THE EFFECTS OF EUTROPHICATION ON CARBON BURIAL AND ATMOSPHERIC CARBON EXCHANGE IN SHALLOW LAKES

The intensity of shallow lakes in processing carbon is commonly 10-1000-times that of terrestrial and marine ecosystems and subtle changes in the function of freshwater ecosystems may have profound influences on carbon cycling and global climate change. Normally, lakes are thought to convert dissolved organic carbon to atmospheric carbon dioxide and sequester modest amounts of carbon when landscapes are unperturbed. However, emerging evidence suggests that most carbon-roles invert in eutrophic ecosystems. Eutrophic lakes sequester and bury carbon at biospherically unprecedented rates, appear to absorb atmospheric carbon as production peaks, but may substantially augment the evasion of aggressive greenhouse gases such as methane. We examined both historic changes in carbon burial and contemporary atmospheric carbon exchange in shallow systems that have undergone intense anthropogenic eutrophication. Our data suggest that shallow lakes in this region are burying significantly more carbon than prior to eutrophication and have significantly lower rates of carbon evasion than in previously measured systems. These results indicate that the role of lakes in carbon sequestration may invert as eutrophication accelerates and these systems will play an increasingly important role in the long-term burial and storage of carbon.