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Why is the South Orkney Island shelf (the world's first high seas marine protected area) a carbon immobilization hotspot?

Why is the South Orkney Island shelf (the world's first high seas marine protected area) a carbon immobilization hotspot?
Why is the South Orkney Island shelf (the world's first high seas marine protected area) a carbon immobilization hotspot?
The Southern Ocean archipelago, the South Orkney Islands (SOI), became the world's first entirely high seas marine protected area (MPA) in 2010. The SOI continental shelf (~44 000 km2), was less than half covered by grounded ice sheet during glaciations, is biologically rich and a key area of both sea surface warming and sea-ice losses. Little was known of the carbon cycle there, but recent work showed it was a very important site of carbon immobilization (net annual carbon accumulation) by benthos, one of the few demonstrable negative feedbacks to climate change. Carbon immobilization by SOI bryozoans was higher, per species, unit area and ice-free day, than anywhere-else polar. Here, we investigate why carbon immobilization has been so high at SOI, and whether this is due to high density, longevity or high annual production in six study species of bryozoans (benthic suspension feeders). We compared benthic carbon immobilization across major regions around West Antarctica with sea-ice and primary production, from remotely sensed and directly sampled sources. Lowest carbon immobilization was at the northernmost study regions (South Georgia) and southernmost Amundsen Sea. However, data standardized for age and density showed that only SOI was anomalous (high). High immobilization at SOI was due to very high annual production of bryozoans (rather than high densities or longevity), which were 2x, 3x and 5x higher than on the Bellingshausen, South Georgia and Amundsen shelves, respectively. We found that carbon immobilization correlated to the duration (but not peak or integrated biomass) of phytoplankton blooms, both in directly sampled, local scale data and across regions using remote-sensed data. The long bloom at SOI seems to drive considerable carbon immobilization, but sea-ice losses across West Antarctica mean that significant carbon sinks and negative feedbacks to climate change could also develop in the Bellingshausen and Amundsen seas.
benthos, carbon sink, climate change, feedback, phytoplankton, Southern Ocean
1354-1013
1110-1120
Barnes, David K.A.
f53924ec-169f-4620-9e9b-c51a405bf6ca
Ireland, Louise
8609d9b7-a53b-48ef-ab8e-45a2053072c3
Hogg, Oliver T.
43f3bdc0-7667-488d-9f9f-963f15f33a10
Morley, Simon
355759b1-87d9-42df-ae82-6be888bdeb4e
Enderlein, Peter
a5ae31b1-e5aa-4a46-96ae-ec9cc9d5226c
Sands, Chester J.
955f6259-4110-4374-b004-ee77758f37fd
Barnes, David K.A.
f53924ec-169f-4620-9e9b-c51a405bf6ca
Ireland, Louise
8609d9b7-a53b-48ef-ab8e-45a2053072c3
Hogg, Oliver T.
43f3bdc0-7667-488d-9f9f-963f15f33a10
Morley, Simon
355759b1-87d9-42df-ae82-6be888bdeb4e
Enderlein, Peter
a5ae31b1-e5aa-4a46-96ae-ec9cc9d5226c
Sands, Chester J.
955f6259-4110-4374-b004-ee77758f37fd

Barnes, David K.A., Ireland, Louise, Hogg, Oliver T., Morley, Simon, Enderlein, Peter and Sands, Chester J. (2016) Why is the South Orkney Island shelf (the world's first high seas marine protected area) a carbon immobilization hotspot? Global Change Biology, 22 (3), 1110-1120. (doi:10.1111/gcb.13157).

Record type: Article

Abstract

The Southern Ocean archipelago, the South Orkney Islands (SOI), became the world's first entirely high seas marine protected area (MPA) in 2010. The SOI continental shelf (~44 000 km2), was less than half covered by grounded ice sheet during glaciations, is biologically rich and a key area of both sea surface warming and sea-ice losses. Little was known of the carbon cycle there, but recent work showed it was a very important site of carbon immobilization (net annual carbon accumulation) by benthos, one of the few demonstrable negative feedbacks to climate change. Carbon immobilization by SOI bryozoans was higher, per species, unit area and ice-free day, than anywhere-else polar. Here, we investigate why carbon immobilization has been so high at SOI, and whether this is due to high density, longevity or high annual production in six study species of bryozoans (benthic suspension feeders). We compared benthic carbon immobilization across major regions around West Antarctica with sea-ice and primary production, from remotely sensed and directly sampled sources. Lowest carbon immobilization was at the northernmost study regions (South Georgia) and southernmost Amundsen Sea. However, data standardized for age and density showed that only SOI was anomalous (high). High immobilization at SOI was due to very high annual production of bryozoans (rather than high densities or longevity), which were 2x, 3x and 5x higher than on the Bellingshausen, South Georgia and Amundsen shelves, respectively. We found that carbon immobilization correlated to the duration (but not peak or integrated biomass) of phytoplankton blooms, both in directly sampled, local scale data and across regions using remote-sensed data. The long bloom at SOI seems to drive considerable carbon immobilization, but sea-ice losses across West Antarctica mean that significant carbon sinks and negative feedbacks to climate change could also develop in the Bellingshausen and Amundsen seas.

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More information

e-pub ahead of print date: 18 December 2015
Published date: March 2016
Keywords: benthos, carbon sink, climate change, feedback, phytoplankton, Southern Ocean
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 385252
URI: http://eprints.soton.ac.uk/id/eprint/385252
ISSN: 1354-1013
PURE UUID: 33436b52-e541-4819-9885-2a6f08e86ecd

Catalogue record

Date deposited: 21 Dec 2015 09:14
Last modified: 15 Jul 2019 20:53

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