Selective preservation of glomalin-related soil protein contributes to centennial-scale organic carbon burial on the East China Sea shelf

Continental shelves store a large fraction of land-derived sediment organic carbon (SOC), yet the fate of soil biomacromolecules after land-sea transfer remains poorly constrained. We analyzed a 210 Pb/ 137 Cs-dated mud-belt core (S0703–2) from the East China Sea shelf off the Changjiang estuary to quantify centennial burial of glomalin-related soil protein (GRSP), an operationally defined citrate-autoclave extract associated with arbuscular mycorrhizal fungi. GRSP was measured as citrate-extractable dry mass (GRSPs) and as its Coomassie-reactive protein fraction (GRSPe), and interpreted using change-point regression together with δ 13 C and δ 15 N, C/N ratios and FTIR spectra. SOC burial ranged from 32.9 to 76.4 g m −2 a −1 (average 60.5 ± 8.0 g m −2 a −1 ). Mean burial rates were 8.38 ± 2.68 g m −2 a −1 for GRSPs and 2.22 ± 0.28 g m −2 a −1 for GRSPe. Across the core, these two fractions contributed 6.01–24.9% and 2.78–5.59% of SOC burial, respectively. Down-core, GRSPe remains 13 C- and 15 N-enriched relative to SOC and increases in fractional importance, consistent with preferential preservation of the protein-rich fraction, whereas GRSPs likely includes a more labile co-extracted component. FTIR fingerprints from representative horizons shift from polysaccharide- and nucleic-acid-like bands toward stronger aliphatic and amide features, consistent with mineral-mediated selective retention during early diagenesis. A breakpoint near 1945 records reduced terrigenous SOC burial (35.9 ± 4.8 to 22.8 ± 6.6 g m −2 a −1 ) but a higher relative contribution of GRSP, consistent with mid-20th-century shifts in land-sea carbon transfer. GRSP thus represents a measurable, previously under-recognized terrigenous pool contributing appreciably to long-term SOC burial on continental shelves.