Summary
During the expedition, which is part of the Swedish national marine monitoring programme, the Skagerrak, the Kattegat, the Sound and the Baltic Proper were visited.
The expedition was a collaboration with Stockholm University, and in addition to SMHI's regular sampling, bottom sediment grabs were made at several positions distributed in four major areas, see the route map.
Concentration of nutrients in the form of dissolved inorganic phosphorus (phosphate) and dissolved inorganic nitrogen in the surface water were, with few exceptions, normal in visited sea areas. For silicon in the form of silicate, levels in the Baltic Proper were normal, while in the Skagerrak, the Kattegat and the Sound levels were above or slightly above normal. In the deep water, it is mainly the deeper stations in the Baltic Proper, for example BY15 and BY32, that have very high levels of nutrients in the form of dissolved inorganic nitrogen and silicate.
The oxygen situation in the Skagerrak, the Kattegat and the Sound, as well as the Arkona Basin, was good. In the other basins in the Baltic Proper, acute oxygen deficiency (<2 ml/l) was measured at a depth of 70 meters. At BY32 in the Western Gotland Basin, hydrogen sulfide was found at a depth of 70 meters, and in the Eastern Gotland Basin, hydrogen sulfide was present at a depth of 90 meters. At several stations, levels of hydrogen sulfide were above normal.