Summary
An early spring bloom occurred in the Skagerrak and Kattegat, resulting in low nutrient concentrations at the surface. In the Baltic Proper, the spring bloom had not started and nutrient concentrations were normal, with the exception of phosphate which was higher than normal. Surface water temperature was normal throughout most of the area. Water below the halocline in the Arkona Basin was well oxygenated with levels of ca. 6 ml/l. Water was flowing in at the bottom in the western part of the Bornholm Basin and in the south of the eastern Gotland Basin, giving oxygen concentrations above 3 ml/l in the Bornholm Basin and 2.5 ml/l in the southern East Gotland Basin. In the rest of the Baltic Sea oxygen concentrations below 2 ml/l were observed at depths exceeding 70 to 80 metres. Hydrogen sulphide was found deeper than 90-100 metres in the Western Gotland Basin. At most stations in the northern and eastern Gotland Basins, it began at depths between 125 and 150 metres.