Cruise report from R/V Aranda week 1-2, 2017

Type: Report
Author: Karin Wesslander


In large parts of the deep water in the Baltic Proper the oxygen concentrations were close to 0 ml/l and the concentrations of hydrogen sulphide were lower than the expedition in December. In the northern part of the Western Gotland Basin (BY31) hydrogen sulphide was found from 175 meters, and in the rest of the region from depths exceeding 80 meters. Low levels of hydrogen sulfhide were observed at the Gotland Deep from 235 meters. In the Bornholm Basin and Hanö Bight, acute hypoxia was found from 80 and 70 meters respectively. However, high oxygen concentrations were observed at the Christiansö (BY4) bottom water at 91 meters which indicates incoming water. Acute hypoxia, < 2 ml/l was found in all basins from 70-80 meters depths in the Baltic Proper. All nutrients in the surface water were generally normal for the season, except in the southern part of the Baltic Proper where concentrations of inorganic nitrogen were higher and in the northern part where the concentrations of phosphate were higher. The surface water temperature was normal for the season except in the Bornholm Basin where it was warmer. The surface salinity was higher than normal in the Eastern and Western Gotland Basin and in the Arkona basin.