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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:... The aims of this study were to identify the taxonomic diversity and abundance of psammonic ciliate communities in mesotrophic and eutrophic lakes (Lczna-Wlodawa Lakeland, eastern Poland). The effect of selected physical and chemical water parameters on ciliates community was also analysed. Psammon samples were collected during three s: spring, summer and autumn of 2010. In each lake, in the psammolittoral, samples were collected in the , higroarenal, and hydroarenal s. 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 (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 s of the eutrophic lake. INTRODUCTION Psammon is an assemblage of organisms living in the moist sand of coastal s of seas, lakes and rivers [5]. Psammonic organisms inhabit beaches of water bodies at various depths. In rivers, the psammon can reach more than 40 cm deep into sand, in seas ­ up to a few centimeters, and in lakes it rarely exceeds 2 cm [6]. Wiszniewski [32] recognises three s within the psammolittoral: the hydroarenal (permanently submerged, reaching approx. 1 m into the lake), higroarenal (fluctuation ), and , including sand up to a distance of 1 m from the water line. Organisms inhabiting the live in spaces between sand grains filled with water. The granulometric composition of the sand may have certain influence on the species composition and numbers of microorganisms inhabiting spaces between its grains [7]. Psammon is a complex of various groups of organisms, e.g. algae, bacteria, protozoa, rotifers, gastrotrichs and nematodes. So far, studies on the occurrence of psammonic rotifers have been relatively numerous [1, 5, 7]. Only a few studies relate to the occurrence of other groups of organisms, particularly ciliates. Ciliates are a significant group of microplankton of aquatic environments [8]. They are an important element of the trophic structure of aquatic ecosystems. They often constitute the main group of bacterial production consumers, transferring matter and energy into higher trophic levels [14, 22, 23, 24]. Ciliates can also be used as indicators of the purity of rivers and lakes [22, 24]. Studies on the structure of psammonic ciliates are usually fragmentary. So far, only one paper on those protozoa in the psammolittoral of a eutrophic lake (Lake Mikolajskie) has been published in Poland [14]. World literature includes a few publications describing ciliates in the psammon of the Caspian Sea [1], the White Sea [18, 19, 20] and Lakes: Kinneret [17], Tanganika [4] and Baikal [27]. According to Wiszniewski [32], "hydropsammon is the main of development of zoopsammon; however it cannot be recognised as a transitional stage between aquatic life and life on the beach. The is specific in all aspects". Therefore, the psammolittoral may constitute a type of ecotone, i.e. a transitional between adjacent ecological systems. Currently, the term is understood much more widely as a transitional between adjacent ecological systems, with unique features determined by the space and time scale, and distinct interactions between the systems [12]. Contact between water and land results in development of a new species structure within its , and in intensification of ecological processes in comparison to adjacent environments [26, 10]. Therefore, assemblages of psammonic ciliates should also show certain species diversity and abundance in the water/land transitional . Studies on the structure of ciliates in aquatic ecosystems indicate strong correlations between numbers of those organisms and physical and chemical water parameters [14, 21, 22, 23]. The most numerous positive correlations were recorded between numbers of ciliates and chlorophyll a, TOC, and Ptot in water. This suggests a distinct relation of abundance of the microorganisms to nutrient concentrations in the lake waters. High horizontal variability of physical and chemical water parameters within the psammolittoral (, higroarenal, hydroarenal) suggests that a similar pattern should be observed in the species richness and abundance of psammonic ciliates. Scarce information on horizontal distribution of psammonic ciliates led to undertake studies on that group of microorganisms. The main objective of the study was to determine the number of taxa and abundances of psammonic ciliates in lakes of different trophic status. The effect of selected physical and chemical water parameters on development of that microorganisms was