A pseudo‐Lagrangian transformation to study a chlorophyll‐a patch in the Ría de Vigo (NW Iberian Peninsula)
A pseudo‐Lagrangian transformation to study a chlorophyll‐a patch in the Ría de Vigo (NW Iberian Peninsula)
Because of the difficulties in tracking a water mass over time and conducting synoptic surveys over large spatial scales, measurements of biological variables in the ocean are often restricted to isolated Eulerian observations. Here a proof-of-concept of a pseudo-Lagrangian transformation was applied to a time series of chlorophyll-a profiles acquired at a single fixed station to diagnose the shape of a phytoplankton patch, and its physical-biological rates of transformation. During August 2013, a 27-hr time series of observations of horizontal currents, hydrographic properties, turbulent mixing and chlorophyll-a was acquired at a central station of the Ría de Vigo (NW Iberian Peninsula). A chlorophyll-a patch, tilted upward toward the inner part of the Ría, was observed moving back and forth past the sampling station. Its shape and position during the sampling period were modulated by the semi-diurnal (M2) tidal currents and the vertically sheared upwelling circulation. The pseudo-Lagrangian transformation allowed estimation of chlorophyll-a net rates of change. These rates were positive between 12 and 14 m depth, and negative elsewhere, with a mean value of −0.001 ± 0.449 days−1 within the patch maximum. After accounting for the effects of diffusion and sinking, the mean net biological production rate in the upper 15 m (0.53 ± 0.25 days−1) was comparable with in vitro estimates of the balance between phytoplankton growth and mortality obtained from dilution experiments carried out under similar conditions (0.2 ± 0.7 days−1). This pseudo-Lagrangian transformation is complementary to traditional analyses for the quantification of ecological processes and biogeochemical budgets.
Ría de Vigo, chlorophyll, coastal upwelling, phytoplankton, pseudo-Lagrangian transformation
Villamaña, M.
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Franks, P.J.S.
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Fernández Castro, B.
8017e93c-d5ee-4bba-b443-9c72ca512d61
Gilcoto, M.
431de478-8e3a-4e3a-83eb-bd6f27c9a82b
Marañón, E.
92f9d2a8-cfe4-4f67-86a1-793af860899a
Mouriño‐Carballido, B.
c1dbf004-40db-4dbb-ac0c-2fe2c96d40b3
11 October 2021
Villamaña, M.
9504a28b-9fee-457d-b71e-690cb5c7a60d
Franks, P.J.S.
6ab2b887-9042-40a8-a6ba-429bfbcdbe6d
Fernández Castro, B.
8017e93c-d5ee-4bba-b443-9c72ca512d61
Gilcoto, M.
431de478-8e3a-4e3a-83eb-bd6f27c9a82b
Marañón, E.
92f9d2a8-cfe4-4f67-86a1-793af860899a
Mouriño‐Carballido, B.
c1dbf004-40db-4dbb-ac0c-2fe2c96d40b3
Villamaña, M., Franks, P.J.S., Fernández Castro, B., Gilcoto, M., Marañón, E. and Mouriño‐Carballido, B.
(2021)
A pseudo‐Lagrangian transformation to study a chlorophyll‐a patch in the Ría de Vigo (NW Iberian Peninsula).
Journal of Geophysical Research: Oceans, 126 (10), [e2021JC017455].
(doi:10.1029/2021JC017455).
Abstract
Because of the difficulties in tracking a water mass over time and conducting synoptic surveys over large spatial scales, measurements of biological variables in the ocean are often restricted to isolated Eulerian observations. Here a proof-of-concept of a pseudo-Lagrangian transformation was applied to a time series of chlorophyll-a profiles acquired at a single fixed station to diagnose the shape of a phytoplankton patch, and its physical-biological rates of transformation. During August 2013, a 27-hr time series of observations of horizontal currents, hydrographic properties, turbulent mixing and chlorophyll-a was acquired at a central station of the Ría de Vigo (NW Iberian Peninsula). A chlorophyll-a patch, tilted upward toward the inner part of the Ría, was observed moving back and forth past the sampling station. Its shape and position during the sampling period were modulated by the semi-diurnal (M2) tidal currents and the vertically sheared upwelling circulation. The pseudo-Lagrangian transformation allowed estimation of chlorophyll-a net rates of change. These rates were positive between 12 and 14 m depth, and negative elsewhere, with a mean value of −0.001 ± 0.449 days−1 within the patch maximum. After accounting for the effects of diffusion and sinking, the mean net biological production rate in the upper 15 m (0.53 ± 0.25 days−1) was comparable with in vitro estimates of the balance between phytoplankton growth and mortality obtained from dilution experiments carried out under similar conditions (0.2 ± 0.7 days−1). This pseudo-Lagrangian transformation is complementary to traditional analyses for the quantification of ecological processes and biogeochemical budgets.
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Accepted/In Press date: 5 October 2021
Published date: 11 October 2021
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Funding Information:
We are grateful to all the technicians, researchers and crew on board the R/V Mytilus for their help during field work. We also thank P. Chouciño, R. Graña and F. de la Granda for microstructure turbulence data collection and processing. This research was funded by projects: STRAMIX (CTM2012‐35155) to Miguel Gilcoto and REMEDIOS (CTM2016‐75451‐ C2‐1‐R) to B. Mouriño‐Carballido from the Spanish Ministry of Economy and Competitiveness. M. Villamaña acknowledges the receipt of a FPU fellowship (FPU014/05,385) from the Spanish Ministry of Education, Culture and Sports. B. Fernández Castro was supported by the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska‐Curie Grant Agreement No. 834330 (SO‐CUP). Funding for open access charge: Universidade de Vigo/CISUG.
Publisher Copyright:
© 2021 The Authors.
Keywords:
Ría de Vigo, chlorophyll, coastal upwelling, phytoplankton, pseudo-Lagrangian transformation
Identifiers
Local EPrints ID: 451825
URI: http://eprints.soton.ac.uk/id/eprint/451825
ISSN: 2169-9275
PURE UUID: d3f39f40-db31-4db1-b5cf-466c76216f8b
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Date deposited: 28 Oct 2021 16:36
Last modified: 17 Mar 2024 04:04
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Contributors
Author:
M. Villamaña
Author:
P.J.S. Franks
Author:
M. Gilcoto
Author:
E. Marañón
Author:
B. Mouriño‐Carballido
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