Extreme supersaturation of nitrous oxide in a poorly ventilated Antarctic lake

• Published in: Limnology and Oceanography
• Main Authors: Prisu, John C., Downes, Malcolm T., McKay, Christopher P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1996
• Subjects: Aquatic Science; Oceanography; Arctic; Antarctic; Arctic Lake; Bonney; Lake Bonney; Antarc*
• Online Access: http://dx.doi.org/10.4319/lo.1996.41.7.1544; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.4319%2Flo.1996.41.7.1544; https://onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1996.41.7.1544; https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1996.41.7.1544

Lake Bonney, a permanently ice‐covered Ant‐ arctic lake, has a middepth maximum N 2 O concentration of 41.6 µ M N (> 580,000% saturation with respect to the global average mixing ratio of N 2 O) in its east lobe, representing the highest level yet reported for a natural aquatic system. Atmospheric N 2 O over the lake was 45% above the global average, indicating that this lake is an atmospheric source of N 2 O. Apparent N 2 O production (ANP) was correlated with apparent oxygen utilization (AOU), and denitrification was not detectable, implying that nitrification is the primary source for this gas. The slope of a regression of ANP on AOU revealed that potential N 2 O production per unit of potential O 2 consumed in the east lobe of Lake Bonney is at least two orders of magnitude greater than reported for the ocean. The maximum yield ratio for N 2 O [ANP/(NO 2 − + NO 3 − )] in Lake Bonney is 26% (i.e. 1 atom of N appears in N 2 O for every 3.9 atoms appearing in oxidized N), which exceeds previous reports for pelagic systems, being similar to values from reduced sediments. Areal N 2 O flux from the lake to the atmosphere is >200 times the areal flux reported for oceanic systems; most of this gas apparently enters the atmosphere through a small moat that occupies ~3% of the surface of the lake and exists for ~10 weeks in summer.