title: Organic Matter Loading Modifies the Microbial Community Responsible for Nitrogen Loss in Estuarine Sediments.
abstract: Coastal marine sediments, as locations of substantial fixed nitrogen loss, are very important to the nitrogen budget and to the primary productivity of the oceans. Coastal sediment systems are also highly dynamic and subject to periodic natural and anthropogenic organic substrate additions. The response to organic matter by the microbial community involved in nitrogen loss processes was evaluated using mesocosms of Chesapeake Bay sediments. Over the course of a 50-day incubation, rates of anammox and denitrification were measured weekly using (15)N tracer incubations, and samples were collected for genetic analysis. Rates of both nitrogen loss processes and gene abundances associated with them corresponded loosely, probably because heterogeneities in sediments obscured a clear relationship. The rates of denitrification were stimulated more, and the fraction of nitrogen loss attributed to anammox slightly reduced, by the higher organic matter addition. Furthermore, the large organic matter pulse drove a significant and rapid shift in the denitrifier community composition as determined using a nirS microarray, indicating that the diversity of these organisms plays an essential role in responding to anthropogenic inputs. We also suggest that the proportion of nitrogen loss due to anammox in these coastal estuarine sediments may be underestimated due to temporal dynamics as well as from methodological artifacts related to conventional sediment slurry incubation approaches.
authors.affiliation: Department of Geosciences, Princeton University, Princeton, NJ, USA. babbin@mit.edu.|Department of Civil and Environmental Engineering, MIT, Cambridge, MA, USA. babbin@mit.edu.
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Babbin
authors.affiliation: Department of Geosciences, Princeton University, Princeton, NJ, USA.
authors.forename: Amal
authors.initials: A
authors.lastname: Jayakumar
authors.affiliation: Department of Geosciences, Princeton University, Princeton, NJ, USA.
authors.forename: Bess B
authors.initials: BB
authors.lastname: Ward
mesh_terms: D064751:Ammonium Compounds / Q000032:analysis / Q000378:metabolism; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D061006:Bays / Q000737:chemistry / Q000382:microbiology*; D044822:Biodiversity; D058440:Denitrification; D019015:Geologic Sediments / Q000032:analysis*; D008396:Maryland; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism*; D010084:Oxidation-Reduction; D010802:Phylogeny
chemical_list: D064751:Ammonium Compounds; D009584:Nitrogen
keywords: Anammox; Denitrification; Marine sediments; Nitrogen cycle