Nitrous Oxide (N₂O) in the Sea Surface Microlayer and Underlying Water During a Phytoplankton Bloom: A Mesocosm Study

Stoltenberg et al. (2026) present measurements of nitrous oxide (N₂O) in both the underlying water (ULW) and, for the first time in the sea surface microlayer (SML) during a five week long mesocosm study. Consistent with field observations, N₂O concentrations did not exhibit a discernible response to a (triggered) phytoplankton bloom, while the in-situ sources of N₂O were balanced by the loss to the atmosphere. SML concentrations were found to be elevated in comparison to the ULW, yet the difference was not statistically significant. This result is considered inconclusive though, as the losses during SML glass plate sampling most probably decreased the actual SML concentrations, and therefore potentially masked a significant enrichment of N₂O in the SML. Thus indicating that the importance of the SML for N₂O cycling and its emission to the atmosphere might have been overlooked so far.

Reference: Stoltenberg, I., Lange, L., and Bange, H.W., et al. (2026). Nitrous oxide (N₂O) in the sea surface microlayer and underlying water during a phytoplankton bloom: a mesocosm study. Biogeosci., 23, 1515-1525. https://doi.org/10.5194/bg-23-1515-2026