Growth and buoyancy of Microcystis aeruginosa Kütz. emend. Elenkin in a shallow eutrophic lake

Abstract

The growth of Microcystis aeruginosa in a small, shallow eutrophic lake was studied during three consecutive seasons. The alga was shown to be continuously present in the plankton throughout the period. Exponential increase in the population was confined to a 5 to 8-week period, following the onset of thermal stratification. Populations appeared to originate near the bottom of the euphotic zone. The possession of an effective light-dependent buoyancy control mechanism enabled the alga to maintain station, though progressive deterioration of the photic conditions forced populations to rise and become dissipated within the epilimnion. Buoyancy increased after the cessation of growth; surface blooms often led to the physical removal of a majority of colonies to lee shores. Surviving colonies became generally less buoyant after the lake destratified in autumn.