also analysed. STUDY AREA Two lakes of Lczna-Wlodawa Lakeland (eastern Poland, 51º N, 23º E) (Fig. 1) were selected: mesotrophic Lake Piaseczno (area 84.7 ha, maximum depth 38.8 m) with well developed sandy psammolittoral, and eutrophic Lake Sumin (area 91.5 ha, maximum depth 6.5 m) with well developed psammolittoral [29]. In the eulittoral of Lake Piaseczno the emergent vegetation is very scarce (Carex arenaria L., Phragmites australis (Cav.)Trin. ex Steud) and the submerged macrophytes, Lczna-Wlodawa Lakeland Fig. 1. Location of study area such as Myriophyllum alternifolium DC. and Ceratophyllum demersum L. dominate. In Lake Sumin well developed belts of emergent (Phragmites australis (Car.), Trinex stend and Typhalatifolia L.) and submerged (Myriophyllum spicatum) dominate in littoral [15]. In Lake Piaseczno samples were taken in the North-East coast whereas in Lake Sumin in the South-East coast. METHODS Ciliates were collected in spring, summer and autumn in 2010. The samples of psammon were taken from three s of arenal: - exposed sand, 1 m of shoreline; higroarenal - at the shoreline; hydroarenal - under water, 1 m from the shoreline. The samples were collected with a plastic sharp-edged tube, 60 mm in diameter at four points of each . The samples were taken to the depth of 2 cm. From each 12 samples were collected in each each sample was analysed at the depth of 2 cm (Fig. 2). Each sample was shaken with saline solution and then condensed by filtering through a mesh net and fixed immediately with Lugol's solution (0.2% final concentration). Ciliate density was calculated per 1 cm3 of sand. Observation of life samples was used for the taxonomic identification. Species identification was based on Foissner and Berger [9]. Ciliate biomass was estimated by multiplying the numerical abundance by the mean cell volume calculated from direct volume measurements using appropriate geometric formulas. Therefore, the calculated cell volume was divided by a correcting factor of 0.4 [13]. Each time the following physical and chemical parameters: pH, conductivity, temperature, total organic carbon (TOC), total phosphorus (Ptot), P-PO4, N-NO3, N-NH4 and chlorophyll a were examined in three sites: (interstitial water), higroarenal and hydroarenal (water above the ground). Temperature, conductivity and pH were determined in situ using the multiparameter sensor 556 MPS (Envag). TOC was determined using the PASTEL UV, and the other parameters were analyzed in laboratory, according to Hermanowicz et al. [11]. Chlorophyll a was determined by the spectrophotometric analysis of alcohol extracts of the algae retained on polycarbonate filters. Fig. 2. The outline of beach ­ littoral with sampling station (I, II, III, IV) The biodiversity index, expressed as the Shannon-Wiener index, was calculated using the formula [16]: H '= - S i =1 pi ln pi (1) were: ni- the number of individuals of i species; the abundance of I species, S - the number of species (species richness), N - the total number of individuals, pi - the relative abundance of each species, calculated as the proportion of individuals of a given species n to the total number of individuals in the community: Ni . The frequency of particular taxa was calculated as the percentage of collected samples in which the species occurs. All the species found were classified into the four groups: very constant species (occurring in 61­100 percent of the samples), constant species (occurring in 41­60 percent), accidental species (occurring in 21­40 percent of the samples), accessory species (occurring in less than 20 percent of the samples) [31]. The index of similarity between assemblages was calculated using the Jaccard formula: JI = S ab S a + S b - S ab (2) were: Sa - abundance taxa in assemblage a, Sb - abundance taxa in assemblage b, Sab - abundance taxa in assemblage a and b. Statistical analyses of results were carried out using the STATISTICA 7.0 software. The differences between samplings were analyzed using T-Student test. Pearson correlation coefficients were calculated between pairs of variables in order to determine the relationship between ciliates and physical and chemical parameters. RESULTS Physical and chemical parameters Irrespective of the lake's trophic status and the analysed, neither water temperature, pH, nor chlorophyll a concentration differed significantly (Table 1). Table 1. Physical and chemical characteristic of the psammon water of investigated lakes (* average and ** range) Lake/ / 91.3 86-101 0.394 0.083-0.578 