Sources and fluxes of particulate organic carbon in the Wujiang cascade reservoirs, southwest China

Abstract

Knowing the sources and behaviors of particulate organic carbon (POC) is essential for calculating the carbon pool of riverine systems, the natural properties of which have been strongly affected by damming. In this study, we investigated POC and related environmental factors in the Wujiang cascade reservoirs, southwest China, to understand sources and fluxes of POC under cascade-damming conditions. The results indicated that POC concentration and δ13CPOC had obvious temporal and spatial variation, with average values of 0.39 mg L−1 and −28.98‰, respectively. Evidence from δ13CPOC indicated that POC in the reservoirs was largely from phytoplankton-derived POC. POC flux was estimated as 2.17 × 109 g yr−1, of which allochthonous POC flux was about 1.5 × 109 g yr−1 in the study area. The reservoir retained a large amount of POC, and the intercept rate of Wujiangdu Reservoir was up to 64.94%. These findings suggest that cascade damming significantly impacts the sources and fluxes of POC in the impounded Wujiang River, southwest China.