Cruise report from R/V Svea week 28, 2020

Type: Report
Author: Anna-Kerstin Thell


The surface water temperature varied between 12.5-17.3 °C, which is lower than normal for the season. The salinity in the surface in the Baltic Proper was above normal at all stations visited.   Dissolved inorganic nitrogen in the surface water was below detection limit from the surface to 2040 m at most every visited station, which is normal for the season. Phosphate levels were normal for the season in all sea areas. The silicate levels were above normal in the Baltic Proper except in the Western Gotland Basin and at BY20 Fårö Depth were the levels were normal. In the Kattegat the silicate levels were normal to below normal and in the Skagerrak measured normal levels.  

The oxygen situation in the Baltic Sea continues to be severe. Completely oxygen-free conditions, when toxic hydrogen sulphide is formed, were found in the Western Gotland Basin from 80 meters deep and in the Eastern Gotland Basin from 125 meters deep. Acute oxygen deficiency (<2 ml/l) was found from 60-75 meters depth throughout the area. At BY1 in Arkona the oxygen level has decreased to the limit for acute oxygen deficiency, 2ml/l. The oxygen situation was good in the Skagerrak and Kattegat.