This core indicator evaluates average oxygen debt below the halocline that separates deep water from the surface water. Oxygen debt is applied in the Bornholm Basin, Gdansk basin, Western Gotland Basin, Eastern Gotland Basin, Northern Baltic Proper and Gulf of Finland. Oxygen debt values below the threshold value have not been achieved in any of these sub-basins.
Oxygen debt below the halocline has increased in all basins since the early 1900's.
Key message figure 1. Status assessment results based on evaluation of the indicator 'Oxygen debt'. The assessment is carried out using open sea areas of Scale 4 HELCOM assessment units (defined in the HELCOM Monitoring and Assessment Strategy Annex 4). See Results section below for details. Click here to access interactive maps at the HELCOM Map and Data Service: Oxygen debt.
The confidence of the presented oxygen debt status estimate is high in all the sub-basins where the indicator was applied.
Organic matter deposition to bottom waters increases along with increasing eutrophication. This leads to increasing oxygen consumption and a subsequent decrease in bottom oxygen concentration.
D5 Human-induced eutrophication
- D5C5 The concentration of dissolved oxygen is not reduced, due to nutrient enrichment, to levels that indicate adverse effects on benthic habitats (including on associated biota and mobile species) or other eutrophication effects.
HELCOM (2018). Oxygen debt. HELCOM core indicator report. Online. [Date Viewed], [Web link].
Oxygen debt HELCOM core indicator 2018 (pdf)