Are winter surface concentrations of nutrients close to natural levels?

Key message 

High levels of dissolved inorganic phosphorus (DIP) remain in the surface waters of the western Baltic, Baltic Proper and the Gulf of Finland and the Gulf of Riga. The HELCOM target level has not been met in these areas. A good/high ecological status was reached in the Kattegat and the Bothnian Sea.

Dissolved inorganic nitrogen (DIN) levels in 2003-2007 remained below the 1993 – 2002 average in the central Baltic Sea and the Kattegat. HELCOM target level has not been met in the northern Baltic Proper, the Gulf of Finland, Gulf of Riga and in the Bothnian Sea.

Figure 1. Ecological status for DIP and DIN based on winter concentrations for the period 2003-2007. The interpolated map has been produced in three steps: 1) the status of coastal assessment units has been interpolated along the shores, 2) the 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 caused by excessive inputs of nutrients (nitrogen and phosphorus) resulting from various human activities.

High concentrations of nutrients and their ratios form the preconditions for huge algal blooms, reduced water clarity and increased oxygen consumption.

Long term nutrient data are key parameters for quantifying the effects of anthropogenic activities and evaluating the success of measures untertaken.

Authors

Günther Nausch - Leibniz Institute for Baltic Sea Research (IOW), Germany
Philip Axe - Swedish Meteorological and Hydrological Institute (SMHI), Sweden
Jacob Carstensen - National Environmental Research Institute (NERI), Denmark
Vivi Fleming-Lehtinen -  Finish Environment Institute (SYKE), Finland

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 26 May 2010