The University of Southampton
University of Southampton Institutional Repository

Mechanisms of dissolved and labile particulate iron supply to shelf waters and phytoplankton blooms off South Georgia, Southern Ocean

Mechanisms of dissolved and labile particulate iron supply to shelf waters and phytoplankton blooms off South Georgia, Southern Ocean
Mechanisms of dissolved and labile particulate iron supply to shelf waters and phytoplankton blooms off South Georgia, Southern Ocean
The island of South Georgia is situated in the iron (Fe) depleted Antarctic Circumpolar Current of the Southern Ocean. Iron emanating from its shelf system fuels large phytoplankton blooms downstream of the island, but the actual supply mechanisms are unclear. To address this we present the first inventory of Fe, manganese (Mn) and aluminium (Al) in shelf sediments, pore waters and the water column in the vicinity of South Georgia, alongside data on zooplankton-mediated Fe cycling processes. The seafloor sediments were the main particulate Fe source to shelf bottom waters as indicated by Fe / Mn and Fe / Al ratios for shelf sediments and suspended particles in the water column. Less than 1 % of the total particulate Fe pool was leachable surface adsorbed (labile) Fe, and therefore potentially available to organisms. Pore waters formed the primary dissolved Fe (DFe) source to shelf bottom waters supplying 0.1–4 μmol DFe m−2 d−1. However, only 0.41 ± 0.26 μmol DFe m−2 d−1 was transferred to the surface mixed layer by vertical diffusive and advective mixing. Other trace metal sources to surface waters included glacial flour released by melting glaciers and zooplankton excretion processes. On average 6.5 ± 8.2 μmol m−2 d−1 of labile particulate Fe was supplied to the surface mixed layer via krill faecal pellets, with further DFe released by krill at around 1.1 ± 2.2 μmol m−2 d−1. The faecal pellets released by krill constituted of seafloor derived lithogenic material and settled algae debris, in addition to freshly ingested suspended phytoplankton specimen. The phytoplankton Fe requirement in the blooms ca. 1250 km downstream the island of South Georgia was 0.33 ± 0.11 μmol m−2 d−1, with the DFe supply by horizontal/vertical mixing, deep winter mixing and via aeolian dust estimated as ~ 0.12 μmol m−2 d−1. We suggest that additionally required DFe was provided through recycling of biogenically stored Fe following luxury Fe uptake by phytoplankton on the Fe rich shelf. This process would allow Fe to be retained in the surface mixed layer of waters downstream of South Georgia through continuous recycling and biological uptake, and facilitate the large scale blooms.
1726-4170
4973-4993
Schlosser, Christian
93df4206-5ae4-48a3-80b9-d6f4fc2d4b0a
Schmidt, Katrin
7d09d5c4-800a-4c9b-9560-3c6097d7bbda
Aquilina, Alfred
a5ce0174-e2d4-40ee-baa5-86ba2f24058c
Homoky, William B.
8e0aa2e9-a88a-4ee5-bfca-1e014cb150ee
Castrillejo, Maxi
05d1d312-12e6-45fb-a4ee-1b2bae677f96
Mills, Rachel
a664f299-1a34-4b63-9988-1e599b756706
Patey, Matthew D.
953bb9e5-e90f-4178-ae55-114c025137d2
Fielding, Sophie
642fd40f-95fa-46e1-a279-3c5169da7027
Atkinson, Angus
3fc96720-5c4f-427a-a9ec-b2b11713be5a
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Schlosser, Christian
93df4206-5ae4-48a3-80b9-d6f4fc2d4b0a
Schmidt, Katrin
7d09d5c4-800a-4c9b-9560-3c6097d7bbda
Aquilina, Alfred
a5ce0174-e2d4-40ee-baa5-86ba2f24058c
Homoky, William B.
8e0aa2e9-a88a-4ee5-bfca-1e014cb150ee
Castrillejo, Maxi
05d1d312-12e6-45fb-a4ee-1b2bae677f96
Mills, Rachel
a664f299-1a34-4b63-9988-1e599b756706
Patey, Matthew D.
953bb9e5-e90f-4178-ae55-114c025137d2
Fielding, Sophie
642fd40f-95fa-46e1-a279-3c5169da7027
Atkinson, Angus
3fc96720-5c4f-427a-a9ec-b2b11713be5a
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9

