Summary
During the cruise, which is part of the Swedish pelagic surveillance program, the Skagerrak, the Kattegat, the Sound and the southern parts of the Baltic Proper were visited. In the Kattegat, nutrient mapping was carried out.
When R/V Svea approached the Bornholm Basin, a crew member fell ill with confirmed covid-19 and it was decided that the cruise would be interrupted and that R/V Svea would go home, but that the stations on the way home could be sampled provided no more fell ill or the crew member became acutely worse. A total of 11 stations in the Baltic Proper were cancelled, but all stations in the Skagerrak and Kattegat as well as the nutrient mapping stations in the Kattegat could be sampled as planned.
The concentrations of nutrients in the surface water had increased slightly further since December and were now approaching winter maxima. The content of dissolved inorganic nitrogen and phosphorus was lower than normal in the south-western and eastern parts of the Kattegat. The silicate content was normal for the season in the entire area except at the coastal station N14 and in the Sound at W Landskrona and Öresund-2 where higher than normal levels were noted. In the deep water, levels were generally lower than normal in the north-eastern parts of the Kattegat. In the southwestern part, dissolved inorganic nitrogen was lower than normal, while phosphate and silicate showed higher levels than normal in deep water.
The oxygen situation in the Kattegatts deep water was good. No oxygen deficiency, i.e. levels below 4 ml / l, were noted. In the Bornholm Basin, the deep water was oxygen-free and hydrogen sulphide was measured from a depth of 80 meters. In Hanö Bight, there were still measurable concentrations of oxygen, but very low from 70 meters and downwards. Acute oxygen deficiency was noted at a depth of 60 meters. No oxygen deficiency was measured in the Arkona basin.
The next cruise with Svea begins on January 20, when SLU-Aqua conducts a fishing survey in the North Sea and the Skagerrak and Kattegat. SMHI participates with two persons who will map nutrients in connection with the test fishing. SMHI's next regular cruise is planned for 8–16 February with R/V Svea, when winter mapping of nutrients also will be carried out in the Baltic Proper.