Tomasz Mieczan

Diet composition of epiphytic chironomids of the Cricotopus sylvestris group (Diptera: Chironomidae) in a shallow hypertrophic lake

The diet composition of epiphytic Cricotopus sylvestris group larvae (Chironomidae) was examined for two size classes (<5 mm and 5–10 mm) from April to December in a shallow hypertrophic lake in eastern Poland. The C. sylvestris group dominated the epiphytic midge community on stems of Phragmites communis, accounting for 90–96% of the total population by number. The diet of both size classes of this midge consisted mostly of detritus and associated protozoa to the exclusion of many other potential food choices, such as epiphytic algae (chlorophytes, diatoms, filamentous green algae Cladophora sp.) numerously present in this microhabitat.

Spatial distribution of brood-bearing females of limnetic species of Cladocera.

In this study, the spatial distribution of brood-bearing females of five species of limnetic cladocerans (Daphnia cucullata, D. longispina, Bosmina coregoni, B.xa0longirostris, Diaphanosoma brachyurum) in the deep mesotrophic lake in relation to the predation pressure of planktivorous fish (roach Rutilus rutilus, perch Perca fluviatilis, catfish Ictalurus nebulosus, white fish Coregonus albula, bleak Alburnus alburnus), and planktonic invertebrates (cyclopoids Mesocyclops leuckartii, Thermocyclops oithonoides, T.xa0crassus, and cladoceran Leptodora kindtii) as well as some environmental variables was estimated. Most cladocerans showed apparent differences in horizontal distribution (ANOVA F=0.2-0.45, P<0.05) in the littoral zone and lack of such differences in the pelagic zone (F=0.07-0.13, P>0.05). Vertical distribution of most species, in turn, showed a clear pattern in the pelagic zone (F=0.31-0.39, P<0.05) and less regularities in the littoral zone (F=0.15-029, P>0.05). The differences in spatial distribution of non-predated and predated species suggest that predation pressure, but not predatory type, was an important factor structuring their distribution. Other factors that affected their distribution were conductivity, dissolved oxygen, TOC and macrophyte biomass; however, most of those variables better explained the distribution of brood-bearing cladocerans in the vertical than horizontal aspect.

Vertical micro-distribution of psammonic ciliates and their relationship to physical and chemical parameters in two lakes of different trophic status

The aim of this study was to examine the community structure and vertical micro-distribution of psammonic ciliates in two lakes of different trophic status in eastern Poland. Additionally, the size and trophic structure of these microorganisms, and the influence of physical and chemical water parameters on their abundance, were analysed. Psammon samples were collected during spring, summer, and autumn of 2010. In each of the lakes samples were collected in the euarenal, higroarenal, and hydroarenal zones of the psammolittoral. In order to determine the micro-vertical distribution of ciliates, each sample was divided into two sub-samples: the upper part (0–1cm) and the lower part (1–2cm). The species diversity of ciliates decreased with depth. The tendency was particularly clear in mesotrophic lakes. Irrespective of the lake’s trophic type and arenal zones, significantly higher numbers and biomass of ciliates were recorded in the surface layer of the psammolittoral. The upper layer of sand was dominated by omnivorous taxa, whereas the deeper layer showed increases in the proportions of bacterivore species. The factors limiting the occurrence of ciliates are mainly concentrations of total organic carbon and nutrients.

Horizontal Distribution of Psammonic Ciliates in Two Lakes of Different Trophic Status: Relationship to Physical and Chemical Parameters

