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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.
The effects of inorganic nutrients (N, P) enrichment of mesotrophic lake water on changes in bacterial and protistan (heterotrophic nanoflagellates and ciliates) communities compositions were studied in the mesocosm experiment. Phosphorus (PO₄³⁻) and nitrogen (NH₄⁺) alone and in combination were added to three types of experimental mesocosms. Mesocosms results suggested that simultaneous addition of P and N stimulated phytoplankton growth and production rates of bacterial biomass its turnover rate. Strong positive correlations between chlorophyll a and bacterial secondary production rates suggested that bacteria were mainly controlled by organic substrates released in course of phytoplankton photosynthesis. Both nutrients increased distinctly protistan biomass and resulted in the shift in ciliate community composition from algivorous to large omnivorous species. The response of bacterial numbers and biomass to nutrients addition was less evident. However, intensive grazing caused their dynamic changes. Fluorescence in situ hybridization (FISH) revealed only small changes in bacterial taxonomic composition. There was an apparent shift in dominance from Cytophaga-Flavobacterium to the Alphaproteobacteria group in the mesocosm with simultaneous addition of P and N, which positively related to increased abundance of bacterivorous protists. Experiment demonstrated that inorganic N and P nutrients directly influenced the bottom-down control of microbial communities, which had a crucial effect on morphological diversity of bacteria.
The importance of ciliates as a trophic link, which is defined as a fraction of the energy bound by primary producers that is transferred through the ciliate community, was assessed in the pelagic zones of shallow, eutrophic, and estuarine lakes. The study was conducted in Lake Gardno and Lake Łebsko located in northern Poland. Each of these lakes is characterized by very high mean annual ciliate biomasses of 115 μg C -1 (Lake Gardno, April 2006 – April 2007), 107 μg C L-1 (Lake Gardno, February 2007 – February 2008), 85 μg C L-1 (Lake Łebsko, April – November 2007), and 127 μg C L-1 (Lake Łebsko, April – September 2008). Ciliate production was estimated using allometric equations and was compared to primary production measured with the light-and-dark bottles method. Annual, depth-integrated ciliate secondary production corresponded to 9 and 11% (Lake Gardno, two consecutive years studied) and 12% (Lake Łebsko, the same value for two growing seasons studied) of primary production. These values exceed the majority of other estimates in the literature, which indicates the high importance of ciliates in such highly-productive, shallow lakes.
Diurnal changes in the structure of the ciliate community in surface waters were studied in the aquaculture area of Dapeng’ao cove, China. Two periods of heavy rainfall occurred during the study period, intensifying water column stratification and influencing the water’s properties. A total of 21 ciliate taxa from 15 genera were identified; the dominant species was Mesodinium rubrum. The maximum abundance of M. rubrum reached 3.92×104 indiv. dm−3, contributing 95.1% (mean value) to the total ciliate abundance. Diurnal changes in M. rubrum abundance were highly variable, the driving force probably being irradiance and food availability. The results suggest that M. rubrum may form blooms in aquaculture areas when there is a suitable physical regime with enriched nutrients, which is potentially harmful to the fish-farming industry.
The abundance and species composition of ciliates were analysed in pelagic zone of two depression reservoirs: Nadrybie and Szczecin (Polesie Lubelskie, eastern Poland) from May to November 2002. Totally 21 ciliates species were found in Szczecin reservoir and 24 in Nadrybie reservoir. The mean abudance of ciliates was 31 ind. ml-1 in Szczecin reservoir and 26 ind. ml-1 in Nadrybie reservoir. Ciliates communities in both reservoirs were dominated by Scuticociliatida (Cinetochilum margaritaceum) and Peritrichida (Vorticella sp.). Densities and species composition of ciliates showed clearly changes. In both reservoirs the correlation between ciliates density and conductivity, pH, TP and TOC was found.
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