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Microbial control of phosphate in the nutrient-depleted North Atlantic subtropical gyre

Microbial control of phosphate in the nutrient-depleted North Atlantic subtropical gyre
Microbial control of phosphate in the nutrient-depleted North Atlantic subtropical gyre
Little is known about the dynamics of dissolved phosphate in oligotrophic areas of the world's oceans, where concentrations are typically in the nanomolar range. Here, we have budgeted phosphate uptake by the dominant microbial groups in order to assess the effect of the microbial control of this depleted nutrient in the North Atlantic gyre. Low concentrations (2.2 ± 1.2 nM) and rapid microbial uptake (2.1 ± 2.4 nM day1) of bioavailable phosphate were repeatedly determined in surface waters of the North Atlantic oligotrophic gyre during spring and autumn research cruises, using a radiotracer dilution bioassay technique. Upper estimates of the concentration of bioavailable phosphate were 7–55% of the dissolved mineral phosphate suggesting that a considerable part of the chemically measured nanomolar phosphate was in a form unavailable for direct microbial uptake. A 1:1 relationship (r2 = 0.96, P < 0.0001) was observed between the bioavailable total phosphate uptake and the phosphate uptake of all the flow sorted bacterioplankton cells, demonstrating that bacterioplankton were the main consumers of phosphate. Within the bacterioplankton a group of heterotrophic bacteria and Prochlorococcus phototrophic cyanobacteria, were the two major competing groups for bioavailable phosphate. These heterotrophic bacteria had low nucleic acid content and 60% of them comprised of SAR11 clade cells based on the results of fluorescence in situ hybridization. Each of the two competing bacterial groups was responsible for an average of 45% of the phosphate uptake, while Synechococcus cyanobacteria (7%) and picoplanktonic algae (0.3%) played minor roles in direct phosphate uptake. We have demonstrated that phosphate uptake in the oligotrophic gyre is rapid and dominated by two bacterial groups rather than by algae.
1462-2920
2079-2089
Zubkov, M.V.
b1dfb3a0-bcff-430c-9031-358a22b50743
Mary, I.
759ba210-d47f-4199-b0cf-27e585371ca9
Woodward, E.M.S.
3ac3b98f-78c7-4b43-acf9-bba3253752b5
Warwick, P.E.
f2675d83-eee2-40c5-b53d-fbe437f401ef
Fuchs, B.M.
1edd27c8-6b61-47f1-9c65-788d3fef9fd3
Scanlan, D.J.
490e6b20-efac-4150-9f3a-418ac8658c00
Burkill, P.H.
91175019-8b55-4fb5-84ea-334c12de2557
Zubkov, M.V.
b1dfb3a0-bcff-430c-9031-358a22b50743
Mary, I.
759ba210-d47f-4199-b0cf-27e585371ca9
Woodward, E.M.S.
3ac3b98f-78c7-4b43-acf9-bba3253752b5
Warwick, P.E.
f2675d83-eee2-40c5-b53d-fbe437f401ef
Fuchs, B.M.
1edd27c8-6b61-47f1-9c65-788d3fef9fd3
Scanlan, D.J.
490e6b20-efac-4150-9f3a-418ac8658c00
Burkill, P.H.
91175019-8b55-4fb5-84ea-334c12de2557

Zubkov, M.V., Mary, I., Woodward, E.M.S., Warwick, P.E., Fuchs, B.M., Scanlan, D.J. and Burkill, P.H. (2007) Microbial control of phosphate in the nutrient-depleted North Atlantic subtropical gyre. Environmental Microbiology, 9 (8), 2079-2089. (doi:10.1111/j.1462-2920.2007.01324.x).

Record type: Article

Abstract

Little is known about the dynamics of dissolved phosphate in oligotrophic areas of the world's oceans, where concentrations are typically in the nanomolar range. Here, we have budgeted phosphate uptake by the dominant microbial groups in order to assess the effect of the microbial control of this depleted nutrient in the North Atlantic gyre. Low concentrations (2.2 ± 1.2 nM) and rapid microbial uptake (2.1 ± 2.4 nM day1) of bioavailable phosphate were repeatedly determined in surface waters of the North Atlantic oligotrophic gyre during spring and autumn research cruises, using a radiotracer dilution bioassay technique. Upper estimates of the concentration of bioavailable phosphate were 7–55% of the dissolved mineral phosphate suggesting that a considerable part of the chemically measured nanomolar phosphate was in a form unavailable for direct microbial uptake. A 1:1 relationship (r2 = 0.96, P < 0.0001) was observed between the bioavailable total phosphate uptake and the phosphate uptake of all the flow sorted bacterioplankton cells, demonstrating that bacterioplankton were the main consumers of phosphate. Within the bacterioplankton a group of heterotrophic bacteria and Prochlorococcus phototrophic cyanobacteria, were the two major competing groups for bioavailable phosphate. These heterotrophic bacteria had low nucleic acid content and 60% of them comprised of SAR11 clade cells based on the results of fluorescence in situ hybridization. Each of the two competing bacterial groups was responsible for an average of 45% of the phosphate uptake, while Synechococcus cyanobacteria (7%) and picoplanktonic algae (0.3%) played minor roles in direct phosphate uptake. We have demonstrated that phosphate uptake in the oligotrophic gyre is rapid and dominated by two bacterial groups rather than by algae.

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Published date: January 2007

Identifiers

Local EPrints ID: 49921
URI: http://eprints.soton.ac.uk/id/eprint/49921
ISSN: 1462-2920
PURE UUID: 4f316d1e-c3a6-4156-92b1-fd0d617e69b4
ORCID for P.E. Warwick: ORCID iD orcid.org/0000-0001-8774-5125

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Date deposited: 18 Dec 2007
Last modified: 13 Oct 2022 01:34

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Contributors

Author: M.V. Zubkov
Author: I. Mary
Author: E.M.S. Woodward
Author: P.E. Warwick ORCID iD
Author: B.M. Fuchs
Author: D.J. Scanlan
Author: P.H. Burkill

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