The daily integral of photosynthesis by Planktothrix rubescens during summer stratification and autumnal mixing in Lake Zurich

Autor: Silvia Micheletti, Anthony E. Walsby, Ferdinand Schanz
Rok vydání: 1998
Předmět:
Zdroj: New Phytologist. 139:233-246
ISSN: 1469-8137
0028-646X
DOI: 10.1046/j.1469-8137.1998.00196.x
Popis: SUMMARY It has been suggested that the populations of planktonic cyanobacteria that occupy the metalimnion of stratified lakes during the summer months may be aestivating between the main periods of growth during entrainment in the epilimnion in spring and summer. We determined the vertical distribution of the biomass and daily integral of photosynthesis of the population of Planktothrix (Oscillatoria) rubescens in Lake Zuirich for 136 d from July to November 1995. The population showed an 80-fold increase during the stratified period but it only doubled over the subsequent period of entrainment. During the first eight days, part of the increase was attributed to recruitment of filaments floating up from greater depths but all of the subsequent production could be accounted for by photoautotrophic growth. On sunny days the biomass-specific photosynthesis of this population reached some of the highest values over the whole period despite its depth (> 13 m). On very cloudy days, however, primary productivity was very low and on 4 days, when the mean depth of the population exceeded 15 m, there was no net production. Over the whole period of the study, the accumulated photosynthetic production exceeded the increase in biomass of the population by a factor of 9-5. Although much of this production occurred during the period of entrainment only a small proportion was translated into growth of the population. It is concluded that the growth that takes place in the period of stratification in the metalimnion is essential to subsequent production.
Databáze: OpenAIRE
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