US EPA

3018442 

Journal Article 

Effects of experimental warming and carbon addition on nitrate reduction and respiration in coastal sediments 

Brin, LD; Giblin, AE; Rich, JJ 

2015 

Yes 

Biogeochemistry
ISSN: 0168-2563
EISSN: 1573-515X 

SPRINGER 

DORDRECHT 

125 

1 

81-95 

10.1007/s10533-015-0113-4 

WOS:000358598200007 

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 (similar to 50 mu M), at winter (4 A degrees C) or summer (17 A degrees 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 N-15-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. 

Anammox; Climate change; Continental shelf; Denitrification; Dissimilatory nitrate reduction to ammonium; Warming