Response of dissolved carbon dioxide and methane concentration to warming in shallow lakes

Shallow lake ecosystems are highly sensitive to temperature fluctuation because of their high water surface-to-volume ratios. Shallow lakes have been increasingly identified as a hotspot of CO₂ and CH₄ emissions, but their response to temperature variation remains unclear. Here, we report from a 5-month outdoor mesocosm experiment where we investigated the impacts of a projected 3.5 °C future warming and monthly temperature changes on lake CO₂ and CH₄, as well as the key drivers affecting the lake carbon cycling. Our results show that CO₂ and CH₄ concentrations had a significantly positive correlation with monthly temperatures. CH₄ concentration was primarily regulated by monthly temperature, while nutrients effects on CO₂ concentration overrode climate warming and temporal temperature changes. These findings imply the varied roles that temperature and nutrient levels can play on CO₂ and CH₄ dynamics in shallow lake systems. The relationship between temperature and CO₂ concentration was nonlinear, showing a threshold of approximately 9 °C, at which CO₂ concentration could be strongly modified by nutrient level in the lake systems. Understanding this complex relationship between temperature with CO₂ and CH₄ concentrations in shallow lakes is crucial for effective lake management and efficient control of greenhouse gases (GHGs) emissions.