title: PHASED OSCILLATIONS IN CELL NUMBERS AND NITRATE IN BATCH CULTURES OF ALEXANDRIUM TAMARENSE (DINOPHYCEAE)(1).
abstract: Alexandrium tamarense (M. Lebour) Balech strains isolated in spring 2007 from a single bloom in Thau lagoon have been grown in nonaxenic artificial media. For three strains showing large oscillations in biomass (crashes followed by recoveries) on a scale of several days, a significant relationship was observed between changes in cell densities (as in vivo fluorescence) and changes in nitrate concentrations. Increases in cell densities were accompanied by decreases in nitrate, while decreases in cell densities corresponded to increases in nitrate, presumably due to nitrification. Net increases in nitrate could reach up to 15 μmol N · L(-1)  · d(-1) indicating a very active nitrifying archaeal/bacterial population. However, following population crashes, algal cells can recover and attain biomass levels similar to those reached during the first growth phase. This finding indicates that those archaea/bacteria do not compete for nutrients or do not hamper algal growth under those conditions. In contrast to diatoms, dinoflagellates such as A. tamarense do not excrete/exude dissolved organic matter, thus preventing excessive bacterial growth. This mechanism could help explain the recovery of this species in the presence of bacteria.
authors.affiliation: Université Montpellier 2, Ecologie des Systèmes Marins Côtiers, UMR 5119 CNRS, IRD, CC093, 34095 Montpellier Cedex 5, FranceIfremer, Laboratoire Environnement Ressources des Pertuis Charentais, BP 7 - 17137 L'Houmeau, FranceUniversité Montpellier 2, Ecologie des Systèmes Marins Côtiers, UMR 5119 CNRS, IRD, CC093, 34095 Montpellier Cedex 5, France.
authors.forename: Yves
authors.initials: Y
authors.lastname: Collos
authors.affiliation: Université Montpellier 2, Ecologie des Systèmes Marins Côtiers, UMR 5119 CNRS, IRD, CC093, 34095 Montpellier Cedex 5, FranceIfremer, Laboratoire Environnement Ressources des Pertuis Charentais, BP 7 - 17137 L'Houmeau, FranceUniversité Montpellier 2, Ecologie des Systèmes Marins Côtiers, UMR 5119 CNRS, IRD, CC093, 34095 Montpellier Cedex 5, France.
authors.forename: Imene
authors.initials: I
authors.lastname: Hadjadji
authors.affiliation: Université Montpellier 2, Ecologie des Systèmes Marins Côtiers, UMR 5119 CNRS, IRD, CC093, 34095 Montpellier Cedex 5, FranceIfremer, Laboratoire Environnement Ressources des Pertuis Charentais, BP 7 - 17137 L'Houmeau, FranceUniversité Montpellier 2, Ecologie des Systèmes Marins Côtiers, UMR 5119 CNRS, IRD, CC093, 34095 Montpellier Cedex 5, France.
authors.forename: Benoit
authors.initials: B
authors.lastname: Plisson
authors.affiliation: Université Montpellier 2, Ecologie des Systèmes Marins Côtiers, UMR 5119 CNRS, IRD, CC093, 34095 Montpellier Cedex 5, FranceIfremer, Laboratoire Environnement Ressources des Pertuis Charentais, BP 7 - 17137 L'Houmeau, FranceUniversité Montpellier 2, Ecologie des Systèmes Marins Côtiers, UMR 5119 CNRS, IRD, CC093, 34095 Montpellier Cedex 5, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Cecchi
authors.affiliation: Université Montpellier 2, Ecologie des Systèmes Marins Côtiers, UMR 5119 CNRS, IRD, CC093, 34095 Montpellier Cedex 5, FranceIfremer, Laboratoire Environnement Ressources des Pertuis Charentais, BP 7 - 17137 L'Houmeau, FranceUniversité Montpellier 2, Ecologie des Systèmes Marins Côtiers, UMR 5119 CNRS, IRD, CC093, 34095 Montpellier Cedex 5, France.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Laabir
authors.affiliation: Université Montpellier 2, Ecologie des Systèmes Marins Côtiers, UMR 5119 CNRS, IRD, CC093, 34095 Montpellier Cedex 5, FranceIfremer, Laboratoire Environnement Ressources des Pertuis Charentais, BP 7 - 17137 L'Houmeau, FranceUniversité Montpellier 2, Ecologie des Systèmes Marins Côtiers, UMR 5119 CNRS, IRD, CC093, 34095 Montpellier Cedex 5, France.
authors.forename: Christian
authors.initials: C
authors.lastname: Bechemin
authors.affiliation: Université Montpellier 2, Ecologie des Systèmes Marins Côtiers, UMR 5119 CNRS, IRD, CC093, 34095 Montpellier Cedex 5, FranceIfremer, Laboratoire Environnement Ressources des Pertuis Charentais, BP 7 - 17137 L'Houmeau, FranceUniversité Montpellier 2, Ecologie des Systèmes Marins Côtiers, UMR 5119 CNRS, IRD, CC093, 34095 Montpellier Cedex 5, France.
authors.forename: Estelle
authors.initials: E
authors.lastname: Masseret
keywords: Alexandrium tamarense; archaea; bacteria; decay; growth; nitrate; nitrification; oscillations