Sediment dynamics in adjacent bays of Fujian during late-spring spring tide

Bays are active land–sea transition zones where the internal hydrodynamic processes control the material exchange between the bay and open sea. Yet, the differences and potential connectivity of those processes between adjacent bays and off-bay areas remains understudied. Using in situ observations during a spring tide in May 2020, complemented with satellite imagery and reanalysis dataset, this study examines sediment dynamics in two neighboring bays of central Fujian—Shenhu Bay (SHB) and Weitou Bay (WTB). Results show that SHB exhibits tidal asymmetry with strong offshore export, while WTB has weaker, vertically divergent residual currents with bottom-layer seaward suspended sediment flux. Outside the bays, residual currents and sediment flux follow a northeastward coastal pathway under late-spring circulation. Sediment transport from bay interiors to mouths and is further transported downstream by regional circulation, potentially entering adjacent bay through exchange between the bay and the open sea. Mechanism analysis indicates that Eulerian residual currents dominate net sediment transport, whereas tidal pumping is minor. These findings reveal sediment export pathways and inter-bay connectivity, advancing understanding of coastal sediment dynamics and material cycling in Fujian waters.