Temperature, salinity and fluorescence (biological activity) at 4m depth were registered continuously throughout the expedition. Over great areas in the Southern Baltic and West Gotland a strong bloom of mainly bluegreen algae was observed. In the Bay of Gdansk the biological activity was even higher than in the surrounding sea. The biological activity around the Swedish south coast and in the Sound increased significantly during the duration of the cruise. In the Western Gotland Basin and in the Bornholm Basin bottom oxygen concentration was below 0.5 ml/l, a decrease since the latest measurements in June. Hydrogensulphide was found in the Eastern Gotland Basin at stations BY20 and BY15 from approximately 175m and downwards. The investigations in the Bay of Gdansk showed that the overflow water remained in the inner parts of the bay. The only elevated nutrient concentrations were registered at the surface in the southern part of the bay. An area of upwelling, with surface temperatures down to 8°C, was found west of the Bay of Gdansk.