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Spring development of hydrolittoral rock shore communities on wave-exposed and sheltered sites in the Northern Baltic proper

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Eriksson Wiklund A.-K., Malm T., Honkakangas J., Eklund B.
Oceanologia
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2012
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tom 54
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nr 1
Spring development in the hydrolittoral zone was investigated at five wave-sheltered and five wave-exposed sites on four occasions from late March to late May (every third week). The number of species was higher at the sheltered locations and increased significantly over time. The difference in community structure was significant: over 95% of the Bray-Curtis dissimilarities were due to the biomass of only eleven taxa, and the total Bray-Curtis dissimilarity between exposed and sheltered sites was 75%. Macroalgae made up 70–80% of the total biomass and was dominated by filamentous species. In contrast to previous studies, macroalgal biomass was higher at the exposed sites, which may be due to the fact that this was a spring study, unlike previous studies, which were conducted during summer.
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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

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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.
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Temporal and spatial changes in the horizontal distribution of planktonic Crustacea between vegetated littoral zone and the zone of open water

100%
Rybak J. I., Weglenska T.
Polish Journal of Ecology
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2003
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tom 51
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nr 2
The research concerned the density, dominance structure and species composition of planktonic Crustacea community, as well as their diel horizontal migrations between aggregations of vegetation and open water in the littoral zone of two lakes. The Cladocera communities of sparse beds of submerged macrophyte showed a sharp domination (70%) of individuals of large-sized tycholimnetic species. In the Cladocera community in a dense beds of macrophyte also individuals of littoral species occurred in greater numbers. The filamentous algal mats were mainly dominated by Copepoda and small tycholimnetic species of Cladocera. We observed a sharp daily gradient of Crustacea density across macrophyte beds and open water. The greatest diel changes were found near the edge of the macrophyte beds (ecotone zone). Daytime density of Cladocera was several times greater in the macrophyte beds than in the open zone, while during the night-time density differences were not so marked. In contrast, in the case of filamentous algal mat, the sharp gradient of abundance remained constant by both day and night. An inverse relationship between chlorophyll a concentration and Cladocera density was noted in the transect between beds of submerged macrophytes and open water, provide to effective control of phytoplankton biomass by Cladocera during their diel migrations.
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The impact of UV radiation on metabolism of neustonic and planktonic bacteria in eutrophic lake

88%
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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