Iron cycling during the decline of a South Georgia diatom bloom
The Southern Ocean is the largest high nutrient low chlorophyll (HNLC) oceanic region, where iron limits phytoplankton growth and productivity and ultimately influences the Biological Carbon Pump (BCP). Natural exceptions to the HNLC regime occur where island wakes cause iron to be mixed into surfac...
Published in: | Deep Sea Research Part II: Topical Studies in Oceanography |
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2023
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ftnerc:oai:nora.nerc.ac.uk:534045 2023-05-15T18:25:49+02:00 Iron cycling during the decline of a South Georgia diatom bloom Ainsworth, Joanna Poulton, Alex J. Lohan, Maeve C. Stinchcombe, Mark C. Lough, Alastair J.M. Moore, C. Mark 2023-01-20 text http://nora.nerc.ac.uk/id/eprint/534045/ https://nora.nerc.ac.uk/id/eprint/534045/1/1-s2.0-S096706452300019X-main.pdf https://doi.org/10.1016/j.dsr2.2023.105269 en eng https://nora.nerc.ac.uk/id/eprint/534045/1/1-s2.0-S096706452300019X-main.pdf Ainsworth, Joanna; Poulton, Alex J.; Lohan, Maeve C.; Stinchcombe, Mark C.; Lough, Alastair J.M.; Moore, C. Mark. 2023 Iron cycling during the decline of a South Georgia diatom bloom. Deep Sea Research Part II: Topical Studies in Oceanography, 208. 105269. https://doi.org/10.1016/j.dsr2.2023.105269 <https://doi.org/10.1016/j.dsr2.2023.105269> cc_by_4 CC-BY Publication - Article PeerReviewed 2023 ftnerc https://doi.org/10.1016/j.dsr2.2023.105269 2023-02-24T00:02:04Z The Southern Ocean is the largest high nutrient low chlorophyll (HNLC) oceanic region, where iron limits phytoplankton growth and productivity and ultimately influences the Biological Carbon Pump (BCP). Natural exceptions to the HNLC regime occur where island wakes cause iron to be mixed into surface waters from sediments, enabling large, prolonged phytoplankton blooms and increased carbon drawdown. Interactions between iron and phytoplankton are reciprocal in blooms: with plankton regulating the (re)cycling of iron through cellular uptake and remineralisation. The depth of iron remineralisation then influences either re-supply to the surface mixed layer biota or sequestration into deeper waters. Water column trace metal observations and shipboard experiments, using bioassays and radioisotope (55Fe, 32Si, 14C) cycling, were undertaken to investigate surface mixed layer phytoplankton iron limitation, iron uptake, and mesopelagic iron remineralisation relative to carbon and silica within the November 2017 bloom downstream of South Georgia. Surface phytoplankton residing in the iron depleted mixed layer were iron limited throughout the four-week sampling period. Experiments designed to investigate particulate water column (re)cycling revealed limited iron remineralisation from freshly produced upper ocean particles. The main pathway of iron transfer from particulates into the dissolved phase was through rapid (<2 d) release of extra-cellular adsorbed iron, which, if occurring in situ, could contribute to observed higher sub-surface dissolved Fe concentrations. This was accompanied by a small loss of cellular carbon, likely through respiration of the fixed 14C, and limited dissolution of particulate 32Si to dissolved 32Si. Decoupling of the remineralisation length scales for Fe, C and Si, with Fe having the fastest turnover, is thus likely in the upper mesopelagic zone beneath the bloom. Article in Journal/Newspaper Southern Ocean Natural Environment Research Council: NERC Open Research Archive Southern Ocean Deep Sea Research Part II: Topical Studies in Oceanography 208 105269 |
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Open Polar |
collection |
Natural Environment Research Council: NERC Open Research Archive |
op_collection_id |
ftnerc |
language |
English |
description |
