Short‐Term Field Observations of Nitrous Oxide Saturations in Lake Taihu, China: The Need for High Temporal Resolution Studies

Abstract

The incomplete understanding of the processes which control aquatic nitrous oxide (N 2 O) production is partially due to a lack of onsite data with which to describe the temporal resolution of N 2 O production. To help resolve this, we directly measured the N 2 O saturation (relative to atmospheric partial pressure) on an hourly basis over two survey periods (July and September 2003) in Lake Taihu, a large eutrophic lake in eastern China. July N 2 O saturations displayed a distinct diurnal pattern, opposite to those observed by others in subtropical streams, but similar to N 2 O emissions observed from incubated estuarine sediments. Correlative analyses indicate that biogeochemical processes operate as important controls on N 2 O production over very short time scales. Nitrous oxide production processes are not only regulated by O 2 dynamics related to microalgal photosynthesis, but also closely related to organic matter decay at the sediment–water interface. While large‐scale changes (∼25‐fold) in N 2 O fluxes in Lake Taihu are a function of variable N loading, biogeochemical processes concerning O 2 and N transformation at the sediment–water interface have significant (∼twofold) impacts on the regulation of N 2 O production over very short time scales. Further, high temporal resolution research focused on developing a comprehensive understanding of lacustrine N 2 O production, including natural and anthropogenic loading and biogeochemical transformation processes, is clearly needed.