The project investigated the formation, composition and relevance of gas bubbles in aquatic ecosystems. Measurements in aquaculture ponds revealed the highest CH₄ ebullition rates reported so far in the literature. Based on these data, we found a relationship between bubble size, gas composition, and bubbling rate. Bubble production rates in the sediment were controlled by organic matter quality rather than quantity. A method to quantify bubble size from bubble O₂ content was developed and validated with direct measurements. The temporal dynamics of ebullition was studied on timescales of hours to seasons across different aquatic ecosystems and could be described by empirical models. For the first time, we showed that storage of gas bubbles in the sediment can be an important component in basin-scale CH₄ budgets and a modulator of ebullition dynamics. We further found that bubbles transport substantial amounts of particulate matter of variable composition from the sediment to the water surface. By analyzing a large dataset, we could show that O₂ ebullition depends both on bubbling rate and bubble composition. The composition of photosynthetic bubbles forming on macrophytes were quantitatively investigated in laboratory experiments. Based on these measurements, we developed theoretical approaches for predicting the gas composition of these bubbles.

Projekct PIs: Andreas Lorke, RPTU Kaiserslautern-Landau, Matthias Koschorreck, Helmholtz Centre for Environmental Research – UFZ; Bertram Boehrer; Helmholtz Centre for Environmental Research – UFZ; 

Key publications:

• Marcon, L., Bleninger, T., Männich, M., Ishikawa, M., Hilgert, S., & Lorke, A. (2024). Exploring the temporal dynamics of methane ebullition in a subtropical freshwater reservoir. Plos One, 19(3), e0298186. https://doi.org/10.1371/journal.pone.0298186
• Marcon, L., Schwarz, M., Backes, L., Offermann, M., Schreiber, F., Hilgert, S., Sotiri, K., Jokiel, C., & Lorke, A. (2023). Linking Sediment Gas Storage to the Methane Dynamics in a Shallow Freshwater Reservoir. Journal of Geophysical Research: Biogeosciences, 128(10), e2022JG007365. https://doi.org/10.1029/2022JG007365
• Marcon, L., Sotiri, K., Bleninger, T., Lorke, A., Männich, M., & Hilgert, S. (2022). Acoustic Mapping of Gas Stored in Sediments of Shallow Aquatic Systems Linked to Methane Production and Ebullition Patterns [Original Research]. Frontiers in Environmental Science, 10, 876540. https://doi.org/10.3389/fenvs.2022.876540
• Schwarz, M., Marcon, L., & Lorke, A. (2023). Quantifying bubble-mediated transport by ebullition from aquatic sediments [Perspective]. Frontiers in Earth Science, 11. https://doi.org/10.3389/feart.2023.1113349
• Waldemer, C., Schwarz, M., Lorke, A., Boehrer, B., & Koschorreck, M. (2024). Bubble sizes inferred from bubble gas composition in a temperate freshwater fish pond. Inland Waters, 14, 1–14. https://doi.org/10.1080/20442041.2024.2327974