Cruise report from R/V Svea week 46, 2023

Type: Report
Author: Karin Wesslander


During the cruise, which is part of the Swedish pelagic monitoring program, the Skagerrak, the Kattegat, the Sound and the Baltic Proper were visited.

The temperature in the surface water had decreased slightly since the last cruise and was now 8–12 °C. This is normal for the time of year except in the East Gotland Basin where it was warmer than normal. The surface salinity was normal along the Swedish west coast and higher than normal in large parts of the Baltic Proper.

The concentration of nutrients has now increased at most stations, which is normal for the time of year. In the Kattegat, the concentration of DIN was still low, but still within the normal range. In the Sound, all nutrients were above normal in the surface. Because of the storm Babet in October, the surface water was mixed and the concentration of nutrients increased significantly in the surface water in the Baltic Proper. Now in November, the concentrations at several stations had decreased, but they were still above normal at some stations.

In the Arkona Basin, the oxygen concentration closest to the bottom was 5.1 ml/l at BY1 and 3.3 ml/l at BY2. In the Bornholm Basin, hydrogen sulphide was measured closest to the bottom and there was an acute lack of oxygen (<2 ml/l) from 70 meters. In Hanö Bay, the oxygen concentration was close to zero at the bottom. At station BCSIII-10 in the south-east of the Baltic Proper, there was no hydrogen sulphide at the bottom, just like in October, but an acute lack of oxygen started at 60 metres. In the Eastern Gotland Basin, there was a lack of oxygen (<4 ml/l) from 60 m and an acute lack of oxygen from 65 m. In the Western Gotland Basin, there was a lack of oxygen already from 45 m and an acute lack of oxygen from 55 m.

The next regular cruise is planned to start on December 5, and mapping of nutrient will be done in the Gulf of Bothnia. The expedition starts in Kalmar, has a shift change in Gävle and ends in Lysekil.