Historical Development and Past Ecological State of Two Danish Shallow Lakes: Determination for the Purpose of Restoration Activities

Sediment cores from two shallow Danish lakes were subjected to lead 210 dating and high performance liquid chromatographic analysis for determination of phytoplankton pigment content. A strong linear relation between sediment age and depth of both lakes was observed. Pigment data for Lake Ladegaard revealed a distinct eutrophication initiated in the early 1930s. Prior to this period, phytoplankton diversity was high. Heavy eutrophication in Lake Soeby occurred during 1950-80, when chlorophyte and cyanobacteria increased.