Thresholds and Status evaluation

Status evaluation is measured in relation to scientifically based and commonly agreed sub-basin specific threshold values, which defines the concentration that should not be exceeded (Thresholds and Status evaluation figure 1).


Thresholds and Status evaluation figure 1. Schematic representation of the threshold value applied in the 'oxygen debt' core indicator, the threshold values are assessment unit specific (see Thresholds and Status evaluation table 1).


These indicator threshold values were based on the results obtained in the TARGREV project (HELCOM 2013a), also taking advantage of the work carried out during the EUTRO PRO process (HELCOM 2009) and national work for EU WFD. The final threshold values were set through an expert evaluation process done by the intersessional activity on development of core eutrophication indicators (HELCOM CORE EUTRO) and the threshold values were adopted by the HELCOM Heads of Delegations 39/2012 (Thresholds and Status evaluation table 1). The threshold values for oxygen debt in Åland Sea, Bothnian Sea and the Bothnian Bay were however endorsed at a later stage by the HELCOM State and Conservation 5E-2017 but the algorithm for calculating the indicator remains to be adjusted and optimized for these areas.


The threshold values for oxygen debt were defined from the 95th percentiles during the pre-eutrophied period before 1940, detected through change-point analysis for all assessment units.

Thresholds and Status evaluation table 1. Assessment unit specific threshold values for the core indicator 'oxygen debt'.

HELCOM_IDAssessment unit (open sea)Threshold value (mg l-1)
SEA-001KattegatNot applicable
SEA-002Great BeltNot applicable
SEA-003The SoundNot applicable
SEA-004Kiel BayNot applicable
SEA-005Bay of MecklenburgNot applicable
SEA-006Arkona SeaNot applicable
SEA-007Bornholm Basin6.37
SEA-008Gdansk Basin8.66
SEA-009Eastern Gotland Basin8.66
SEA-010Western Gotland Basin8.66
SEA-011Northern Baltic Proper8.66
SEA-012Gulf of RigaNot available
SEA-013Gulf of Finland8.66
SEA-014Åland Sea2.02
SEA-015Bothnian Sea2.02
SEA-016The QuarkNot available
SEA-017Bothnian Bay0.81