Cruise report from R/V Svea week 6-7, 2022

Type: Report
Author: Lena Viktorsson


During the cruise, which is part of the Swedish pelagic surveillance program, the Skagerrak, the Kattegat, the Sound and the southern parts of the Baltic Proper were visited. In the Baltic Proper, nutrient mapping was carried out.

The temperature in the surface water was above normal for the month, except in the Northern Baltic Proper and the Western Gotland Basin. The surface temperature varied from just below 3 degrees in the entrance of the Gulf of Finland to just above 6 degrees in the Skagerrak.

The concentrations of nutrients in the surface water had increased slightly since January and were now approaching winter maxima. Nutrient levels were normal in the Skagerrak and Kattegat. In the Baltic Proper, where mapping of nutrients was carried out, the levels of phosphate and dissolved inorganic nitrogen were normal at most stations, while the levels of silicon were above normal at most stations.

The oxygen situation in the Kattegat's deep water was good, no oxygen deficiency, i.e. levels below 4 ml/l, were found. The oxygen situation in the Baltic Proper is still poor with acute oxygen deficiency (<2 ml/l) from 60–80 m. In the basins around Gotland, hydrogen sulphide was measured from 80–100 m. In the Bornholm Basin, the bottom water was anoxic and hydrogen sulphide was measured from a depth of 80 m. In the Bornholm Basin, the bottom water was anoxic with low concentrations of hydrogen sulphide, while no hydrogen sulphide was measured in Hanö Bay, but the oxygen concentration in the bottom water is close to zero. In Gdansk Bay, there was acute oxygen deficiency from 80 m, but no hydrogen sulphide was measured. No oxygen deficiency was measured in the Arkona basin.