Three Gorges Dam enhanced organic carbon burial within the sediments of Poyang Lake, China

Lakes play a dominant role in the global carbon cycle, serving as crucial long-term carbon (C) sinks. Carbon burial within lakes is influenced by changes in both inflowing and outflowing processes. While considerable attention has been given to studying the former, the latter has often been overlooked and remains insufficiently documented. In this study, we investigated the variations in organic carbon burial within Poyang Lake, the largest freshwater lake in China, which mainly discharges into the Changjiang River. This study focused on the response of organic carbon burial to the regulation of a mega dam, the Three Gorges Dam, along the lake's main channel. The mean organic carbon accumulation rate in Poyang Lake sediments increased substantially by 3.82–4.60 times after the year 2000, compared to the preceding period. Furthermore, the Three Gorges Dam induced an abnormal reduction in lake levels by 1.38 m during the dry season, leading to a translocation of approximately 0.42 billion m² of water area toward vegetated systems. The pronounced expansion of vegetation across the shallow floodplain of Poyang Lake is identified as the primary driver behind the enhanced organic carbon burial within the lake sediments. These findings emphasize the imperative to further investigate and address the global issue of organic carbon accumulation in lake floodplain sediments, particularly in the context of riverine dams. These results shed light on the ecological implications of mega-dam regulation on organic carbon dynamics and underscore the significance of understanding and mitigating the associated environmental impacts. Copyright © 2024 Elsevier B.V. All rights reserved.