Organic carbon deposition of a typical plateau deep lake across 150 years.

Lakes are waterbodies, and their organic carbon (OC) depositions are one of the important C pools in the terrestrial ecosystem. The characteristics, size and change of these C pools are closely related to climate issues and human activities. Here Lake Chenghai was chosen as a representative, and the distribution, property and source of OC deposition were systematically investigated using isotopes and chemical biomarkers methods and 24-index indicators. The results showed that distribution pattern of OC deposition could be divided into two types, including a relative stable stage in the bottom layer (48.8-38.4 cm), and an upswing stage in the middle layer (38.4-16.8 cm) and surface layer (16.8-0 cm) of lake sediments, where the OC deposition was stable below 5.00 g m-2yr-1, and increased from 5.00 to 21.87 g m-2yr-1, respectively. The chemical composition of OC deposition showed that the bottom layer had higher aromaticity, hydrophobicity and the relative molecular weight. The three components, i.e. humic acid, fulvic acid and protein-like component, all rose from the bottom to the surface of lake sediment. Plants (47.7-82.0 %) were the main OC source. C₃ plants dominated the bottom layer, while microorganisms and algae contributed more to the middle and surface layers. The OC deposition fluctuated largely due to the disturbance from warming and anthropogenic activities. This study is expected to provide comprehensive scientific references for reconstructing OC deposition of plateau lake, and lay a good foundation for preventing and controlling plateau lake eutrophication, and evaluating and reducing carbon dioxide emission in plateau lake.