Study on the influence of Typhoon “Muifa” on the macrobenthic community of tidal flat

Typhoons can have serious impacts on tidal flat ecosystems, particularly on the composition and distribution of macrobenthic communities. However, there is a lack of field data during typhoons, and the understanding of how typhoons affect the ecosystem is still limited. Therefore, this study conducted hydrodynamic observations and synchronous sampling of macrobenthic organisms before, during, and after Typhoon “Muifa”in September 2022, along the salt marsh-mudflat transect in the Chongming Dongtan area of the Changjiang River estuary. The study found: (1) During Typhoon “Muifa”, the effective wave height in the salt marshes was 2−4 times that of normal weather, and the combined wave-current shear stress was 10 times higher. (2) Within a week after Typhoon “Muifa”, the species number, abundance, and biomass of macrobenthic organisms in the salt marshes were 1.9, 3.8, and 3.0 times higher than before the typhoon, respectively. The dominant species of the salt marsh (Ilyoplax deschampsi, Assiminea sp., Assiminea violacea, Corbicula fluminea) increased by one (Assiminea violacea) compared with that before the typhoon (Assiminea sp., Ilyoplax deschampsi, Corbicula fluminea), and the primary dominant species shifting from Assiminea sp. to Ilyoplax deschampsi. (3) Within a week after Typhoon “Muifa”, the indicators of species number, abundance, and biomass of macrobenthos in the salt marsh increased, while the abundance of macrobenthic organisms on the mudflats at the forefront of the salt marsh decreased. This is attributed to the macrobenthic organisms (Ilyoplax deschampsi, Assiminea sp., Corbicula fluminea) on the mudflats migrating rapidly to the relatively less hydrodynamically stressed salt marshes during the strong hydrodynamic stress caused by the typhoon. (4) Two weeks after Typhoon “Muifa”, the abundance of macrobenthos in salt marshes recovered. The results of this study indicate that salt marsh vegetation not only provides ecological services such as wave attenuation, flow reduction, and shoreline protection, but also serves as a refuge for macrobenthic organisms during typhoons.