Enhanced sequestration of carbon in ocean sediments as a means to reduce global emissions: A case study from a coastal wetland restoration project in the Liaohe Delta, Northeast China.

Enhanced sequestration of carbon in ocean sediments is a promising approach to mitigate the adverse effects of climate warming. To assess the capacity of coastal regions to uptake and bury carbon, a wetland restoration project was carried out in the degraded coastal wetlands of the Liaohe Delta between 2011 and 2013. A 13.33-ha degraded salt marsh was selected to create two enhanced carbon sink experimental areas, one dominated by Phragmites australis and the other dominated by Suaeda salsa. Improvements to the wetland matrix, hydrological processes, and vegetation colonization were designed and constructed. Results revealed that after the three-year restoration effort, the biomass of vegetation in the demonstration area was 1.2–4.0 times that of a natural wetland, and the rate of organic carbon sequestration in the sediments was about 60–80% of the rate in a natural salt marsh. We show that restoring vegetation can significantly increase the rate of sedimentation and thus enhance the carbon sequestration capacity of a wetland dominated by S. salsa or P. australis. Carbon sequestration capacity can be restored more rapidly in salt marsh wetlands than in mangrove wetlands, and we argue that restoration of salt marsh wetlands is an urgent task suitable for the application of large-scale ocean carbon sequestration technologies. • A case study on a novel technology for ocean negative ocean emissions was detailed. • Soil organic carbon sequestration rates of restored wetlands were about 60–80% of the rates in natural wetlands after three years. • Restoring vegetation can significantly increase the rate of sedimentation and thus enhance the carbon sequestration in the soils. [ABSTRACT FROM AUTHOR]