The catchment and climate regulation of pCO2 in boreal lakes

The regulation of surface water pCO(2) was studied in a set of 33 unproductive boreal lakes of different humic content, situated along a latitudinal gradient (57degreesN to 64degreesN) in Sweden. The lakes were sampled four times during one year, and analyzed on a wide variety of water chemistry parameters. With only one exception, all lakes were supersaturated with CO2 with respect to the atmosphere at all sampling occasions. pCO(2) was closely related to the DOC concentration in lakes, which in turn was mainly regulated by catchment characteristics. This pattern was similar along the latitudinal gradient and at different seasons of the year, indicating that it is valid for a variety of climatic conditions within the boreal forest zone. We suggest that landscape characteristics determine the accumulation and subsequent supply of allochthonous organic matter from boreal catchments to lakes, which in turn results in boreal lakes becoming net sources of atmospheric CO2.