Mixing and Phytoplankton Growth in an Upwelling System
Mixing and Phytoplankton Growth in an Upwelling System
Previous studies focused on understanding the role of physical drivers on phytoplankton bloom formation mainly used indirect estimates of turbulent mixing. Here we use weekly observations of microstructure turbulence, dissolved inorganic nutrients, chlorophyll a concentration and primary production carried out in the Ría de Vigo (NW Iberian upwelling system) between March 2017 and May 2018 to investigate the relationship between turbulent mixing and phytoplankton growth at different temporal scales. In order to interpret our results, we used the theoretical framework described by the Critical Turbulent Hypothesis (CTH). According to this conceptual model if turbulence is low enough, the depth of the layer where mixing is active can be shallower than the mixed-layer depth, and phytoplankton may receive enough light to bloom. Our results showed that the coupling between turbulent mixing and phytoplankton growth in this system occurs at seasonal, but also at shorter time scales. In agreement with the CTH, higher phytoplankton growth rates were observed when mixing was low during spring-summer transitional and upwelling periods, whereas low values were described during periods of high mixing (fall-winter transitional and downwelling). However, low mixing conditions were not enough to ensure phytoplankton growth, as low phytoplankton growth was also found under these circumstances. Wavelet spectral analysis revealed that turbulent mixing and phytoplankton growth were also related at shorter time scales. The higher coherence between both variables was found in spring-summer at the ~16–30 d period and in fall-winter at the ~16–90 d period. These results suggest that mixing could act as a control factor on phytoplankton growth over the seasonal cycle, and could be also involved in the formation of occasional short-lived phytoplankton blooms.
NW Iberian upwelling system, Ría de Vigo, critical turbulence hypothesis, phytoplankton, turbulent mixing, wavelet analysis
Comesaña, Antonio
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Fernández-Castro, Bieito
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Chouciño, Paloma
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Fernández, Emilio
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Fuentes-Lema, Antonio
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Gilcoto, Miguel
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Pérez-Lorenzo, María
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Mouriño-Carballido, Beatriz
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6 September 2021
Comesaña, Antonio
3c29ae16-3834-4e3b-972c-d417b557b355
Fernández-Castro, Bieito
8017e93c-d5ee-4bba-b443-9c72ca512d61
Chouciño, Paloma
b0ebda43-f5f6-4c1a-a710-520be10023cd
Fernández, Emilio
c7f88845-c168-4466-a1c2-e6470a1f63d5
Fuentes-Lema, Antonio
94e10418-131b-4d62-8ef4-bad50c41cea3
Gilcoto, Miguel
431de478-8e3a-4e3a-83eb-bd6f27c9a82b
Pérez-Lorenzo, María
2d744955-4e8c-4a87-b192-707750b40ef6
Mouriño-Carballido, Beatriz
1bfd941d-9ec6-473f-94bd-bb6faac56fa5
Comesaña, Antonio, Fernández-Castro, Bieito, Chouciño, Paloma, Fernández, Emilio, Fuentes-Lema, Antonio, Gilcoto, Miguel, Pérez-Lorenzo, María and Mouriño-Carballido, Beatriz
(2021)
Mixing and Phytoplankton Growth in an Upwelling System.
Frontiers in Marine Science, 8, [712342].
(doi:10.3389/fmars.2021.712342).
Abstract
Previous studies focused on understanding the role of physical drivers on phytoplankton bloom formation mainly used indirect estimates of turbulent mixing. Here we use weekly observations of microstructure turbulence, dissolved inorganic nutrients, chlorophyll a concentration and primary production carried out in the Ría de Vigo (NW Iberian upwelling system) between March 2017 and May 2018 to investigate the relationship between turbulent mixing and phytoplankton growth at different temporal scales. In order to interpret our results, we used the theoretical framework described by the Critical Turbulent Hypothesis (CTH). According to this conceptual model if turbulence is low enough, the depth of the layer where mixing is active can be shallower than the mixed-layer depth, and phytoplankton may receive enough light to bloom. Our results showed that the coupling between turbulent mixing and phytoplankton growth in this system occurs at seasonal, but also at shorter time scales. In agreement with the CTH, higher phytoplankton growth rates were observed when mixing was low during spring-summer transitional and upwelling periods, whereas low values were described during periods of high mixing (fall-winter transitional and downwelling). However, low mixing conditions were not enough to ensure phytoplankton growth, as low phytoplankton growth was also found under these circumstances. Wavelet spectral analysis revealed that turbulent mixing and phytoplankton growth were also related at shorter time scales. The higher coherence between both variables was found in spring-summer at the ~16–30 d period and in fall-winter at the ~16–90 d period. These results suggest that mixing could act as a control factor on phytoplankton growth over the seasonal cycle, and could be also involved in the formation of occasional short-lived phytoplankton blooms.
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fmars-08-712342
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Published date: 6 September 2021
Keywords:
NW Iberian upwelling system, Ría de Vigo, critical turbulence hypothesis, phytoplankton, turbulent mixing, wavelet analysis
Identifiers
Local EPrints ID: 453056
URI: http://eprints.soton.ac.uk/id/eprint/453056
ISSN: 2296-7745
PURE UUID: 83774e9c-4fed-4eda-9cf1-a1db186c673c
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Date deposited: 07 Jan 2022 17:48
Last modified: 17 Mar 2024 04:04
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Contributors
Author:
Antonio Comesaña
Author:
Paloma Chouciño
Author:
Emilio Fernández
Author:
Antonio Fuentes-Lema
Author:
Miguel Gilcoto
Author:
María Pérez-Lorenzo
Author:
Beatriz Mouriño-Carballido
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