Secchi depth-chlorophyll relationship in the Baltic

Abstract

The paper presents data on Secchi depth in the Southern Baltic waters. The mean annual Secchi depth is 8.2 m in the Gdańsk Deep, 9.6 m in the Bornholm Deep, 9.9 m in the southern Secchi depth is subject to seasonal fluctuations, their amplitude being approximately 35% of the mean annual value. A trigonometric polynomial was applied to describe periodic intra-annual changes of Secchi depth in the Baltic. The largest water transparency was observed in winter, the transparency being lowest in summer. Effects of chlorophyll a concentrations on water transparency are presented in a graphic form.