Summary
As part of the Swedish pelagic monitoring program, the cruise visited the Skagerrak, Kattegat, Öresund, and the Baltic Proper.
The cooling of surface waters had begun, with temperatures ranging between 11–13°C, which is normal for the season.
Nutrient levels were relatively normal in the Skagerrak and Kattegat.
In the northern parts of the Baltic Proper (BY31), higher-than-normal levels of DIN were observed. These areas are typically influenced by a southward current carrying outflowing water from the Bothnian Sea.
The concentration of phosphate in surface waters was normal for the season, except in the southern part of the Western Gotland Basin (BY38), northwestern Baltic Proper (BY31), and BY20 in the Eastern Gotland Basin. Concentrations ranged from 0.2–0.5 µmol/l.
Acute oxygen deficiency, defined as oxygen levels below 2 ml/l, was observed from 70 meters depth in the Eastern and Western Gotland Basin. In the Hanö Bight and Bornholm Basin, oxygen deficiency occurred at shallower depths of 60 meters. In the Arkona Basin (BY2), acute oxygen deficiency was present near the bottom, while further west at BY1, oxygen levels were just above 4 ml/l, bordering on oxygen deficiency.
Hydrogen sulphide was detected from 80 meters depth in both the Western and Eastern Gotland Basin. Vertical profiles also showed that hydrogen sulphide levels, represented as negative oxygen, were significantly above normal in deep waters at many stations. In the Gotland Deep, hydrogen sulphide levels near the bottom were at a record high of 240 µmol/l.
The next routine cruise is scheduled to begin on November 8th.