Distribution and Sources of Organic Carbon in Surface Intertidal Sediments of the Rudong Coast, Jiangsu Province, China

Yinan Mao,Jiaxin Lin,Ye Chen,Qiang Shu,Qingyun Ma

doi:10.3390/jmse9090992

Abstract

In this study, total organic carbon (TOC), total nitrogen (TN), and stable carbon isotopes (δ13C) were measured in surface intertidal saltmarsh and bare tidal flat sediments along the Rudong coast. The distribution and sources of organic carbon were examined under different depositional environments based on C/N ratios and a two-terminal mixing model. The results showed that the average TOC content of the vegetated saltmarsh sediments, bare tidal flat areas near vegetation (BF1), and bare tidal flat areas far from vegetation (BF2) were 4.05, 2.72, and 1.22 mg/g, respectively. The mean δ13C value within the vegetated saltmarsh area was −22.37‰, and the C/N ratio was 9.3; the corresponding values in the BF1 area were −23.27‰ and 7.95, respectively; and in the BF2 area, the corresponding values were −21.91‰ and 5.36, respectively. These C/N ratios reflect an increasing marine contribution with distance from the vegetated zone. Combined with the two-terminal mixing model, the organic carbon in the vegetated saltmarsh sediments was dominated by terrestrial sources, while the bare tidal flat sediments were more influenced by marine sources, and the bare tidal flat sediments nearer to the vegetated zone (BF1) were influenced by a combination of vegetation, marine sources, and other terrestrial factors.

Highlights

Coastal zones connect the ocean and land, and are areas of dynamic land–ocean–atmosphere interaction influenced by various terrestrial and marine physical, chemical, and biological factors
The vegetation types in the sampled wetland areas were dominated by S. alterniflora, P. australis, S. glauca, and I. cylindrica, which show a successional sequence in the listed order
Δ13 C, total organic carbon (TOC) content, and C/N ratios were measured in the surface sediments of the vegetated saltmarsh area and bare tidal flat areas of the Rudong coastal zone

Summary

Introduction

Coastal zones connect the ocean and land, and are areas of dynamic land–ocean–. Atmosphere interaction influenced by various terrestrial and marine physical, chemical, and biological factors. This results in complex energy flows and material input and output processes, with active carbon flows and transformations. Carbon in the ocean includes autochthonous organic carbon from marine benthic organisms and phytoplankton, and allochthonous organic carbon from riverine inputs and human activity. Sediments in highly productive coastal wetlands—including mangroves, saltmarshes, and seagrass beds—capture and store significant amounts of carbon, acting as carbon sinks and contributing to climate change mitigation [1,2]. Nahlik and Fennessy [3] found that the total carbon sequestered in the upper 0–1.2 m of saltmarsh and mangrove soils in the coastal zone of the United States was

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Conclusion