Particle dynamics of the surface, intermediate, and benthic nepheloid layers under contrasting conditions of summer monsoon and typhoon winds on the boundary between the Taiwan Strait and East China Sea

A comprehensive sediment dynamics study of a major mud belt system on the inner shelf along an energetic coast

“…However, the coarsest size of >153 μm showed weak resuspension in the lower water column, some presence in the upper water column and a strong presence as a thin layer that co-located with high E values at mid-depth (Figs 4e and 6b ). This points to a set of similar mechanisms as the result of coupling between physical processes (mixing vs. stratification) and large-sized biogenic particles such as phytoplankton that contains chlorophyll-a observed off the mouth of Minjiang River 44 (Fig. 4c ).…”

“…The shear stresses (U * ) induced by waves, currents, and wave-current interaction over a diurnal tidal cycle were estimated using the method described before 43 , 44 were compared against entrainment thresholds of non-cohesive sediment of the grain sizes of 10, 63, and 153 μm, respectively (Fig. 6a ).…”

“…Yet, summer is the flood season of all rivers in the region, the effluent from other rivers along the mud belt replaces the role of the Changjiang buoyant plume and the vertical stratification in the water column still exists 21 . A sediment dynamics study off the mouth of Minjiang River in summer shows under contrasting wind conditions of SW summer monsoon and NE typhoon winds, a stratified/isopycnal layer existed at mid-depth 44 . Under both conditions a benthic nepheloid layer below the dynamic barrier formed by the isopycnal layer was also present.…”

“…When the summer monsoon dominates, the system receives sediment delivered from small rivers on the Zhe-Min Coast, but little from Taiwan 49 . The buoyant water and colder and more saline water brought to the coast by upwelling forms stratification that could create a similar barrier in the vertical 21 , 32 , 44 . The amount of suspended sediment in the lower water column is less than that in winter 34 .…”

“…The profiling included hourly salinity, temperature, chlorophyll-a, and volume concentration of suspended particles of thirty-two grain sizes (using LISST-100X). Water samples were taken at the surface, mid-depth, and near seabed for the analysis of suspended sediment concentration (SSC) at 2-hr intervals using the method described before 44 . Seabed sediment samples were analyzed for grain-size distribution using the methods described before 44 .…”