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<p>Eutrophic urban lakes with CO<sub>2</sub>-supersaturation represent potential carbon (C) sources; however, the drivers behind the reported C-source–sink shift remain poorly understood. This study provides a systematic assessment of daytime/seasonal <i>p</i>CO<sub>2</sub> and <i>f</i>CO<sub>2</sub> dynamics in a subtropical moderately eutrophic urban lake (Bailuwan, China), based on over a year of high-frequency monitoring, aiming to clarify the mechanisms regulating CO<sub>2</sub> exchange at the water–air interface in such ecosystems. Our work revealed consistent daytime declines in <i>p</i>CO<sub>2</sub> (and <i>f</i>CO<sub>2</sub>) on 12 sampling days, though morning–afternoon differences were not significant (<i>n</i> = 24). Novel episodic undersaturation events were newly observed in October 2020 and March 2021, contrasting with the prevailing supersaturation. Annual mean values (<i>n</i> = 48) reached 1789 µatm (<i>p</i>CO<sub>2</sub>) and 130 mmol m<sup>−2</sup> h<sup>−1</sup> (<i>f</i>CO<sub>2</sub>). Critically, we identified a pronounced semi-annual divergence: <i>p</i>CO<sub>2</sub> from January to June significantly exceeded values from July to November. Both periods maintained a net source status (&gt; 420 µatm), lacking the typical spring-sink/summer-source transition reported in previous studies. Key regulators, such as pH, chlorophyll a, and dissolved oxygen, influence C-sink-source dynamics, with eutrophication further modulating these shifts. These original findings highlight the need for targeted strategies to reduce pollutants and enhance carbon sequestration in urban lakes.</p>

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High-frequency monitoring reveals a CO2 source-sink shift in a subtropical eutrophic urban lake

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年12月5日

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  • Shiliang Liu,
  • Yingying Chen,
  • Rongjie Yang,
  • Yuling Qiu,
  • Aamir Mehmood Shah,
  • Kezhu Lu,
  • Xinyu Wang,
  • Di Li,
  • Wenbao Ma,
  • Xinhao Cao,
  • Qibing Chen

摘要

Eutrophic urban lakes with CO2-supersaturation represent potential carbon (C) sources; however, the drivers behind the reported C-source–sink shift remain poorly understood. This study provides a systematic assessment of daytime/seasonal pCO2 and fCO2 dynamics in a subtropical moderately eutrophic urban lake (Bailuwan, China), based on over a year of high-frequency monitoring, aiming to clarify the mechanisms regulating CO2 exchange at the water–air interface in such ecosystems. Our work revealed consistent daytime declines in pCO2 (and fCO2) on 12 sampling days, though morning–afternoon differences were not significant (n = 24). Novel episodic undersaturation events were newly observed in October 2020 and March 2021, contrasting with the prevailing supersaturation. Annual mean values (n = 48) reached 1789 µatm (pCO2) and 130 mmol m−2 h−1 (fCO2). Critically, we identified a pronounced semi-annual divergence: pCO2 from January to June significantly exceeded values from July to November. Both periods maintained a net source status (> 420 µatm), lacking the typical spring-sink/summer-source transition reported in previous studies. Key regulators, such as pH, chlorophyll a, and dissolved oxygen, influence C-sink-source dynamics, with eutrophication further modulating these shifts. These original findings highlight the need for targeted strategies to reduce pollutants and enhance carbon sequestration in urban lakes.