Cruise report from R/V Svea week 28, 2023

Type: Report
Author: Helena Björnberg


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.

Sea surface temperatures were found to be within normal range at all visited areas, with values between 15 - 18℃. Likewise, surface salinity was observed to be within normal range at all sampling points, with the exception of the south Baltic Proper, where sea surface salinity was slightly above normal. Dissolved inorganic nitrogen and phosphorus displayed low concentrations, which is normal for the season. The silicate levels in all sampled areas were within normal range for the season.

The oxygen conditions in the Baltic Proper continues to be critical. At the majority of stations, anoxic conditions occurred from a depth of 80 meters. At these sampling points, hydrogen sulphide could also be measured. The levels of nutrients in the bottom waters of the Baltic also reflected the oxygen deficiency, with values above normal, and levels that increased as the oxygen had been depleted in the water column. In the Arkona basin, the oxygen situation was somewhat better, with bottom water values between 2,33 – 3,33 ml/l.

Surface accumulations of cyanobacteria could be observed to some extent. Wind before the cruise had temporarily mixed down the accumulations from the surface. Despite this, microscopy that was carried out throughout the cruise could identify a few different species of cyanobacteria that are currently blooming in the Baltic. More information about the algal situation can be found in the AlgAware-report for July (

The next regular monitoring cruise carried out by SMHI on board R/V Svea is planned between 10th – 16th of August, starting and finishing in Lysekil.