Cruise report from R/V Aranda week 33-34, 2019

Type: Report
Author: Karin Wesslander


The surface temperature was normal for the season and varied between 17-19 °C. Windy weather had mixed the warmer surface water in Skagerrak down to 60 meters and the thermocline was partly broken or deeper. The thermocline was observed at 15-20 meters in the rest of the area.
The nutrient concentrations were low, as is normal in the summer. The dissolved inorganic nitrogen was depleted down to the halocline both at the West coast and in the Baltic Proper while phosphate remained in the surface water, although at low levels. 
Acute hypoxia (< 2ml/l) was noted from 70 meters in the Baltic Proper. In the Bornholm Basin and in the southern part of the Eastern Gotland Basin low concentrations of hydrogen sulphide was measured near the bottom. The deepest part of the Eastern Gotland Basin, BY15, was oxygen depleted from 150 meters and high concentrations of hydrogen sulphide was observed. At station BY20, north of BY15, hydrogen sulphide was noted at 80 meters and below it was low concentrations of oxygen (0.3 ml/l) down to 125 meters where again hydrogen sulphide was present. In the Western Gotland Basin hydrogen sulphide was noted from 80 meters.