In open sea areas, good environmental status (GES) for water clarity has been achieved in the Kattegat and Bothnian Bay. In the remaining 15 sub-basins, GES has not been achieved.
During the last century, the summer-time water clarity has decreased in all Baltic Sea areas. During the last two decades, water clarity turned to an increase in the southern Baltic Sea sub-basins.
The confidence of the presented water clarity status estimate is low in the Western Gotland Basin, Gulf of Riga, ÅlaSea and the Quark, due to lack of monitoring data.
Average Secchi depth during summer (June – September). (Open dynamic map viewer in new tab)
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. This core indicator focuses on one important aspect of the complex phenomenon, but does not alone assess the eutrophication status.
BSAP segment and objective
A Baltic Sea unaffected by eutrophication
MSFD descriptor and criteria
5.2. Direct effects of nutrient enrichment
Other relevant legislation
Water Framework Directive
Pyhälä M, Fleming-Lehtinen V, Laamanen M, Łysiak-Pastuszak E, Carstens M, Leppänen J-M, Leujak W, Nausch G, 2014. Water clarity - HELCOM Core Indicator Report. Online. [Date Viewed], http://www.helcom.fi/baltic-sea-trends/indicators/water-clarity