The coastal areas of the Baltic Sea represent highly variable environments. In order to record the environmental conditions in shallow water habitats of the SW Baltic Sea, a monitoring program was established. The monitoring sites are located along the Baltic Sea coast of Schleswig-Holstein, Germany. Thirteen stations were established, with samplings for dissolved inorganic nutrient concentrations at all stations and continuous recordings of environmental parameters (temperature, salinity, dissolved oxygen) at nine stations, respectively.
Twice per month water samples were collected from a water depth of 1 m at all stations. The samples were analyzed for the concentration of dissolved inorganic nutrients (total oxidized nitrogen, nitrite, ammonia, phosphate and silicate) by UV/VIS spectroscopy using a Continuous Flow Analyzer (San++ Automated Wet Chemistry Analyzer, Skalar Analytical B.V.).
For continuous recordings of temperature, salinity and dissolved oxygen concentrations, self-contained data loggers were deployed at 2.5 m depth. Two types of data loggers were used in this study: (I) MiniDOT loggers (Precision Measurement Engineering; http://pme.com; ±10 µmol L-1 or ±5 % saturation) including antifouling copper option (copper plate and mesh) to measure dissolved oxygen concentration and (II) DST CT salinity & temperature loggers (Star-Oddi; http://star-oddi.com; ±1.5 mS cm-1) recorded the conductivity. Both sensors additionally recorded water temperature with an accuracy of ± 0.1 °C. The sampling interval was set to 10 minutes for all parameters.
The data for dissolved oxygen concentration was corrected for a depth of 2.5 m using the software provided by the manufacturer. Additionally, a manual compensation for salinity was calculated (see details in related article). Quality control was carried out by implementing spike and gradient tests, following recommendations of SeaDataNet quality control procedures (see https://seadatanet.org/Standards/Data-Quality-Control). All data values were flagged according to applied quality checks using the following flags: 1 = Pass, 2 = Suspect, 3 = Fail, 4 = Visually suspect, 5 = Salinity compensation fail (further explanations can be found in related article). Please note that for station 6 no data for temperature, salinity and dissolved oxygen concentration are available, since the complete logger station failed.
