Seabird-affected taluses are denitrification hotspots and potential N2O emitters in the High Arctic

• Published in: Scientific Reports
• Main Authors: Hayashi, Kentaro, Tanabe, Yukiko, Ono, Keisuke, Loonen, Maarten J. J. E., Asano, Maki, Fujitani, Hirotsugu, Tokida, Takeshi, Uchida, Masaki, Hayatsu, Masahito
• Format: Text
• Language: English
• Published: Nature Publishing Group UK 2018
• Subjects: Article; Arctic; Ny-Ålesund; Svalbard; Ny Ålesund; Tundra
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6250683/; http://www.ncbi.nlm.nih.gov/pubmed/30467371; https://doi.org/10.1038/s41598-018-35669-w

In High Arctic tundra ecosystems, seabird colonies create nitrogen cycling hotspots because of bird-derived labile organic matter. However, knowledge about the nitrogen cycle in such ornithocoprophilous tundra is limited. Here, we determined denitrification potentials and in-situ nitrous oxide (N2O) emissions of surface soils on plant-covered taluses under piscivorous seabird cliffs at two sites (BL and ST) near Ny-Ålesund, Svalbard, in the European High Arctic. Talus soils at both locations had very high denitrification potentials at 10 °C (2.62–4.88 mg N kg−1 dry soil h−1), near the mean daily maximum air temperature in July in Ny-Ålesund, with positive temperature responses at 20 °C (Q10 values, 1.6–2.3). The talus soils contained abundant denitrification genes, suggesting that they are denitrification hotspots. However, high in-situ N2O emissions, indicating the presence of both active aerobic nitrification and anaerobic denitrification, were observed only at BL (max. 16.6 µg N m−2 h−1). Rapid nitrogen turnover at BL was supported by lower carbon-to-nitrogen ratios, higher nitrate content, and higher δ15N values in the soils at BL compared with those at ST. These are attributed to the 30-fold larger seabird density at BL than at ST, providing the larger organic matter input.