title: Heterotrophic Bacteria Show Weak Competition for Nitrogen in Mediterranean Coastal Waters (Thau Lagoon) in Autumn.
abstract: The importance of heterotrophic bacteria relative to phytoplankton in the uptake of ammonium and nitrate was studied in Mediterranean coastal waters (Thau Lagoon) during autumn, when the Mediterranean Sea received the greatest allochthonous nutrient loads. Specific inhibitors and size-fractionation methods were used in combination with isotopic (15)N tracers. NO3 (-) and NH4 (+) uptake was dominated by phytoplankton (60 % on average) during the study period, which included a flood event. Despite lower biomass specific NH4 (+) and NO3 uptake rates, free-living heterotrophic bacteria contributed significantly (>30 %) to total microbial NH4 (+) and NO3 (-) uptake rates in low chlorophyll waters. Under these conditions, heterotrophic bacteria may be responsible for more than 50 % of primary production, using very little freshly produced phytoplankton exudates. In low chlorophyll coastal waters as reported during the present 3-month study, the heterotrophic bacteria seemed to depend to a greater extent on allochthonous N and C substrates than on autochthonous substrates derived from phytoplankton.
authors.affiliation: Laboratoire Ecologie des Systèmes Marins Côtiers, UMR 5119 ECOSYM (Université Montpellier 2-CNRS-IRD IFREMER, Université Montpellier 1), Montpellier, France.|Station Marine de l'Environnement Littoral, 2 rue des Chantiers, 34200, Sète, France.|DHI Water & Environment (S) Pte Ltd, 1 Cleantech Loop #03-05 CleanTech One, Singapore, 637141, Singapore.
authors.forename: Aurore
authors.initials: A
authors.lastname: Trottet
authors.affiliation: Laboratoire Ecologie des Systèmes Marins Côtiers, UMR 5119 ECOSYM (Université Montpellier 2-CNRS-IRD IFREMER, Université Montpellier 1), Montpellier, France.|UMR 9190 MARBEC (CNRS-UM-IRD IFREMER), Montpellier, France.|Station Marine de l'Environnement Littoral, 2 rue des Chantiers, 34200, Sète, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Leboulanger
authors.affiliation: Laboratoire Ecologie des Systèmes Marins Côtiers, UMR 5119 ECOSYM (Université Montpellier 2-CNRS-IRD IFREMER, Université Montpellier 1), Montpellier, France.|UMR 9190 MARBEC (CNRS-UM-IRD IFREMER), Montpellier, France.|Université de Montpellier, Place E. Bataillon, CC 093, 34095, Montpellier, France.
authors.forename: Francesca
authors.initials: F
authors.lastname: Vidussi
authors.affiliation: Laboratoire Ecologie des Systèmes Marins Côtiers, UMR 5119 ECOSYM (Université Montpellier 2-CNRS-IRD IFREMER, Université Montpellier 1), Montpellier, France.|UMR 9190 MARBEC (CNRS-UM-IRD IFREMER), Montpellier, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Pete
authors.affiliation: Laboratoire Ecologie des Systèmes Marins Côtiers, UMR 5119 ECOSYM (Université Montpellier 2-CNRS-IRD IFREMER, Université Montpellier 1), Montpellier, France.|UMR 9190 MARBEC (CNRS-UM-IRD IFREMER), Montpellier, France.|Université de Montpellier, Place E. Bataillon, CC 093, 34095, Montpellier, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Bouvy
authors.affiliation: Laboratoire Ecologie des Systèmes Marins Côtiers, UMR 5119 ECOSYM (Université Montpellier 2-CNRS-IRD IFREMER, Université Montpellier 1), Montpellier, France. eric.fouilland@cnrs.fr.|UMR 9190 MARBEC (CNRS-UM-IRD IFREMER), Montpellier, France. eric.fouilland@cnrs.fr.|Station Marine de l'Environnement Littoral, 2 rue des Chantiers, 34200, Sète, France. eric.fouilland@cnrs.fr.
authors.forename: Eric
authors.initials: E
authors.lastname: Fouilland
mesh_terms: D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D018533:Biomass; D019083:Mediterranean Region; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism*; D010839:Phytoplankton / Q000145:classification / Q000378:metabolism; D012621:Seasons; D012623:Seawater / Q000032:analysis / Q000382:microbiology*
chemical_list: D009584:Nitrogen
keywords: Bacteria; Dissolved inorganic nitrogen; Inhibitors; Nitrogen uptake; Phytoplankton; Size fractionation