BENTHIC NITROUS OXIDE CYCLING IN A CHANGING COASTAL SEA

Nitrous oxide (N₂O) is a powerful greenhouse gas that is naturally produced and partly consumed by the microbial processes nitrification, denitrification, and nitrifier denitrification. The contribution of each process to net marine N₂O production is still uncertain due to methodological constrains. This is a fundamental gap for assessing present, and even more importantly, future marine N₂O cycling, assuming that each microbial process responds differently to changes in environmental conditions based on its specific metabolic requirements. Coastal sediments are potential hotspots of marine N₂O cycling due to seasonally changing availability of organic matter, nutrients, and oxygen, as well as high exposure to anthropogenic pressures causing eutrophication and oxygen deficiency. Hence, advanced mechanistic knowledge on N₂O cycling in coastal sediments is urgently needed. By using a state-of-the-art multidisciplinary approach that combines microsensor techniques with microbial functional gene expressions and reactive transport modelling, this project aims to disentangle the present and future contribution of the different microbial processes to net benthic N₂O production in the coastal Baltic Sea, northern Europe, where increasing climate change pressures meet an ecosystem struggling with long-term eutrophication. Here, we present data on the seasonal dynamics of benthic N₂O cycling at a representative site in the coastal Baltic Sea over the course of one year, covering, beyond others, benthic fluxes, benthic and pelagic concentrations, and functional gene expressions.

Presentation Preference: Oral

Primary Presenter: Dana Hellemann, Finnish Environment Institute SYKE (Dana.hellemann@syke.fi)

Authors:

Dana Hellemann, Finnish Environment Institute SYKE  (dana.hellemann@syke.fi)

Hermann Bange, GEOMAR Helmholtz Centre for Ocean Research Kiel  (hbange@geomar.de)

Bärbel Mueller-Karulis, Baltic Sea Centre, Stockholm University  (barbel.muller.karulis@su.se)

Xiaole Sun, Institute of Oceanology, Chinese Academy of Sciences  (xiaole.sun@su.se)

Ossi Tonteri, Finnish Environment Institute SYKE  (ossi.tonteri@syke.fi)