Anaerobic N2 production in Arctic sea ice

• Main Authors: Søren Rysgaard, Ronnie Nøhr Glud
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2004
• Subjects: Arctic; Greenland; Greenland Sea; Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.484.5390; http://www.aslo.org/lo/toc/vol_49/issue_1/0086.pdf

We quantified anaerobic N2 production through bacterial denitrification and anaerobic NH oxidation (anammox)14 in first-year ice from Young Sound (748N) and in an ice floe off Northeast Greenland (798N). Bacterial denitrification activity (100–300 nmol N L21 sea ice d21) occurred in the lower 0.5 m of the sea ice, which had high concentrations of NO, NH, and dissolved organic carbon (DOC). Despite sea-ice algal production in the lower sea-ice layers,2 13 4 heterotrophic activity resulted in a net O2 consumption of 13 mmol O2 L21 sea ice d21 in the lower 0.5-m ice layers. Together with melting of deoxygenated ice crystals, this led to anoxic conditions in the brine system favoring conditions for anaerobic NO reduction. Numbers of anaerobic NO-reducing bacteria in the same ice layers were2 23 3 high (1.1 3 105 cells ml21 sea ice, corresponding to 1.2 3 106 cells ml21 brine). Area-integrated denitrification rates were 10–45 mmol N m22 sea ice d21, which corresponds to 7–50 % of the sediment activity in the area. Although the proportion of anammox to total N2 production was up to 19 % in layers of the ice floe from the Greenland Sea, the integrated rate only accounted for 0–5 % of total NO reduction at the investigated localities.23 With a global average extent of 19–29 3 106 km2 (Gloer-sen et al. 1992), sea ice provides a vast low-temperature habitat for many species of bacteria, fungi, algae, protozoa