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The relative roles of modified circumpolar deep water and benthic sources in supplying iron to the recurrent phytoplankton blooms above Pennell and Mawson Banks, Ross Sea, Antarctica

The relative roles of modified circumpolar deep water and benthic sources in supplying iron to the recurrent phytoplankton blooms above Pennell and Mawson Banks, Ross Sea, Antarctica
The relative roles of modified circumpolar deep water and benthic sources in supplying iron to the recurrent phytoplankton blooms above Pennell and Mawson Banks, Ross Sea, Antarctica
The role that dissolved iron (dFe) rich Circumpolar Deep Water (CDW) might play in sustaining the consistently observed discrete patches of high chlorophyll biomass over Pennell Bank (PB) and Mawson Bank (MB) in the Ross Sea, was investigated during January/February 2011. Over a 26-day period, hydrographic and trace metal clean water sampling was carried out adjacent to both of these banks, in some cases repeatedly. Particulate sampling was also accomplished at selected stations by in situ pumping. The results indicate that the dFe content of the CDW is in fact reduced by on-shelf mixing with Antarctic Surface Water as it transitions into modified CDW (MCDW). Our stations above PB, where the maximum bloom is encountered, show no evidence of MCDW presence. In contrast, above MB, where there is a smaller persistent bloom, MCDW was observed. Although both of these stations displayed the imprint of sedimentary Fe input connected to the strong tidal cycles above the banks, the stronger near-bottom density gradient that MCDW produces appears to contribute to reduced vertical mixing of the sedimentary source. Thus, ironically, the presence of MCDW may be hindering the Fe supply to the surface waters, rather than being the source, as originally hypothesized.
0924-7963
61-72
Hatta, Mariko
b8c210ca-90aa-4660-b1b7-3538b120e31d
Measures, Chris I.
9f8e1866-4690-46f1-b5af-856a58f78c5a
Lam, Phoebe J.
edd6ad71-e42a-4157-bb1d-ef0ec23e8210
Ohnemus, Daniel C.
309c9c20-4a9d-4430-b5c5-09812703f2ce
Auro, Maureen E.
70a47c36-288f-4b88-a9d7-a602b3852ceb
Grand, Maxime M.
659acbde-d639-42b7-9fab-52fa1b3655ff
Selph, Karen E.
70cbf564-8633-4fae-896d-c0aebbc3705a
Hatta, Mariko
b8c210ca-90aa-4660-b1b7-3538b120e31d
Measures, Chris I.
9f8e1866-4690-46f1-b5af-856a58f78c5a
Lam, Phoebe J.
edd6ad71-e42a-4157-bb1d-ef0ec23e8210
Ohnemus, Daniel C.
309c9c20-4a9d-4430-b5c5-09812703f2ce
Auro, Maureen E.
70a47c36-288f-4b88-a9d7-a602b3852ceb
Grand, Maxime M.
659acbde-d639-42b7-9fab-52fa1b3655ff
Selph, Karen E.
70cbf564-8633-4fae-896d-c0aebbc3705a

Hatta, Mariko, Measures, Chris I., Lam, Phoebe J., Ohnemus, Daniel C., Auro, Maureen E., Grand, Maxime M. and Selph, Karen E. (2017) The relative roles of modified circumpolar deep water and benthic sources in supplying iron to the recurrent phytoplankton blooms above Pennell and Mawson Banks, Ross Sea, Antarctica. Journal of Marine Systems, 166, 61-72. (doi:10.1016/j.jmarsys.2016.07.009).

Record type: Article

Abstract

The role that dissolved iron (dFe) rich Circumpolar Deep Water (CDW) might play in sustaining the consistently observed discrete patches of high chlorophyll biomass over Pennell Bank (PB) and Mawson Bank (MB) in the Ross Sea, was investigated during January/February 2011. Over a 26-day period, hydrographic and trace metal clean water sampling was carried out adjacent to both of these banks, in some cases repeatedly. Particulate sampling was also accomplished at selected stations by in situ pumping. The results indicate that the dFe content of the CDW is in fact reduced by on-shelf mixing with Antarctic Surface Water as it transitions into modified CDW (MCDW). Our stations above PB, where the maximum bloom is encountered, show no evidence of MCDW presence. In contrast, above MB, where there is a smaller persistent bloom, MCDW was observed. Although both of these stations displayed the imprint of sedimentary Fe input connected to the strong tidal cycles above the banks, the stronger near-bottom density gradient that MCDW produces appears to contribute to reduced vertical mixing of the sedimentary source. Thus, ironically, the presence of MCDW may be hindering the Fe supply to the surface waters, rather than being the source, as originally hypothesized.

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Accepted Manuscript Hatta et al., 2017
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Accepted/In Press date: 15 July 2016
Published date: 1 February 2017
Organisations: Marine Biogeochemistry

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Local EPrints ID: 406742
URI: https://eprints.soton.ac.uk/id/eprint/406742
ISSN: 0924-7963
PURE UUID: b1b00c2e-0de4-437e-a22e-d3562a8c5429
ORCID for Maxime M. Grand: ORCID iD orcid.org/0000-0001-9338-694X

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Date deposited: 22 Mar 2017 02:01
Last modified: 09 Dec 2019 18:57

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