title: Impact of oil on bacterial community structure in bioturbated sediments.
abstract: Oil spills threaten coastlines where biological processes supply essential ecosystem services. Therefore, it is crucial to understand how oil influences the microbial communities in sediments that play key roles in ecosystem functioning. Ecosystems such as sediments are characterized by intensive bioturbation due to burrowing macrofauna that may modify the microbial metabolisms. It is thus essential to consider the bioturbation when determining the impact of oil on microbial communities. In this study, an experimental laboratory device maintaining pristine collected mudflat sediments in microcosms closer to true environmental conditions--with tidal cycles and natural seawater--was used to simulate an oil spill under bioturbation conditions. Different conditions were applied to the microcosms including an addition of: standardized oil (Blend Arabian Light crude oil, 25.6 mg.g⁻¹ wet sediment), the common burrowing organism Hediste (Nereis) diversicolor and both the oil and H. diversicolor. The addition of H. diversicolor and its associated bioturbation did not affect the removal of petroleum hydrocarbons. After 270 days, 60% of hydrocarbons had been removed in all microcosms irrespective of the H. diversicolor addition. However, 16S-rRNA gene and 16S-cDNA T-RFLP and RT-PCR-amplicon libraries analysis showed an effect of the condition on the bacterial community structure, composition, and dynamics, supported by PerMANOVA analysis. The 16S-cDNA libraries from microcosms where H. diversicolor was added (oiled and un-oiled) showed a marked dominance of sequences related to Gammaproteobacteria. However, in the oiled-library sequences associated to Deltaproteobacteria and Bacteroidetes were also highly represented. The 16S-cDNA libraries from oiled-microcosms (with and without H. diversicolor addition) revealed two distinct microbial communities characterized by different phylotypes associated to known hydrocarbonoclastic bacteria and dominated by Gammaproteobacteria and Deltaproteobacteria. In the oiled-microcosms, the addition of H. diversicolor reduced the phylotype-richness, sequences associated to Actinobacteria, Firmicutes and Plantomycetes were not detected. These observations highlight the influence of the bioturbation on the bacterial community structure without affecting the biodegradation capacities.
authors.affiliation: Equipe Environnement et Microbiologie, Institut Pluridisciplinaire de Recherche en Environnement et Matériaux, Université de Pau et des Pays de l'Adour, Pau, France.
authors.forename: Magalie
authors.initials: M
authors.lastname: Stauffert
authors.forename: Cristiana
authors.initials: C
authors.lastname: Cravo-Laureau
authors.forename: Ronan
authors.initials: R
authors.lastname: Jézéquel
authors.forename: Sandra
authors.initials: S
authors.lastname: Barantal
authors.forename: Philippe
authors.initials: P
authors.lastname: Cuny
authors.forename: Franck
authors.initials: F
authors.lastname: Gilbert
authors.forename: Christine
authors.initials: C
authors.lastname: Cagnon
authors.forename: Cécile
authors.initials: C
authors.lastname: Militon
authors.forename: David
authors.initials: D
authors.lastname: Amouroux
authors.forename: Fatima
authors.initials: F
authors.lastname: Mahdaoui
authors.forename: Brice
authors.initials: B
authors.lastname: Bouyssiere
authors.forename: Georges
authors.initials: G
authors.lastname: Stora
authors.forename: François-Xavier
authors.initials: FX
authors.lastname: Merlin
authors.forename: Robert
authors.initials: R
authors.lastname: Duran
mesh_terms: D001419:Bacteria / Q000145:classification* / Q000235:genetics* / Q000254:growth & development; D004269:DNA, Bacterial / Q000032:analysis*; D021903:DNA, Ribosomal Spacer / Q000032:analysis; D015723:Gene Library; D019015:Geologic Sediments / Q000032:analysis* / Q000382:microbiology; D006838:Hydrocarbons / Q000032:analysis*; D059392:Petroleum Pollution / Q000009:adverse effects*; D010802:Phylogeny; D012150:Polymorphism, Restriction Fragment Length; D012333:RNA, Messenger / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000032:analysis*; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D021903:DNA, Ribosomal Spacer; D006838:Hydrocarbons; D012333:RNA, Messenger; D012336:RNA, Ribosomal, 16S