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Zooplankton gut passage mobilizes lithogenic iron for ocean productivity

Zooplankton gut passage mobilizes lithogenic iron for ocean productivity
Zooplankton gut passage mobilizes lithogenic iron for ocean productivity
Iron is an essential nutrient for phytoplankton, but low concentrations limit primary production and associated atmospheric carbon drawdown in large parts of the world’s oceans [ 1, 2 ]. Lithogenic particles deriving from aeolian dust deposition, glacial runoff, or river discharges can form an important source if the attached iron becomes dissolved and therefore bioavailable [ 3–5 ]. Acidic digestion by zooplankton is a potential mechanism for iron mobilization [ 6 ], but evidence is lacking. Here we show that Antarctic krill sampled near glacial outlets at the island of South Georgia (Southern Ocean) ingest large amounts of lithogenic particles and contain 3-fold higher iron concentrations in their muscle than specimens from offshore, which confirms mineral dissolution in their guts. About 90% of the lithogenic and biogenic iron ingested by krill is passed into their fecal pellets, which contain ?5-fold higher proportions of labile (reactive) iron than intact diatoms. The mobilized iron can be released in dissolved form directly from krill or via multiple pathways involving microbes, other zooplankton, and krill predators. This can deliver substantial amounts of bioavailable iron and contribute to the fertilization of coastal waters and the ocean beyond. In line with our findings, phytoplankton blooms downstream of South Georgia are more intensive and longer lasting during years with high krill abundance on-shelf. Thus, krill crop phytoplankton but boost new production via their nutrient supply. Understanding and quantifying iron mobilization by zooplankton is essential to predict ocean productivity in a warming climate where lithogenic iron inputs from deserts, glaciers, and rivers are increasing [ 7–10 ].
antarctic krill, iron, phytoplankton bloom, glacial flour, South Georgia, fecal pellets, zooplankton, grazing, digestion, fertilization
0960-9822
2667-2673
Schmidt, Katrin
1eccc7f0-b656-4c41-a9bd-543ef7aefb5c
Schlosser, Christian
93df4206-5ae4-48a3-80b9-d6f4fc2d4b0a
Atkinson, Angus
77d9c544-2749-46fe-b991-df2a11d1d6be
Fielding, Sophie
b6810aca-528b-41d9-b23e-3e05647c5fab
Venables, Hugh J.
076cfe85-e2f9-4e69-8793-0ab225e7fadd
Waluda, Claire M.
adcaad72-758d-4d3c-a2da-05fc06fc68ee
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Schmidt, Katrin
1eccc7f0-b656-4c41-a9bd-543ef7aefb5c
Schlosser, Christian
93df4206-5ae4-48a3-80b9-d6f4fc2d4b0a
Atkinson, Angus
77d9c544-2749-46fe-b991-df2a11d1d6be
Fielding, Sophie
b6810aca-528b-41d9-b23e-3e05647c5fab
Venables, Hugh J.
076cfe85-e2f9-4e69-8793-0ab225e7fadd
Waluda, Claire M.
adcaad72-758d-4d3c-a2da-05fc06fc68ee
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9

Schmidt, Katrin, Schlosser, Christian, Atkinson, Angus, Fielding, Sophie, Venables, Hugh J., Waluda, Claire M. and Achterberg, Eric P. (2016) Zooplankton gut passage mobilizes lithogenic iron for ocean productivity. Current Biology, 26 (19), 2667-2673. (doi:10.1016/j.cub.2016.07.058).

Record type: Article

Abstract

Iron is an essential nutrient for phytoplankton, but low concentrations limit primary production and associated atmospheric carbon drawdown in large parts of the world’s oceans [ 1, 2 ]. Lithogenic particles deriving from aeolian dust deposition, glacial runoff, or river discharges can form an important source if the attached iron becomes dissolved and therefore bioavailable [ 3–5 ]. Acidic digestion by zooplankton is a potential mechanism for iron mobilization [ 6 ], but evidence is lacking. Here we show that Antarctic krill sampled near glacial outlets at the island of South Georgia (Southern Ocean) ingest large amounts of lithogenic particles and contain 3-fold higher iron concentrations in their muscle than specimens from offshore, which confirms mineral dissolution in their guts. About 90% of the lithogenic and biogenic iron ingested by krill is passed into their fecal pellets, which contain ?5-fold higher proportions of labile (reactive) iron than intact diatoms. The mobilized iron can be released in dissolved form directly from krill or via multiple pathways involving microbes, other zooplankton, and krill predators. This can deliver substantial amounts of bioavailable iron and contribute to the fertilization of coastal waters and the ocean beyond. In line with our findings, phytoplankton blooms downstream of South Georgia are more intensive and longer lasting during years with high krill abundance on-shelf. Thus, krill crop phytoplankton but boost new production via their nutrient supply. Understanding and quantifying iron mobilization by zooplankton is essential to predict ocean productivity in a warming climate where lithogenic iron inputs from deserts, glaciers, and rivers are increasing [ 7–10 ].

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More information

Accepted/In Press date: 22 July 2016
e-pub ahead of print date: 15 September 2016
Published date: 10 October 2016
Additional Information: Original title: Where bio- meets geochemistry: Zooplankton gut passage mobilises lithogenic iron for ocean productivity
Keywords: antarctic krill, iron, phytoplankton bloom, glacial flour, South Georgia, fecal pellets, zooplankton, grazing, digestion, fertilization
Organisations: Ocean and Earth Science

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Local EPrints ID: 402980
URI: http://eprints.soton.ac.uk/id/eprint/402980
ISSN: 0960-9822
PURE UUID: 831d7b14-a8f1-4b53-a376-9d62c3e762f5

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Date deposited: 16 Nov 2016 10:38
Last modified: 27 Apr 2022 04:16

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Contributors

Author: Katrin Schmidt
Author: Christian Schlosser
Author: Angus Atkinson
Author: Sophie Fielding
Author: Hugh J. Venables
Author: Claire M. Waluda

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