An unexpected source of CO2 and CH4 emissions: a case of littoral zones of small wetlands during the growing season

Context Freshwater ecosystems significantly influence global carbon budgets from greenhouse gas (GHG) emissions. However, GHG emissions from littoral zones of small wetlands remain understudied. Aims Examining if carbon dioxide (CO2) and methane (CH4) emissions from littoral zones to the atmospheric of small wetlands can be an unexpected carbon source. Methods Carbon were measured during the growing season (from May to October) by a cavity-enhanced absorption technique. Water vapour (H2O), atmospheric pressure (AP), wind speed (WS), soil pH, air temperature (AT), and −5-cm soil temperature (ST) were also investigated. Key results The mean emission rate was 9.94 ± 0.27 g CO2 eq m−2 day−1, with 18.24 ± 0.40 and 0.26 ± 0.04 g CO2-eq m−2 day−1 of CO2 and CH4 respectively. The mean CO2:CH4 ratio was 1.84. Except for WS and soil pH, WS, AT and ST showed significant non-linear relationships with both CO2 and CH4 emissions. Conclusion This study demonstrated that littoral zones of small wetlands can play an unexpected major role in the C cycle budget and should be included in GHG inventories. Implications In the future, GHG emissions from small wetlands could be not neglected as a carbon source and should be included in GHG inventories.