Revealing carbon balance characteristics in a water conveyance-type lake and differences in carbon sources through its connective hydrological channels

Abstract

Abstract Most of the world’s lakes are fed through water conveyance, namely, lakes that continuously receive and discharge water. However, the complex hydrological processes of such lakes make it difficult to determine their specific biogeochemical carbon (C) cycles. Poyang Lake was selected for this study, whose capacity to receive and discharge through water conveyance is the largest in China. We used both main and trace elements in the lake as stable isotopes of surface water and its tributaries to trace C sources and to reveal the C–water coupling relationship. Poyang Lake has a high river–lake connectivity, and results show that it undergoes rapid water renewal. The effect of this is that a large amount of dissolved inorganic carbon (DIC) cannot be converted and deposited into sediment, resulting in an annual DIC input and output of 1.3×109 kg year-1. The main DIC sources in Poyang Lake are atmospheric deposition (27%), carbonate weathering (27%) and silicate weathering (26%). Furthermore, the coupling characteristics of C and water in the Poyang Lake Basin change continuously under such conditions. Results from this study provide a reference for the investigation of such water conveyance-type lakes and the coupling effects associated with C and water.