxygenated environments. The reasoning behind this trend is that only the oxidized species of iodine, iodate, is incorporated in foraminiferal calcite. The I/Ca of foraminiferal calcite is thought to reflect iodate contents in seawater. To test this hypothesis, we compare planktic foraminifera I/Ca ratios, obtained from plankton tows, with published and new seawater iodate concentrations from 1) the Eastern North Pacific with extensive oxygen depletion, 2) the Benguela Current System with moderately depleted oxygen concentrations, and 3) the well oxygenated North and South Atlantic. We find the lowest I/Ca ratios (0.07 µmol/mol) in planktic foraminifera retrieved from the Eastern North Pacific, and higher values for samples (up to 0.72 µmol/mol) obtained from the Benguela Current System and North and South Atlantic. The I/Ca ratios of plankton tow foraminifera from environments with well oxygenated subsurface waters, however, are an order of magnitude lower compared to core-tops from similarly well-oxygenated regions. This would suggest that planktic foraminifera gain iodine post-mortem, either when sinking through the water column, or during burial.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.3389/fmars.2023.1095570
Additional Keywords:	I/Ca, Planktic foraminifera, Plankton nets, oxygen concentraiton, oxygen proxy
Date made live:	02 Feb 2023 11:40 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/533913

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