Eutrophic Lake Taihu as a significant CO₂ source during 2000-2015

Area of Science:

• Environmental Science
• Limnology
• Biogeochemistry

Background:

• Inland lakes are crucial for the global carbon cycle, but long-term data on their carbon dioxide (CO2) emissions are scarce.
• Eutrophication in lakes significantly impacts their role in carbon cycling.
• Understanding CO2 flux from large, shallow, eutrophic lakes is vital for global carbon budget assessments.

Purpose of the Study:

• To investigate the carbon dioxide (CO2) flux from Lake Taihu, a large subtropical eutrophic lake.
• To establish a long-term (2000-2015) record of CO2 emissions and partial pressure of CO2 (pCO2) with high spatiotemporal resolution.
• To identify factors influencing CO2 dynamics and emissions in a eutrophic lake system.

Main Methods:

• Long-term monitoring (2000-2015) of the partial pressure of carbon dioxide (pCO2) in Lake Taihu.
• High spatiotemporal resolution measurements to capture variations in CO2 flux.
• Analysis of seasonal and interannual variations in pCO2 and CO2 emission flux.

Main Results:

• Lake Taihu was identified as a significant source of atmospheric CO2, with an average emission flux of 18.2 ± 8.4 mmol m⁻² d⁻¹.
• Mean annual pCO2 was 778 ± 169 μatm, with highest values in eutrophic zones receiving high carbon and nutrient inputs.
• CO2 flux and pCO2 exhibited a seasonal pattern, negatively correlated with chlorophyll a, and were highly sensitive to human-induced nutrient input.

Conclusions:

• Human activities, particularly watershed nutrient input, are the predominant drivers of CO2 emissions from Lake Taihu.
• High external nutrient and carbon loads counteract in-lake primary production, leading to elevated CO2 levels.
• The findings suggest that human-driven CO2 emissions from eutrophic lakes may be a widespread phenomenon globally.