Glomalin-related soil protein deposition and carbon sequestration in the Old Yellow River delta

Abstract

Glomalin-related soil protein (GRSP), a particular terrigenous-derived carbon (C), is transported to the coastal oceans, where it accumulates in sediments. We hypothesized that terrigenous C (GRSP) accumulation could enhance marine C sequestration, and sediment fertility would increase the C stock in the marine ecosystem. In this study, we tested GRSP contribution to marine sediment C, nitrogen (N) and iron (Fe), and explored whether GRSP deposition varied with sediment fertility levels in the Old Yellow River delta. The mean concentration of total GRSP was 1.10±0.04mgg−1 (0.24MgCha−1), accounting for 6.41±0.17% of total organic C and 3.75±0.13% of total N in the 0–10cm marine sediments, indicating that the coastal marine system is an important sink of GRSP. GRSP also contained 1.46±0.06% Fe (20.7kgFeha−1), accounting for 0.058±0.003% of total Fe in marine sediments. Meanwhile, Fe-content in GRSP significantly decreased with distance from the shore, indicating that Fe was released with GRSP transfer and thus GRSP was a new natural Fe fertilization in marine environment. Furthermore, GRSP enhanced marine C sequestration by its rapid deposition and Fe contribution. Combined indicators of sediment fertility (factor 1) were significantly positively correlated with GRSP concentrations by Principal Component Analysis. Co-deposited with nutrient elements, GRSP fractions were accumulated more in more fertile sediments but less in less fertile sediments. GRSP, a mixture of co-existent multiple elements, can be used as a nutrient controlled-release agent in the marine ecosystem. GRSP fractions were responsive to marine sediment fertility levels and the understanding of their function in sediment C sequestration will provide new insights into the importance of terrestrial-marine linkages.