Effects of experimental warming and carbon addition on nitrate reduction and respiration in coastal sediments
- 538 Downloads
Climate change may have differing effects on microbial processes that control coastal N availability. We conducted a microcosm experiment to explore effects of warming and carbon availability on nitrate reduction pathways in marine sediments. Sieved continental shelf sediments were incubated for 12 weeks under aerated seawater amended with nitrate (~50 μM), at winter (4 °C) or summer (17 °C) temperatures, with or without biweekly particulate organic C additions. Treatments increased diffusive oxygen consumption as expected, with somewhat higher effects of C addition compared to warming. Combined warming and C addition had the strongest effect on nitrate flux across the sediment water interface, with a complete switch early in the experiment from influx to sustained efflux. Supporting this result, vial incubations with added 15N-nitrate indicated that C addition stimulated potential rates of dissimilatory nitrate reduction to ammonium (DNRA), but not denitrification. Overall capacity for both denitrification and DNRA was reduced in warmed treatments, possibly reflecting C losses due to increased respiration with warming. Anammox potential rates were much lower than DNRA or denitrification, and were slightly negatively affected by warming or C addition. Overall, results indicate that warming and C addition increased ammonium production through remineralization and possibly DNRA. This stimulated nitrate production through nitrification, but without a comparable increase in nitrate consumption through denitrification. The response to C of potential DNRA rates over denitrification, along with a switch to nitrate efflux, raises the possibility that DNRA is an important and previously overlooked source of internal N cycling in shelf sediments.
KeywordsAnammox Climate change Continental shelf Denitrification Dissimilatory nitrate reduction to ammonium Warming
Thank you to Michaeline Nelson, Amber Hardison, Heather Leslie, Stephen Porder and Ruby Ho for help in the lab and the field, and to Elise Heiss, Lindsey Fields, Shelley Brown, Wally Fulweiler, Scott Nixon, Bethany Jenkins, Jane Tucker, Steve Granger, Rodman Sykes, Rebecca Robinson, Catherine Luria, Marshall Otter, David Murray, Joe Orchardo and Karen Kidd. This material is based upon work supported by the National Science Foundation by OCE-0852289 to JJR and OCE-0852263 and OCE-0927400 to AEG, and Rhode Island Sea Grant to JJR.
Conflict of Interest
The authors declare that they have no conflict of interest.
- Burgin AJ, Hamilton SK (2007) Have we overemphasized the role of denitrification in aquatic ecosystems? A review of nitrate removal pathways. Front Ecol Environ 5:89–96. doi: 10.1890/1540-9295(2007)5[89:HWOTRO]2.0.CO;2
- Codispoti LA, Brandes JA, Christensen JP et al (2000) The oceanic fixed nitrogen and nitrous oxide budgets: Moving targets as we enter the anthropocene. Sci Mar 65:85–105Google Scholar
- Gruca-Rokosz R, Tomaszek JA, Koszelnik P (2009) Competitiveness of dissimilatory nitrate reduction processes in bottom sediment of Rzeszów reservoir. Environ Prot Eng 35:5–13Google Scholar
- Jensen K, Revsbech NP, Nielsen LP (1993) Microscale distribution of nitrification activity in sediment determined with a shielded microsensor for nitrate. Appl Environ Microbiol 59:3287–3296Google Scholar
- Jensen K, Sloth NP, Risgaard-Petersen N, Rysgaard S (1994) Estimation of nitrification and denitrification from microprofiles of oxygen and nitrate in model sediment systems. Appl Environ Microbiol 60:2094–2100Google Scholar
- Jørgensen KS (1989) Annual pattern of denitrification and nitrate ammonification in estuarine sediment. Appl Environ Microbiol 55:1841–1847Google Scholar
- King D, Nedwell DB (1984) Changes in the nitrate-reducing community of an anaerobic saltmarsh sediment in response to seasonal selection by temperature. J Gen Microbiol 130:2935–2941Google Scholar
- Koroleff F (1983) Determination of nutrients. In: Grasshoff K (ed) Methods of seawater analysis. Verlag Chemie, Weinheim, pp 125–187Google Scholar
- MacFarlane GT, Herbert RA (1984) Dissimilatory nitrate reduction and nitrification in estuarine sediments. J Gen Microbiol 130:2301–2308Google Scholar
- R Development Core Team R: A language and environment for statistical computing. http://www.r-project.org
- Tiedje JM (1988) Ecology of denitrification and dissimilatory nitrate reduction to ammonium. In: Zehnder AJB (ed) Biology of anaerobic microorganisms. Wiley, New York, pp 179–244Google Scholar
- Trimmer M, Engström P (2011) Distribution, activity, and ecology of anammox bacteria in aquatic environments. In: Ward BB, Arp DJ, Klotz MG (eds) Nitrification, 1st edn. ASM Press, Washington, pp 201–236Google Scholar