anglicky - Institute of Hydrobiology

5.5 Importance of dissolved organic carbon for phytoplankton nutrition in a eutrophic
reservoir
This study was supported by the Grant Agency of the Czech Republic
(Project No. 206/07/P407)
In 2008–2009, P. Znachor (znachy@hbu.cas.cz), Jiří Nedoma, and Pavel Rychtecký
performed in situ experiments examining the effect of glucose addition on silica deposition
kinetics and growth rates of Fragilaria crotonensis in the eutrophic Římov Reservoir (Czech
Republic). Silica deposition kinetics was measured at four-hour intervals over a 24-hour
incubation period with PDMPO (2-(4-pyridyl)-5{[4-dimethylaminoethyl-aminocarbamyl)-
methoxy] phenyl}oxazole] fluorescence probe. A significant stimulatory effect of glucose
supplemented at the concentration of 10 –4 mol l –1 on Fragilaria silification was observed at
time 20 and 24 hours. Fragilaria growth rates almost doubled upon glucose enrichment
compared to the untreated control at 24 h (Fig. 9). In addition, we conducted a dose-response
experiment testing glucose additions from 10 –8 –10 –3 mol l –1 in 24-hour incubation. Glucose
stimulated both Fragilaria silification and growth at concentrations >10 –7
mol l –1 (Fig. 10), which might occasionally occur in a reservoir as a result of e.g. accidental
contamination of water by organic pollution [1].
Fig. 9: Kinetics of Fragilaria silification rates measured as PDMPO fluorescence at 4-hour intervals
over 24 hours (a, c). Columns represent mean values (n ~ 50); bars are SEMs (standard errors
of the mean). Fragilaria growth rates based on an increase in cell counts over 24 hours are
given in the right panels (b, d). Asterisks denote significant differences between control and
glucose amended samples (p