Summary
During the cruise, which is part of the Swedish pelagic monitoring program, the Skagerrak, the Kattegat, the Sound, and the Baltic Proper were visited.
Surface water temperatures in all sea areas were around normal, between 16–19°C, except at BY39, south of Öland, where it was 9°C, which is below normal.
Dissolved inorganic nitrogen was around the detection limit, 0.1 µmol/l, down to the thermocline, which is normal for this time of year. The surface concentration of phosphate was low and at most stations, it was normal for the season. Silica levels in surface water were above normal at most stations in the Gotland basins, while in the Arkona and Bornholm basins, as well as in the Sound, they were below normal.
In the Arkona Basin, the oxygen concentration in the bottom water had decreased since July and was now just over 2 ml/l. In the Bornholm Basin, the concentration had increased slightly and was now 0.5–0.8 ml/l. At station BCS III-10, the oxygen concentration near the bottom had increased to 1.2 ml/l. In the rest of the Baltic Proper, there was no oxygen in the bottom water.
Acute oxygen deficiency, i.e., oxygen levels less than 2 ml/l, was observed from 70 meters in the Bornholm Basin and in the Eastern Gotland Basin, and in the Western Gotland Basin already from 50 meters. Hydrogen sulfide was measured from 90 meters in the Eastern Gotland Basin and from 60 meters depth in the Western Gotland Basin.
The next regular cruise is scheduled to start on September 14th in Lysekil.