title: Benzo(a)pyrene inhibits the role of the bioturbator Tubifex tubifex in river sediment biogeochemistry.
abstract: The interactions between invertebrates and micro-organisms living in streambed sediments often play key roles in the regulation of nutrient and organic matter fluxes in aquatic ecosystems. However, benthic sediments also constitute a privileged compartment for the accumulation of persistent organic pollutants such as PAHs or PCBs that may affect the diversity, abundance and activity of benthic organisms. The objective of this study was to quantify the impact of sediment contamination with the PAH benzo(a)pyrene on the interaction between micro-organisms and the tubificid worm, Tubifex tubifex, which has been recognized as a major bioturbator in freshwater sediments. Sedimentary microcosms (slow filtration columns) contaminated or not with benzo(a)pyrene (3 tested concentrations: 0, 1 and 5 mg kg(-1)) at the sediment surface were incubated under laboratory conditions in the presence (100 individuals) or absence of T. tubifex. Although the surface sediment contaminations with 1 mg kg(-1) and 5 mg kg(-1) of benzo(a)pyrene did not affect tubificid worm survival, these contaminations significantly influenced the role played by T. tubifex in biogeochemical processes. Indeed, tubificid worms stimulated aerobic respiration, denitrification, dehydrogenase and hydrolytic activities of micro-organisms in uncontaminated sediments whereas such effects were inhibited in sediments polluted with benzo(a)pyrene. This inhibition was due to contaminant-induced changes in bioturbation (and especially bio-irrigation) activities of worms and their resulting effects on microbial processes. This study reveals the importance of sublethal concentrations of a contaminant on ecological processes in river sediments through affecting bioturbator-microbe interactions. Since they affect microbial processes involved in water purification processes, such impacts of sublethal concentrations of pollutants should be more often considered in ecosystem health assessment.
authors.affiliation: Université de Lyon, UMR5023 Ecologie des Hydrosystèmes Naturels et Anthropisés, Université Lyon 1, ENTPE, CNRS, 6 rue Raphaël Dubois, 69622 Villeurbanne, France. mermillo@univ-lyon1.fr
authors.forename: F
authors.initials: F
authors.lastname: Mermillod-Blondin
authors.forename: A
authors.initials: A
authors.lastname: Foulquier
authors.forename: F
authors.initials: F
authors.lastname: Gilbert
authors.forename: S
authors.initials: S
authors.lastname: Navel
authors.forename: B
authors.initials: B
authors.lastname: Montuelle
authors.forename: F
authors.initials: F
authors.lastname: Bellvert
authors.forename: G
authors.initials: G
authors.lastname: Comte
authors.forename: V
authors.initials: V
authors.lastname: Grossi
authors.forename: F
authors.initials: F
authors.lastname: Fourel
authors.forename: C
authors.initials: C
authors.lastname: Lecuyer
authors.forename: L
authors.initials: L
authors.lastname: Simon
mesh_terms: D000818:Animals; D001564:Benzo(a)pyrene / Q000032:analysis* / Q000633:toxicity; D017753:Ecosystem; D004784:Environmental Monitoring; D005602:France; D019015:Geologic Sediments / Q000032:analysis / Q000382:microbiology; D009835:Oligochaeta / Q000187:drug effects* / Q000254:growth & development; D045483:Rivers / Q000737:chemistry / Q000382:microbiology; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000633:toxicity
chemical_list: D014874:Water Pollutants, Chemical; D001564:Benzo(a)pyrene