Lacustrine carbon cycling since the last interglaciation in northeast China: Evidence from n-alkanes in the sediments of Lake Xingkai

Organic carbon mineralization and storage in the inland water bodies is an important component of global carbon cycling. However, the mechanisms influencing carbon cycling in the inland water bodies remain uncertain. In this study, n-alkane data from a sediment core spanning the last glacial-interglacial cycle from Lake Xingkai in northeast China, were analyzed to determine response of regional carbon cycling to climate change. Prior to MIS 1 the sedimentary n-alkanes were mainly derived from terrigenous higher plants and helophytes in the wetland. By contrast, non-photosynthetic bacteria are probable major alternating source of sedimentary n-alkanes during MIS 1. The n-alkanes in the sediments are mainly influenced by the variations of lake level and deposition of mineral dust. The total organic carbon content (TOC) and TOC-normalized middle- and long-chain n-alkane concentrations increased during glacial times and decreased during interglacial periods, reflecting higher rates of organic matter decomposition under warmer climatic conditions. The temperature dependence of lacustrine organic matter mineralization suggests that the carbon burial potential of lakes in northeast China will decrease in the future as global warming intensifies.