Changes of thermal and oxygen conditions in a dystrophic Lake Smolak in 1953-1995

Abstract

Thermal and oxygen conditions in the dystrophic Lake Smolak in 1993-1995 were typical of a bradymictic lake type: short period of spring overturn, stable summer stratification, shallow (0-1 m) and well oxigenated epilimnion, and bottom-reaching metalimnion with a strong ther- mocline. In summer, the near-bottom layers were characterised by total oxygen depletion and the appearance of hydrogen sulphide. Such pattern, however, was not observed in all years of the study. In 1953 and 1955 there was an overall homothermy, and oxygen content was high in the entire water column. In 1961 and 1962, and during mineral fertilisation and liming (1971-1974), epilimnion comprised 80% of water column, and a much warmer metalimnion developed from the depth of 4 m to the bottom.