Field experiments investigating biodiversity and ecosystem functioning require observation of abiotic parameters, especially when carried out in the intertidal zone. An experiment for biodiversity-ecosystem functioning at the intersection of land and sea was set up in the intertidal zone of the back-barrier salt marsh of Spiekeroog Island in the German Bight. Here we report the accompanying instrumentation, maintenance, data acquisition, data handling and data quality control as well as monitoring results observed over a continuous period from September 2014 through April 2017. Time series of abiotic conditions were measured at several sites in the vicinity of newly built experimental "salt-marsh islands" on the tidal flat. Meteorological measurements were conducted from a weather station (WS, doi: 10.1594/PANGAEA.870988 ), oceanographic conditions were sampled through a bottom mounted recording current meter (RCM, doi: 10.1594/PANGAEA.877265 ) and a bottom mounted tide and wave recorder (TWR, doi: 10.1594/PANGAEA.877258 ). Tide data are essential to calculate flooding duration and flooding frequency with respect to different salt marsh elevation zones. Data loggers (DL) for measuring water level (DL-W, doi: 10.1594/PANGAEA.877267 ), temperature (DL-T, doi: 10.1594/PANGAEA.877257 ), light intensity (DL-L, doi: 10.1594/PANGAEA.877256 ) and conductivity (DL-C, doi: 10.1594/PANGAEA.877266 ) were deployed at different elevational zones within the experimental islands and the investigated salt marsh plots.