Seasonal variations of nutrients, seston and phytoplankton, and upwelling intensity off La Coruña (NW Spain)

This study describes the main seasonal stages in oceanographic conditions and phytoplankton off La Coruña (Galicia, NW Spain), during 1991 and 1992, based mainly on monthly cruises near the coast. Upwelling conditions were studied using an upwelling index calculated from local winds. The Galician co...

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Detalles Bibliográficos
Autores: Casas, B., Varela-Rodríguez, Manuel, Canle, M., González, N., Bode, Antonio
Tipo de recurso: artículo
Fecha de publicación:1997
País:España
Institución:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/316413
Acceso en línea:http://hdl.handle.net/10261/316413
Access Level:acceso abierto
Palabra clave:Centro Oceanográfico de A Coruña
Medio Marino
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spelling Seasonal variations of nutrients, seston and phytoplankton, and upwelling intensity off La Coruña (NW Spain)Casas, B.Varela-Rodríguez, ManuelCanle, M.González, N.Bode, AntonioCentro Oceanográfico de A CoruñaMedio MarinoThis study describes the main seasonal stages in oceanographic conditions and phytoplankton off La Coruña (Galicia, NW Spain), during 1991 and 1992, based mainly on monthly cruises near the coast. Upwelling conditions were studied using an upwelling index calculated from local winds. The Galician coast is affected by a long upwelling season for most of the year. The upwelling pulses interact with the thermal stratification-mixing cycle of surface waters, primarily affecting the dynamics of phytoplankton. In addition, the presence of water masses of different salinity in the subsurface layers changes the stratification of the water column. The less-saline North Atlantic Central Water (NACW) was normally associated with upwelling events during summer. However, on several occasions during the study, the presence of Eastern North Atlantic Water (ENAW) of subtropical origin was observed with salinities up to 36·22 and temperatures between 13 and 14 °C. Observations were grouped into five main stages related to the degree of surface stratification and characteristics of phytoplankton communities. These stages were recognized in both annual cycles, and were termed: winter mixing, spring and autumn blooms, summer upwelling, thermal stratification and special events (red tides and downwelling). A homogeneous water column was the main characteristic of the winter stage, with high nutrient concentrations and low phytoplankton biomass. Eastern North Atlantic Water appeared at the end of this stage, which lasted from November to February. The spring and autumn blooms occurred along with weak thermohaline gradients at the surface, producing high phytoplankton concentrations. Favourable upwelling conditions and the presence of ENAW in a subsurface layer were the factors that most likely induced earlier blooms, while thermal gradients developed at the surface could have been more important for later blooms. Upwelling events during summer were related to a reduction in the depth of the surface mixed layer as the pycnocline moved upwards, and can produce significant phytoplankton accumulations. These summer blooms interrupted the thermal stratification stage, characterized by low nutrient and phytoplankton concentrations at the surface. The dominant phytoplankton in the study was composed mainly of diatoms, especially during blooms. However, a proliferation of red-tide dinoflagellates was observed along with weak upwelling conditions in late summer. Also in late summer, strong downwelling conditions caused the accumulation of warmer shelf waters inshore, inducing the sinking of particulate matter produced at the surface.Sí202320231997info:eu-repo/semantics/articlehttp://purl.org/coar/resource_type/c_6501http://hdl.handle.net/10261/316413reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)InglésCentro Oceanográfico de A Coruñahttps://www.sciencedirect.com/science/article/pii/S0272771496901559info:eu-repo/semantics/openAccessoai:digital.csic.es:10261/3164132026-05-22T06:33:51Z
dc.title.none.fl_str_mv Seasonal variations of nutrients, seston and phytoplankton, and upwelling intensity off La Coruña (NW Spain)
title Seasonal variations of nutrients, seston and phytoplankton, and upwelling intensity off La Coruña (NW Spain)
spellingShingle Seasonal variations of nutrients, seston and phytoplankton, and upwelling intensity off La Coruña (NW Spain)
Casas, B.
Centro Oceanográfico de A Coruña
Medio Marino
title_short Seasonal variations of nutrients, seston and phytoplankton, and upwelling intensity off La Coruña (NW Spain)
