Salt marshes are valuable but complex biophysical systems with associated ecosystems. This presents numerous challenges when trying to understand and predict their behaviour and evolution, which is essential to facilitate their continued and sustainable use, conservation and management1. Detailed understanding of the hydrodynamics, sediment dynamics, and ecology that control the system is required, as well as their numerous interactions2,3, but is complicated by spatial and temporal heterogeneity at a range of scales4,5. These complex interactions and feedbacks between the physical, biological, and chemical processes can be investigated in situ following natural, unintentional, or intentional manipulation6, but the mechanistic basis of any observations are confounded by the presence of collinear variables. Hence, laboratory investigations can be beneficial, as they provide the opportunity for systematic testing of subsets of coastal processes, mechanisms, or conditions typical of salt marsh systems, in the absence of confounding variables. With appropriate scaling, this allows a better understanding of the overall function of the salt marsh, and better predictions of their evolution.