2014-2019: Since September 2014, temperature, salinity, pH (only 2014-2015) and oxygen data were additionally logged in 10-minutes intervals at the GEOMAR pier (54°19'48.8N 10°08'59.6E) (AANDERAA oxygen sensor 3835 & SEABIRD SBE 37-SI MicroCAT CT(D)). The sensor system is mounted to a floating platform so that a continuous depth of 1 m is guaranteed at every time point. Oxygen data were corrected for salinity, temperature and depth following the manual for Aanderaa Optodes using the salinity and temperature measurements from the SEABIRD SBE 37-SI MicroCAT CT(D) sensor. pH was also corrected for salinity, temperature and depth following Martz et al. (2010). After cleaning and other re-boots of the sensor package, temperature, salinity and oxygen data tend to deviate from true values. Hence, 60 minutes of data after any re-boot (after sensor servicing with re-deployment, data download or power failure) were deleted. Furthermore, salinity data lower than 8 and pH data lower than 5 and larger than 10 were removed from the data set as these values were identified as outliers. On May 22nd 2018 as well as on May 26th (22:00) til 27th (15:00) 2019 oxygen data were identified as outliers and removed from the data set. The logged oxygen data were plotted against titration data (doi:10.1594/PANGAEA.930974) to check for drifts in the optode's data. But no drift pattern could be detected and the fit of the regression was very good R2adj. = 0.673, p < 0.001)