Cruise report from R/V Svea week 32-33, 2023

Type: Report
Author: Karin Wesslander


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 water temperature in the surface water varied between 10 – 17°C which is low for the season and at several stations it had decreased from last month.

Levels of dissolved inorganic nitrogen in the surface water were around the detection limit in all basins. The phosphate concentration was also low, which is normal this time of year, but in some places, it was above normal, such as in the Bornholm Basin and the Kattegat. The concentration of silicate was normal except in the Bornholm Basin and the Kattegat where it was above normal.

The oxygen situation in the Arkona Basin was normal and as low as 2.9 ml/l in the bottom water, no hydrogen sulphide was measured. In the Bornholm Basin and Hanö Bay, acute oxygen deficiency (<2 ml/l) was noted from 70 m with low oxygen levels around 0.1 ml/l in the bottom water, but no hydrogen sulphide. In the Eastern Gotland Basin, the acute oxygen deficiency began at a depth of 70 meters and hydrogen sulphide was noted from 80 m. In the Western Gotland Basin, acute oxygen deficiency and also hydrogen sulphide were measured already from 60 m. At the southern tip of Öland, there was an acute oxygen deficiency from 50 meters, which is a deterioration from last month.

The next regular monitoring cruise carried out by SMHI on board R/V Svea is planned to begin the 15th September from Gothenburg.