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EN
Microplastics (MPs) are small fraction of plastics that are less than 5 mm in length. They are bountiful and widespread pollutants in the aquatic environment. A wide range of organisms which play an important role in the food web, ingest microplastic particles and transfer them to the higher trophic levels. In this work, ingestion of fluorescent polystyrene beads 2 µm of diameter by ciliated protozoa Paramecium aurelia in different concentrations and times of exposure was studied. We studied also the ingestion and clearance rate as well as formation of food vacuoles. The highest uptake of beads by ciliates reached 1047.2 ± 414.46 particles after 10 min of incubation. Food vacuoles formation reflected the ingestion rate of P. aurelia, which increased at higher beads concentration up to the10th minute of incubation and decreased afterwards. On the contrary, the clearance rate persisted to be higher at low concentration. These findings showed that maximum capacity of microplastics ingestion by paramecia depended on beads concentration and on time of exposure.
EN
The distribution of bacterial and ciliate abundance, ciliate community composition and other parameters were studied during summer along a transect from the mouth of the Słupia River to offshore waters (southern Baltic Sea). Bacteria were examined under an epifluorescence microscope and ciliates were observed under an inverted microscope. Two water masses were identified along the transect. Less saline waters in the river mouth and in the surface layer in the port of Ustka were characterized by high bacterial abundance (5.51–6.16 × 106 ml-1) and low ciliate abundance (0.34–0.90 cells ml-1). More saline waters in the near-bottom zone in the port of Ustka and in the surface layer outside the port contained smaller numbers of bacteria (0.99–2.14 × 106 ml-1) and larger numbers of ciliates (2.65–5.40 cells ml-1). The differences were statistically significant. The separation of the two water masses indicated that the Słupia River exerted a minor impact on the marine waters. The ciliate community composition changed along the transect studied. The main statistically significant difference observed was the low contribution of oligotrichs and choreotrichs to ciliate biomass (3–4%) in less saline waters and their dominance (45–80% of ciliate biomass) in more saline waters.
EN
Dilution experiments were performed to estimate phytoplankton growth and microzooplankton grazing rates at two sites: freshwater (Nida) and brackish water (Smiltyne) in the Curonian Lagoon (SE Baltic Sea). Using the size-fractionation approach and dilution experiments, we found that the microzooplankton community was able to remove up to 78% of nanophytoplankton (2–20 μm) standing stock and 130% of the total daily primary production in the brackish waters of the lagoon, and up to 83% of standing stock and 76% of the primary production of picophytoplankton (0.2–2 μm) in the freshwater part. The observed differences were attributed to the changes in ciliate community size and trophic structure, with larger nano-filterers (30–60 μm) dominating the brackish water assemblages and pico-nano filterers (<20 μm and 20–30 μm) prevailing in the freshwater part of the lagoon.
EN
This paper presents results of the studies of ciliate assemblage in benthos of lowland river influenced by sewage discharged from the municipal wastewater treatment plant. During the presented research the 47 ciliate species, including 45 species from the benthos of the river and 18 from the activated sludge of aeration chamber were identified. Only two species registered in the activated sludge were not observed in the river. Against the background of the lowest number of species in the point located in the distance of 50 m below the discharge of sewage the maximum amount and biomass of these species were observed. Whereas, 200 m below the discharge the decrease in number and biomass of ciliate to the level noted for location before the discharge was observed. Thus, generalizing, one may state that influence of municipal WWTP sewage discharge for ciliate assemblage in the river’s benthos was clearly visible but local.
EN
Protozoan communities were studied in the coastal zone of the southern Baltic Sea. Stable environmental conditions and typical, bimodal seasonal changes in the protozoan biomass were observed at the sampling site in Sopot (2003–2004). At the sampling site in Ustka (2007–2008), strong benthic resuspension and irregular impacts of fresh water resulted in atypical seasonal changes in the protozoan biomass with a summer peak only. The mean annual biomass had similar values at both sites: 43.2 μg C dm−3 in Sopot and 38.6 μg C dm−3 in Ustka. The protozoan community in Sopot was dominated by ciliates (48% of the biomass), whereas in Ustka — by heterotrophic nanoflagellates (53%).
