Terrestrial Biomolecular Burial Efficiencies on Continental Margins

Abstract

The fate of terrestrial organic carbon (OCterr) exported from large rivers in marginal seas is an integral component of land-ocean-atmosphere carbon dynamics and influences on atmospheric CO2 concentrations on millennial and longer timescales. In this study, we employ a novel approach to constrain burial efficiencies for source-specific terrestrial biomolecules (long-chain n-alkanes and n-fatty acids) in two river-marginal sea systems. We find for the Pearl River-South China Sea system that 34 ± 19% and 11 ± 4% of n-alkanes and n-fatty acids, respectively, are preserved across the transport pathway from the river mouth to inner shelf. In contrast, terrestrial biomolecular burial efficiencies were markedly higher (64 ± 17% and 84 ± 30% of n-alkanes and n-fatty acids, respectively) in the Yellow River-Bohai Sea/Yellow Sea system. These findings reveal markedly different fates of OCterr in these two fluvial-marine systems, as well as sharp contrasts in OCterr reactivity within each system.