Abstract
Context Metabolic balance determines whether an ecosystem acts as a source or sink of carbon dioxide (CO2) and considering that a substantial portion of inland aquatic ecosystems act as a source of CO2 to the atmosphere, it is important to highlight that there is still no agreement on how global change will affect the ecosystem metabolic-balance response. It then becomes more important to study the interactions between global-change drivers and aquatic metabolism. Aims Assess possible shifts in ecosystem metabolic balance owing to global-change factors. Methods Collapsed factorial designs and novel experimental units have been used to study responses to future conditions. Key results In the study site, bacterial production was not affected by an increased temperature alone; however, increased nutrient availability may unmask UV or CO2 as a source of stress to bacteria. A synergistic effect between temperature and the combined effect of nutrients and CO2 on primary producers was also found. Conclusions In future scenarios, some heterotrophic inland water ecosystems may shift from heterotrophic to autotrophic states and therefore act as CO2 sinks. Implications This study provides a framework to support a deepening of knowledge on this topic.