Original paper

Seasonal development of Planktothrix agardhii Anagnostidis et Komarek and Limnothrix redekei (Van Goor) Meffert in a sharply stratified hypertrophic lake

Kangro, Kersti; Nõges, Peeter

Abstract

Thermal and chemical regime and phytoplankton development in hypertrophic sharply stratified L. Verevi (S-E Estonia) were studied from April to October 2000. The lake stratified shortly after the ice break-up in April. Even in the homothermal conditions in October the lake remained chemically and biologically stratified. Limnothrix redekei being a minor component of the cyanobacterial community, reached its maximum (1.4 g.m−3) in the metalimnion in May. The biomass peak of the dominating Plankothrix agardhii followed in July (37.6 g.m−3). The biomass maximum of L. redekei was reached in cooler water at lower nitrogen and phosphorus concentrations compared with P. agardhii. Light conditions and the total N: total P ratio in the layer of the biomass peaks were similar. Nitrogen limitation was suggested as the main reason for the observed seasonal succession of the two cyanobacterial species.

Keywords

stratified lakelimnothrix redekeiplanktohrix agardhii