Yan Zheng

Coastal salt marsh restoration can support blue carbon sequestration, but spatial pre-assessment is needed to identify where environmental conditions support vegetation establishment before restoration design and carbon accounting. This study developed a threshold-based framework for spatial pre-assessment of coastal salt marsh restoration suitability. The framework combines species-specific limits for tidal inundation duration, seawater salinity and sediment salinity with sediment type in a geographic information system workflow. Tidal inundation limits are translated into critical-elevation boundaries, and retained polygons are examined against planning, historical-distribution and use-right conditions. A general threshold library was compiled for five representative native salt marsh species, while regional records define the candidate set for each application. In Yingkou, China, Suaeda heteroptera and Phragmites australis formed the candidate set. For S. heteroptera, the 3 h d⁻¹ inundation limit corresponded to a critical elevation of 1.90 m. July 2024 sediment salinity (0.96–1.08%) and September 2025 seawater salinity (29.715–29.825‰) met the corresponding screening limits for S. heteroptera and excluded P. australis. The integrated restoration-suitability area covered 76.5 ha, and 99.5% of the mapped current S. heteroptera distribution fell within it. The framework identifies candidate restoration space for field verification, restoration planning and subsequent carbon accounting.

Vegetated coastal wetlands, especially mangroves, seagrass beds, and salt marshes, are biodiversity-rich ecosystems whose blue carbon outcomes depend on living communities, sediment dynamics, hydrological connectivity, and landscape context. Biodiversity conservation and blue carbon management are often assessed through separate scientific, monitoring, and policy frameworks. This review uses a staged literature search and thematic synthesis to examine biodiversity–blue carbon linkages across the three major vegetated coastal wetland types. It considers how taxonomic, genetic, functional, and habitat diversity influence productivity, sediment stabilization, trophic exchange, carbon stocks, carbon burial, and carbon retention. It also evaluates how climate change, habitat fragmentation, hydrological alteration, pollution, and anthropogenic disturbance weaken these linkages. The synthesis compares representative carbon-stock and burial-rate baselines, examines conservation and restoration synergies and trade-offs, and expands the discussion of seagrass regime shifts. Field surveys, remote sensing, unmanned aerial vehicles, environmental DNA, and AI-enabled data integration are placed within a tiered monitoring framework. The review further develops an operational decision pathway for biodiversity-centered blue carbon management. Persistent blue carbon benefits arise where conservation and restoration maintain native communities, hydrological exchange, sediment stability, habitat complexity, migration space, and long-term stewardship capacity.

Site-level carbon density data remain limited for many seagrass meadows, especially where the mapped meadow extent has not been paired with repeated carbon-pool measurements. This study quantified biomass carbon density, 0–1 m sediment organic carbon density, total carbon density, and sediment contribution at 10 fixed stations in a meadow dominated by Zostera marina Linnaeus in Caofeidian, Bohai Bay, China, in 2021, 2024, and 2025. Sediment grain-size composition and five water-quality variables were also summarized for 2025 as environmental context. Sediment organic carbon dominated the station-level carbon pool. In 2025, biomass carbon density was 0.269–0.900 Mg C ha⁻¹, sediment organic carbon density was 8.108–39.730 Mg C ha⁻¹, and total carbon density was 8.377–40.566 Mg C ha⁻¹. The median total carbon density was 23.391 Mg C ha⁻¹ in 2021, 18.827 Mg C ha⁻¹ in 2024, and 20.040 Mg C ha⁻¹ in 2025. The rank association between fine sediment fraction and carbon density was positive in 2025 (Spearman’s ρ = 0.491, p = 0.150). These fixed-station records support seagrass monitoring, restoration planning, and sustainable coastal management. They also help link the mapped meadow extent with field carbon data for blue carbon assessment under climate and marine sustainability goals.

Temperate seagrass carbon-stock data remain limited in northern China, especially for island meadow systems with mapped distribution and repeated field verification. This study quantified standing seagrass ecosystem carbon stocks in the Changshan Archipelago, Dalian, using a standardized field survey covering eight meadow zones, 39 sampling stations, and 323.37 ha of confirmed seagrass area. Plant biomass carbon and sediment organic carbon were assessed, and the 0–100 cm sediment profile was sampled at all stations. The mapped meadows stored 29,305.75 Mg C in total ecosystem carbon. Sediment organic carbon accounted for 28,965.71 Mg C, representing 98.84% of the total stock. Plant biomass carbon contributed 340.04 Mg C, or 1.16%. The area-weighted ecosystem carbon stock per unit area was 90.63 Mg C ha⁻¹. This per-area stock ranged from 52.11 Mg C ha⁻¹ in Xiaochangshan to 209.50 Mg C ha⁻¹ in Haiyang Island. Guanglu Island contained the largest total carbon stock, with 9247.73 Mg C, because of its large meadow area and relatively high per-area carbon stock. The results show how mapped meadow area, sediment carbon dominance, and local sediment setting jointly shape regional carbon-storage patterns. This standardized baseline provides field-based evidence for comparing northern Chinese seagrass meadows with other temperate Zostera systems. The estimates describe standing ecosystem carbon stocks. Annual carbon sequestration rates were outside the scope of the assessment.