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.