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.