6
Content available remote Community structure of psammon ciliates in sandy beaches of lakes
EN
Ciliate abundance and species composition were studied in the sandy beaches of six lakes of different trophic status (Poland). Samples of wet sand were taken in June 2007 from the euarenal (emergent sand), hygroarenal (sand wetted by lake waves) and hydroarenal (submerged sand) zones. The numbers of ciliates ranged from 105 to 2933 ind. cm-3 of sand and did not show any visible trend with lake productivity. In all the studied lakes, ciliates were much more numerous in the euarenal than in the hydroarenal. Small bacterivorous scuticociliates dominated in the euarenal, while Hymenostomatida, Cyrtophorida, Hypotrichida as well as Scuticociliatida comprised a significant part of the ciliate community in the hygro- and hydroarenal zones. There were positive correlations between ciliates and the concentrations of chlorophyll a and total nitrogen.
EN
The protists notably ciliates and testate amoebas in the conditions of modernized wastewater treatment plants "Hajdow" (Lublin, Poland) and the nitrogen removal efficiency were studied. Sampling took place every week during the period of August-September 2010. The total of 31 taxa of ciliates and 3 taxa of testate amoebas were identified. Most of the species were registered during the whole research period. Significant abundance reached the following species: Acineria uncinata, Aspidisca cicada, Aspidisca lynceus, Vorticella aquadulcis, Vorticella infusionum, Arcella vulgaris, Euglypha acanthophora and Pyxidicula operculata. In September increase in efficiency of nitrogen removal process was registered. The research shows that the increase of nitrogen reduction efficiency was accompanied by increase of ciliates quantity, mainly due to peritrichid ciliates.
PL
Przedstawiono analizę zgrupowań pierwotniaków obejmującą orzęski oraz ameby skorupkowe, zasiedlające kolejne urządzenia głównego ciągu technologicznego oczyszczalni ścieków "Hajdów" na tle zmian w stężeniach związków azotu. Badania prowadzono po modernizacji części biologicznej realizowanej w celu podniesienia skuteczności usuwania ze ścieków związków biogennych, a w szczególności związków azotu. Pobór próbek prowadzony był raz w tygodniu w okresie sierpień-wrzesień 2010 roku. W badanym materiale biologicznym wyodrębniono 31 gatunków orzęsków oraz 3 gatunki ameb skorupkowych. Większość ze wspomnianych gatunków pierwotniaków odnotowywana była przez cały okres badań. Najbardziej licznie w analizowanym materiale biologicznym reprezentowane były następujące gatunki: Acineria uncinata, Aspidisca cicada, Aspidisca lynceus, Vorticella aquadulcis, Vorticella infusionum, Arcella vulgaris, Euglypha acanthophora i Pyxidicula operculata. We wrześniu odnotowany został wzrost skuteczności procesu usuwania związków azotu. Prezentowane badania wskazują, iż wzrostowi stopnia usuwania ze ścieków związków azotu towarzyszył wzrost ilości orzęsków odnoszący się głównie do form peritricha.
8
EN
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 [mu]g 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.
EN
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.
EN
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.
EN
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.
PL
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.
EN
Species composition of plankton ciliates was studied in the Curonian Lagoon in 2007-2008 and compared to long term investigations dating back to the 1980th. In total, 152 taxa were identified at the level of species or genera. More species (76 species/higher taxa) was found in the estuarine part of the Lagoon due to temporally unstable salinity and the presence of both freshwater and brackish/marine species. Some of the brackish/marine species: Tintinnopsis baltica, Tintinnopsis kofoidi, Cothurnia maritima, Lohmaniella oviformis, Lohmaniella spiralis and Helicostomella subulatum were recorded for the first time in the lagoon. The ciliate community at the freshwater sites was less diverse, containing 63 species/higher taxa in the central stagnant part of the Lagoon and 47 – in the Nemunas River avandelta. The comparison of present and past studies revealed that the use of a single live-counting method could lead to underestimation of small nanociliate species, whereas examination of Lugol fixed material provides relatively poor taxonomic information.
