ThepCO₂dynamics in lakes in the boreal region of northern Québec, Canada

In this study, we examine the magnitude and temporal variability of surface water p CO 2 in a set of lakes in boreal Québec, and explore the links between lake and catchment properties. The study lakes were consistently supersaturated in CO 2 , with the mean lake p CO 2 ranging from 400 to over 1800 μ atm. There was significant interannual variability in p CO 2 , apparently driven by regional patterns in precipitation. The best multivariate model of average p CO 2 included dissolved organic carbon (DOC), lake area and chlorophyll as independent variables, suggesting that external carbon (C) loading to lakes plays a central role in lake CO 2 dynamics and that lake trophic status may modulate the influence of external C loading. We show that even if the key drivers of lake p CO 2 are similar, they interact differently among regions and the resulting models may be dramatically different. In particular, we show that although p CO 2 is invariably correlated to DOC, the shape of this relationship varies greatly among regions, suggesting large‐scale regional differences in C delivery, quality, and in‐lake processing. As a consequence, current models cannot be extrapolated across regions unless we apply region‐specific variables.