title: Reductive dechlorination of 2,4-dichlorophenol and related microbial processes under limiting and non-limiting sulfate concentration in anaerobic mid-Chesapeake Bay sediments.
abstract: The effects of sulfate, added electron donors, and metabolic inhibitors on reductive dechlorination of 2,4-dichlorophenol (DCP) in anaerobic sediment from a relatively unpolluted site in the mesohaline region of Chesapeake Bay were investigated. The onset of ortho reductive dechlorination of DCP was often rapid in sulfate-depleted sediments and the metabolite, 4-chlorophenol, persisted for >44-60 days at nearly stoichiometric levels, relative to the DCP lost, with no further degradation or dechlorination observed. Dechlorination rates increased by a factor of 6-10 after re-feeding DCP, suggesting enrichment of dechlorinators. Sulfate inhibited reductive dechlorination greatly in fresh sediments, but only partially in aged, methanogenic or DCP-acclimated sediments. Exogenous H2 stimulated rates of reductive dechlorination in the absence, but not presence of sulfate. Molybdate severely inhibited reductive dechlorination and also significantly inhibited methanogenesis in sulfate-depleted sediments. Direct inhibition of methanogenesis with bromoethane sulfonic acid did not negatively affect dechlorination rates, suggesting that molybdate may have inhibited production of electron donors for methanogenesis and reductive dechlorination. These results demonstrate a potential for rapid dechlorination of DCP in relatively uncontaminated estuarine sediments and reveal confounding effects of a putative 'specific' metabolic inhibitor, molybdate.
authors.affiliation: University of Maryland Center for Environmental Science, Chesapeake Biological Laboratory, P.O. Box 38, Solomons, MD 20688, USA. kwarner@biology.as.ua.edu
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Warner
authors.forename: Cynthia C
authors.initials: CC
authors.lastname: Gilmour
authors.forename: Douglas G
authors.initials: DG
authors.lastname: Capone