Epikarst springs as atmospheric CO₂ sinks in a tropical Karst environment: Evidence from the Gunungsewu Karst, Indonesia

Karst ecosystems, covering 15% of global land, serve as vital carbon sinks, especially in the epikarst zone. This study examines the carbon sink capacity of epikarst spring catchments using field data from August 2022 to July 2023. Applying the hydrochem-discharge method, discharge and dissolved bicarbonate (HCO₃^-) concentrations were analyzed at two-week intervals. The results reveal that epikarst springs absorb atmospheric CO₂ at rates of 747.34-787.00 tons/km²/year, significantly surpassing non-epikarst springs (576.92 tons/km²/year). This sequestration capacity is driven by seasonal rainfall, discharge volume, and ion levels. Compared to other karst regions on Java Island, these springs demonstrate superior absorption, highlighting their critical importance in the global carbon cycle.