Horizontal Distribution of Psammonic Ciliates in Two Lakes of Different Trophic Status: Relationship to Physical and Chemical Parameters The aims of this study were to identify the taxonomic diversity and abundance of psammonic ciliate communities in mesotrophic and eutrophic lakes (Łęczna-Włodawa Lakeland, eastern Poland). The effect of selected physical and chemical water parameters on ciliates community was also analysed. Psammon samples were collected during three seasons: spring, summer and autumn of 2010. In each lake, in the psammolittoral, samples were collected in the euarenal, higroarenal, and hydroarenal zones. A total of 53 ciliate taxa were recorded. The highest value of the Shannon-Weaver index was recorded in summer in eutrophic lake (2.79). At the same time in mesotrophic lake, a lower value of the index was determined (0.79). The mean numbers of ciliates ranged from 516 ind.cm-3 in the eutrophic lake to 191 ind. cm-3 in the mesotrophic lake. In eutrophic lake, the highest number of ciliates was recorded in the euarenal (649 ind. cm-3), and the lowest in the higroarenal (425 ind. cm-3). In the mesotrophic lake, the highest average numbers were determined in the higroarenal (235 ind. cm-3), and the lowest in the hydroarenal (155 ind. cm-3). Irrespective of the lake trophy, Hymenostomata (Paramecium sp., Glaucoma sp., Uronema nigricans) occurred in the highest numbers (from 13 to 95%). The results demonstrated that N-NH4, P-PO4 and TOC can strongly regulate the abundance and taxonomic composition of ciliates. The strongest correlations between numbers of ciliates and physical and chemical water parameters were observed in the higro- and hydroarenal zones of the eutrophic lake. Horyzontalne Rozmieszczenie Orzęsków Psammonowych W Dwóch Zróżnicowanych Troficznie Jeziorach: Zależności Z Parametrami Fizycznymi I Chemicznymi Celem pracy było poznanie struktury jakościowej i ilościowej orzęsków psammonowych w jeziorze mezotroficznym i eutroficznym (Pojezierze Łęczyńsko-Włodawskie). Analizowano również wpływ wybranych właściwości fizycznych i chemicznych wód na kształtowanie się tego specyficznego zespołu mikroorganizmów. Próby psammonu pobierano wiosną, latem i jesienią 2010 roku. W każdym zbiorniku, w psammolitoralu próby pobierano w euarenalu, higroarenalu i hydroarenalu. Łącznie stwierdzono 53 taksony orzęsków. Średnie zagęszczenie orzęsków wyniosło 516 osobn. cm-3 w jeziorze eutroficznym, zaś w mezotroficznym było niemal 2 razy niższe i osiągało 191 osobn. cm-3 piasku. W jeziorze Sumin najwyższe średnie zagęszczenie zanotowano w euarenalu 649 osobn.cm-3, najniższe zaś w higroarenalu (425 osobn. cm-3). W jeziorze mezotroficznym najwyższe średnie wartości liczebności zanotowano w higroarenalu 235 osobn. cm-3, najniższe zaś w hydroarenalu 155 osobn. cm-3. Najwyższą wartość wskaźnika Shanonna-Weavera odnotowano latem w jeziorze Sumin (2.79), w tym samym czasie w jeziorze Piaseczno odnotowano najniższą wartość tego współczynnika (0.79). Niezależnie od trofii jeziora największy udział w ogólnej liczebności orzęsków osiągały Hymenostomata (Paramecium sp., Glaucoma sp., Uronema nigricans) stanowiące od 13 do 95% ogólnej liczebności orzęsków. Stwierdzono istotne zależności pomiędzy obfitością orzęsków, a stężeniami w wodzie związków biogennych oraz całkowitego węgla organicznego, przy czym najsilniejsze korelacje odnotowano w strefach higro- i hydroarenalu jeziora eutroficznego.

Ecology of testate amoebae (Protists) in a Sphagnum-dominated peat bog and the relationship between species assemblages and environmental parameters

Abstract Despite its ecological importance, little information is available regarding spatial and seasonal changes in the testate amoebae community in peat bogs. The objectives of this study were to examine the structure of communities and horizontal distribution of testate amoebae fauna, to improve the understanding of factors affecting the distribution of moss testate amoebae communities and to analyze the seasonal changes in testate amoebae communities in a Sphagnum-dominated peat bog (eastern Poland). A total of 45 testate amoebae species were identified in the samples. The highest species richness occurred in hollows dominated by Sphagnum angustifollum, much lower numbers of taxa were observed in hummocks dominated by Sphagnum magellanicum and Polytrichum. The Monte Carlo permutation test showed the significance of Ntot, temperature, pH, and the depth to the water table for the variability of testate amoebae in all microhabitats. Species found in spring samples were associated with the increased Ntot content. Species occurring in summer samples were associated with the increasing pH gradient and species developing in late spring and autumn preferred a greater depth to the water table.