Southern Ocean phytoplankton under climate change: shifting balance of bottom-up and top-down control
Phytoplankton forms the base of the marine food web by transforming CO2 into organic carbon via photosynthesis. Some of the organic carbon is then transferred through the food web and exported into the deep ocean, a process known as the biological carbon pump. Despite the importance of phytoplankton...
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ftoceanrep:oai:oceanrep.geomar.de:59229 2024-04-28T08:39:13+00:00 Southern Ocean phytoplankton under climate change: shifting balance of bottom-up and top-down control Xue, Tianfei Frenger, Ivy Terhaar, Jens Prowe, A. E. Friederike Frölicher, Thomas L. Oschlies, Andreas 2024-04-09 text https://oceanrep.geomar.de/id/eprint/59229/ https://oceanrep.geomar.de/id/eprint/59229/1/bg-2023-171.pdf https://bg.copernicus.org/preprints/bg-2023-171/ https://doi.org/10.5194/bg-2023-171 en eng Copernicus Publications (EGU) https://oceanrep.geomar.de/id/eprint/59229/1/bg-2023-171.pdf Xue, T. , Frenger, I. , Terhaar, J., Prowe, A. E. F. , Frölicher, T. L. and Oschlies, A. (In Press / Accepted) Southern Ocean phytoplankton under climate change: shifting balance of bottom-up and top-down control. Open Access Biogeosciences (BG) . DOI 10.5194/bg-2023-171 <https://doi.org/10.5194/bg-2023-171>. doi:10.5194/bg-2023-171 cc_by_4.0 info:eu-repo/semantics/openAccess Article PeerReviewed 2024 ftoceanrep https://doi.org/10.5194/bg-2023-171 2024-04-10T00:05:17Z Phytoplankton forms the base of the marine food web by transforming CO2 into organic carbon via photosynthesis. Some of the organic carbon is then transferred through the food web and exported into the deep ocean, a process known as the biological carbon pump. Despite the importance of phytoplankton for marine ecosystems and the global carbon cycle, projections of phytoplankton biomass in response to climate change differ strongly across Earth system models, illustrating uncertainty in our understanding of the underlying processes. Differences are especially large in the Southern Ocean, a region that is notoriously difficult to represent in models. Here, we argue that water column-integrated phytoplankton biomass in the Southern Ocean is projected to largely remain unchanged under climate change by the CMIP6 multi-model ensemble because of a shifting balance of bottom-up and top-down processes driven by a shoaling mixed layer depth. A shallower mixed layer is projected to improve growth conditions and consequently weaken bottom-up control. In addition to enhanced phytoplankton growth, the shoaling of the mixed layer also compresses phytoplankton closer to the surface and promotes zooplankton grazing efficiency, thus intensifying top-down control. Overall, our results suggest that while changes in bottom-up conditions stimulate enhanced growth, intensified top-down control opposes an increase in phytoplankton and becomes increasingly important for phytoplankton response under climate change in the Southern Ocean. Article in Journal/Newspaper Southern Ocean OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
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Open Polar |
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OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
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ftoceanrep |
language |
English |
description |
Phytoplankton forms the base of the marine food web by transforming CO2 into organic carbon via photosynthesis. Some of the organic carbon is then transferred through the food web and exported into the deep ocean, a process known as the biological carbon pump. Despite the importance of phytoplankton for marine ecosystems and the global carbon cycle, projections of phytoplankton biomass in response to climate change differ strongly across Earth system models, illustrating uncertainty in our understanding of the underlying processes. Differences are especially large in the Southern Ocean, a region that is notoriously difficult to represent in models. Here, we argue that water column-integrated phytoplankton biomass in the Southern Ocean is projected to largely remain unchanged under climate change by the CMIP6 multi-model ensemble because of a shifting balance of bottom-up and top-down processes driven by a shoaling mixed layer depth. A shallower mixed layer is projected to improve growth conditions and consequently weaken bottom-up control. In addition to enhanced phytoplankton growth, the shoaling of the mixed layer also compresses phytoplankton closer to the surface and promotes zooplankton grazing efficiency, thus intensifying top-down control. Overall, our results suggest that while changes in bottom-up conditions stimulate enhanced growth, intensified top-down control opposes an increase in phytoplankton and becomes increasingly important for phytoplankton response under climate change in the Southern Ocean. |
format |
Article in Journal/Newspaper |
author |
Xue, Tianfei Frenger, Ivy Terhaar, Jens Prowe, A. E. Friederike Frölicher, Thomas L. Oschlies, Andreas |
spellingShingle |
Xue, Tianfei Frenger, Ivy Terhaar, Jens Prowe, A. E. Friederike Frölicher, Thomas L. Oschlies, Andreas Southern Ocean phytoplankton under climate change: shifting balance of bottom-up and top-down control |
author_facet |
Xue, Tianfei Frenger, Ivy Terhaar, Jens Prowe, A. E. Friederike Frölicher, Thomas L. Oschlies, Andreas |
author_sort |
Xue, Tianfei |
title |
Southern Ocean phytoplankton under climate change: shifting balance of bottom-up and top-down control |
title_short |
Southern Ocean phytoplankton under climate change: shifting balance of bottom-up and top-down control |
title_full |
Southern Ocean phytoplankton under climate change: shifting balance of bottom-up and top-down control |
title_fullStr |
Southern Ocean phytoplankton under climate change: shifting balance of bottom-up and top-down control |
title_full_unstemmed |
Southern Ocean phytoplankton under climate change: shifting balance of bottom-up and top-down control |
title_sort |
southern ocean phytoplankton under climate change: shifting balance of bottom-up and top-down control |
publisher |
Copernicus Publications (EGU) |
publishDate |
2024 |
url |
https://oceanrep.geomar.de/id/eprint/59229/ https://oceanrep.geomar.de/id/eprint/59229/1/bg-2023-171.pdf https://bg.copernicus.org/preprints/bg-2023-171/ https://doi.org/10.5194/bg-2023-171 |
genre |
Southern Ocean |
genre_facet |
Southern Ocean |
op_relation |
https://oceanrep.geomar.de/id/eprint/59229/1/bg-2023-171.pdf Xue, T. , Frenger, I. , Terhaar, J., Prowe, A. E. F. , Frölicher, T. L. and Oschlies, A. (In Press / Accepted) Southern Ocean phytoplankton under climate change: shifting balance of bottom-up and top-down control. Open Access Biogeosciences (BG) . DOI 10.5194/bg-2023-171 <https://doi.org/10.5194/bg-2023-171>. doi:10.5194/bg-2023-171 |
op_rights |
cc_by_4.0 info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.5194/bg-2023-171 |
_version_ |
1797570350637121536 |