Saltmarshes are important natural ecosystems along many temperate (and other) coastlines. They stabilize sediments and act as biofilters for a range of industrial pollutants and, potentially, microplastics. Accumulation of microplastics along estuarine coastlines may be enhanced by the presence of saltmarsh species, as they offer better particle trapping efficiency than adjacent intertidal mudflats under prevailing flood and ebb tidal currents. However, the trapping efficiency of entire saltmarsh systems under varying flow conditions has not been widely assessed. While the effects of saltmarsh systems on water flow, and on sediment transport and trapping, have been relatively well studied, little is known about the contributions of saltmarsh halophytes, resident organisms and the associated saltmarsh sediments to the trapping of microplastics. To address this, a series of flume experiments were undertaken to examine transport and accumulation of Bakelite particles (~ 500 µm) and PVC nurdles (~ 5 mm) as model plastics in sub-sampled saltmarsh and intertidal mudflat monoliths. The results showed that saltmarsh systems influenced the hydrodynamics within and above the canopy, enhancing turbulence and shear stresses. With increasing flow velocities (≤ 0.51 m s −1 ), negligible quantities (2 × 10 −4 mg L −1 ) of sediments and Bakelite particles were eroded and resuspended. The algal biogenic roughness from the mudflat, and the vegetative roughness from the Spartina plants on the saltmarsh, inhibited the transportation of the microplastics within the tested systems. Resident burrowing crabs (Carcinus maenas) promoted the burial, release and transport of microplastics. The results of this study provide evidence of the contributory roles of saltmarsh systems in the sequestration of microplastics and sediment stabilization. Estuarine saltmarsh systems can act as sinks for microplastics with enhanced burial from burrowing crabs under favourable flow conditions. Vegetated intertidal habitats provide diverse support to natural, coastal and estuarine systems and valuable ecosystem services including protection against coastal hazards, regulation of contaminants and pathogens, and provision of habitats for macrobenthos such as bivalves, fishes, gastropods, crustaceans, and other invertebrates [1][2][3][4] . The positive contribution of coastal vegetated habitats to shoreline protection 5 is partly attributed to the combined inputs of the flora and fauna which occupy these habitats. The flora provide an enhanced biogeneic roughness which reduces the hydrodynamic shear stress 6-8 thus decreasing the erosion rate and prompting accumulation/ deposition of sediments. Meanwhile, the fauna offer biostabilization of the sediments through the secretion of biopolymers 9 , generation of armoured surfaces and other mechanisms that minimize the risk of erosion 10,11 . Mangroves, saltmarshes, seagrasses and reed beds occupy most estuarine coastlines that provide these biomorphodynamic and bioengineering functions 3,12,13 . Benthic organisms...