SMHI performed an oxygen and nutrient mapping survey within SLU Aqua’s cruise; 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 nutrients, chlorophyll and oxygen. Two of SMHIs standard stations; Anholt E and Fladen were also visited during the cruise. SMHI also help SLU-Aqua to take water samples close to the bottom for analysis av eDNA.
Most parts of Kattegat's bottom water suffered from hypoxia as oxygen levels below 4 ml/l were found in the bottom water. Below this oxygen level, the first signs of oxygen deficiency in marine organisms are normally detected. In the south-eastern parts, levels were lower, close to the limit for acute hypoxia of < 2 ml/l. In acute oxygen deficiency, most benthic animals are negatively affected. In Skagerrak the oxygen levels in open water was generally good while hypoxic conditions were found at one stationer in the North Sea.