Cruise report from R/V Svea week 34-35, 2021

Type: Report
Author: Martin Hansson


SMHI performed an oxygen and nutrient survey within SLU Aqua’s cruise; the International Bottom Trawl Survey (IBTS Q3), that covers the Skagerrak, the North Sea and the Kattegat. SMHI joins the cruise to perform CTD measurements in connection to each trawl and to take water samples for the annual oxygen survey. Samples for nutrients and chlorophyll were also taken. Two of SMHIs standard stations; Anholt E and Fladen were also visited during the cruise.

The bottom water oxygen situation in the central and eastern parts of Kattegat and northwest of Läsö were below the limit for hypoxia. Oxygen concentrations below 4 ml/l were found in these areas. However, no areas were found to be suffering from acute oxygen deficiency (< 2 ml/l). The oxygen concentrations ranged from 3.4 – 5.5 ml/l in the bottom water. In the Skagerrak the oxygen situation was good with bottom water concentrations above 4 ml/l. The only exception was the coastal station Släggö, in the outer part of the Gullmars fjord, where oxygen concentrations was measured to 3.6 ml/l in the bottom water.