Cruise report from R/V Svea week 2, 2023

Type: Report
Author: Madeleine Nilsson


During the expedition, which is part of the Swedish pelagic monitoring program, the Skagerrak, Kattegat, the Sound and the Baltic Sea were visited. In the Kattegat, the annual mapping of nutrients was also carried out.

Despite bad weather during most of the expedition, 37 out of 41 planned stations could be visited. Two stations in the Western Gotland Basin and one of the mapping stations had to be cancelled. Neither could reference measurement at Flinten 7 be carried out. The bad weather also affected the possibilities of using the MVP and therefore relatively few measurements were made with it. Svea's ferry box and ADCP were running during almost the entire expedition.

Nutrient concentrations in the surface water remained at high winter levels in the Skagerrak, a slight decrease in silicate was noted but levels were still within, or just below normal for the month. In the Kattegat, the levels of nutrients in the surface water were somewhat low for the month. The surface water of the Baltic Sea continued to show high levels of nutrients overall, but in the eastern (BY15 and BY20) and northern Baltic Sea (BY31) the levels of dissolved inorganic nitrogen were lower than normal for the month.

The oxygen situation in the deep waters of the Kattegat and Skagerrak was good, no oxygen deficiency/hypoxia (< 4 ml/l) was noted. In the Bornholm Basin and Hanö Bay, there was a severe lack of oxygen (< 2 ml/l) from a depth of approx. 60 – 70 meters, but no hydrogen sulphide was measured. There was no oxygen deficiency in the Arkona Basin. In the eastern and western Gotland basins, the oxygen situation was still poor, with a lack of oxygen from a depth of 60 – 70 m. Hydrogen sulphide was present from 80 m and the levels in the bottom waters were high above normal.

The next expedition with R/V Svea is planned for January 23 - February 6, when SLU-Aqua will carry out fishing survey in the North Sea, Kattegat and Skagerrak, SMHI will participate with two people to carry out nutrient mapping. Mapping of nutrients in the Baltic Sea will take place 8 – 16 February during SMHI's regular expedition with R/V Svea.