Integrating carbon emissions from lakes and streams in a subarctic catchment

Northern inland waters emit CO 2 and CH 4 to the atmosphere but the importance of these emissions is poorly understood due to a lack of integrated catchment‐scale estimates of carbon (C) emissions from lakes and streams. In this study we quantified the annual emission of CO 2 and CH 4 from 27 lakes and 23 stream segments in a 15 km 2 subarctic catchment in northern Sweden. All lakes and streams were net sources of C to the atmosphere on an annual basis. Streams dominated (96%) the aquatic CO 2 emission while lakes (61%) dominated the aquatic CH 4 emission. Total aquatic C emission from the catchment was estimated to be 9.1 g C m −2  yr −1 (98% as CO 2 ). Although streams only accounted for 4% of the aquatic area in the catchment, they accounted for 95% of the total emission. The C emissions from lakes and streams were considerably larger than previously reported downstream waterborne export of C from the catchment, indicating that the atmospheric losses of C in the aquatic systems are an important component in the catchment C balance.