Large River Overrides Tidal Marsh Outwelling in Spatial Gradients of Dissolved Organic Carbon: Observations Across Yangtze Estuary–Coastal Marsh Complex

Authors:
Open Access
Publisher website
Google Scholar
Abstract
Estuarine wetlands have been shown to be an important source of dissolved organic carbon (DOC) to surrounding waters by consistently exporting optically and compositionally distinctive organic materials with tidal draining. Numerous studies have been conducted in marshes mostly drained by coastal creeks and regional rivers, yet the spatial biogeochemical gradients of DOC developed from coastal marshes influenced by world's mega rivers are little studied. Using high resolution Landsat-8/-9 and Sentinel-2, we focused on characterizing the spatial gradients of marsh-DOC exported with tidal exchanges over a unique estuarine background impacted by a globally significant river. Designated as the ‘Wetlands of International Importance’ by the Ramsar Convention, the Chongming Dongtan Nature Reserve is the largest, representative estuarine wetlands in China, influenced by Yangtze River — the fifth largest river worldwide by discharge. LaSRC and Sen2Cor were found to be the preferred atmospheric correction models for Landsat-8/-9 and Sentinel-2A/B, respectively, for this turbid nearshore environment. An ocean color DOC algorithm based on the strong linear correlation between DOC concentration and the absorption coefficient of its chromophoric component (CDOM, aCDOM) retrieved from Landsat-8/-9 and Sentinel-2A/B remote sensing reflectance showed good DOC estimates, with a mean absolute percent difference of 11% for aCDOM(300) and 5% for DOC. Maps of marsh-to-estuary DOC distribution emphasized the predominance of Yangtze River, with less identifiable biogeochemical gradients of DOC in this mega-river-impacted estuary. This implies the impact of lateral carbon transfer from coastal marshes influenced by world's large rivers might be limited in altering coastal biogeochemistry.
Funding Information
  • National Natural Science Foundation of China (41906145, 42141016)
  • Natural Science Foundation of Shanghai Municipality (19ZR1415000)
  • Innovation Program of Shanghai Municipal Education Commission (2021-01-07-00-08-E00102)

This publication has 60 references indexed in Scilit: