Parallelism of Nutrients and CO₂ Dynamics: Evidence Based on Long-Term Data in Taihu Lake

Inland lakes are important ecosystems for the carbon cycle at both regional and global scales. However, a knowledge gap still exists about the correlations between the partial pressure of CO₂ (pCO₂) and nutrient dynamics in lakes. In this study, we analysed the long-term dynamics of nutrient and pCO₂ in Taihu Lake. Strong spatial heterogeneity was observed with highest nutrient concentrations occurring in the River mouth and significant lower concentrations (p < 0.01) occurring in East Taihu and Other zone. For pCO₂, the average values were 1136.81 ± 1240.16 μatm, 433.07 ± 305.45 μatm, and 487.05 ± 414.02 μatm in Rive mouth, East Taihu, and Other zone, respectively. Statistical analysis revealed that pCO₂ was significantly and positively related to nutrient (TN: total nitrogen and NH₄⁺: ammonium) concentrations (p < 0.01), but negatively related to Chla (Chlorophyll a) concentrations in River mouth and Other zone (p < 0.01). The parallelism of nutrient concentrations and pCO₂ in Taihu Lake highlights the dual effects of external pollution inputs from the surrounding catchment. In addition, progressive mitigation was found for not only nutrients but also pCO₂, which was attributed to the previous effort in the environmental protections in Taihu Lake basin. Our results also suggest the importance of long-term monitoring for the future assessment of anthropogenic impacts on nutrient and CO₂ dynamics in freshwater lakes.