Assessing factors underlying variation of CO2 emissions in boreal lakes vs. reservoirs

Reservoirs and lakes were compared to test the hypothesis that they are similar with respect to factors driving the variation in CO2 emissions to the atmosphere. Understanding this variation is necessary for the assessment of the contribution of these freshwater ecosystems to the global carbon cycle. This study, in contrast to previous ones, included analyses of the relationships between CO2 emissions and microbial communities. Pooled data (lakes and reservoirs) showed that variations in CO2 emissions were strongly related to variations in temperature, dissolved organic matter (DOM) quality, and bacte-rial production (BP). Results also showed that lakes were characterized by higher water temperature, lower DOM quality, larger size of Daphnia, and enriched d13C zooplankton compared to reservoirs. Moreover, interactions within plankton communities and relationships between CO2 emissions and zooplankton d13C signatures differed in lakes vs. reservoirs, indicating among-system type differences in food web structure and carbon cycling. As a result o