Summer succession of ultraphytoplankton at the EPEA coastal station (Northern Argentina)

SILVA, R.I.; NEGRI, R.M.; LUTZ, V.A.

JOURNAL OF PLANKTON RESEARCH

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2009 vol. 31 p. 447 - 458

0142-7873

&amp;amp;lt;!-- /* Font Definitions */ @font-face {font-family:"MS Mincho"; panose-1:2 2 6 9 4 2 5 8 3 4; mso-font-alt:"Arial Unicode MS"; mso-font-charset:128; mso-generic-font-family:roman; mso-font-format:other; mso-font-pitch:fixed; mso-font-signature:1 134676480 16 0 131072 0;} @font-face {font-family:"@MS Mincho"; panose-1:0 0 0 0 0 0 0 0 0 0; mso-font-charset:128; mso-generic-font-family:roman; mso-font-format:other; mso-font-pitch:fixed; mso-font-signature:1 134676480 16 0 131072 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0pt; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"MS Mincho"; mso-fareast-language:ES;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 85.05pt 70.85pt 85.05pt; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --&amp;amp;gt; Ultraphytoplankton (<5 µm) are important members of food webs in any pelagic system. Temporal succession in their community structure was studied at a coastal station (38º28’S – 57º41’W), ‘Estación Permanente de Estudios Ambientales (EPEA)’, during summer 2001-2002. Prokaryotic and eukaryotic algae of this fraction, and small protozoa were identified, enumerated and optically characterized using a combination of methods: classic and fluorescence microscopy, flow cytometry and absorption spectra. Ultraphytoplankton contributed up to 90 % of total chlorophyll a during this summer. Synechococcus dominated this community and their highest biomass was related to high temperature and high stability during January. Chlorophyta coccal algae showed a maximum biomass in February, when the water column was weakly stratified. Cryptophyceae, Prymnesiophyceae, Prasinophyceae, Bacillariophyceae and Chrysophyceae ultra-algae were present in variable proportions throughout the period. Variations in optical properties were significantly related to the shift from prokaryotic to eukaryotic coccal cells, which would allow the possibility of bio-optically inferring phytoplankton types. The ultraphytoplankton succession was mainly driven by physical forces, especially the degree of stability. Algae with coccal life-forms strategies seem to be a major source of biogenic carbon supporting the functioning of this pelagic coastal ecosystem during summer.