Resumo

HERNANDEZ-BECERRIL, David Uriel; LOPEZ-TACHIQUIN, Luis Felipe; MACHAIN-CASTILLO, María Luisa  e  MONREAL-GOMEZ, María Adela. Distribution of photosynthetic pigments of phytoplankton from the Gulf of Tehuantepec in summer (June, 2003): importance of the picophytoplankton. Hidrobiológica [online]. 2015, vol.25, n.3, pp.365-374. ISSN 0188-8897.

There exist previous studies on phytoplankton, its taxonomic groups and species, its biomass and primary productivity, mainly in winter and spring, but the structure of the phytoplankton from the Gulf of Tehuantepec in summer is poorly known. The composition and distribution of the phytoplankton photosynthetic pigments in summer conditions are provided in this paper. Hydrographic data from nine stations, during an oceanographic cruise in June, 20013, and analysis of five major phytoplanktonic pigments, Fucoxanthin, Prasinoxanthin, Violaxanthin, Zeaxanthin (marker of Synechococcus, picoplanktonic prokaryote) and Divinyl-chlorophyll a (diagnostic of Prochlorococcus, another picoplanktonic prokaryote) are given. Column water was well-stratified: surface layers had a thickness between 20 and 35 m, with well-defined thermoclines at those depths. Values of all pigments were low, but they showed similar vertical distribution patterns, with subsurface maxima peaks (between 30 and 40 m), especially Divinyl-chlorophyll a in most stations, except 3 and 4, where Fucoxanthin was the most important pigment. These peaks did not always coincide with the depths of the main thermocline at each station, buy usually they were found below the thermocline. This scenery shows the picoplankton as a very important size-fraction group in summer (at least in June), strongly contrasting with the winter-spring conditions, of intense turbulent mix and upwellings, where microplankton and diatoms appear to predominate.

Palavras-chave : Gulf of Tehuantepec; phytoplankton; picoplankton; photosynthetic pigments; seasonal phases.

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