13
Content available remote The Influence of Cadmium and Copper Ions on Microfauna of Activated Sludge
EN
The prevalence of heavy metals in wastewater is the cause of death of numerous organisms which take part in biological treatment of wastewater, that is why the aim of the study has been to asses the influence of cadmium and copper ions upon the microfauna of activated sludge. 5, 10, 50, and 100 mg/l of Cd2+ and Cu2+ were added into the samples of activated sludge and then, after 24 hours, the microscopic observations of activated sludge microfauna were carried out, and all changes concerning the amount of microfauna, functional groups, and species composition were determined. The results obtained allowed to find a high level of toxicity of Cd2+ and Cu2+ ions to activated sludge microfauna, which resulted in the changes in the value of the Sludge Biotic Index and classes of sludge, survivability of microfauna, and reduction in the number of taxonomic units. It was observed that Cu2+ ions are more toxic to activated sludge microfauna than Cd2+ ions in identical doses. Organisms sensitive to Cd2+ and Cu2+ ions have been found to be testate amoebae, Aspidisca sp. and Epistylis sp., as well as organisms relatively sensitive to tested metals, which turned out to be ciliates of Opercularia and Vorticella convalaria genera.
PL
Powszechne występowanie metali ciężkich w ściekach jest przyczyną obumierania wielu organizmów biorących udział w biologicznym oczyszczaniu ścieków, dlatego celem pracy była ocena wpływu jonów kadmu i miedzi na mikrofaunę osadu czynnego. Do prób osadu czynnego wprowadzano 5, 10, 50 i 100 mg/l jonów Cd2+ oraz Cu2+ a następnie po 24 godzinach dokonywano obserwacji mikroskopowych mikrofauny osadu czynnego i określano wszelkie zachodzące zmiany dotyczące liczebności organizmów, składu gatunkowego i grup funkcyjnych. W uzyskanych wynikach stwierdzono wysoką toksyczność jonów Cd2+ i Cu2+ wobec mikrofauny osadu czynnego. Jony te powodowały zmiany wartości Biotycznego Indeksu Osadu i klas osadu, spadek przeżywalności mikrofauny oraz spadek ilości jednostek taksonomicznych, przy czym zaobserwowano, iż jony Cu2+ są bardziej toksyczne dla mikrofauny osadu niż jony Cd2+ w tych samych dawkach. W populacji osadu czynnego organizmami wrażliwymi na obecność jonów Cd2+ i Cu2+, są ameby domkowe (Testacea), orzęski Aspidisca sp. i Epistylis sp.. Zaobserwowano również występowanie w osadzie czynnym gatunków mało wrażliwych na testowane metale ciężkie, którymi okazały się orzęski osiadłe Opercularia sp. i Vorticella convalaria.
EN
Peatbogs have both horizontal and vertical differences in moisture, pH, light and nutrient availability. Micro-distribution of testate amoebae taxa has been observed along the Sphagnum stem but there is no data concerning the vertical micro-distribution of protozoa in water column under the peatbog surface and in the interstitial waters. The research was made in a small (ca 16 ha) peatbog complex in the eastern Poland. Vertical microzonation of testate amoebae and ciliates in relation to physical, chemical and biological parameters (peat porosity, temperature, dissolved oxygen, chlorophyll a, TN, TP, DOC and TOC) in Sphagnum hollows, mud bottom hollows and interstitial waters in peatbog were studied. Samples were taken once a month from April to November 2009 from three layers: free water mass up to 10 cm (FW), bottom water (BW) and interstitial, pore water - IW (water between particles of peat on depth 20-25 cm). During each sampling occasion 3 samples were collected from each site. At each type of micro-habitat and each sampling date water was sampled using a plexiglass core. The water column sampled from the top surface to the bottom was 25 cm high. Interstitial waters were collected from mini-piezometers located into the peat. Temperature, dissolved oxygen, conductivity, chlorophyll a and nutrients contents were always lower in interstitial water than in free and bottom waters. The highest numbers of testate amoebae and ciliates taxa occurred in the bottom water (31 and 13 taxa, respectively) and became much lower in interstitial water (17 and 5 taxa, respectively). The density and biomass of protozoa differed significantly between the studied layers, with the lowest numbers in the interstitial water and the highest in the bottom water. Ordination analysis indicated that chlorophyll a, TOC and TP can strongly regulate the abundance and species composition of protozoa. The RDA ordination showed that the testate amoebae species can be divided into three groups associated with: 1) free water mass, 2) bottom water and 3) interstitial water, while the ciliate species into two groups associated with: 1) interstitial water and 2) free water mass and bottom waters. The free water mass and bottom water were dominated by mixotrophic taxa, whereas the deepest layer showed the increase of the contribution of small, bacterivorous species. In all the examined micro-habitats the highest abundance and biomass of these microorganisms occurred in early spring and late autumn, while the lowest values were recorded in late summer.
