In addition to data collection by the logger units, nutrients are measured at 23 locations. Sampling occurs every 14 days at each site. Samples are taken from a water depth of approximately 0.5 meters, filtered (filter size 40 µm), and cooled for further transport. Furthermore, on the sampling day, salinity and temperature are measured at the respective locations using the WTW Cond 3110. After each tour, the water samples are frozen at -20 °C at GEOMAR for later analysis. Since 2020/2021, the analyses have been conducted by Research Area 3: Marine Ecology, FE Experimental Ecology. GEOMAR, Kiel. The samples are analyzed for the concentration of dissolved inorganic nutrients (total oxidized nitrogen, nitrite, ammonium, phosphate and silicate) by UV/VIS spectroscopy using a continuous flow analyzer (type QuAAtro 30; comp. SEAL Analytical, Hamburg, Germany, equipped with a SEAL XY-2 autosampler). Quality control for nutrient measurements is ensured by certified reference material (CRM) by KANSO TECHNOS CO, LTD, Osaka, Japan. Standard analysis methods developed by SEAL Analytical were followed.

Temperature and salinity were measured druing collection of the watersample.