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Aquatic Microbial Ecology

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AME 49:255-265 (2007)  -  DOI:

Size-fractionated phytoplankton diversity in the NW Iberian coast: a combination of microscopic, pigment and molecular analyses

Fabrice Not1,4, Manuel Zapata2, Yolanda Pazos3, Emilia Campaña2, Marylo Doval3, Francisco Rodríguez1,5,*

1Station Biologique de Roscoff, UMR 7144 CNRS et Université Pierre et Marie Curie, BP 74, 29682 Roscoff Cedex, France
2Centro de Investigacións Mariñas, Xunta de Galicia, Apdo. 13, 36620 Vilanova de Arousa, Spain
3Instituto Tecnolóxico para o Control do Medio Mariño de Galicia (INTECMAR), Xunta de Galicia, Peirao de Vilaxoan, 36611 Villagarcía de Arosa, Spain
4Present address: Institut de Ciències del Mar (CMIMA-CSIC), Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain
5Present address: Centro Oceanográfico de Canarias (IEO), Ctra. San Andrés 45, 38180 S/C Tenerife, Spain
*Corresponding author. Email:

ABSTRACT: The aim of our study was to describe the diversity and dynamics of size-fractionated phytoplankton at a fixed station (P2, Ría de Pontevedra, NW Spain) from late spring to early winter. Phytoplankton successions were assessed weekly from May to November 2004 using pigment analyses, light microscopy and fluorescence in situ hybridization coupled with tyramide signal amplification (FISH-TSA). Periodic upwelling events triggered the development of diatom populations followed by periods of relaxation/downwelling conditions where remineralization processes (maxima of NH4+), raised temperatures and/or low salinity waters from rainfall favored the increase of picophytoplankton. Marked differences were observed between diversity and dynamics of the micro-nano (>3 µm) and pico (<3 µm) size fractions. Micro-nanoplankton organisms contributed 85% of chl a on average (range, 55 to 99%); diatoms and cryptophytes were the dominant pigment groups (~70% chl a in this size category). In the picoplankton, chlorophytes and non-chlorophytes contributed to an identical proportion (50%) of total picoeukaryotes determined by FISH-TSA. A large fraction of these (~65%) could be accounted for by group-specific probes. Molecular data suggested that chl b-containing picoplankton were mostly accounted for by prasinophyceans belonging to the order Mamiellales (55% of total chlorophyte cells), with Micromonas pusilla as its major component (~70% of Mamiellales, ~20% of all picoeukaryotes), similar to that found in other temperate coastal locations. In contrast, HPLC analyses severely underestimated the contribution of prasinophyceans and indicated <10% Mamiellales among chlorophytes. Among chromophytes, the haptophyte probe targeted ~25% of non-chlorophyte cells, and pelagophyceans were sporadically abundant (13% non-chlorophyte cells, May to September). After pigment analyses the main chromophytes were diatom II (chl c3-containing), pelagophyceans and haptophytes with 20, 13 and 8% of picoplanktonic chl a, respectively.

KEY WORDS: Phytoplankton diversity · Pigments · FISH-TSA · Microscopy · Picoplankton · Ría de Pontevedra

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Cite this article as: Not F, Zapata M, Pazos Y, Campaña E, Doval M, Rodríguez F (2007) Size-fractionated phytoplankton diversity in the NW Iberian coast: a combination of microscopic, pigment and molecular analyses. Aquat Microb Ecol 49:255-265.

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