Microbial Communities in Coastal Salt Marshes Along the Southeast Coast of China and Their Effects on Carbon Storage

Background: Wetlands are vital carbon sinks, with coastal salt marshes being particularly effective in carbon sequestration. Understanding how different vegetation types influence soil carbon storage and microbial composition can enhance our knowledge of these ecosystems' roles in global carbon cycling. Methods: This study investigates soil physicochemical properties, soil carbon storage, and microbial community composition and diversity at three depths (10, 30, and 60 cm) in five salt marsh plots from five coastal salt marshes: Bare flat (a non-vegetated marsh) and plots dominated by Imperata cylindrica, Solidago canadensis, Suaeda spp., and Phragmites australis. Carbon storage was evaluated by measuring soil organic carbon (SOC) content. At the same time, high-throughput sequencing was employed to analyze microbial communities, aiming to elucidate their relationships with soil carbon storage and wetland vegetation. Results: The average SOC contents in the five plots were in the order of S. canadensis (13.33 g·kg– 1) > Bare flat (11.45 g·kg–1) > Suaeda spp. (8.10 g·kg–1) > I. cylindrica (6.15 g·kg–1) > P. australis (5.80 g·kg–1). S. canadensis and Bare flat marshes had the highest carbon content, which is mainly attributed to the presence of the most abundant carbon-fixation microbes, Fulvivirgaceae (family) and Acidobacteria RB41 (genus), in the soil of these two plots. Both organic and dissolved organic carbon contents at 10 cm were higher than those at the other two depths for all five marshes. Conclusion: The Bare flat exhibited strong carbon sequestration capability, second only to the invasive S. canadensis plot among the five plots surveyed. It also showed the highest microbial abundance and the greatest number of carbon-sequestration-related functional genes. The S. canadensis plot exhibited the lowest microbial community diversity and abundance despite having the highest carbon storage capacity. As an invasive species, S. canadensis should be removed to mitigate its ecological impact.