0.293 0.058-0.710 0.070 0.005-0.190 0.096 0.019-0.23 8.6 4.6-12.1 Temp. pH Conductivity S·cm-1 N-NH4 mgN·dm-3 N-NO3 mgN·dm-3 PO4 mgPO4·dm-3 Ptot mgP·dm-3 TOC mgC·dm-3 Chlorophyll a g·l-1 32.76 11.21-73.90 *19.34 **14.83-25.00 6.77 6.68-6.86 Piaseczno *20.15 **16.80-27.44 7.13 6.74-7.50 76.0 62-89 0.423 0.015-0.94 0.326 0.065-0.840 0.049 0.001-0.140 0.175 0.025-0.390 9.2 4.0-17.8 23.40 3.44-53.07 hydroarenal higroarenal *20.19 **16.33-26.74 7.47 6.60-8.60 111.7 90-137 0.111 0.010-0.275 0.280 0.054-0.630 0.035 0.002-0.100 0.153 0.015-0.150 4.2 3.0-5.9 25.91 13.40-50.42 *17.98 **13.25-21.00 8.33 7.2710.75 395.0 273-477 1.131 0.675-1.650 0.620 0.211-1.320 384.7 361-412 0.362 0.246-0.430 0.334 0.102-0.750 0.282 0.049-0.730 0.254 0.195-0.289 31.2 16.4-55.5 26.71 18.75-40.46 Sumin *19.20 **15.27-24.58 7.37 7.24-7.63 0.028 0.001-0.080 0.337 0.029-0.870 15.2 14.6-16.4 26.31 20.26-32.97 hydroarenal higroarenal *19.08 **15.35-24.78 7.33 7.14-7.70 417.7 403-427 0.342 0.199-0.420 0.366 0.087-0.860 0.005 0.001-0.010 0.062 0.016-0.101 14.8 13.4-16.4 23.79 17.38-29.86 Conductivity, N-NO3, N-NH4, Ptot, and TOC, in turn, reached their highest values in eutrophic Lake Sumin. The tendency was particularly distinct in the eu- and higroarenal s. In mesotrophic Lake Piaseczno, conductivity reached from 62 S cm-1 in the higroarenal to 137 S cm-1 in the hydroarenal. P-PO4 concentrations reached the highest values in the in both lakes (Sumin ­ 0.289 mg PO4 dm-3, Piaseczno ­ 0.190 mg PO4 dm-3). The highest content of TOC was noted in the of the eutrophic lake (55.5 mgC dm-3), and the lowest in the hydroarenal of the mesotrophic lake (3.0 mgC dm-3). The highest total phosphorus concentrations were recorded in the higroarenal of eutrophic lake (0.87 mgP dm-3), and the lowest in the hydroarenal (0.015 mgP dm-3) of the mesotrophic lake (Table 1). Taxonomic composition and species frequency In the lakes studied, a total of 53 ciliate taxa were recorded; in the eutrophic lake ­ 44 taxa, and in the mesotrophic lake ­ 35 ciliate taxa (Table 2). Species diversity was highly varied between the studied s. In the eutrophic lake, the highest number of taxa occurred in summer in the hydroarenal (23 taxa), and the lowest number of taxa (4 taxa) was observed in the higroarenal in autumn. In the mesotrophic lake, in turn, a considerable increase in the number of psammonic ciliate taxa occurred in autumn in the higroarenal , where 14 taxa of the protozoa were identified, and the lowest number of taxa (5 taxa) was observed in spring and summer. The highest species similarity in the eutrophic lake, expressed by the Jaccard index, occurred between the hydroarenal and higroarenal s. In the mesotrophic lake, the index was the highest between the hydro- and s (Table 3). The analysis of species frequency revealed one constant species in Lake Sumin, i.e., Codonella cratera. In Lake Piaseczno, no constant species were determined. Accessory species were recorded in each of the lakes - in Lake Sumin: Cyclidium glaucoma, Paramecium sp., Brachonella spiralis, Euplotes sp; and in Lake Piaseczno: Cyclidium glaucoma, Paramecium sp., Glaucoma sp. The remaining species were classified as random. Irrespective of the lake tropic status, within the and higroarenal, constant taxa were Paramecium sp. and Codonella cratera. In the hydroarenal, Cyclidium glaucoma reached the highest frequency. The highest numbers of psammonic ciliates were determined in eutrophic Lake Sumin (516 ind. cm-3). In mesotrophic Lake Piaseczno, densities were even twice lower, and amounted to 191 ind. cm-3. In the zonal distribution the highest density of those microorganisms in Lake Sumin was observed in spring in the hydroarenal. The lowest numbers in the lake were recorded in the higroarenal in autumn (Fig. 3). In the mesotrophic lake, the highest abundance was observed in spring in the ­ 280 ind. cm-3, and the lowest in the hydroarenal ­ 98 ind. cm-3. Differences in protozoa biomasses were also distinctive, both between the s and lakes (Fig. 4). The average ciliate biomass in Lake Sumin amounted to 73.39 g cm-3, and in Lake Piaseczno to 27.65 g cm-3. The t-student analysis (level of significance p = 0.05) of numbers of ciliates between individual s revealed no significant differences in numbers of the organisms between s in individual lakes. The highest biomass was recorded in summer in the hydroarenal in Lake Sumin (240 g cm-3), and the lowest in autumn in the higroarenal (5.12 g cm-3). In Lake Piaseczno, the highest biomass occurred in spring in the hydroarenal (51.46 g cm-3), and the lowest within the same Table 2. Taxonomic composition of psammonic ciliates of three s in investigated lakes (Eu-, Hi-higroarenal, Hy-hydroarenal) Autumn Hi Lake Sumin Hy Taxa + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Colpodea Colpoda sp. Cyrtrophorida Trochilia minuta (Roux) Pseudochilodonopsis sp. Gymnostomatida Lagynophyra acuminata (Kahl) Mesodinum pulex (Clap. & Lach.) Tracheophyllum sp. Spatidium spatula (Dujardin) Heterotrichida Blepharisma sp. Brachonella spiralis (Smith) Hymenostomatida Colpidium sp. Colpidium colpoda (Losana) Colpidium kleini (Foissner) Dexiostoma campylum (Stokes) Table 2. Taxonomic composition of psammonic ciliates of three s in investigated lakes (Eu-, Hi-higroarenal, Hy-hydroarenal) ­ continuation Taxa + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Dexiotricha granulosa (Kent) Dexiotrichides centralis (Stokes) Frontonia sp. Frontonia angusta (Kahl) Frontonia atra (Ehrenberg) Frontonia leucas (Ehrenberg) Glaucoma sp. Glaucoma reniforme (Schewiakoff) Lembadion sp. Lembadion bullinum (Müller) Lembadion lucens (Maskell) Paracolpidium truncatum (Stokes) Paramecium sp. Paramecium bursaria (Ehrenberg) Paramecium putrinum (Claparede) Sathrophilus muscorum (Kahl) Stokesia vernalis (Werich) Tetrahymena sp. Table 2. Taxonomic composition of psammonic ciliates of three s in investigated lakes (Eu-, Hi-higroarenal, Hy-hydroarenal) ­ continuation Taxa + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Uronema nigricans (Müller) Unindetified Hymenostomata Hypotrichida Aspidisca cicada (Müller) Euplotes sp Euplotes affinis (Dujardin) Euplotes moebiusi (Kahl) Holosticha kessleri (Wrzeniowski) Holostichia monilata (Kahl) Oxytrichia similis (Engelmann) Unindentified Hypotrichia Loxodes Loxodes sp. Nassulida Chilodontopsis sp. Oligotrichida Codonella cratera (Leidy) Strombilidium humile (Penard) Table 2. Taxonomic composition of psammonic ciliates of three s in investigated lakes (Eu-, Hi-higroarenal, Hy-hydroarenal) ­ continuation Taxa + + + + + + + + + + + + + + + + + + + + + + + + + + + + + 12 11 5 6 5 5 6 14 10 12 13 10 14 9 23 15 4 8 + + + + Odontostomatida Unindentified Odontostomatida Peritrichida Vorticella sp. Pleurostomatida Acineria sp. Acineria incurvata (Dujardin) Litonotus sp. Litonotus lamella (Müller) Prostomatida Holophyra sp. Holophrya discolor (Ehrenberg) Scuticociliatida Cinetochilum margaritaceum (Ehrenberg) Cyclidium glaucoma (Müller) Suctoria Actineta sp. Total number of taxa: 53 Table 3. Pearson correlation between ciliate density and physical and chemical factors of investigated lakes (p 0.05) Variables Density Lake Piaseczno Higroarenal Hydroarenal -0.32 n.s. 0.31 -0.31 0.50 n.s. 0.31 0.29 n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. -0.31 n.s. n.s. 0.40 0.40 n.s. 0.28 -0.27 2500 2000 Higroarenal Hydroarenal Lake Sumin Higroarenal 0.51 0.29 0.58 0.49 0.50 0.54 0.49 0.31 Hydroarenal -0.45 0.43 0.28 -0.51 -0.58 0.63 -0.63 -0.74 pH Conductivity N-NH4 N-NO3 P-PO4 Ptot TOC Chlorophyll a n.s. n.s. n.s. n.s. n.s. n.s. n.s. -0.29 Cialiate density (ind.·cm ) -3 0 Spring -500 Summer Lake Piaseczno Autumn Spring Summer Lake Sumin Autumn -1000 Fig. 3. Density of psammonic ciliates in investigated lakes (± standard deviation) in autumn (11.93 g cm-3). The statistical significance analysis for biomass between s and lakes revealed no significant discrepancy between the values compared. Irrespective of the lake's trophic status, Hymenostomata reached the highest participation in total numbers (from 13 to 95% of total numbers of ciliates) (Fig. 5). Irrespective of the , the eulittoral was dominated by Hymenostomata. In the two remaining s, participation of Oligotrichida (from < 1% to 40%) and Hypotrichida (from < 1% to 35%) increased. In the mesotrophic lake, participation of Scuticociliatida increased from 1% in spring to 60% in autumn. Relationship between psammonic ciliates and physical and chemical factors Total numbers of psammonic ciliates correlated positively with all of the physical and chemical water parameters analysed in the hydroarenal . The lowest correlation was Higroarenal Hydroarenal Biomass ( g·cm-3) 0 Spring -200 Summer Lake Piaseczno Autumn Spring Summer Lake Sumin Autumn -400 Fig. 4. Biomass of psammonic ciliates in investigated lakes (± standard deviation) 100% 80% 60% 40% 20% 0% Summer Summer Summer Summer Summer Summer Autumn Autumn Autumn Autumn Autumn Autumn Spring Spring Spring Spring Spring Spring Others Scuticociliatida Prostomatida Pleurostomatida Oligotrichida