Summary
Nutrient concentrations were, with few exceptions, normal throughout the investigated area. In the western part of the Arkona Basin the water below the halocline was well oxygenated with levels exceeding 4 ml/l. In the rest of the Baltic Proper oxygen concentrations below 2 ml/l were observed at depths exceeding 70 to 80 meters. In the West Gotland Basin and Northern Baltic Proper, hydrogen sulphide was found below 70-90 metres. In the East Gotland Basin hydrogen sulphide began at depths between 125 and 150 metres. A plankton bloom was in progress at intermediate depths in the Kattegat. Phytoplankton activity was relatively low in the remainder of the area.