title: Interactions between Zn and bacteria in marine tropical coastal sediments.
abstract: OBJECTIVE
  The main goals of this study were (1) to examine the effects of zinc on the microbial community structure of anthropogenically impacted sediments in a tropical coastal ecosystem and (2) to determine whether these microbial benthic communities may enhance the adsorption of zinc.
  
  
  METHODS
  The interactions between zinc and bacteria in tropical sediments were studied in sediment microcosms amended with 2.5 mg L⁻¹ of Zn in the water phase and incubated for 8 days under different environmental conditions, oxic/anoxic and glucose addition. At the end of incubation, microbial structure was assessed by molecular fingerprints (T-RFLP) analysis and Zn speciation in the sediment was determined by sequential extraction.
  
  
  RESULTS
  In the three studied sediments, Zn spiking resulted in only slight changes in bacterial community structure. In contrast, the addition of low concentrations of glucose (5 mM) strongly modified the bacterial community structure: <20% of similarity with the initial structure concomitant with a strong diminution of the specific richness. Overall, these results suggest that highly labile organic matter has a larger impact on microbial structure than heavy metal. These weak impacts of Zn on bacteria diversity might be partly explained by (1) the strong adsorption of Zn in the presence of bacteria and/or (2) the incorporation of Zn into a nonbioavailable fraction. Nevertheless, Zn spiking resulted in significant changes in nutrient cycles, suggesting that bacterial metabolisms were impacted by the heavy metal. This led to an increase in nutrient supplies to the water column, potentially enhancing eutrophication in a nutrient-limited, oligotrophic ecosystem.
authors.affiliation: Institut de Recherche pour le Développement, UMR 5119, IRD, CNRS, Université Montpellier 2, Station Méditerranéenne de l'Environnement Littoral 2 Rue des Chantiers, 34200 Sete, France. olivier.pringault@ird.fr
authors.forename: Olivier
authors.initials: O
authors.lastname: Pringault
authors.forename: Héléna
authors.initials: H
authors.lastname: Viret
authors.forename: Robert
authors.initials: R
authors.lastname: Duran
mesh_terms: D000327:Adsorption; D054458:Amplified Fragment Length Polymorphism Analysis; D059001:Aquatic Organisms / Q000145:classification / Q000254:growth & development* / Q000302:isolation & purification / Q000378:metabolism; D044822:Biodiversity; D017753:Ecosystem; D019015:Geologic Sediments / Q000382:microbiology*; D005947:Glucose / Q000378:metabolism; D006090:Gram-Negative Bacteria / Q000145:classification / Q000254:growth & development* / Q000302:isolation & purification / Q000378:metabolism; D006094:Gram-Positive Bacteria / Q000145:classification / Q000254:growth & development* / Q000302:isolation & purification / Q000378:metabolism; D058889:Molecular Typing; D009510:New Caledonia; D010100:Oxygen / Q000378:metabolism; D010140:Pacific Ocean; D012623:Seawater / Q000737:chemistry / Q000382:microbiology; D013054:Spectrophotometry, Atomic; D014329:Tropical Climate; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D015032:Zinc / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*
chemical_list: D014874:Water Pollutants, Chemical; D005947:Glucose; D015032:Zinc; D010100:Oxygen