Hypotrichida Hymenostomatida Heterotrichidia Higroarenal Lake Piaseczno Hydroarenal Higroarenal Lake Sumin Hydroarenal Fig. 5. Domination structure of psammonic Ciliata orders in psammolittoral of investigated lakes (% of total numbers) determined between the numbers of ciliates and conductivity (r = 0.29, p = 0.05), and the highest between the numbers of ciliates and N-NH4 concentration in water (r = 0.58, p = 0.05). In the eutrophic lake, the characterised by the strongest correlations between the physical and chemical factors analysed and ciliate numbers was the hydroarenal. In the mesotrophic lake, a significant correlation was observed in the hydroarenal between N-NO3 concentration and ciliate numbers (r = 0.50, p = 0.05) (Table 4). DISCUSSION The number of psammonic ciliate taxa (53 taxa) in the lakes studied was similar to that determined in the hydroarenal of eutrophic Lake Mikolajskie in Mazury Lakeland (56 taxa) [14] and above 3 times higher than values observed by Madoni [16] in the psammolittoral of Lake Kinneret (Israel) (16 taxa). Such differences may result from local climatic conditions (rain, fluctuation, wind) [7]. Also Wiszniewski [33] mentioned the effect of atmospheric conditions and anthropopressure as the main reasons for the variability of taxonomic composition of psammonic organisms, even in the diurnal cycle. Table 4. Jaccard similarity coefficient value for the analyzed Lake Piaseczno /Higroarenal Higroarenal/Hydroarenal Hydroarenal/ Lake Sumin /Higroarenal Higroarenal/Hydroarenal Hydroarenal/ Spring 0.15 0.21 0.23 0.47 0.53 0.47 Summer 0.22 0.00 0.38 0.21 0.14 0.23 Autumn 0.13 0.22 0.23 0.12 0.20 0.28 The factors are often difficult to measure or distinguish, due to their specificity and simultaneous occurrence. The average numbers of psammonic ciliates in the eutrophic lake Sumin (266-703 ind. cm-3) were similar to those recorded in the eutrophic lake Mikolajskie [14]. In the psammolittoral of Lake Kinneret, the average numbers of ciliates amounted to 378 ind. cm-3 [17]. The available literature provides no information on the dynamics of al changes in the abundance of psammonic ciliates. Studies by Pennak [28] revealed that psammonic organisms show high al variability. Their numbers decrease significantly in autumn, and increase in spring and summer. A similar pattern was observed in the present research. In the lakes studied, a moderate effect (depending on the analysed) of a number of physical and chemical factors on protozoa occurrence was recorded. The influence of food abundance seems to be more significant (correlation between numbers of ciliates and chlorophyll a concentration). Studies by Czerna [3] revealed substantial abundance of psammonic algae in the lakes studied. Significant correlations between numbers of psammonic ciliates and nutrient concentration in the eutrophic Lake Sumin also suggest a considerable importance of the food source for the occurrence of ciliates. Both TOC and nutrients influence bacteria abundance. Therefore, they may have direct impact on the occurrence of protozoa, feeding on bacteria [22]. The trophic structure of ciliates was dominated by omnivorous and bacteriovorous species, which is in accordance with data from the eutrophic lake [14]. The psammolittoral is a variable environment, and according to Schmid-Aray [30], it is suitable for organisms with the ability of fast population growth and wide ecological tolerance. Therefore, it seems that sand is an environment adequate for organisms easily adapting to changes in environmental conditions. Moreover, ciliates may play a significant role in phosphorus regeneration, which should also result in an increase in abundance of algae and bacteria. The process may be largely influenced by the participation of small ciliate taxa, due to their high metabolic activity and fast generation. They are able to provide much more phosphorus than organisms of higher trophic levels [7]. The edge effect also seems to have a significant impact on the organisms analysed. The distribution of numbers and biomass between individual s and s suggests a substantial influence of rapid changes of environmental conditions on the occurrence of protozoa. A high water level in spring could also favour an increase in numbers of protozoa. The psammolittoral in the included large amounts of decomposing plant remains which could condition the occurrence of bacteria constituting the main sustenance of ciliates. Irrespective of the lake trophic status, Hymenostomata reached a significant