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High lability Fe particles sourced from glacial erosion can meet previously unaccounted biological demand: Heard Island, Southern Ocean

Citation

van der Merwe, P and Wuttig, K and Holmes, T and Trull, TW and Chase, Z and Townsend, AT and Goemann, K and Bowie, AR, High lability Fe particles sourced from glacial erosion can meet previously unaccounted biological demand: Heard Island, Southern Ocean, Frontiers in Marine Science, 6, (JUNE) Article 332. ISSN 2296-7745 (2019) [Refereed Article]


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Copyright Statement

Copyright 2019 van der Merwe, Wuttig, Holmes, Trull, Chase, Townsend, Goemann and Bowie. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) https://creativecommons.org/licenses/by/4.0/

DOI: doi:10.3389/fmars.2019.00332

Abstract

Iron (Fe) is an essential micronutrient that controls phytoplankton growth in the Southern Ocean. Dissolved Fe (<0.4 μm) has been extensively studied due to its relatively high bioavailability. However, particulate Fe (>0.4 μm) is far more abundant and may also become bioavailable through biogeochemical processing. To assess natural Fe fertilisation from the particulate fraction, we surveyed suspended particles in the water column at 11 stations in the vicinity of Heard and McDonald Islands (HIMI), in the Indian sector of the Southern Ocean and compared these to downstream plateau and reference stations. We quantified the labile (potentially bioavailable) fraction using a chemical leach. Suspended particles sourced from glacial erosion and fluvial outflow, including nanoparticulate Fe oxides near Heard Island, contained a significantly higher fraction of labile Fe (18 ± 2.8% of total Fe, or 115 ± 34 nM, n = 9) than all other coastal areas surveyed. In contrast, waters around McDonald Island, proximal to diffuse gasohydrothermal sites, contained poorly labile, highly refractory titanium and Fe bearing minerals such as ilmenite. We conclude that glacial erosion of Heard Island in combination with a unique elemental signature of the source rock, is an important mechanism of Fe supply to downstream waters. Our calculations show that the labile Fe supplied from primarily glacial erosion on Heard Island is sufficient to satisfy previously unmet estimates of phytoplankton demand for the region, and therefore critical to the area’s productivity. As we move into a world facing major ecosystem shifts under a changing climate, it is important to understand those ecosystem services that may change into the future. At the current rate of glacier retreat, this ecosystem service of glacial erosion and Fe supply to coastal waters will cease with the eventual loss of glacial cover with direct impacts for this historically highly productive region.

Item Details

Item Type:Refereed Article
Keywords:particulate trace metals, McDonald Island, suspended particles, chemical leach, hydrothermal, iron, labile particulate Fe, GEOTRACES
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Chemical Oceanography
Objective Division:Environment
Objective Group:Climate and Climate Change
Objective Field:Effects of Climate Change and Variability on Antarctic and Sub-Antarctic Environments (excl. Social Impacts)
UTAS Author:van der Merwe, P (Dr Pier van der Merwe)
UTAS Author:Wuttig, K (Dr Kathrin Wuttig)
UTAS Author:Holmes, T (Mr Thomas Holmes)
UTAS Author:Trull, TW (Professor Thomas Trull)
UTAS Author:Chase, Z (Associate Professor Zanna Chase)
UTAS Author:Townsend, AT (Associate Professor Ashley Townsend)
UTAS Author:Goemann, K (Dr Karsten Goemann)
UTAS Author:Bowie, AR (Professor Andrew Bowie)
ID Code:133183
Year Published:2019
Web of Science® Times Cited:2
Deposited By:Oceans and Cryosphere
Deposited On:2019-06-17
Last Modified:2019-09-24
Downloads:3 View Download Statistics

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