Cruise report from R/V Svea week 45-46, 2024

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 surface water temperature at most stations was above normal for the month, ranging between 11–12 °C in the Skagerrak and Kattegat and 8–11 °C in the Baltic Proper. The concentration of dissolved inorganic nitrogen (DIN) in the surface water was normal in the Skagerrak and Kattegat but mostly below normal in the Baltic Proper. Phosphate and silicate levels were mostly normal.

The oxygen concentration in the bottom water was normal in the Skagerrak (3.5–5.6 ml/l) but below normal in the Kattegat (3.4–4.2 ml/l). In the Arkona Basin, the oxygen situation in the bottom water was good, with concentrations around 4–5 ml/l. In the Bornholm Basin and Hanö Bight, acute oxygen deficiency (<2 ml/l) was observed from 70 meters depth, and bottom water oxygen concentrations were only 0.1–0.3 ml/l. At station BCS III-10, the oxygen concentration in the bottom water was 1.2 ml/l, which is normal, while at station BY10, the concentration was 0.7 ml/l, which is above normal. In other parts of the Eastern Gotland Basin, hydrogen sulphide was detected from 90 meters depth, and acute oxygen deficiency was observed from 75 meters depth. In the Western Gotland Basin, hydrogen sulphide was detected from 60–80 meters depth, and acute oxygen deficiency occurred from 55–65 meters depth.

The next expedition with R/V Svea is scheduled to start on December 5 in Kalmar, during which nutrient mapping in the Gulf of Bothnia will also be conducted.