Cruise report from R/V Aranda week 42, 2019

Type: Report
Author: Lena Viktorsson


The surface temperature was normal for the season and varied between 10-14 ° C, much colder than in the previous expedition in September. A thermocline still existed in the Baltic Sea at about 30 m depth, about 15 m depth in the Kattegat and in the Skagerrack almost no thermocline was left. The salinity in the surface water (0-10 m) was higher than normal in the Skagerrack and the southern Baltic Sea.
The levels of nutrients in the surface water (0-10 m) were still low after the summer. Dissolved inorganic nitrogen was lower than normal at several stations in the Baltic Sea, especially in the southern parts. Phosphate was mostly normal except for the Eastern Gotland Basin, the Sound and the outermost Skagerack where it was lower than normal. Silicon levels were lower than normal in the Skagerrack and Kattegat and above normal at most stations in the Baltic Sea. 
In the Western Gotland Basin, the water was completely anoxic from 70-80 m depth and acute oxygen deficiency (<2 ml / l) was measured at 60 m depth, which is significantly lower than normal at this depth. Hydrogen sulphide was also measured at 70-80 m depth in the Eastern Gotland Basin, but oxygen was also measured below it, and hydrogen sulphide did not increase significantly until at about 130 m. In the Bornholm Basin there was an oxygen deficiency from 80 m and hydrogen sulphide was measured near the bottom in the Bornholm deep. In the Arkona Basin, acute oxygen deficiency was measured only closest to the bottom.
The station RefM1V1 south of Öland had to be cancelled.