title: Bacterial carbon dependence on freshly produced phytoplankton exudates under different nutrient availability and grazing pressure conditions in coastal marine waters.
abstract: The effects of grazing pressure and inorganic nutrient availability on the direct carbon transfer from freshly produced phytoplankton exudates to heterotrophic bacteria biomass production were studied in Mediterranean coastal waters. The short-term incorporation of ¹³C (H¹³CO₃) in phytoplankton and bacterial lipid biomarkers was measured as well as the total bacterial carbon production (BP), viral lysis and the microbial community structure under three experimental conditions: (1) High inorganic Nutrient and High Grazing (HN + HG), (2) High inorganic Nutrient and Low Grazing (HN + LG) and (3) under natural in situ conditions with Low inorganic Nutrient and High Grazing (LN + HG) during spring. Under phytoplankton bloom conditions (HN + LG), the bacterial use of freshly produced phytoplankton exudates as a source of carbon, estimated from ¹³C enrichment of bacterial lipids, contributed more than half of the total bacterial production. However, under conditions of high grazing pressure on phytoplankton with or without the addition of inorganic nutrients (HN + HG and LN + HG), the ¹³C enrichment of bacterial lipids was low compared with the high total bacterial production. BP therefore seems to depend mainly on freshly produced phytoplankton exudates during the early phase of phytoplankton bloom period. However, BP seems mainly relying on recycled carbon from viral lysis and predators under high grazing pressure.
authors.forename: Eric
authors.initials: E
authors.lastname: Fouilland
authors.forename: Imma
authors.initials: I
authors.lastname: Tolosa
authors.forename: Delphine
authors.initials: D
authors.lastname: Bonnet
authors.forename: Corinne
authors.initials: C
authors.lastname: Bouvier
authors.forename: Thierry
authors.initials: T
authors.lastname: Bouvier
authors.forename: Marc
authors.initials: M
authors.lastname: Bouvy
authors.forename: Patrice
authors.initials: P
authors.lastname: Got
authors.forename: Emilie
authors.initials: E
authors.lastname: Le Floc'h
authors.forename: Behzad
authors.initials: B
authors.lastname: Mostajir
authors.forename: Cécile
authors.initials: C
authors.lastname: Roques
authors.forename: Richard
authors.initials: R
authors.lastname: Sempéré
authors.forename: Télesphore
authors.initials: T
authors.lastname: Sime-Ngando
authors.forename: Francesca
authors.initials: F
authors.lastname: Vidussi
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D018533:Biomass; D002244:Carbon / Q000378:metabolism*; D002247:Carbon Isotopes / Q000032:analysis; D020387:Food Chain; D005602:France; D052836:Heterotrophic Processes; D008055:Lipids / Q000032:analysis; D008522:Mediterranean Sea; D010839:Phytoplankton / Q000737:chemistry / Q000254:growth & development*; D012621:Seasons; D012623:Seawater / Q000737:chemistry / Q000382:microbiology*
chemical_list: D002247:Carbon Isotopes; D008055:Lipids; D002244:Carbon