The Southern Ocean is the largest high nutrient low chlorophyll (HNLC) oceanic region, where iron limits phytoplankton growth and productivity and ultimately influences the Biological Carbon Pump (BCP). Natural exceptions to the HNLC regime occur where island wakes cause iron to be mixed into surface waters from sediments, enabling large, prolonged phytoplankton blooms and increased carbon drawdown. Interactions between iron and phytoplankton are reciprocal in blooms: with plankton regulating the (re)cycling of iron through cellular uptake and remineralisation. The depth of iron remineralisation then influences either re-supply to the surface mixed layer biota or sequestration into deeper waters. Water column trace metal observations and shipboard experiments, using bioassays and radioisotope (55Fe, 32Si, 14C) cycling, were undertaken to investigate surface mixed layer phytoplankton iron limitation, iron uptake, and mesopelagic iron remineralisation relative to carbon and silica within the November 2017 bloom downstream of South Georgia. Surface phytoplankton residing in the iron depleted mixed layer were iron limited throughout the four-week sampling period. Experiments designed to investigate particulate water column (re)cycling revealed limited iron remineralisation from freshly produced upper ocean particles. The main pathway of iron transfer from particulates into the dissolved phase was through rapid (<2 d) release of extra-cellular adsorbed iron, which, if occurring in situ, could contribute to observed higher sub-surface dissolved Fe concentrations. This was accompanied by a small loss of cellular carbon, likely through respiration of the fixed 14C, and limited dissolution of particulate 32Si to dissolved 32Si. Decoupling of the remineralisation length scales for Fe, C and Si, with Fe having the fastest turnover, is thus likely in the upper mesopelagic zone beneath the bloom. |
format |
Article in Journal/Newspaper |
author |
Ainsworth, Joanna Poulton, Alex J. Lohan, Maeve C. Stinchcombe, Mark C. Lough, Alastair J.M. Moore, C. Mark |
spellingShingle |
Ainsworth, Joanna Poulton, Alex J. Lohan, Maeve C. Stinchcombe, Mark C. Lough, Alastair J.M. Moore, C. Mark Iron cycling during the decline of a South Georgia diatom bloom |
author_facet |
Ainsworth, Joanna Poulton, Alex J. Lohan, Maeve C. Stinchcombe, Mark C. Lough, Alastair J.M. Moore, C. Mark |
author_sort |
Ainsworth, Joanna |
title |
Iron cycling during the decline of a South Georgia diatom bloom |
title_short |
Iron cycling during the decline of a South Georgia diatom bloom |
title_full |
Iron cycling during the decline of a South Georgia diatom bloom |
title_fullStr |
Iron cycling during the decline of a South Georgia diatom bloom |
title_full_unstemmed |
Iron cycling during the decline of a South Georgia diatom bloom |
title_sort |
iron cycling during the decline of a south georgia diatom bloom |
publishDate |
2023 |
url |
http://nora.nerc.ac.uk/id/eprint/534045/ https://nora.nerc.ac.uk/id/eprint/534045/1/1-s2.0-S096706452300019X-main.pdf https://doi.org/10.1016/j.dsr2.2023.105269 |
geographic |
Southern Ocean |
geographic_facet |
Southern Ocean |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_relation |
https://nora.nerc.ac.uk/id/eprint/534045/1/1-s2.0-S096706452300019X-main.pdf Ainsworth, Joanna; Poulton, Alex J.; Lohan, Maeve C.; Stinchcombe, Mark C.; Lough, Alastair J.M.; Moore, C. Mark. 2023 Iron cycling during the decline of a South Georgia diatom bloom. Deep Sea Research Part II: Topical Studies in Oceanography, 208. 105269. https://doi.org/10.1016/j.dsr2.2023.105269 <https://doi.org/10.1016/j.dsr2.2023.105269> |
op_rights |
cc_by_4 |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.1016/j.dsr2.2023.105269 |
container_title |
Deep Sea Research Part II: Topical Studies in Oceanography |
container_volume |
208 |
container_start_page |
105269 |
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1766207485439377408 |