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Fe and Zn effects on the Si cycle and diatom community structure in two contrasting high and low-silicate HNLC areas

Fe and Zn effects on the Si cycle and diatom community structure in two contrasting high and low-silicate HNLC areas
Fe and Zn effects on the Si cycle and diatom community structure in two contrasting high and low-silicate HNLC areas

We compared the importance of Fe, Zn and Si availability for diatom growth and silicification through microcosm enrichment experiments in two contrasting HNLC systems of the Sub-Arctic and Sub-Antarctic Pacific. The Bering Sea was characterized by low Fe and Zn concentrations (<0.2 nM) but relatively high silicic acid (5.6-15.9 μM). The addition of 0.25 nM Fe induced a 2-7-fold increase in diatom cell abundance (Pseudo-nitzschia sp. and Cylindrotheca closterium), an increase in Chl a, biogenic silica, and particulate organic carbon and nitrogen, and a 2-3-fold decrease in the average cellular Si content. Zn had no impact on biomass parameters or diatom community structure in this region. The Sub-Antarctic Zone (SAZ) was a low Si-HNLC system, with initial silicic acid levels of 0.45 μM and Fe and Zn concentrations <0.03 nM. Si was the proximate limiting factor controlling diatom growth, followed by a secondary role for Fe on non-siliceous phytoplankton. In this region, we also found evidence for Zn-mediated changes in diatom community structure. The presence of Zn (+1 nM) shifted the community away from a large colonial pennate (Pseudo-nitzschia sp.) towards a smaller and less silicified solitary pennate (Cylindrotheca closterium), potentially prone to more rapid silica dissolution in the surface layer. Despite the dominance by the same two diatom genera, these two high-latitude regimes exhibited different nutrient limitation scenarios. Diatom growth in the Bering Sea was strongly Fe-limited, while the SAZ was mainly limited by Si and only secondarily by Fe.

Diatoms, HNLC, HNLSiLC, Iron, Silicate, Trace metal limitation, Zinc
0967-0637
1842-1864
Leblanc, K.
43dcedc1-8bb0-4929-ac9d-b3eeccad74c5
Hare, C. E.
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Boyd, P. W.
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Bruland, K. W.
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Sohst, B.
336cba59-1fee-4030-92ca-7609cc4a3a3f
Pickmere, S.
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Lohan, M. C.
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Buck, K.
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Ellwood, M.
76b57ff7-d44f-4a23-ab7a-83e15a701efb
Hutchins, D. A.
bd90dd2f-634c-4fab-a562-006da365298e
Leblanc, K.
43dcedc1-8bb0-4929-ac9d-b3eeccad74c5
Hare, C. E.
79e04724-f7fd-4a4d-a8e7-be4424a0c6db
Boyd, P. W.
0b90174f-a392-497c-8efe-a02dbc74f869
Bruland, K. W.
6e7b150c-b99c-4bf8-b473-cb3a086c0eb3
Sohst, B.
336cba59-1fee-4030-92ca-7609cc4a3a3f
Pickmere, S.
5e2e98b5-6018-45c4-a6f3-6abef8109e46
Lohan, M. C.
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Buck, K.
503b205e-52d5-4c1d-bb93-7d2c2c978d60
Ellwood, M.
76b57ff7-d44f-4a23-ab7a-83e15a701efb
Hutchins, D. A.
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Leblanc, K., Hare, C. E., Boyd, P. W., Bruland, K. W., Sohst, B., Pickmere, S., Lohan, M. C., Buck, K., Ellwood, M. and Hutchins, D. A. (2005) Fe and Zn effects on the Si cycle and diatom community structure in two contrasting high and low-silicate HNLC areas. Deep Sea Research Part I: Oceanographic Research Papers, 52 (10), 1842-1864. (doi:10.1016/j.dsr.2005.06.005).

Record type: Article

Abstract

We compared the importance of Fe, Zn and Si availability for diatom growth and silicification through microcosm enrichment experiments in two contrasting HNLC systems of the Sub-Arctic and Sub-Antarctic Pacific. The Bering Sea was characterized by low Fe and Zn concentrations (<0.2 nM) but relatively high silicic acid (5.6-15.9 μM). The addition of 0.25 nM Fe induced a 2-7-fold increase in diatom cell abundance (Pseudo-nitzschia sp. and Cylindrotheca closterium), an increase in Chl a, biogenic silica, and particulate organic carbon and nitrogen, and a 2-3-fold decrease in the average cellular Si content. Zn had no impact on biomass parameters or diatom community structure in this region. The Sub-Antarctic Zone (SAZ) was a low Si-HNLC system, with initial silicic acid levels of 0.45 μM and Fe and Zn concentrations <0.03 nM. Si was the proximate limiting factor controlling diatom growth, followed by a secondary role for Fe on non-siliceous phytoplankton. In this region, we also found evidence for Zn-mediated changes in diatom community structure. The presence of Zn (+1 nM) shifted the community away from a large colonial pennate (Pseudo-nitzschia sp.) towards a smaller and less silicified solitary pennate (Cylindrotheca closterium), potentially prone to more rapid silica dissolution in the surface layer. Despite the dominance by the same two diatom genera, these two high-latitude regimes exhibited different nutrient limitation scenarios. Diatom growth in the Bering Sea was strongly Fe-limited, while the SAZ was mainly limited by Si and only secondarily by Fe.

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Published date: October 2005
Keywords: Diatoms, HNLC, HNLSiLC, Iron, Silicate, Trace metal limitation, Zinc

Identifiers

Local EPrints ID: 413773
URI: https://eprints.soton.ac.uk/id/eprint/413773
ISSN: 0967-0637
PURE UUID: 1f462e9c-25ce-4bec-973a-5fdb195b5051

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Date deposited: 05 Sep 2017 16:31
Last modified: 13 Mar 2019 20:11

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Contributors

Author: K. Leblanc
Author: C. E. Hare
Author: P. W. Boyd
Author: K. W. Bruland
Author: B. Sohst
Author: S. Pickmere
Author: M. C. Lohan
Author: K. Buck
Author: M. Ellwood
Author: D. A. Hutchins

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