Summary
During the expedition, which is part of the Swedish pelagic monitoring program, the Skagerrak, the Kattegat, the Sound and the Baltic Proper were visited.
The sunny and calm weather in May led to surface water temperatures increasing by up to 10°C since the previous expedition at stations in the Baltic Proper, and by 5–6°C in the Skagerrak and the Kattegat.
Concentrations of nutrients in the form of dissolved inorganic phosphorus (phosphate) and dissolved inorganic nitrogen in the surface water were, with few exceptions, normal for the season in the sea areas visited. For silicon in the form of silicate, concentrations were above normal in large parts of the Baltic Proper and the Sound, while in the Skagerrak and the Kattegat, normal or slightly below normal concentrations.
In the deep water it is mainly the deeper stations in the Baltic Proper that have concentrations of nutrients above normal, in particular dissolved inorganic nitrogen and silicon. Concentrations of silicon were at some stations in the Baltic Proper above normal at all sampled depth.
The oxygen situation in the Skagerrak and the Kattegat, as well as the Arkona Basin, was good. In Hanö Bay and the Bornholm Basin, as well as at the station in the south-eastern Baltic Proper, acute oxygen deficiency (<2 ml/l) was recorded. In both the Western and Eastern Gotland Basins, acute oxygen deficiency occurred at a depth of 70 meters. And hydrogen sulphide was present at 80 meters in the Western Gotland Basins, and at 90-meters depth in the Eastern Gotland Basins. In several cases, hydrogen sulphide concentrations were above normal.
The next scheduled expedition with the vessel Svea is planned for July 13–19, starting in Falkenberg and ending in Lysekil.