Schlosser, Christian, Schmidt, Katrin, Aquilina, Alfred, Homoky, William B., Castrillejo, Maxi, Mills, Rachel, Patey, Matthew D., Fielding, Sophie, Atkinson, Angus and Achterberg, Eric P. (2018) Mechanisms of dissolved and labile particulate iron supply to shelf waters and phytoplankton blooms off South Georgia, Southern Ocean. Biogeosciences, 15 (16), 4973-4993. (doi:10.5194/bg-15-4973-2018).

Record type: Article

Abstract

The island of South Georgia is situated in the iron (Fe) depleted Antarctic Circumpolar Current of the Southern Ocean. Iron emanating from its shelf system fuels large phytoplankton blooms downstream of the island, but the actual supply mechanisms are unclear. To address this we present the first inventory of Fe, manganese (Mn) and aluminium (Al) in shelf sediments, pore waters and the water column in the vicinity of South Georgia, alongside data on zooplankton-mediated Fe cycling processes. The seafloor sediments were the main particulate Fe source to shelf bottom waters as indicated by Fe / Mn and Fe / Al ratios for shelf sediments and suspended particles in the water column. Less than 1 % of the total particulate Fe pool was leachable surface adsorbed (labile) Fe, and therefore potentially available to organisms. Pore waters formed the primary dissolved Fe (DFe) source to shelf bottom waters supplying 0.1–4 μmol DFe m−2 d−1. However, only 0.41 ± 0.26 μmol DFe m−2 d−1 was transferred to the surface mixed layer by vertical diffusive and advective mixing. Other trace metal sources to surface waters included glacial flour released by melting glaciers and zooplankton excretion processes. On average 6.5 ± 8.2 μmol m−2 d−1 of labile particulate Fe was supplied to the surface mixed layer via krill faecal pellets, with further DFe released by krill at around 1.1 ± 2.2 μmol m−2 d−1. The faecal pellets released by krill constituted of seafloor derived lithogenic material and settled algae debris, in addition to freshly ingested suspended phytoplankton specimen. The phytoplankton Fe requirement in the blooms ca. 1250 km downstream the island of South Georgia was 0.33 ± 0.11 μmol m−2 d−1, with the DFe supply by horizontal/vertical mixing, deep winter mixing and via aeolian dust estimated as ~ 0.12 μmol m−2 d−1. We suggest that additionally required DFe was provided through recycling of biogenically stored Fe following luxury Fe uptake by phytoplankton on the Fe rich shelf. This process would allow Fe to be retained in the surface mixed layer of waters downstream of South Georgia through continuous recycling and biological uptake, and facilitate the large scale blooms.

Text
bg-2017-299 - Accepted Manuscript
Available under License Creative Commons Attribution.
Download (2MB)
Text
Schlosser et al 2018 - Version of Record
Available under License Creative Commons Attribution.
Download (13MB)

More information

Accepted/In Press date: 26 July 2017
e-pub ahead of print date: 28 July 2017
Published date: 31 August 2018

Identifiers

Local EPrints ID: 416081
URI: http://eprints.soton.ac.uk/id/eprint/416081
ISSN: 1726-4170
PURE UUID: b226a8c6-3d64-41ee-9d20-2f75cefb06ea
ORCID for Rachel Mills: ORCID iD orcid.org/0000-0002-9811-246X

Catalogue record

Date deposited: 01 Dec 2017 17:30
Last modified: 18 Feb 2021 16:42

Export record

Altmetrics

Contributors

Author: Christian Schlosser
Author: Katrin Schmidt
Author: Alfred Aquilina
Author: William B. Homoky
Author: Maxi Castrillejo
Author: Rachel Mills ORCID iD
Author: Matthew D. Patey
Author: Sophie Fielding
Author: Angus Atkinson

University divisions

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×