EN
The experiment, with the use of sand deposit from hygroarenal (shore sand beach wetted by lake waves) of the beach of eutrophic Lake Mikołajskie (Masurian Lakeland, Poland), was performed in order to test the hypothesis that shore sand deposit is the bank of resting forms of ciliate, rotifer and crustacean species. The experiment was conducted over a 38 days period in March-April 2004. Frozen sand taken in winter was exposed in aquariums filled with pre-filtered (GF/C) lake water in stable temperature (20[degrees]C), oxygen saturation and 12:12 light/dark conditions. Samples (three replicates) were taken each day. A total number of 44 ciliate, 59 rotifer and 9 crustacean taxa were identified during the studied period. Resting forms of different species and/or taxonomic groups developed in different time and it may be the result of different strategies in colonization of new habitats. Organisms forming resting cysts such as ciliates (11 species) and bdelloid rotifers appeared after the first day of the incubation whereas organisms hatching from resting eggs (monogonont rotifers and crustacea) were observed from the 2nd-3rd day of the experiment. The numbers of all the studied groups of organisms increased gradually and then strongly decreased indicating probably nutrient and/or organic matter limitation. The highest numbers of ciliates (731 ind. cm[^-2] of sand) was found on the 5th day, rotifers (987 ind. 100 cm[^-2]) on the 23rd day, cladocerans (60 ind. 100 cm[^-2]) on the 21st day and copepods (30 ind. 100 cm[^-2]) on the 33rd day of the experiment. The results of this study suggests that shore sand deposits being the temporal refugium for the small-bodied invertebrates transported here with the wave action may also play an important role as the transfer for their further dispersal in addition to postulated ways of expansions such as wind, rain, animals and surface runoff.
EN
Testate amoebae and ciliates are common inhabitants of moist soils, lakes and peatbogs. These microorganisms are important consumers of bacteria, flagellates and algae; they also participate in transformation of the organic matter and nutrient regeneration. The complexity of micro-environmental conditions present in peatbogs and the challenges associated with the proper sampling may partly explain the fact that these microorganisms are still much less studied than other components of the ecosystem. The influence of emergent and submerged plants on community composition, abundance and biomass of testate amoebae and ciliates were investigated in two peatbogs in the eastern Poland. The raised and carbonate bogs selected for this study were considered to be representative of the bogs of the region and contained a broad diversity of habitats. Samples were collected in patches of Sphagnum angustifolium (C.C.O. Jensen ex Russow), Sphagnum cuspidatum Ehrh. ex Hoffm., Sphagnum palustre L., belts of Phragmites australis (Car.), Typha latifolia L., Carex acutiformis Ehrhart., Calliergonella cuspidata (Hedw.) and beds of Utricularia sp. Sampling was done on a monthly basis from April to November. At each plant patch (microhabitat) and each sampling date the water was sampled using a plexiglass core (length 1.0 m, [Radius]50 mm). Comparison of the species number, abundance and biomass (estimated in C organic units) of testate amoebae and ciliates between Sphagnum patches did not show statistically significant differences. The significant differences were noted in patches of plants in carbonate peatbog. The highest species number (40-46) was found in the Utricularia and Calliergonella, and the lowest richness (26-20) in the Typha, Phragmites and Carex. The density and biomass of protozoa communities, increase together with the abundance and the level of the complicated spatial structure of the plants. Based on differences in plant structure, two groups of habitats with similar patterns of size-related testate amoebae and ciliate distribution were distinguished. The first group consisted of three vegetated zones of smooth stem structure (Phragmites, Typha and Carex), the second group comprised plant species, which were more complex (Sphagnum, Utricularia and Calliergonella). In the redundancy analysis, water level, pH, concentration of TP, chlorophyll a and TOC together explain 45% of the variation in the species distribution data. The contribution of conductivity, dissolved oxygen TN and DOC was not (or marginally) statistically significant.
EN
Relationships between ciliates and the presence of emergent and submerged vegetation were studied in a shallow lake in eastern Poland. Samples were collected in zones of Phragmites, Typha, Batrachium, Elodea, Stratiotes and from the open water zone. The abundance and biomass of ciliates were significantly higher at sites with structurally most complex plants than in the open water or sparsely vegetated sites. The redundancy analysis indicated that bacterial abundance and total organic carbon were the most influential variables that determine the distribution of ciliates. However, chlorophyll a and Ptot have a lesser influence on the distribution of these microorganisms. Based on differences in macrophyte structure, two groups of habitats with similar patterns of size-related ciliate distribution were distinguished. The first group consisted of three vegetation zones of sparse stem structure and the open water zone, the second group comprised submerged macrophyte species, which were more complex.
