How far are we from clear water?

Key message 

The summer-time water clarity has decreased in all Baltic regions during the last century.

During the last two decades, water clarity has increased in the southern Baltic sub-areas.

Figure: Ecological status for water clarity measured as Secchi depth, during 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

Water clarity reflects eutrophication through changes in phytoplankton biomass and other small organic particles. Water clarity is also affected by changes in the amount of other coloured substances, unrelated to eutrophication.

Author(s) and institutions

Vivi Fleming-Lehtinen, Pirkko Kauppila, Hermanni Kaartokallio - Finnish 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 11 May 2010