Cruise report from R/V Svea week 15-16, 2023

Type: Report
Author: Anna-Kerstin Thell


The Skagerrak, the Kattegat, The Sounds and the Baltic Proper was visited during the cruise, as a part of the National Marine Monitoring Programme of Sweden.

Sea surface temperature was within normal range for the season at all visited stations. 

Concentrations of phosphate and dissolved inorganic nitrogen were low across all sampling points, which is considered normal for this time of year. Silicate concentrations in the sea surface was slightly above normal range for the season in the Skagerrak and the Kattegat, and within normal range in the Baltic Proper.

In the Arkona basin, the oxygen levels in the bottom waters was observed to be in good condition. Oxygen levels in the Bornholm basin and the Bay of Hanö had decreased since sampling in the March expedition and hypoxi (oxygen concentration <2 ml/l) occurred in the bottom waters of the Bornholm basin, and below 70 m in the Hanö Bay. Despite the oxygen deficiency, no hydrogen sulphide was recorded at the sampling points.  

At station BCSIII-10, the oxygen levels had improved since sampling in March, and no hydrogen sulphide was detected. Hypoxi could be observed below 80 m. In the Eastern and Western Gotland Basins, oxygen deficiency started occurring around a depth of 70-80 m. Hydrogen sulphide could be observed at a depth of 80 m in the Eastern Gotland Basin, and around 90 m in the Western Gotland Basin.

The next cruise is planned to depart on May 8th from Lysekil.