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Marine Ecology Progress Series

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MEPS 498:55-71 (2014)  -  DOI:

Factors controlling phytoplankton physiological state around the South Shetland Islands (Antarctica)

Cristina García-Muñoz1,*, Cristina Sobrino2, Luis M. Lubián1, Carlos M. García3, Sandra Martínez-García2,5, Pablo Sangrà4

1Departamento de Ecología y Gestión costera, Instituto de Ciencias Marinas de Andalucía (ICMAN-CSIC),
11510 Puerto Real, Cádiz, Spain
2Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, 36200 Vigo, Pontevedra, Spain
3Departamento de Biología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, 11510 Puerto Real, Cádiz, Spain
4Departamento de Física, Facultad de Ciencias del Mar, Universidad de Las Palmas de Gran Canaria, Campus de Tafira,
35017 Las Palmas de Gran Canaria, Spain
5Present address: C-MORE, University of Hawaii, C-MORE Hale, 1950 East West Road, Honolulu, Hawaii 96822, USA
*Corresponding author:

ABSTRACT: To investigate factors controlling phytoplankton physiological state around the South Shetland Islands, phytoplankton abundance and structure, fluorescence properties, photoprotective pigment composition and physicochemical variables were studied. Nanophytoplanktonic cells (<20 µm) contributed 84% of total chlorophyll a (chl a), except for the station closest to the Antarctic Peninsula where microplanktonic cells (>20 µm) predominated (up to 85% of total chl a). Daily irradiance over the mixed layer depth (MLD) was inversely related with integrated nanoplanktonic chl a; however, its relative contribution to total chl a increased at mid-irradiance values. The average maximum quantum yield of photosystem II (Fv/Fm) below 20 m depth ranged from 0.17 to 0.53 and showed that cells were under suboptimal physiological conditions in the Drake region, but had higher performance around the South Shetland Islands and towards the Antarctic Peninsula. A reverse pattern in the fluorescence yield was detected. A deeper examination of the Fv/Fm vertical profiles according to the sampling time detected surface photoinhibition during the day and a spatial modulation of Fv/Fm related to irradiance and the silicic acid:nitrate ratio. It appears that cells’ photosynthetic performance was controlled by iron limitation in the Drake region, whereas irradiance regime controlled phytoplankton physiological state in the rest of the studied regions. Vertical mixing differences among stations, the relative position of the euphotic layer depth with respect to the MLD and the photoprotective pigment ratios revealed contrasting responses to light stress among the different phytoplanktonic groups, revealing a better adaptation of medium size cells, especially diatoms, to stratified waters receiving high irradiance.

KEY WORDS: South Shetland Islands · Phytoplankton · Fv/Fm · Irradiance · Size · Mixed layer · Nutrients

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Cite this article as: García-Muñoz C, Sobrino C, Lubián LM, García CM, Martínez-García S, Sangrà P (2014) Factors controlling phytoplankton physiological state around the South Shetland Islands (Antarctica). Mar Ecol Prog Ser 498:55-71.

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