It is well-known that opportunistic macroalgae starts to drift at low current velocities (Flindt et al. 2007) and that the nutrient transport in many aquatic systems are dominated by this process. New studies have shown, that at this current velocities, macroalgae moves as bedload transport creating sediment resuspension. Thresholds of sediment stability are very depending on light availability, due to most of the stability is created by benthic diatom production (Lundkvist et al. 2007). Depending on light and nutrient avaliability the sediment stability thresholds may increase by a factor of 2-3 and hereby becomes the magnitude of sediment transport dependent on the activities of the benthic diatoms. Therefore, the aim of this study was to create a dynamic model, which simulates the sediment resuspension at low free stream velocities (5-15 cm s-1), created by different densities of macroalgae movements in cohesive sediments with different development of sediment stability. Results of simulations shows, that the amount of suspended matter is highly dependent both on the algal densities and the current velocities. The results obtained by the model, appear to be consistent with the ones obtained by flume experiments and field observations in protected and semi-protected shallow estuarine waters.