Cruise report from R/V Aranda week 11-12, 2016

Type: Report
Author: Karin Wesslander


The temperature in the surface water was above normal in the Baltic Proper. The spring bloom had started in the Skagerrak, Kattegat and in the south western parts of Baltic Proper. Inorganic nitrogen was completely exhausted down to 10 meters in the south western parts of Baltic Proper. The concentration of phosphate in the Baltic Proper surface water, that has previously been elevated, had now decreased to normal values for the season. Concentrations of silicate were however still elevated in the Western- and Eastern Gotland Basin. At the Gotland Deep, no hydrogen sulphide was measured in the deep water but very low concentrations of oxygen were observed; only 1.02 ml/l was observed at 225 meters which is a decrease with 0.5 ml/l since February. In the Western Gotland Basin, anoxic conditions occurred at depths exceeding 90 meters. In the Hanö Bight, acute hypoxia was observed nearest the bottom. Bottom water with high oxygen levels was observed at the south western and southern parts of the Baltic Proper.