New insights from the Silkeborg Aquatic Facility
Freshwater ecosystems are among the most significant yet underestimated sources of greenhouse gases (GHGs) in the global carbon budget. Lakes, ponds, and streams emit both carbon dioxide (CO₂) and methane (CH₄) — but capturing these emissions accurately requires measurements at the right place and, crucially, at the right time.
A new study published in Limnology and Oceanography: Methods (Bucak et al., 2026) puts the question of sampling frequency centre stage, drawing on seven months of continuous, high-frequency GHG measurements conducted at Aarhus University’s Lake Mesocosm Warming Experiment (LMWE) — one of the long-running experimental aquatic facilities operated within the ANAEE-ERIC infrastructure network.
What the research found
Using a low-cost sensor system built around Arduino-based CO₂ and CH₄ sensors, the team collected up to six flux measurements per day across six mesocosms from May to December 2022. This high temporal resolution allowed the researchers to test what happens when you sample less frequently — simulating daily, weekly, biweekly, monthly, and seasonal field campaigns.
What the Study Found
The results are a clear warning for researchers relying on infrequent or daytime-only measurements:
- CO₂ fluxes are overestimated when only daytime measurements are used, because photosynthesis suppresses emissions during the day. Nighttime fluxes, routinely missed in standard field campaigns, paint a different picture.
- Methane ebullition (bubble emissions) dominates total CH₄ fluxes — reaching 86% of total flux in peak periods — and is highly episodic. Sampling less than weekly drastically increases the risk of missing these events and severely underestimating total emissions.
- Weekly sampling offers the best balance between measurement effort and accuracy, closely approximating the true mean for both CO₂ and CH₄ fluxes across the study period.
- Low-cost sensors proved robust over the seven-month deployment period, continuing to function well beyond the experiment’s conclusion — demonstrating the feasibility of affordable, long-term GHG monitoring in experimental and natural freshwater systems.
Why this matters for AnaEE
ANAEE-ERIC facilities like the Silkeborg Aquatic Facility are uniquely positioned to generate the long-term, high-frequency environmental datasets needed to constrain global carbon budgets. This study exemplifies how experimental infrastructure can be used not only to ask ecological questions, but to refine the methods we use to answer them — an essential step as freshwater GHG emissions gain growing attention in international climate policy.
The work also demonstrates the value of affordable, open sensor technology that can be replicated across facilities and natural sites worldwide, broadening the spatial and temporal coverage of freshwater carbon assessments.
Full reference: Bucak T., Levi E.E., Melvad C., Deng J., Mastepanov M., Ladwig R., Davidson T.A. (2026). Quantifying temporal dynamics of greenhouse gas emissions in lake mesocosms: Deployment of a low-cost measurement system. Limnology and Oceanography: Methods, e70060. https://doi.org/10.1002/lom3.70060
Paper in the Spotlight: Quantifying temporal dynamics of greenhouse gas emissions in lake mesocosms: Deployment of a low-cost measurement system
Tuba Bucak, Eti Ester Levi, Claus Melvad, Jianming Deng et al., 2026.
Limnology and Oceanography: Methods.
Watch a facility presentation by facility manager Thomas Davidson, Aarhus University.
