The temperature and nutrient concentrations in the surface layer, were normal for the season in all areas. The spring bloom of phytoplankton had terminated in most of the areas covered. Only in the east part of the Baltic proper it was still going on. Hydrogen sulphide was present at depths greater than 125 metres in the eastern andwestern Gotland Basins. Oxygen concetrations below 2 ml/l was found at depths greater than 80 metres in the whole Baltic Proper.