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Thin layers of phytoplankton and harmful algae events in a coastal upwelling system

Thin layers of phytoplankton and harmful algae events in a coastal upwelling system
Thin layers of phytoplankton and harmful algae events in a coastal upwelling system

We combined time-series from a monitoring program and specific field observations in order to: 1) describe the characteristics of thin layers of phytoplankton (TLP) in the Galician Rías Baixas (NW Iberian Peninsula), 2) investigate the relationship between spatially-extended TLP (se-TLP) events and environmental variables, and 3) analyze the relationship between TLP occurrence and cell densities of toxin-producing harmful algal bloom (THAB) species. Between 2012 and 2015, a total of 118 TLP were detected in any of the 39 stations weekly sampled in the study area in the frame of the monitoring program, which represents a frequency of occurrence of 2%. Most TLP (84%) were detected between May-August and located slightly below shallow pycnoclines. Eight se-TLP events, i.e., when at least five stations were simultaneously influenced by the occurrence of a TLP, were identified during the period 2012–2015. Six out eight of these events happened during summer-upwelling conditions, and according to a Principal Component Analysis (PCA) they were positively correlated with thermal stratification. The other two events, detected during spring-downwelling, were positively correlated with haline stratification. A logistic regression model including six variables (surface temperature, relative humidity, bottom salinity, a proxy for the intrusion of the Miño River plume into Ría de Vigo, Miño River flow, and bottom temperature) explained 42% of the variance in the occurrence of se-TLP events. The temporal persistence of TLP events was confirmed by observations carried out during specific cruises, which showed how TLP were formed and disappeared over short periods of time in response to changes in vertical mixing. TLP were more frequently observed in Ría de Pontevedra, which was characterized by longer harvesting closures due to detection of Dinophysis toxins (DSP: diarrhetic shellfish poisoning toxins and pectenotoxins) above regulatory levels. s10ֽ𾺲 25% of the TLP detected in the Rías Baixas were associated with increased cell densities of potentially toxic Pseudo-nitzschia species (ASP: amnesic shellfish poisoning) and of D. acuminata. These results suggest that a relationship may be established between the occurrence of TLP and the growth and/or accumulation of the main THAB species in the Galician Rías Baixas.

Dinophysis acuminata, Galician Rías, Logistic Regression, NW Iberian upwelling system, Pseudo-nitzschia, Stratification, Thin layers of phytoplankton (TLP)
0079-6611
Broullón, Esperanza
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López-mozos, Marta
29de67a1-2059-47c9-aec5-cf32babf9456
Reguera, Beatriz
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Chouciño, Paloma
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Doval, María Dolores
d349ed84-ace5-4298-9eee-9e1e2367e2ef
Fernández-castro, Bieito
8017e93c-d5ee-4bba-b443-9c72ca512d61
Gilcoto, Miguel
431de478-8e3a-4e3a-83eb-bd6f27c9a82b
Nogueira, Enrique
28843ec2-b3ba-4835-a8ce-53d770b776bc
Souto, Carlos
e3a36b84-6dc1-4e7d-a924-f62ea6ae0527
Mouriño-carballido, Beatriz
1bfd941d-9ec6-473f-94bd-bb6faac56fa5
Broullón, Esperanza
f90cfa74-83be-4bed-8ef6-32cc679c1049
López-mozos, Marta
29de67a1-2059-47c9-aec5-cf32babf9456
Reguera, Beatriz
12afee73-3c30-487b-8228-fc4955c2391b
Chouciño, Paloma
b0ebda43-f5f6-4c1a-a710-520be10023cd
Doval, María Dolores
d349ed84-ace5-4298-9eee-9e1e2367e2ef
Fernández-castro, Bieito
8017e93c-d5ee-4bba-b443-9c72ca512d61
Gilcoto, Miguel
431de478-8e3a-4e3a-83eb-bd6f27c9a82b
Nogueira, Enrique
28843ec2-b3ba-4835-a8ce-53d770b776bc
Souto, Carlos
e3a36b84-6dc1-4e7d-a924-f62ea6ae0527
Mouriño-carballido, Beatriz
1bfd941d-9ec6-473f-94bd-bb6faac56fa5

Broullón, Esperanza, López-mozos, Marta, Reguera, Beatriz, Chouciño, Paloma, Doval, María Dolores, Fernández-castro, Bieito, Gilcoto, Miguel, Nogueira, Enrique, Souto, Carlos and Mouriño-carballido, Beatriz (2020) Thin layers of phytoplankton and harmful algae events in a coastal upwelling system. Progress in Oceanography, 189, [102449]. ().

Record type: Article

Abstract

We combined time-series from a monitoring program and specific field observations in order to: 1) describe the characteristics of thin layers of phytoplankton (TLP) in the Galician Rías Baixas (NW Iberian Peninsula), 2) investigate the relationship between spatially-extended TLP (se-TLP) events and environmental variables, and 3) analyze the relationship between TLP occurrence and cell densities of toxin-producing harmful algal bloom (THAB) species. Between 2012 and 2015, a total of 118 TLP were detected in any of the 39 stations weekly sampled in the study area in the frame of the monitoring program, which represents a frequency of occurrence of 2%. Most TLP (84%) were detected between May-August and located slightly below shallow pycnoclines. Eight se-TLP events, i.e., when at least five stations were simultaneously influenced by the occurrence of a TLP, were identified during the period 2012–2015. Six out eight of these events happened during summer-upwelling conditions, and according to a Principal Component Analysis (PCA) they were positively correlated with thermal stratification. The other two events, detected during spring-downwelling, were positively correlated with haline stratification. A logistic regression model including six variables (surface temperature, relative humidity, bottom salinity, a proxy for the intrusion of the Miño River plume into Ría de Vigo, Miño River flow, and bottom temperature) explained 42% of the variance in the occurrence of se-TLP events. The temporal persistence of TLP events was confirmed by observations carried out during specific cruises, which showed how TLP were formed and disappeared over short periods of time in response to changes in vertical mixing. TLP were more frequently observed in Ría de Pontevedra, which was characterized by longer harvesting closures due to detection of Dinophysis toxins (DSP: diarrhetic shellfish poisoning toxins and pectenotoxins) above regulatory levels. s10ֽ𾺲 25% of the TLP detected in the Rías Baixas were associated with increased cell densities of potentially toxic Pseudo-nitzschia species (ASP: amnesic shellfish poisoning) and of D. acuminata. These results suggest that a relationship may be established between the occurrence of TLP and the growth and/or accumulation of the main THAB species in the Galician Rías Baixas.

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Thinlayersofphytoplankton - Accepted Manuscript
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Accepted/In Press date: 29 September 2019
e-pub ahead of print date: 3 October 2019
Published date: 1 November 2020
Keywords: Dinophysis acuminata, Galician Rías, Logistic Regression, NW Iberian upwelling system, Pseudo-nitzschia, Stratification, Thin layers of phytoplankton (TLP)

Identifiers

Local EPrints ID: 445090
URI: http://eprints.soton.ac.uk/id/eprint/445090
DOI:
ISSN: 0079-6611
PURE UUID: 1db1e5ce-47ed-4303-b511-34022f89365f

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Date deposited: 19 Nov 2020 17:31
Last modified: 19 Nov 2020 17:31

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Contributors

Author: Esperanza Broullón
Author: Marta López-mozos
Author: Beatriz Reguera
Author: Paloma Chouciño
Author: María Dolores Doval
Author:
Author: Miguel Gilcoto
Author: Enrique Nogueira
Author: Carlos Souto
Author: Beatriz Mouriño-carballido

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