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Dissolved iron in the vicinity of the Crozet Islands, Southern Ocean

Dissolved iron in the vicinity of the Crozet Islands, Southern Ocean
Dissolved iron in the vicinity of the Crozet Islands, Southern Ocean
The annual phytoplankton bloom occurring north of the Crozet Plateau provides a rare opportunity to examine the hypothesis that natural iron fertilization can alleviate high-nutrient low-chlorophyll (HNLC) conditions normally associated with the Southern Ocean. Therefore, during CROZet natural iron bloom and EXport experiment (CROZEX), a large multidisciplinary study performed between November 2004 and January 2005, measurements of total dissolved iron (DFe0.2 ?m) were made on seawater from around the islands and atmospheric iron deposition estimated from rain and aerosol samples.

DFe concentrations were determined by flow injection analysis with N,N-dimethyl-p-phenylenediamine dihydrochloride (DPD) catalytic spectrophotometric detection. DFe concentrations varied between 0.086 and 2.48 nM, with low values in surface waters. Enrichment of dissolved iron (>1 nM) at close proximity to the islands suggests that the plateau and the associated sediments are a source of iron. Waters farther north also appear to be affected by this input of coastal and shelf origin, although dissolved iron concentrations decrease as a function of distance to the north of the plateau with a gradient of 0.07 nM km?1 at the time of sampling. Using lateral and vertical diffusion coefficients derived from Ra isotope profiles and also estimates of atmospheric inputs, it was then possible to estimate a DFe concentration of 0.55 nM to the north of the islands prior to the bloom event, which is sufficient to initiate the bloom, the lateral island source being the largest component. A similar situation is observed for other Sub-Antarctic Islands such as Kerguelen, South Georgia, that supply dissolved iron to their surrounding waters, thus enhancing chlorophyll concentrations.
Dissolved iron, Crozet Islands, Southern Ocean, HNLC
0967-0645
1999-2019
Planquette, H.
cf8631d8-c16a-4ee4-8713-736766936d24
Statham, P.J.
51458f15-d6e2-4231-8bba-d0567f9e440c
Fones, G.R.
5b71916c-4859-4a6f-b9ad-b6b1f541cbfa
Charette, M.A.
c0850a57-65a0-4429-b2f0-23a18f301f21
Moore, C.M.
7ec80b7b-bedc-4dd5-8924-0f5d01927b12
Salter, I.
805cba99-e754-417b-aac1-cee3a259aced
Nedelec, F.H.
a870d008-02c5-431b-949a-1e8ba7c6b0b5
Taylor, S.L.
11e5a6dc-5775-4479-9542-3ee8578cf488
French, M.
d0581006-ea32-4760-bd1f-060ee4a66bc5
Baker, A.R.
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Mahowald, N.
3eb4d13d-5919-48d8-857b-af747294a801
Jickells, T.D.
d85be7a3-239c-402f-83a6-8014b78cc4cc
Planquette, H.
cf8631d8-c16a-4ee4-8713-736766936d24
Statham, P.J.
51458f15-d6e2-4231-8bba-d0567f9e440c
Fones, G.R.
5b71916c-4859-4a6f-b9ad-b6b1f541cbfa
Charette, M.A.
c0850a57-65a0-4429-b2f0-23a18f301f21
Moore, C.M.
7ec80b7b-bedc-4dd5-8924-0f5d01927b12
Salter, I.
805cba99-e754-417b-aac1-cee3a259aced
Nedelec, F.H.
a870d008-02c5-431b-949a-1e8ba7c6b0b5
Taylor, S.L.
11e5a6dc-5775-4479-9542-3ee8578cf488
French, M.
d0581006-ea32-4760-bd1f-060ee4a66bc5
Baker, A.R.
2e470bae-1030-49cb-999e-1a0bfb0abfc9
Mahowald, N.
3eb4d13d-5919-48d8-857b-af747294a801
Jickells, T.D.
d85be7a3-239c-402f-83a6-8014b78cc4cc

Planquette, H., Statham, P.J., Fones, G.R., Charette, M.A., Moore, C.M., Salter, I., Nedelec, F.H., Taylor, S.L., French, M., Baker, A.R., Mahowald, N. and Jickells, T.D. (2007) Dissolved iron in the vicinity of the Crozet Islands, Southern Ocean. Deep Sea Research Part II: Topical Studies in Oceanography, 54 (18-20), 1999-2019. (doi:10.1016/j.dsr2.2007.06.019).

Record type: Article

Abstract

The annual phytoplankton bloom occurring north of the Crozet Plateau provides a rare opportunity to examine the hypothesis that natural iron fertilization can alleviate high-nutrient low-chlorophyll (HNLC) conditions normally associated with the Southern Ocean. Therefore, during CROZet natural iron bloom and EXport experiment (CROZEX), a large multidisciplinary study performed between November 2004 and January 2005, measurements of total dissolved iron (DFe0.2 ?m) were made on seawater from around the islands and atmospheric iron deposition estimated from rain and aerosol samples.

DFe concentrations were determined by flow injection analysis with N,N-dimethyl-p-phenylenediamine dihydrochloride (DPD) catalytic spectrophotometric detection. DFe concentrations varied between 0.086 and 2.48 nM, with low values in surface waters. Enrichment of dissolved iron (>1 nM) at close proximity to the islands suggests that the plateau and the associated sediments are a source of iron. Waters farther north also appear to be affected by this input of coastal and shelf origin, although dissolved iron concentrations decrease as a function of distance to the north of the plateau with a gradient of 0.07 nM km?1 at the time of sampling. Using lateral and vertical diffusion coefficients derived from Ra isotope profiles and also estimates of atmospheric inputs, it was then possible to estimate a DFe concentration of 0.55 nM to the north of the islands prior to the bloom event, which is sufficient to initiate the bloom, the lateral island source being the largest component. A similar situation is observed for other Sub-Antarctic Islands such as Kerguelen, South Georgia, that supply dissolved iron to their surrounding waters, thus enhancing chlorophyll concentrations.

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Published date: 2007
Keywords: Dissolved iron, Crozet Islands, Southern Ocean, HNLC

Identifiers

Local EPrints ID: 49509
URI: http://eprints.soton.ac.uk/id/eprint/49509
ISSN: 0967-0645
PURE UUID: 5967a671-4603-41da-ba5a-202cd4a16b74
ORCID for C.M. Moore: ORCID iD orcid.org/0000-0002-9541-6046

Catalogue record

Date deposited: 12 Nov 2007
Last modified: 16 Mar 2024 03:10

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Contributors

Author: H. Planquette
Author: P.J. Statham
Author: G.R. Fones
Author: M.A. Charette
Author: C.M. Moore ORCID iD
Author: I. Salter
Author: F.H. Nedelec
Author: S.L. Taylor
Author: M. French
Author: A.R. Baker
Author: N. Mahowald
Author: T.D. Jickells

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