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

Abstract

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.