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Microbial abundance, activity and iron uptake in vicinity of the Crozet Isles in November 2004-January 2005

Microbial abundance, activity and iron uptake in vicinity of the Crozet Isles in November 2004-January 2005
Microbial abundance, activity and iron uptake in vicinity of the Crozet Isles in November 2004-January 2005
Iron leached from volcanic islands was hypothesised to naturally fertilise the high-nutrient low-chlorophyll (HNLC) waters of the Antarctic Circum Polar Current and to cause recurrent phytoplankton blooms or high-chlorophyll (HC) areas in the wake of the Crozet Islands. As part of CROZEX, the effect of Fe-fertilisation on microbial community was examined by comparing microbial standing stocks and microbial turnover rates of dissolved organic molecules and iron in the HNLC and HC waters in the vicinity of the Crozet Isles. Bacterioplankton and ultraplanktonic algae were enumerated by flow cytometry. Microbial turnover and ambient concentrations of amino acids and glucose in surface waters were bioassayed using an isotopic dilution technique. Microbial uptake of iron was estimated using a carrier-free 55Fe tracer approach. The data set generated did not reveal statistically significant seasonal changes above the observed high spatial variability in the studied area. Statistically significant higher biomass (1.5 times) of heterotrophic bacterioplankton (HB) as well as higher microbial turnover of organic molecules (10 times) were observed in the HC waters relative to the HNLC waters, while relative iron uptake was nearly eight times lower in the HC waters. However, the difference in HB standing stocks in the 100–200 m water layer between the two compared water types was statistically insignificant. Hence, the HC surface waters in austral summer showed higher microbial activity with decreased iron dependency relative to the HNLC waters of the Southern Ocean, in agreement with higher productivity of the waters to the north of the Crozet Islands.
Ultraplankton, Microbial bioassay, Bacterioplankton production, Iron tracer uptake, Southern Ocean, HNLC regions
0967-0645
2126-2137
Zubkov, M.V.
b1dfb3a0-bcff-430c-9031-358a22b50743
Holland, R.J.
4fa388a7-6f5d-4c05-ae3a-bbf254c04483
Burkill, P.H.
91175019-8b55-4fb5-84ea-334c12de2557
Croudace, I.W.
24deb068-d096-485e-8a23-a32b7a68afaf
Warwick, P.E.
f2675d83-eee2-40c5-b53d-fbe437f401ef
Zubkov, M.V.
b1dfb3a0-bcff-430c-9031-358a22b50743
Holland, R.J.
4fa388a7-6f5d-4c05-ae3a-bbf254c04483
Burkill, P.H.
91175019-8b55-4fb5-84ea-334c12de2557
Croudace, I.W.
24deb068-d096-485e-8a23-a32b7a68afaf
Warwick, P.E.
f2675d83-eee2-40c5-b53d-fbe437f401ef

Zubkov, M.V., Holland, R.J., Burkill, P.H., Croudace, I.W. and Warwick, P.E. (2007) Microbial abundance, activity and iron uptake in vicinity of the Crozet Isles in November 2004-January 2005. Deep Sea Research Part II: Topical Studies in Oceanography, 54 (18-20), 2126-2137. (doi:10.1016/j.dsr2.2007.06.020).

Record type: Article

Abstract

Iron leached from volcanic islands was hypothesised to naturally fertilise the high-nutrient low-chlorophyll (HNLC) waters of the Antarctic Circum Polar Current and to cause recurrent phytoplankton blooms or high-chlorophyll (HC) areas in the wake of the Crozet Islands. As part of CROZEX, the effect of Fe-fertilisation on microbial community was examined by comparing microbial standing stocks and microbial turnover rates of dissolved organic molecules and iron in the HNLC and HC waters in the vicinity of the Crozet Isles. Bacterioplankton and ultraplanktonic algae were enumerated by flow cytometry. Microbial turnover and ambient concentrations of amino acids and glucose in surface waters were bioassayed using an isotopic dilution technique. Microbial uptake of iron was estimated using a carrier-free 55Fe tracer approach. The data set generated did not reveal statistically significant seasonal changes above the observed high spatial variability in the studied area. Statistically significant higher biomass (1.5 times) of heterotrophic bacterioplankton (HB) as well as higher microbial turnover of organic molecules (10 times) were observed in the HC waters relative to the HNLC waters, while relative iron uptake was nearly eight times lower in the HC waters. However, the difference in HB standing stocks in the 100–200 m water layer between the two compared water types was statistically insignificant. Hence, the HC surface waters in austral summer showed higher microbial activity with decreased iron dependency relative to the HNLC waters of the Southern Ocean, in agreement with higher productivity of the waters to the north of the Crozet Islands.

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More information

Published date: 2007
Keywords: Ultraplankton, Microbial bioassay, Bacterioplankton production, Iron tracer uptake, Southern Ocean, HNLC regions

Identifiers

Local EPrints ID: 49516
URI: http://eprints.soton.ac.uk/id/eprint/49516
ISSN: 0967-0645
PURE UUID: 6be29782-de20-4f42-becf-3969557c0812
ORCID for P.E. Warwick: ORCID iD orcid.org/0000-0001-8774-5125

Catalogue record

Date deposited: 12 Nov 2007
Last modified: 16 Mar 2024 02:49

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Contributors

Author: M.V. Zubkov
Author: R.J. Holland
Author: P.H. Burkill
Author: I.W. Croudace
Author: P.E. Warwick ORCID iD

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