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Periphytic ciliate communities were investigated in three lakes of different trophic status of the Łęczyńsko-Włodawskie Lake District (Eastern Poland). Observations were made of the periphyton growing on glass-slides. Samples were taken from April to November 2000–2001. Once a month, four periphyton samples were collected in littoral zone. Seventy three ciliate taxa occurred in the studied lakes. The biggest number, 60 species, was found in eutrophic lake, a little less, 55 species, in mesotrophic lake and the least, 49 species, in dystrophic lake. The lowest density was observed in mesotrophic lake and it was 13 × 10³ ind. m⁻², being a little higher in dystrophic lake – 16 × 10³ ind. m⁻², and the highest – 20 × 10³ ind. m⁻² in eutrophic lake. All of the studied lakes were generally dominated by ciliates belonging to the order Cyrtophorida (Chilodonella uncinata Ehrenberg 1983) constituted >30% of the total numbers. In all lakes bacterivorous ciliates occurred in the highest numbers (>50%), while algivorous and histophagous – in the lowest (<5%). In the eutrophic and dystrophic lakes the proportion of omnivorous and predatory species was high. The number of significant correlations differed among lakes. In mesotrophic lake the correlation between ciliates abundance and total organic carbon was found. In eutrophic lake total number of ciliates was positively correlated with the conductivity, TP and TOC. In dystrophic lake the correlations between ciliates abundance and abiotic parameters were not observed. In mesotrophic and dystrophic lakes the content of organic matter positively correlated with the biomass of ciliates, while in eutrophic lake conductivity showed positive correlation with their biomass.
Inorganic phosphorus released from littoral bottom sediments plays significant role in phosphorus budget of a whole ecosystem. An aim of the study was to assess a role of small invertebrates in phosphorus remineralization in hydroarenal (See Fig.1 in Preface). Hydropsammon organisms (i.e. bacteria, algae, ciliates, rotifers and crustaceans) living in a layer of submerged sands along the edge of a lake (=hydroarenal) were studied in psammolittoral of the deep, eutrophic Lake Mikołajskie (North-eastern Poland) in 2005. Sampling cores were taken at a station 1.5 m from water’s edge once or twice a month since April until October 2005. Each time three samples were taken: 5-cm thick water layer (AWL – adjacent water layer), 0.5-cm thick layer of water and sand from the transitory level (EPIH – epihydroarenal) and 2-cm thick slice of sand (ENDOH – endohydroarenal). The rate of phosphorus excretion was calculated using the appropriate regression equations expressing the relation between individual weight of organism and P excretion adjusted to the ambient temperature. Phosphorus remineralization by the psammon community (calculated for all ciliates, rotifers and crustaceans) was ca. 10 times higher than the maximum rate noted in lake pelagial. The most important role in the process was played by small ciliates, and in periods of high remineralization rate – by small cladocerans. Omnivores, feeding mostly on bacteria and small algae, played the most important role in all three studied layers, especially in periods of the highest rate of P remineralization, thus all kinds of food were used and mineralized. Predators do not seem to play significant role in P remineralization. In hydroarenal significant role seems to be played by processes involved in microbial loop. This suggestion is supported by strong domination of ciliates, main consumers of nanoflagellates, in the process of P remineralization. It seems that phytopsammon and psammic bacteria demands for phosphorus cannot be satisfied merely through the in situ remineralization by microinvertebrates.
Studies on parasitism in zooplankton and periphyton assemblages were carried out on samples of water collected from Lakes Płociczno and Płociowe in the Drawa National Park in 2008-2011. Occurrence of the fungal mycobiotal and protozoan parasites of invertebrates was recorded in both lakes. Parasitism of Chydorus sp. (Cladocera) by Saprolegnia sp. occurred on 0.8% of individuals of the host population, of Brachionus calyciflorus (Rotifera) by Microsporidium sp. on 1.2% of the host population, and of Nematoda members by Pythium sp. on 5% of the host population. Parasites were recorded only in springtime.
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