Subproject P2 will study the rates of oxic and anoxic respiratory processes as a function of temporal fluctuations and spatial, physical and chemical heterogeneities. We hypothesize that the heterogeneous distribution of particulate and dissolved organic matter lead to heterogeneities in metabolic rates within the dynamic STE, and that spatial zonation of metabolic processes is further complicated by the co-occurrence of multiple metabolisms, particularly at dynamic boundaries. We will experimentally determine the respiration rates of oxic and anoxic processes and their responses to heterogeneous organic matter distribution, porewater velocities and redox conditions driven by changes in beach morphodynamics and subsurface flow. Scientific drilling, multi-level observation wells, direct push and manual coring will enable collection of undisturbed sediment cores and porewaters on which we will carry out rate measurements of respiratory metabolisms by combining incubation experiments with sophisticated oxygen sensing, chemical analytics, and isotope labelling techniques. Respiratory metabolisms of microorganisms impact nutrient, trace metal and redox conditions in sediments, as well as driving the transformation and turnover of organic matter. Thereby, we will provide information on the distribution, reaction rates, overlaps of respiratory metabolisms throughout the STE, as well as assessing the impact of changing boundary conditions on these parameters. This knowledge is essential to interpret the results in P3-P5 and will provide critical details to modelling approaches in P6, allowing DynaDeep to describe the functioning of the dynamic STE.