In the Kattegat phytoplankton sampling according to BMP was performed. Maxima of fluorescence were seen in the Kattegat below the halocline at about 20 m and in the Sound at about 10 m. Almost all over the area there were low concentrations of phosphate and depletion of nitrite and nitrate. Hydrogen sulphide was found in the Bornholm Basin and in the East Gotland Basin. At the Gotland Deep it had extended to 190 m. In the Skagerrak near the Danish coast (HS5) there was low oxygen saturation in the surface water (79%). The water had a lower temperature (9.35 degrees C) than the rest of the Skagerrak (13.5 degrees C), which indicated an event of upwelling.