ORCID

0000-0001-5212-6228 (Chappell)

Document Type

Article

Publication Date

2026

DOI

10.1002/lno.70510

Publication Title

Limnology and Oceanography

Volume

71

Issue

9

Pages

e70510 (14 pp.)

Abstract

The chemical speciation of iron (Fe) has important ramifications for the stabilization, transport, and bioavailability of this critical nutrient. Organic ligands mediate dissolved Fe biogeochemistry such that ligand concentration and molecular composition help shape dissolved Fe distributions. Electroactive Fe-binding humic-like substances ("humic substances") are one such class of ligands, a mixture thought to be predominantly comprised of degradation products of marine and terrestrial origin. Here, we examine the distributions of humic substances across large environmental gradients in dissolved Fe along the West Antarctic Peninsula in early austral spring. We found that the distributions of humic substances and dissolved Fe were decoupled. Concentrations of total Fe-binding humic substances were tightly correlated with Fe bound to humic substances, or ambient Fe-bound humic substances, but not with Fe, and total Fe-binding humic substances were undersaturated in Fe across the study region. In the low Fe (< 1 nM) waters of the Drake Passage, ambient Fe-bound humic substances accounted for 10-100% of the dissolved Fe pool. Increases in Fe near the continent, however, were not associated with increases in humic substances. Rather, humic substances remained unsaturated even in elevated Fe (2.3-9.5 nM) waters inshore and ambient Fe-bound humic substances only accounted for 2-49% of the dissolved Fe pool. Our results suggest distinct sources of Fe and humic substances near the West Antarctic Peninsula and that organic complexation of Fe by humic substances here may be strongly influenced by competition for binding sites by other cations and/or with other Fe-binding organic ligands.

Rights

© 2026 The Authors.

Published under the terms of a Creative Commons Attribution 4.0 International (CC BY 4.0) License.

Data Availability

Article states: "Water column chlorophyll, dissolved iron, and humic-like substance data are available through the Biological and Chemical Oceanography Data Management Office via https://www.bco-dmo.org/dataset/740939, https://www.bco-dmo.org/dataset/781773, and https://www.bco-dmo.org/dataset/988663, respectively, with Creative Commons Attributions 4.0 international License (Chappell et al. 2018; Buck et al. 2019, 2026). Temperature, salinity, and oxygen data are available through the Marine Geoscience Data System via https://www.marine-geo.org/tools/search/Files.php?data_set_uid=24323#datasets (DOI: 10.1594/IEDA/324323), with license CC BY-NC-SA 3.0 (Jenkins 2016). Version 3.5.2 of ggplot2 used in the creation of Figs. 2 and 5 is preserved at https://ggplot2.tidyverse.org, available via the MIT license, and developed openly at 10.32614/CRAN.package.ggplot2 (Wickham 2016). This package was used in RStudio, available at http://www.posit.co/ via the GNU Affero General Public license (Posit Team 2025). Map was created using GeoMapApp at https://www.geomapapp.org available through a Creative Commons Attribution International License with the Global Multi-Resolution Topography (GMRT) base map (Ryan et al. 2009) available through a Creative Commons Attribution International License. Electro Chemical Data SOFT ware (ECDSOFT) was used to extract peak heights on voltammograms and is available and developed openly at https://puh.srce.hr/s/eAJb6M6mTpgaZos?path=ECDSOFT (Omanović 2025)."

Original Publication Citation

Moore, L. E., Kisiday, A., Yang, S. M., Chappell, P. D., Bundy, R. M., Jenkins, B. D., & Buck, K. N. (2026). Decoupling of dissolved iron and iron-binding humic-like substances along the West Antarctic Peninsula. Limnology and Oceanography, 71(9), Article e70510. https://doi.org/10.1002/lno.70510

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