Cruise report from R/V Svea week 2-3, 2020

Type: Report
Author: Karin Wesslander


The surface temperature in January was above normal at all stations and varied between 7.5°C in the Skagerak and 5.4°C in the Baltic Proper. At the west coast, the pycnocline was observed at 15 – 20 meters and in the Baltic Proper the surface water was well mixed down to 25 – 70 meters, shallowest in the Arkona Basin and deepest in the Northern Gotland Basin.

The levels of nutrients in the surface water (0-10 m) had increased since last month. The concentration of phosphate was normal at all stations and the dissolved inorganic nitrogen was below normal in the off shore Skagerak as well as parts of the Baltic Proper. Concentrations of silicate were lower than normal in the Kattegat and the Sound and above normal in the Eastern Gotland Basin.

The oxygen condition in the Arkona Basin was normal and without oxygen deficit. The Bornholm Basin was anoxic in December and hypoxia was noted at the bottom, but now in January the bottom concentration of oxygen had increased to 4.7 ml/l, probably as a consequence of the inflow in December. In the Eastern- and Northern Gotland Basin anoxia was noted from 60 – 70 meters. In the southern part of the Eastern Gotland Basin, at BCS III-10, the concentration of oxygen was 2.8 ml/l at the bottom, which is also probably because of the inflow in December. At the station BY15, it was low oxygen levels, about 0.5 ml/l, from 70 to 150 meters and below 150 meters hydrogen sulphide was present. At the more northern station BY20, hypoxia was noted already from 80 meters.