Vertical structure and photosynthetic activity of Lake Shira phytoplankton
Gaevsky, N.A.; Zotina, T.A.; Gorbaneva, T.B.
Aquatic Ecology 36(2): 165-178
2002
ISSN/ISBN: 1386-2588 DOI: 10.1023/a:1015609011227
Accession: 011639677
This study was conducted to analyse vertical dynamics of phytoplankton distribution in Shira Lake during the summer stratification regime. From late June to September phytoplankton in Shira Lake were stratified with the maximum in the lower part of the thermocline, at a depth of 8-12 m, with a chlorophyll concentration up to 23 mug and biomass up to 5 mg l-1. Maxima of chlorophyll and biomass of cyanobacteria and green algae were in different layers. From June to September a major part of chlorophyll a was in green algae, while under ice - in cyanobacteria. The variable fluorescence proves high photosynthetic activity of algae in the depth assemblage. Epifluorescent analysis disclosed that additional light-harvesting pigments were better developed in cells from the depth maximum. The maximum of gross primary production calculated from fluorescence corresponded to the depth maximum of phytoplankton. Primary production over a season was 2.7 gO2 m-2. Formation mechanisms of the depth maximum of phytoplankton are discussed in this paper.