Summary
Nutrient concentrations were normal throughout the investigated area with the exception of silicate, concentrations, which were elevated in the Kattegat. The water below the halocline in the Arkona Basin was well oxygenated with levels of ca. 6 ml/l. In the rest of the Baltic Sea, oxygen concentrations below 2 ml/l were observed at depths exceeding 70 to 80 metres. Hydrogen sulphide was found deeper than 100-125 metres in the Western Gotland Basin. In the eastern Gotland Basin hydrogen sulphide began at depths between 125 and 160 metres. A plankton bloom was ongoing in the Baltic Proper and in the Kattegat. The spring bloom was over in the Skagerrak surface layer, though still in progress in deeper layers.