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Distribution and habitat conditions of the phytocoenoses of Sphagnum denticulatum Bridel and Warnstorfia exannulata [B.,S. and G.] Loeske in Polish Lobelia lakes

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Szankowski M., Klosowski S.
Acta Societatis Botanicorum Poloniae
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2004
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tom 73
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nr 3
Phytosociological and habitat studies of Sphagnum denticulatum and Warnstorfia exannulata phytocoenoses from Polish Lobelia lakes have been conducted. The present results were compared with data on Isoetes lacustris community. It is demonstrated that both communities of mosses are distinct with respect to their floristic composition. Moreover, they differ significantly from the patches of I. lacustris with regard to many properties of water and substrates. The phytocoenoses of S. denticulatum are associated with softer waters, poorer in Ca2+, Na+, NH4+ and dissolved organic matter, but richer in total Fe than those of I. lacustris. They are also distinguished by lower values of electrolytic conductivity. The substrates they inhabit are more strongly hydrated and richer in organic matter, total N, dissolved SiO2, Ca2+ and Na+, but poorer in PO43-. The W. exannulata phytocoenoses are also confined to softer waters with lower Ca2+, NH4+ and dissolved organic matter contents than those of I. lacustris. Their substrates are more strongly hydrated and have higher contents of organic matter, total N and Na+ but lower amounts of PO43-. In addition the waters of W. exannulata phytocoenoses are characterized by higher pH values and lower concentration of dissolved SiO2. The substrates are less acidic and richer in NO3-, but poorer in total Fe. The differences between the habitats of the S. denticulatum and W. exannulata phytocoenoses are also distinct. The former inhabit more acidic waters, richer in dissolved SiO2 and total Fe, but with lower values of electrolytic conductivity and concentration of Na+. Their substrates are distinguished by higher contents of organic matter and Ca2+, as well as by lower amount of NO3-. In view of the fact that the above phytocoenoses of mosses are distinct with respect to their floristic composition and are associated with specific habitats in which they form dense mats close to the bottom of the lake, they should be classified as distinct associations (Sphagnetum denticulati and Warnstorfietum exannulatae) in the system of aquatic communities (Class: Utricularietea intermedio-minoris).
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Effect of light competition with filamentous algae on the population dynamics and development of the moss species Warnstorfia exannulata in a softwater lake

80%
Szmeja J., Bociag K., Mierdalski M.
Polish Journal of Ecology
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2010
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tom 58
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nr 2
The effect of a massive bloom of filamentous algae on the long-term abundance dynamics of the moss Warnstorfia exannulata (B., S. & G.) Loeske was studied in an acidic lowproductivity lake in NW Poland. Individuals were counted on 4 experimental plots, 1 × 1 m each, at a depth of 2.5 m. The studies were conducted for 36 months, every 30 days, by SCUBA diving. Over the three years the seasonal changes in water pH, conductivity, HCO₃⁻ concentration, sediment hydration and pH were not statistically significant (P> 0.05), and light intensity was higher in winter than in summer. Over the three years 4 consecutive stages of population development were observed: regeneration, stabilisation of abundance (fluctuations), regression and repeated regeneration. These stages appeared and lasted at different temperatures and light intensity. The greatest monthly increase in abundance took place in summer and lasted until the beginning of autumn under conditions of high temperature and relatively low light intensity. Long-term abundance variations were strongly correlated with the appearance of filamentous algae, less strongly with the dynamics of the dominant species (Sphagnum denticulatum), and the least with water temperature, light intensity, water and sediment pH, conductivity and HCO₃⁻ concentration. As a result of a massive bloom of these algae, light intensity decreased in the water, Warnstorfia shed its leaves, and then the entire population disappeared. In winter that year it began to regenerate from vegetative propagules (leafless shoots), which were the remains of individuals growing before the filamentous algae appeared. In softwater lakes such massive algal blooms are a common phenomenon which limits light transmission to the substrate and as a result leads to changes in the submerged vegetation structure, especially that of bryophytes.
3

The impact of UV radiation on metabolism of neustonic and planktonic bacteria in eutrophic lake

70%
Burkowska A., Walczak M., Donderski W.
Polish Journal of Ecology
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2010
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tom 58
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nr 2
The range of solar radiation reaching the air-water inter-phase, medium wave UV radiation, i.e. UVB 290–320 nm and UVA 320–400 nm, is of the highest biological importance due to its harmful effects. Radiation within this range causes DNA damage (lethal effect) or limits the growth of organisms by inhibiting enzyme synthesis, reducing active transport, or by inducing mutations. The studies were carried out in 2007 based on samples water collected from surface microlayer (SM) (up to 150 μm) and subsurface water (SSW) (25 cm) of pelagic zone of eutrophic lake. The representative collection of bacterial strains was isolated from collected samples. The following are measured: the DNA and cellular protein synthesis activity, respiration activity of the bacteria and activity of hydrolytic enzymes in control cultures, subjected to UVB radiation (applied dose 100 mW cm⁻²) and with and without humic substances (HS) (final concentration 100 mg L⁻¹) playing role of compounds potentially protective from UV radiation. UVB irradiation had the strongest inhibiting impact on production of DNA in bacterial cells (12–23% of that in non-irradiated samples). UVB radiation also inhibits the synthesis of cellular protein (27–43% of that in non-irradiated samples) and bacterial respiration activity (44–48%). UVB radiation had by far the lowest impact on the activity of hydrolytic enzymes. HS may function as a protective agent against UV radiation only in DNA synthesis. No significant differences in response to UVB were found between planktonic and neustonic bacteria.
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