Assessment Protocol

The open-sea core indicators are updated using data reported by Contracting Parties to the HELCOM COMBINE database hosted by ICES, using the algorithms developed for the eutrophication assessment work flow. The values are achieved using indicators specifications shown in Assessment protocol table 1 (see HELCOM Eutrophication assessment manual).


Assessment table 1.png 

Assessment protocol table 1. Specifications of the core indicator Secchi depth.

 

The indicators within the criteria were weighted according to their relevance for eutrophication in each sub-basin. The weight was evenly distributed within the criterion, unless there was a justification to do otherwise. For Secchi depth, the weight was assigned according to the available information on the light absorption by colored dissolved organic matter (CDOM) and the relationship between CDOM absorption and chlorophyll a concentration in the sub-basin (Assessment protocol table 2), respectively. The weight was distributed equally (no weight assigned) for most sub-basins but in the Gulf of Finland and especially in the Gulf of Bothnia Secchi depth received a reduced weight due to increased absorption of light by CDOM. This makes Secchi depth a less reliable indicator of eutrophication, and therefore it received a smaller weight in those basins.

 

Assessment protocol table 2. Secchi depth and chlorophyll a have been weighted according to available information on CDOM absorption of light and the relationship between CDOM light absorption and chlorophyll a (chl-a) concentration in the sub-basin. 

BasinReduction in Secchi weightJustification (Ylöstalo et al. in prep., Stedmon et al. 2000)
Kattegat- 
The Sound-Low CDOM absorption 1
Great Belt-Low CDOM absorption 1
Little Belt-Low CDOM absorption 1
Kiel Bay-
Assumed similar as in the Belts and Arkona Sea
Mecklenburg Bight-Assumed similar as in the Belts and Arkona Sea
Arkona Sea-Low CDOM absorption 2, medium in relation to chl-a
Bornholm Sea-Low CDOM absorption 2, medium in relation to chl-a
Eastern Gotland Basin-Assumed similar as in the Northern Baltic Proper
Western Gotland Basin-Low CDOM absorption 2, medium in relation to chl-a
Gdansk Basin-No info
Northern Baltic Proper-Medium CDOM absorption 2, medium in relation to chl-a
Gulf of Finland-20 %High CDOM absorption 2, medium in relation to chl-a
Gulf of Riga-40 %Extremely high CDOM absorption 2, high in relation to chl-a.
Åland Sea-Interpolated between Bothnian Sea and Northern Baltic Proper
Bothnian Sea-20 %Medium CDOM absorption 2, medium-high in relation to chl-a
Quark-40 %Interpolated between Bothnian Bay and Bothnian Sea
Bothnian Bay-60 %
High CDOM absorption 2, extremely high in relation to chl-a.


Assessment units

The core indicator is applicable in the 17 open sea assessment units (from one nautical mile from the baseline seawards).

The assessment units are defined in the HELCOM Monitoring and Assessment Strategy Annex 4.