Eutrophic Lake Taihu as a significant CO(2) source during 2000-2015.

Affiliation

Xiao Q(1), Xu X(2), Duan H(3), Qi T(1), Qin B(4), Lee X(5), Hu Z(6), Wang W(6), Xiao W(6), Zhang M(6).
Author information:
(1)Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China.
(2)Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, 130102, China; Biology Department, San Diego State University, San Diego, CA, 92182, USA.
(3)Key Laboratory of Watershed Geographic Sciences, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China. Electronic address: [Email]
(4)Taihu Laboratory for Lake Ecosystem Research, State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing, 210008, China.
(5)Yale-NUIST Center on Atmospheric Environment, International Joint Laboratory on Climate and Environment Change
(ILCEC), Nanjing University of Information Science and Technology, Nanjing, 210044, China; School of Forestry and Environmental Studies, Yale University, New Haven, CT, 06511, USA.
(6)Yale-NUIST Center on Atmospheric Environment, International Joint Laboratory on Climate and Environment Change
(ILCEC), Nanjing University of Information Science and Technology, Nanjing, 210044, China.

Abstract

Inland lakes receive growing attentions on eutrophication and their roles in global carbon cycle. However, understanding how inland lakes contribute to global carbon cycle is seriously hampered due to a shortage of long-term records. This study investigated the carbon dioxide (CO2) flux from the Lake Taihu, a large (2400 km2) and shallow (mean depth 1.9 m) eutrophic lake in subtropical region, based on a long-term (2000-2015) measurement of the partial pressure of carbon dioxide (pCO2) at high spatiotemporal resolution. We found that the Lake Taihu was a significant source of atmospheric CO2 with an average CO2 emission flux at 18.2 ± 8.4 mmol m-2 d-1 (mean±1standard deviation) and a mean annual pCO2 value of 778 ± 169 μatm. The highest pCO2 and CO2 flux were observed in eutrophic zone with a high external input of carbon and nutrient, and the lowest in non-eutrophic zones with no direct external input of nutrient and carbon. A substantial seasonal pattern in pCO2 was observed, particularly in eutrophic pelagic area, and was significantly negatively correlated with chlorophyll a. Long-term measurement showed the interannual variation in annual lake CO2 dynamics, which was highly sensitive to human-induced nutrient input. Watershed input of carbon and nutrient leads to the high CO2 level, counterbalancing the in-lake primary production. All lines of evidence suggest that human activities may have predominate contribution to CO2 source in the Lake Taihu, and this mechanism might be widespread in global freshwater lakes.