Climate and land-cover controls of aquatic carbon dynamics since the last glacial maximum: Evidence from stable carbon isotopes of subfossil Cladocera

Abstract

Lake metabolism and associated emissions of CO2 in lakes are heavily subsidized by terrestrial carbon. However, how land-cover change and long-term climate interact to influence landscape biogeochemistry remains unclear. A ∼26,000-year sediment record from a lake in Southwest China shows how terrestrial-aquatic carbon dynamics responded to climate changes, atmospheric CO2 levels, and changing land-cover (vegetation composition) prior to cultural disturbances. Decoupled and coupled variations in the δ13C of Zooplankton (Bosmina) and sedimentary organic carbon from the Last Glacial Maximum tracked changes in atmospheric CO2 and the δ18O records of monsoonal intensity (Dykoski et al., 2005; Wang et al., 2005), highlighting a primary climatic control on coupled terrestrial-aquatic carbon dynamics. Zooplankton and algal production, alongside Bosmina δ13C-inferred lake CO2 concentrations, exhibited synchronous variations with the intensification of the southwest monsoon from ∼10 cal kyr BP, reflecting both increased aquatic production and enhanced terrestrial carbon export driven by forest expansion. These results highlight the critical role of monsoon-driven hydrological changes in regulating terrestrial organic matter inputs to lakes and shaping aquatic carbon dynamics at timescales of 102–103 year.