Data presented here were collected between January 2022 to November 2022 within the research unit DynaCom (Spatial community ecology in highly dynamic landscapes: From island biogeography to metaecosystems) of the Universities of Oldenburg, Göttingen, and Münster, the iDiv Leipzig and the Nationalpark Niedersächsisches Wattenmeer. Experimental islands and saltmarsh enclosed plots were created in the back barrier tidal flat and in the saltmarsh zone of the island of Spiekeroog. Sediment samples for the determination of pH, water content and loss on ignition were taken bi-/monthly in surface sediments (0-3 cm depth) from the experimental plots. Samples were stored dark and cool (8°C) until measurement. Samples were measured in the laboratory within two months after sampling. Water content (w, [-]) was determined by first weighing the fresh sample (mf; ~ 3-7 g) in pre-weighed aluminium trays and than placed in the drying chamber at 105 °C for 12 hours. After placing samples in the exsiccator for 60 min., samples were re-weight to determine dry weight (md). Water content was calculated using w = (mf - md) / md . Afterwards, samples were placed in the muffle furnace for 2 hours at 430 °C within their aluminium trays, and placed again in the exsiccator for 60 min. Samples were re-weighed to determine the new dry weight (mgl) to calculate loss on ignition (LOI, [%]) using LOI = ((md – mgl) / md ) * 100 . Values of pH were measured according to DIN ISO 10390. Therefore, soil samples were weighed in pre-weighed Falcon™ 50 mL conical centrifuge tubes. Sediment samples were homogenized using a pestle. Ultrapure water was used to measure pH directly within the tubes using a HQ40D digital two channel multi meter and an Intellical PHC101 field low maintenance gel filled pH electrode (Hach Lange GmbH, Germany). The pH electrode was calibrated before measurement using singlet pH buffer sets (pH 4.01, 7.00, 10.01) for single use (Hach Lange GmbH, Germany). Post-processing of measured values were done using MATLAB (R2018a). Quality control was performed by (a) removing outliers, (b) visually checks, and hence (c) the classification into quality control flags using quality check algorithms.