Coupling between upper ocean layer variability and size-fractionated phytoplankton in a non-nutrient-limited environment

Pablo Sangrà; Cristina García-Muñoz; Carlos M. García; Ángeles Marrero-Díaz; Cristina Sobrino; Beatriz Mouriño-Carballido; Borja Aguiar-González; Cristian Henríquez-Pastene; Ángel Rodríguez-Santana; Luis M. Lubián; Mónica Hernández-Arencibia; Santiago Hernández-León; Elsa Vázquez; Sheila N. Estrada-Allis

doi:10.3354/meps10668

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MEPS 499:35-46 (2014) - DOI: https://doi.org/10.3354/meps10668

Coupling between upper ocean layer variability and size-fractionated phytoplankton in a non-nutrient-limited environment

Pablo Sangrà^1,*, Cristina García-Muñoz², Carlos M. García³, Ángeles Marrero-Díaz⁴, Cristina Sobrino⁵, Beatriz Mouriño-Carballido⁵, Borja Aguiar-González⁴, Cristian Henríquez-Pastene⁶, Ángel Rodríguez-Santana⁴, Luis M. Lubián², Mónica Hernández-Arencibia⁴, Santiago Hernández-León¹, Elsa Vázquez⁵, Sheila N. Estrada-Allis⁴

¹Instituto Universitario de Oceanografía y Cambio Global, Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas de Gran Canaria, Spain
²Departamento de Ecología y Gestión Costera, Instituto de Ciencias Marinas de Andalucía (ICMAN-CSIC), 11510 Puerto Real, Cádiz, Spain
³Departamento de Biología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, 11510 Puerto Real, Cádiz, Spain
⁴Departamento de Física, Universidad de Las Palmas de Gran Canaria, 35017 Las Palmas de Gran Canaria, Spain
⁵Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, 36200 Vigo, Pontevedra, Spain
⁶Departamento de Geofísica, Universidad de Concepciín, 160-C Concepcíon, Chile

*Corresponding author: pablo.sangra@ulpgc.es

ABSTRACT: We describe the coupling between upper ocean layer variability and size-fractionated phytoplankton distribution in the non-nutrient-limited Bransfield Strait region (BS) of Antarctica. For this purpose we use hydrographic and size-fractionated chlorophyll a data from a transect that crossed 2 fronts and an eddy, together with data from 3 stations located in a deeply mixed region, the Antarctic Sound (AS). In the BS transect, small phytoplankton (<20 µm equivalent spherical diameter [ESD]) accounted for 80% of total chl a and their distribution appeared to be linked to cross-frontal variability. On the deepening upper mixed layer (UML) sides of both fronts we observed a deep subducting column-like structure of small phytoplankton biomass. On the shoaling UML sides of both fronts, where there were signs of restratification, we observed a local shallow maximum of small phytoplankton biomass. We propose that this observed phytoplankton distribution may be a response to the development of frontal vertical circulation cells. In the deep, turbulent environment of the AS, larger phytoplankton (>20 µm ESD) accounted for 80% of total chl a. The proportion of large phytoplankton increases as the depth of the upper mixed layer (Z_UML), and the corresponding rate of vertical mixing, increases. We hypothesize that this change in phytoplankton composition with varying Z_UML is related to the competition for light, and results from modification of the light regime caused by vertical mixing.

KEY WORDS: Physical-biological coupling · Mesoscale · Submesoscale · Vertical mixing · Phytoplankton composition · Antarctica

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Cite this article as: Sangrà P, García-Muñoz C, García CM, Marrero-Díaz Á and others (2014) Coupling between upper ocean layer variability and size-fractionated phytoplankton in a non-nutrient-limited environment. Mar Ecol Prog Ser 499:35-46. https://doi.org/10.3354/meps10668

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