Unravelling the mesoscale saltmarsh accretion on the tropical barrier estuarine regime: A case study from the Chandipur Saltmarsh, India

Coastal wetlands are seen as efficient coastal stabilizers and provide an optimal natural ecosystem for the sequestration and storage of carbon. Thus, it is critically important for scientists and environmental managers to understand the future dynamics of coastal wetlands. The understanding of yearly to decadal development in coastal ecosystems can assist in the coastal management activity, to sustain biodiversity. In the current study, high-resolution granulometric analysis of a back-barrier salt-marsh deposit of tropical barrier estuary environments at Chandipur, India, is utilized to provide an overview of the mesoscale geomorphic processes and history of changing sediment dynamics. The multivariate statistical examination with coefficients of probability density functions and compositional data analysis helps to determine the four lithofacies of the deposit. Granulometric analysis combined with satellite image analysis reveals that relatively coarser facies were deposited during the incipient stage of the barrier development, when the marshland vegetation was relatively less dense as suggested by the lower Normalized Difference Vegetation Index (NDVI) and the saline sea water easily drowned the area and high saline sediment was deposited. After rapid marsh accretion, the flow dynamics shifted to a negligible flow component in the final stage when finer facies were deposited in vegetated marshland, and the organic carbon concentration increased up to 3.5%. As plant organic matter and sediment continuously accumulates in this marshland, elevation capital grows and the marsh continues to develop and expand, reaching a densely vegetated marsh with a considerable increase in NDVI values. The findings of this multiproxy study, in conjunction with multivariate statistical analysis, provide valuable insight into the characteristics of accretion in a tropical saltmarsh, which is unique in such a geological setting.