In 2021, the hydrochemistry of surface water was monitored at Helgoland Roads station on every workday, typically before 9 a.m. Temperature was measured on board immediately after sampling. Visibility was measured immediately on board using a Secchi Disk. Salinity, dissolved inorganic nutrients, pH and oxygen were measured from a bucket sample in the laboratory. Further information regarding the methodology and the devices used can be found in the metadata description.