Summary
During the cruise, which is part of the Swedish pelagic monitoring program, the Skagerrak, the Kattegat, the Öresund, and the Baltic Proper were visited.
The surface water temperatures in all sea areas were around normal, between 13.7 – 18.6 ℃, except for BY39 where it was 9.4 ℃, which is below normal.
Dissolved inorganic nitrogen and phosphate in the surface water showed low levels, which is normal for the season. Silicate levels in the surface water were slightly above to above normal at all stations in the Baltic Proper, the Öresund and the southern and coastal stations in the Skagerrak.
In the Baltic Proper, the oxygen situation was still very poor, only in the Arkona Basin and on BY39 good oxygen conditions were found. Acute oxygen deficiency, i.e. oxygen levels less than 2 ml/l, was noted from 55 - 75 meters in the Western and Eastern Gotland Basin, with the exception of the shallow station BY39. Hydrogen sulfide was measured from 70 to 80 meters deep in the Western Gotland Basin and from 80 to 125 meters deep in the Eastern Gotland Basin. In the Bornholm Basin and Hanö Bay, there was an acute oxygen deficiency from a depth of 70 meters, but no hydrogen sulphide in the bottom water
At several stations in the Baltic Proper, high peaks of chlorophyll fluorescence occurred from the surface down to a depth of 15 meters. Surface accumulations of cyanobacteria were noted at stations BY2 and BY4 in the Arkona and Bornholm Basins. More information about the algae situation can be found in the Algaware report for July; https://www.smhi.se/publikationer/publikationer/algrapporter.
The next cruise is planned to start August 10th in Lysekil.