Application of the PDMPO technique in studying silica deposition in natural populations of Fragilaria crotonensis (Bacillariophyceae) at different depths in a eutrophic reservoir

In July – October 2006 at weekly intervals, we measured silica deposition in the summer diatom assemblage at various depths in a eutrophic Římov Reservoir using PDMPO labelling technique. Diatom assemblage was exclusively dominated by Fragilaria crotonensis, which formed pronounced subsurface maxima (2 – 6.5 m). Concentrations of the main nutrients (Si and P) were low over the whole season, however, at depth the nutrient availability was higher than at the surface. Fragilaria silica deposition rates were eight times higher at the surface than at depth. A half of the population was involved in silica deposition at the surface while only 20 % active cells were found at depth. At the surface, silica deposition was limited by phosphorus deficiency; the effect of dissolved Si was not statistically significant. Silica deposition at depth was significantly constrained by low light availability despite the 1 % average light attenuation at depth, which is supposed sufficient for photosynthesis. This study represents the first attempt to employ the PDMPO technique coupled with quantitative image analysis of PDMPO fluorescence in freshwater limnology. Based on our results, PDMPO probe appears to be an appropriate proxy for resource limitation studies of natural diatom populations.

Znachor, P. - Nedoma J. (2008): Application of the PDMPO technique in studying silica deposition in natural populations of Fragilaria crotonensis (Bacillariophyceae) at different depths in a eutrophic reservoir. J. Phycol. 44: 518–525.

Znachor, P. - Zapomělová, E. - Řeháková, K. - Nedoma, J. - Šimek, K. (2008): The effect of extreme rainfall on summer succession and vertical distribution of phytoplankton in a lacustrine part of a eutrophic reservoir. Aquatic Sci. 70: 77–86