Sedimentation rates of microplastics can be influenced by the complex and dynamic nature in estuaries which show variable conditions (high turn-over) and strong gradients of physicochemical (salinity, temperature, pH, etc.) and biological parameters . As items of plastics travel along waterways, they become colonized by algae and bacteria creating biofilms. This biofouling can affect the density of particles, causing them to sink faster. Another factor that can affect the biofouling and sinking of particles is salinity . Factors such as the hydrology of the surrounding estuary, wind, tidal regimes and sedimentation rates, which are beyond the scope of this study may also play an important role in the movement and transport of microplastics . The removal of biofilms caused by disturbances (bioturbation, wave action, tidal movement) of the upper surface of the benthos also affects the vertical migration of microplastics altering the rates of sedimentation, resuspension and removal of particles.