Benthic nitrous oxide cycling in a changing coastal sea (BENNO)

  • Duration: 2022 - 2025
  • Status: Ongoing

Will the coastal Baltic Sea become a source or sink of nitrous oxide in the future? By using a multidisciplinary approach that combines micro-sensor techniques with microbial functional gene expressions, I aim to disentangle the contribution of the different microbial processes to net nitrous oxide production in coastal sediment representative for the northern Baltic Sea under different environmental scenarios.

Project management
Dana Hellemann (Finnish Environment Institute, Syke)
Project team
Kirsten Jørgensen, Kristian Spilling (Syke), Aleksandra Lewandowska (University of Helsinki), Mikko Kiljunen (University of Jyväskylä ), Hermann Bange (GEOMAR Helmholtz Centre for Ocean Research Kiel Germany), Bärbel Mueller-Karulis, Xiaole Sun (Baltic Sea Centre at Stockholm University Sweden), Robinson Fulweiler (Boston University United States)
Partners
University of Helsinki, University of Jyväskylä, GEOMAR Helmholtz Centre for Ocean Research Kiel, Baltic Sea Centre at Stockholm University, Boston University
Subject area
Sea, Research, Climate

Background

Nitrous oxide (N2O) is a powerful greenhouse gas that is naturally produced by the microbial processes nitrification, nitrifier denitrification, and denitrification, with the latter one also consuming N2O.   

Coastal sediments contribute considerably to marine N2O cycling due to their high loading of organic matter and nutrients, yet the significance of each microbial process is still uncertain owing to methodological constrains in qualitative and quantitative assessments. This is a fundamental gap for assessing present, but even more importantly, future coastal N2O cycling, considering that the microbial processes involved are proposed to respond differently to changes in environmental conditions based on their specific metabolic requirements.

In the coastal Baltic Sea, where increasing climate change pressures meet an ecosystem struggling with long-term eutrophication, rapid changes in environmental conditions are expected for the very near future, which is why mechanistic knowledge on benthic N2O cycling is urgently needed.

Aim

By using a state-of-the-art multidisciplinary approach that combines micro-sensor techniques with microbial functional gene expressions, I aim to disentangle the contribution of the different microbial processes to net N2O production in coastal sediment representative for the northern Baltic Sea 

  • (i) under present and future eutrophication status and water temperature, and 
  • (ii) over seasonal changes in environmental conditions. 

The ultimate aim is to assess whether the coastal Baltic Sea will become a sink or source of N2O in the future.

These objectives are approached via benthic mesocosm experiments and seasonal field sampling at Tvärminne Zoological Station, Finland. The data and mechanistic understanding obtained will be applied in a coupled microbial reactive transport model to simulate scenarios of future benthic N2O cycling. The knowledge gained in this project will add to science-based decision-making regarding mitigation measures for future greenhouse gas emissions and ecosystem degradation in the coastal Baltic Sea.

 

Additional info

  • Postdoctoral researcher Dana Hellemann,
    Finnish Environment Institute
    firsname.lastname@syke.fi, +358 (0) 503067238
Published 11.4.2023 / Updated 22.5.2025