Changing dynamics of terrestrial organic carbon burial in marginal seas: Coupling impacts of climate change and anthropogenic activities
Description
River-dominated marginal seas play a crucial role in the global carbon cycle. However, the recent burial record of organic carbon (OC) remains unclear. In this study, we conducted a comprehensive analysis of bulk OC, its isotopic composition (δ13C and Δ14C), biomarkers (lignin and n-alkanes), and sedimentological evolution based on sediment core from the Bohai Sea (BS). We also compiled several published OC burial records for the last century from the Eastern China Marginal Seas. Our findings indicate that sedimentary OC in the BS is characterized by a recent decrease in terrestrial signals (e.g., terrigenous/aquatic ratio of alkanes, BIT), which could be attributed to the sharp decline in sediment load from the Yellow River since the 1950s. More intense resuspension due to stronger hydrodynamics driven by the increasing frequency of winter storms could account for the observed sediment coarsening trend and concomitant increase in the proportions of degraded lignin and old-OC since the 1980s, suggesting that sediment coarsening could influence the selective transport and recent accumulation of allochthonous OC. Vertical evolution patterns of lignin composition indicated spatial heterogeneity of terrestrial OC burial records among large river-dominated Chinese coastal margin areas. Compared to the source dominance of OC burial in the Yangtze River and Pearl River offshore areas, we found significant coupling of enhanced hydrodynamic forcing due to climate change with recent changes in coastal OC burial, especially in the BS, which has experienced a substantial decrease in sediment load due to anthropogenic activities.