title: Similar temperature responses suggest future climate warming will not alter partitioning between denitrification and anammox in temperate marine sediments.
abstract: Removal of biologically available nitrogen (N) by the microbially mediated processes denitrification and anaerobic ammonium oxidation (anammox) affects ecosystem N availability. Although few studies have examined temperature responses of denitrification and anammox, previous work suggests that denitrification could become more important than anammox in response to climate warming. To test this hypothesis, we determined whether temperature responses of denitrification and anammox differed in shelf and estuarine sediments from coastal Rhode Island over a seasonal cycle. The influence of temperature and organic C availability was further assessed in a 12-week laboratory microcosm experiment. Temperature responses, as characterized by thermal optima (Topt) and apparent activation energy (Ea), were determined by measuring potential rates of denitrification and anammox at 31 discrete temperatures ranging from 3 to 59 °C. With a few exceptions, Toptand Eaof denitrification and anammox did not differ in Rhode Island sediments over the seasonal cycle. In microcosm sediments, Eawas somewhat lower for anammox compared to denitrification across all treatments. However, Toptdid not differ between processes, and neither Eanor Toptchanged with warming or carbon addition. Thus, the two processes behaved similarly in terms of temperature responses, and these responses were not influenced by warming. This led us to reject the hypothesis that anammox is more cold-adapted than denitrification in our study system. Overall, our study suggests that temperature responses of both processes can be accurately modeled for temperate regions in the future using a single set of parameters, which are likely not to change over the next century as a result of predicted climate warming. We further conclude that climate warming will not directly alter the partitioning of N flow through anammox and denitrification.
authors.affiliation: Canadian Rivers Institute, University of New Brunswick, 100 Tucker Park Road, Saint John, NB, E2L 4L5, Canada.
authors.forename: Lindsay D
authors.identifier: 0000-0003-0605-0394
authors.initials: LD
authors.lastname: Brin
authors.affiliation: Ecosystems Center, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA, 02543, USA.
authors.forename: Anne E
authors.initials: AE
authors.lastname: Giblin
authors.affiliation: School of Marine Sciences, Darling Marine Center, University of Maine, Walpole, ME, 04573, USA.
authors.forename: Jeremy J
authors.initials: JJ
authors.lastname: Rich
mesh_terms: D002980:Climate; D058440:Denitrification; D019015:Geologic Sediments; D009584:Nitrogen; D013696:Temperature
chemical_list: D009584:Nitrogen
keywords: activation energy; anammox; climate change; denitrification; marine sediment; temperature dependence