Water transparency in June-September measured as Secchi depth (m) between years 1903 and 2008 in the Bothnian Sea

Secchi depth observations (m) are plotted against the year of observation and the curves fitted with non-linear smoothing and shown with 95 % confidence intervals. The estimation of reference conditions provided by HELCOM Eutro Pro is shown as a red line, the target value with a blue line and the assessment status during 2001-06 as a gray solid line. The number of observations (n) is shown on each figure.