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National Committee on Marine Sciences (NCMS)

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    Relationship between sediment conditions and mangrove Rhizophora apiculata seedling growth and nutrient status
    Duarte, C. M.; Geertz-Hansen, O.; Thampanya, U.; Terrados, J.; Fortes, M. D.; Kamp-Nielsen, L.; Borum, J.; Boromthanarath, S. (Inter-Research Science Center, 1998)
    The growth rate and nutritional status of Rhizophora apiculata seedlings were analyzed across mangrove stands with different sediment composition in The Philippines and Southern Thailand. Plant growth differed 10-fold and the production of new leaves, roots and branches varied between 50- and 100-fold across sites. Most (>60%) of the variance in mangrove growth rate across systems could be accounted for by differences in the nutrient concentration of the leaves, which was in turn related to the interstitial nutrient concentration and the silt plus clay content of the sediments. Nutrient-poor coarse sediments were characteristic of mangroves located in the mouths of rivers draining small watersheds, while sediments at the mouths of large rivers had high silt, clay, and nutrient contents, thus allowing the development of nutrient-sufficient, fast-growing R. apiculata seedlings. The growth of R. apiculata seedlings increased significantly when the plants grew adjacent to rivers draining areas >10 km2. The results provide evidence that growth of R. apiculata seedlings at the edge of the progressing mangrove forests is often nutrient limited, and that the extent of nutrient limitation depends on the delivery of silt and nutrients from the rivers. The coastal zones adjacent to small (<10 km2) drainage areas seem unsuitable to support adequate growth of R. apiculata seedlings, and afforestation programmes should, therefore, target mud flats adjacent to large rivers instead.
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    Clay mineral nanostructures regulate sequestration of organic carbon in typical fluvial sediments
    Song, Hongzhe; Liu, Zhifei; Lin, Baozhi; Zhao, Yulong; Siringan, Fernando P.; You, Chen-Feng (Elsevier, 2024-02-15)
    The association between clay minerals and organic carbon is pivotal for understanding transport, burial, and preservation processes of sedimentary organic carbon. However, fine-scale microscopic studies are still limited in assessing the effect of diverse clay mineral structures and properties on organic carbon sequestration. In this study, we employed X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy coupled with energy dispersive spectroscopy and electron energy loss spectroscopy analyses to investigate the nanoscale interaction between clay minerals and organic carbon of two typical fluvial sediment samples with contrasting clay mineral compositions and organic carbon origins. Sample from Taiwan shows abundant illite and chlorite with petrogenic organic carbon, while sample from Luzon has significant smectite with pedogenic organic carbon. We observed that the nanostructure of the clay minerals controls the distribution of organic carbon. In the Luzon sample, the organic carbon is tightly associated with smectite, occupying expandable interlayer spaces. In the Taiwan sample, however, the organic carbon is primarily confined on the surface and edge of illite. These findings offer valuable insights into the selective association of organic carbon with clay minerals and underscore the role of clay mineral nanolayer structures in governing the occurrence and preservation of organic carbon in sediments. A comprehensive understanding of these interactions is crucial for accurate assessments of carbon cycling and sequestration in the natural environment.
    We sincerely thank Shunai Che and Lu Han for their help in TEM experiments and data processing. We thank Editor Dr. Andrew Hursthouse for handling the manuscript and two anonymous reviewers for their constructive comments on the early version of this paper. This work was supported by the National Natural Science Foundation of China (42130407, 42188102, 42306066) and the Interdisciplinary Project of Tongji University (ZD-22-202102).