title_full Seasonal variations of nutrients, seston and phytoplankton, and upwelling intensity off La Coruña (NW Spain)
title_fullStr Seasonal variations of nutrients, seston and phytoplankton, and upwelling intensity off La Coruña (NW Spain)
title_full_unstemmed Seasonal variations of nutrients, seston and phytoplankton, and upwelling intensity off La Coruña (NW Spain)
title_sort Seasonal variations of nutrients, seston and phytoplankton, and upwelling intensity off La Coruña (NW Spain)
dc.creator.none.fl_str_mv Casas, B.
Varela-Rodríguez, Manuel
Canle, M.
González, N.
Bode, Antonio
author Casas, B.
author_facet Casas, B.
Varela-Rodríguez, Manuel
Canle, M.
González, N.
Bode, Antonio
author_role author
author2 Varela-Rodríguez, Manuel
Canle, M.
González, N.
Bode, Antonio
author2_role author
author
author
author
dc.subject.none.fl_str_mv Centro Oceanográfico de A Coruña
Medio Marino
topic Centro Oceanográfico de A Coruña
Medio Marino
description This study describes the main seasonal stages in oceanographic conditions and phytoplankton off La Coruña (Galicia, NW Spain), during 1991 and 1992, based mainly on monthly cruises near the coast. Upwelling conditions were studied using an upwelling index calculated from local winds. The Galician coast is affected by a long upwelling season for most of the year. The upwelling pulses interact with the thermal stratification-mixing cycle of surface waters, primarily affecting the dynamics of phytoplankton. In addition, the presence of water masses of different salinity in the subsurface layers changes the stratification of the water column. The less-saline North Atlantic Central Water (NACW) was normally associated with upwelling events during summer. However, on several occasions during the study, the presence of Eastern North Atlantic Water (ENAW) of subtropical origin was observed with salinities up to 36·22 and temperatures between 13 and 14 °C. Observations were grouped into five main stages related to the degree of surface stratification and characteristics of phytoplankton communities. These stages were recognized in both annual cycles, and were termed: winter mixing, spring and autumn blooms, summer upwelling, thermal stratification and special events (red tides and downwelling). A homogeneous water column was the main characteristic of the winter stage, with high nutrient concentrations and low phytoplankton biomass. Eastern North Atlantic Water appeared at the end of this stage, which lasted from November to February. The spring and autumn blooms occurred along with weak thermohaline gradients at the surface, producing high phytoplankton concentrations. Favourable upwelling conditions and the presence of ENAW in a subsurface layer were the factors that most likely induced earlier blooms, while thermal gradients developed at the surface could have been more important for later blooms. Upwelling events during summer were related to a reduction in the depth of the surface mixed layer as the pycnocline moved upwards, and can produce significant phytoplankton accumulations. These summer blooms interrupted the thermal stratification stage, characterized by low nutrient and phytoplankton concentrations at the surface. The dominant phytoplankton in the study was composed mainly of diatoms, especially during blooms. However, a proliferation of red-tide dinoflagellates was observed along with weak upwelling conditions in late summer. Also in late summer, strong downwelling conditions caused the accumulation of warmer shelf waters inshore, inducing the sinking of particulate matter produced at the surface.
publishDate 1997
dc.date.none.fl_str_mv 1997
2023
2023
dc.type.none.fl_str_mv info:eu-repo/semantics/article
http://purl.org/coar/resource_type/c_6501
format article
dc.identifier.none.fl_str_mv http://hdl.handle.net/10261/316413
url http://hdl.handle.net/10261/316413
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv Centro Oceanográfico de A Coruña
https://www.sciencedirect.com/science/article/pii/S0272771496901559
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.source.none.fl_str_mv reponame:DIGITAL.CSIC. Repositorio Institucional del CSIC
instname:Consejo Superior de Investigaciones Científicas (CSIC)
instname_str Consejo Superior de Investigaciones Científicas (CSIC)
reponame_str DIGITAL.CSIC. Repositorio Institucional del CSIC
collection DIGITAL.CSIC. Repositorio Institucional del CSIC
repository.name.fl_str_mv
repository.mail.fl_str_mv
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score 15,812429

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