Hydrodynamic conditions associated with the formation, maintenance and dissipation of a phytoplankton thin layer in a coastal upwelling system

Type Article
Date 2010-02
Language English
Author(s) Velo-Suarez Lourdes1, Fernand Liam2, Gentien Patrick3, Reguera Beatriz1
Affiliation(s) 1 : Ctr Oceanog Vigo, Inst Espanol Oceanog, E-36200 Vigo, Spain.
2 : CEFAS, Lowestoft NR33 OHT, Suffolk, England.
3 : IFREMER, Ctr Brest, DYNECO, F-29280 Plouzane, France.
Source Continental Shelf Research (0278-4343) (Pergamon-elsevier Science Ltd), 2010-02 , Vol. 30 , N. 2 , P. 193-202
DOI 10.1016/j.csr.2009.11.002
WOS© Times Cited 14
Keyword(s) Thin layer, Phytoplankton, Shear, Coastal upwelling system, Physical forcing, Coastal circulation
Abstract During May-June 2005, a 17-d cruise was carried out in Ria de Pontevedra (Galician Rias Baixas) to study the physical-biological interactions that may lead to subsurface aggregations of phytoplankton organisms in thin layers (TLs). Physical processes governed the initiation and development, maintenance, and decline of a diatom (toxin producing Pseudo-nitzschia spp. and Chaetoceros socialis) TL during an upwelling relaxation-upwelling-downwelling sequence. Differences in shear profiles appeared to lead to the formation of a TL during upwelling events. These results reveal that the coupling between maximum values of shear and buoyancy frequency can shape a subsurface chlorophyll maximum (SCM) into a TL. The effect of shear upon phytoplankton patches, which has been predicted on the basis of theoretical studies, has been corroborated in this study in which the vertical distribution of an observed TL was controlled by physical processes. Understanding both local fine-scale circulation patterns and regional physical processes will improve our knowledge of the spatial and temporal occurrence of these layers. Results here bring new understanding in TL dynamics at coastal upwelling sites and provide information about the physical processes involved in TL development, which can be used to predict their occurrence and understand their ecological implications. (C) 2009 Elsevier Ltd. All rights reserved.
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