Lake metabolism and associated emissions of CO in lakes are heavily subsidized by terrestrial carbon but the role of climate forcing remains unclear. The carbon stable isotope composition of zooplankton in a sediment core from a sub-tropical alpine lake in SW China tracked atmospheric CO and δO records of monsoonal strength (Dykoski et al., 2005; Wang et al., 2005) over the last ~26 kyr. The lake was CO-limited during the Last Glacial Maximum (LGM) when C vegetation dominated the catchment. Zooplankton production and inferred-lake CO (from δC) increased from 10 ka with strengthening of the SW Asian monsoon and forest expansion. These results highlight the importance of land-cover and hydrology in controlling terrestrial organic matter inputs to lakes and aquatic carbon dynamics at 10-10 yr timescales.