What was the eutrophication status of the Baltic Sea in 2003-2007?

Key message 

The whole Baltic Sea except the open Bothnian Bay and certain coastal areas in the Gulf of Bothnia were affected by eutrophication during 2003-2007.

Figure: The eutrophication status of the Baltic Sea based on average data for 2003-2007 at 110 assessment units in the Baltic Sea. The assessments are based on an integration of the results from core set indicators on nutrient (nitrogen and phosphorus) concentrations, chlorophyll a concentrations, water transparency and zoobenthos communities using the HELCOM Eutrophication Assessment Tool (HEAT). The interpolated map has been produced in three steps: 1) the integrated status of coastal assessment units have been interpolated along the shores, 2) the integrated status of open sea basins have been interpolated and 3) the coastal and open interpolations have been combined using a smoothing function. The larger circles indicate the status of open sea assessment units and the smaller circles that of the coastal assessment units. 

Policy relevance

Eutrophication is addressed by one of the four thematic segments of the HELCOM Baltic Sea Action Plan. The strategic goal of HELCOM related to eutrophication is a Baltic Sea unaffected by eutrophication.

This Integrated Core Set Indicator Report provides an assessment of the eutrophication status of the Baltic Sea based on averaged data for the years 2003-2007. The assessment is derived using the HELCOM eutrophication assessment tool (HEAT) and HELCOM Core Set Indicators for eutrophication. The methodology and an assessment for the period 2001-2006 are described in the Integrated thematic assessment of the effects of nutrient enrichment in the Baltic Sea (HELCOM 2009).

The HELCOM goal for eutrophication is broken down into five ecological objectives: Concentrations of nutrients close to natural levels, clear water, natural level of algal blooms, natural distribution and occurrence of plants and animals, natural oxygen levels. Each objective is reflected by one or more HELCOM Core Set Indicators for eutrophication. These indicators are weighted depending on their ecological significance for the site being assessed and combined under the quality elements physico-chemical features, plankton and benthic invertebrate fauna. Finally the overall integration of the eutrophication status is derived from the results of each of the quality assessments using the HEAT tool.

Eutrophication is also addressed by the EU Marine Strategy Framework Directive, as one of the qualitative descriptors of Good Environmental Status contained in Annex I of the Directive is “Human induced eutrophication does not cause adverse effects to the ecosystem”.

Author and institutions

Pyhälä, Minna,¹ Frias Vega, Manuel,¹ Laamanen, Maria,¹ Fleming-Lehtinen, Vivi,² Nausch, Günther³ and Norkko, Alf²

¹ HELCOM Secretariat
² Finnish Environment Institute, Finland 
³ Leibniz Institute for Baltic Sea Research, Germany

References

Andersen, J.H., P. Axe, H. Backer, J. Carstensen, U. Claussen, V. Fleming-Lehtinen, M. Järvinen, H. Kaartokallio, S. Knuuttila, S. Korpinen, M. Laamanen, E. Lysiak-Pastuszak, G. Martin, F. Møhlenberg, C. Murray, G. Nausch, A. Norkko, & A. Villnäs. 2010. Getting the measure of eutrophication in the Baltic Sea: towards improved assessment principles and methods. Biogeochemistry. DOI: 10.1007/s10533-010-9508-4.

HELCOM 2009a. Eutrophication in the Baltic Sea. An integrated thematic assessment of the effects of nutrient enrichment in the Baltic Sea region. Baltic Sea Environment Proceedings No. 115B.

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Last updated 12 May 2010