Lipid biomarkers in Lake Wudalianchi record abrupt environmental changes from the volcanic eruption in 1776

Volcanic eruptions can cause abrupt changes in surrounding environments, but detailed sediment records of such changes are rare. The very high sediment accumulation rate in Lake Wudalianchi, a volcanic-dammed freshwater lake in northeastern China, provides an excellent opportunity for reconstructing volcanic-induced environmental change. Here we use multiple lipid biomarkers to reconstruct changes in aquatic ecosystems, hydrology, and methane cycling before and after a regional explosive volcanic eruption in 1776. Our results indicate that the Wudalianchi catchment was a shallow organic-rich marsh environment with abundant aquatic emergent macrophytes and an intense microbial methane cycle before the volcanic eruption. Following the volcanic eruption, the marsh was rapidly transformed into an oligohaline lake environment due to river channel damming by lava. Associated with the abrupt environmental change, we observe corresponding changes of cyclisation ratios of branched glycerol dialkyl glycerol tetraethers or brGDGTs (CBT and CBT′ indices), and the inferred pH displays an abrupt increase of ∼1.3. Group 1 alkenones emerge abruptly after the eruption when the inferred pH exceeds 8. Our results provide the first high-resolution reconstruction of environmental change induced by volcanic eruption and demonstrate the high efficacy of the lipid biomarkers in recording aquatic and terrestrial changes.