Understanding the mechanisms driving carbon dioxide (CO₂) concentrations in inland waters is important to foresee CO₂ responses to environmental change, yet knowledge gaps persist regarding which processes are the key drivers. Here we investigated possible drivers across 13 Swedish lakes and streams where the partial pressure of CO₂ (pCO₂) has increased over a 21-year period. Overall, we could not identify a single dominating mechanism responsible for the observed pCO₂ increase. In the 8 lakes, we found that pCO₂ increased, driven either by a possible dissolved organic carbon (DOC) stimulation of microbial mineralization or by water color primary production suppression. In streams, the dominating mechanism for a pCO₂ increase was either a change in the carbonate system distribution or a possible nutrient-driven decrease in primary production. This is the first study to demonstrate and explain consistent positive pCO₂ temporal trends in freshwater ecosystems, and our results should be taken into account when predicting future emission of CO₂ from inland waters.

了解内陆水域中二氧化碳（CO ₂）浓度的驱动机制对于预测CO ₂对环境变化的响应很重要，但是关于哪些过程是关键驱动因素的知识差距仍然存在。在这里，我们调查了13个瑞典湖泊和溪流中可能的驱动因素，其中CO ₂（p CO ₂）的分压在21年内增加了。总体而言，我们无法确定导致观察到的p CO ₂增加的单一主导机制。在8个湖泊中，我们发现p CO ₂可能是由于溶解的有机碳（DOC）刺激了微生物的矿化作用，或者是由于抑制了水的颜色而导致产量增加。在物流中，p CO ₂增加的主要机制是碳酸盐体系分布的变化或一次生产中可能由养分驱动的下降。这是第一项证明和解释淡水生态系统中一致的p CO ₂时空趋势的研究，在预测未来内陆水域的CO ₂排放时应考虑到我们的结果。