Changes in freshwater carbon exports from Canadian terrestrial basins to lakes and estuaries under a 2xCO(2) atmospheric scenario

Rain water running through soils and wetlands will leach decomposing plant organic matter into streams and lakes in the form of dissolved organic carb on (DOC). In streams, lakes and eventually estuaries, DOC can be mineralize d to CO2, precipitated to sediments or taken up in biological matter, and i s thus an important part of many aquatic ecosystems. Using hydrological, cl imatological and geographical data from 32 sites located in Canada, we deve loped a neural network model which allowed us to estimate DOC export from t he Canadian land mass. We reapplied the model to the 32 sites plus a furthe r 43 basins to estimate area normalized exports for various regions of the country. We estimated that 14.3x10(6) t of DOC are currently exported from Canadian terrestrial ecosystems. We then modified climatological inputs to the model to reflect the predicted temperature and precipitation conditions under a doubled atmospheric CO2 regime. Our model suggests that DOC export s will increase by approximately 14% under a doubled CO2 atmosphere, mostly owing to increases in runoff, Our analysis also shows that DOC export is g reatest in the spring in southern Canada and summer in the north.