Light penetration in different types of lakes in Central Finland

Abstract

Light penetration measurements of blue (Schott filter BG 12), green (VG 9), and red (RG 630) light was made in 30 Finnish lakes with different degree of humus content and eutrophy for the comparison of the structure of phytoplankton communities and the light environment in the waters. The relations between Secchi disc visibility and the penetrations of different spectral regions and relations between the light conditions and the colour of the water was examined. The increase of ɛ min m −1 caused by humus material is 0.008 In units per colour unit (mg Pt l −1 ). The optical depth was especially in brown waters smaller than calculated by Formula after Talling (1965).