Sammanfattning
The surface nutrient concentrations were still at winter level in the Baltic with the exception of the Bornholm and Arkona basins . The spring bloom had started as was seen from the nitrate and chlorophyll analyses and from measurements of fluorescence. In the northern Kattegat and the southern Skagerrak the spring bloom was more pronounced. The surface water had an oxygen saturation of more than 100%. In the eastern Kattegat nitrate and silicate concentration was below the limit of detection. At P2 , 15-40m, and Fladen, 20-30m, high nitrate values were registered, more than twice the normal level, about 25mmol/l. It is probably water from the southern North Sea, that has been transported into the Skagerrak and the Kattegat. Oxygen concentrations less than 2 ml/l were found from 70m and downwards in the northern and eastern Baltic as well as in the Hanö Bight, from 90m in the western Baltic and from 80m in the southern Baltic. Hydrogen sulphide was observed from 140m in the eastern Gotland Basin.