18
Content available remote Planktonic ciliates in the coastal medium-size river : diversity and productivity
EN
Annual changes in abundance, biomass, and taxonomic composition of potamoplanktonic ciliates were assessed in the 139 km long, coastal (Baltic coast) river (the Słupia River, Northern Poland) having mean annual flow - 18 m[^3] s[^-1] and flowing through several natural lakes and reservoirs. The samples were taken from one site, once a week from December 2005 to December 2006, then concentrated by sedimentation and counted and measured under an inverted microscope. Ciliate production was assessed with relevant published formulas. Mean annual abundance and biomass amounted to 6448 cells l[^-1] and 6.60 [my]g C l[^-1], respectively. During the year two distinct peaks of biomass were observed: a spring peak in April and May, and a winter one in December. Spring peak was formed by prostomatids and oligotrichs, whereas winter one by peritrichs. Three aforementioned orders contributed altogether to 64% of abundance and 82% of ciliate biomass. Prevalence of prostomatids seemed to be characteristic for the studied river. Most of ciliates were surprisingly small, fraction below 20 [my]m contributed 77% of the mean annual abundance. Domination of small ciliates indicated high mean annual potential growth rates ranging from 0.6 d[^-1] to 0.7d[^-1]. The river is characterised by a narrow variability of the water level and numerous through-flow lakes. As a result ciliate community in the river resembled communities encountered in lakes - free-swimming organisms dominated and sessile forms and those detached from sediments contributed not more than one fifth of ciliate biomass.
19
Content available remote Psammon ciliates : diversity and abundance in hygroarenal of eutrophic lake
EN
Taxonomic composition, spatial distribution and seasonal changes in abundance of ciliates were investigated in hygroarenal (the zone of the beach adjacent to lake littoral and affected by wave action) of the eutrophic Lake Mikołajskie (area 498 ha, max. depth 26 m, Masurian Lake District, Poland). The choosen beach amounted 10.8 x 1.5 m in size and 30 sampling points were distributed according to regular network 60 x 30 cm. Three sampling points were located in each of 10 sampling stations parallel to water line and at an increasing 0, 30, 60 cm distance from it). The small-scale distribution of ciliates was recognized from the set of 30 samples taken once in June 2003 from all stations and sampling points. The seasonal changes of ciliate density were analysed on the set of 41 samples taken from March to November 2004 from the middle sampling points (about 30 cm from water line) in 3 sampling stations. Ciliate community was characterised by relatively high taxonomic richness (56 ciliate taxa) and numbers (up to 2750 ind. cm[^-3] of sand). The numbers of ciliates varied seasonally from 4.6 to 1630 ind. per 1 cm[^3] of sand, showed three distinct peaks (maximum in summer) and were markedly differentiated among the sampling stations distributed along the 10 m of homogenous beach. Significant correlations between ciliates and the share of largest grain size fraction suggest that grain size of sand may be responsible for the observed spatial heterogeneity of ciliates. Hymenostomes, particularly the omnivorous Pleuronema coronatum Kent, dominated the ciliate assemblages. The statistical analysis showed a significant correlation between ciliate numbers and total phosphorus and total nitrogen concentrations in interstitial water, but there was no correlation with chlorophyll a.
EN
The density and biomass of planktonic ciliates significantly differed between sample sites in a deep, mesotrophic lake, with the lowest numbers in the hypolimnion and the highest in the epilimnion. The community composition varied greatly with depth. Oligotrichs dominated in the epilimnion, where prostomatids and peritrichs were also important components of the community. The density of oligotrichs and peritrichs decreased in the metalimnion, and they were absent from the hypolimnion. In the deep metalimnion the most abundant groups were prostomatids, haptorids and scuticociliates. In the hypolimnion, the ciliate community was dominated by scuticociliates and heterotrichs. In the epilimnion and metalimnion a significant positive correlation was observed between ciliate numbers, chlorophyll a and heterotrophic flagellate density. In all three zones the number of ciliates was most strongly correlated with water temperature, concentrations of total organic carbon (TOC), total phosphorus (Ptot) and bacterial density, whilst in the hypolimnion there was a significant correlation between ciliate numbers and the dissolved oxygen concentration.
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