Cruise report from M/V Meri week 11-12, 2018

Type: Report
Author: Martin Hansson


Due to the rough and cold weather and the resulting icing situation, the central parts of the Baltic Proper could not be visited. During the cruise, which is part of the Swedish pelagic monitoring programme, the Skagerrak, the Kattegat, the Sound, the Arkona Basin, the Bornholm Basin, the Hanö Bight and the Kalmarsund was visited.

The spring bloom in the Skagerrak and the Kattegat was ongoing, which was noted with high fluorescence peaks noted from the CTD probe and low nutrient concentrations in the surface water. In the visited parts of the Baltic Proper there were still winter conditions. For more information on species composition see separate algae report "AlgAware". Nutrients in the form of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) in the surface layer were generally at normal levels throughout the investigated area. The silicate concentrations in the southern Baltic Proper were still much higher than normal.

In the bottom water of the Hanö Bight and the Bornholm Basin, oxygen levels were found close to 0 ml/l. Acute oxygen deficiency (<2 ml/l) was found here from 65-70 meters deep. In the Skagerrak, oxygen concentrations were noted that were lower than normal. However, the concentrations in the deep water ranged between 5-6 ml/l which is above the limit of acute oxygen deficiency. In the Sound, low oxygen levels were also observed near the bottom, just under 3 ml/l.