dominance. However, their participation changed depending on the and analysed. This group (mainly taxa: Paramecium sp., Glaucoma sp., and Uronema nigricans) also prevailed in the hydroarenal of the eutrophic lake in Mazurian Lakeland [14]. In the psammon of Lake Kinneret, in turn, Pleuronema sp. predominated [17]. Typical (exclusive) taxa inhabiting only one of the s analysed were species Colpidium kleini and Frontonia atra, occurring only in the higroarenal. Both species are categorised as benthic species. Colpidium kleini is bacteriovorous, and Frontonia atra prefers diatoms [9]. The analysis of the correlation between physical and chemical water parameters and numbers of ciliates reveals a variable relation between those values. In the hydro- and higroarenal of the eutrophic lake, a strong correlation between chemical parameters and numbers of the studied group of microorganisms was recorded. In the mesotrophic lake, a weak correlation occurred only between numbers of ciliates and nitrogen concentration. In the of both lakes, no correlations between chlorophyll a concentration and numbers of ciliates were observed, which is in accordance with results from the eutrophic lake [14]. The study confirms the presumption that psammon is a structure subject to continuous transformation. It also proves the thesis of higher concentrations of microorganisms in lakes of higher trophy, which is probably related to food availability. It seems that the factor has a crucial impact on the differences observed between the meso- and eutrophic lakes. Within the , no significant correlations between physical and chemical water parameters and numbers of ciliates were determined. In the remaining s, positive correlations were observed, whereas the most numerous significant correlations occurred in the eutrophic lake. However, with the aim of clarifying the understanding of the role of factors conditioning the presence of psammonic ciliates, in future research it is necessary to explain the biotic factors such as the abundance of bacteria and flagellates, among others. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Archives of Environmental Protection de Gruyter

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

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de Gruyter
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Copyright © 2012 by the
ISSN
2083-4772
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2083-4810
DOI
10.2478/v10265-012-0018-4
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Abstract

The aims of this study were to identify the taxonomic diversity and abundance of psammonic ciliate communities in mesotrophic and eutrophic lakes (Lczna-Wlodawa Lakeland, eastern Poland). The effect of selected physical and chemical water parameters on ciliates community was also analysed. Psammon samples were collected during three s: spring, summer and autumn of 2010. In each lake, in the psammolittoral, samples were collected in the , higroarenal, and hydroarenal s. 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 (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 s of the eutrophic lake. INTRODUCTION Psammon is an assemblage of organisms living in the moist sand of coastal s of seas, lakes and rivers [5]. Psammonic organisms inhabit beaches of water bodies at various depths. In rivers, the psammon can reach more than 40 cm deep into sand, in seas ­ up to a few centimeters, and in lakes it rarely exceeds 2 cm [6]. Wiszniewski [32] recognises three s within the psammolittoral: the hydroarenal (permanently submerged, reaching approx. 1 m into the lake), higroarenal (fluctuation ), and , including sand up to a distance of 1 m from the water line. Organisms inhabiting the live in spaces between sand grains filled with water. The granulometric composition of the sand may have certain influence on the species composition and numbers of microorganisms inhabiting spaces between its grains [7]. Psammon is a complex of various groups of organisms, e.g. algae, bacteria, protozoa, rotifers, gastrotrichs and nematodes. So far, studies on the occurrence of psammonic rotifers have been relatively numerous [1, 5, 7]. Only a few studies relate to the occurrence of other groups of organisms, particularly ciliates. Ciliates are a significant group of microplankton of aquatic environments [8]. They are an important element of the trophic structure of aquatic ecosystems. They often constitute the main group of bacterial production consumers, transferring matter and energy into higher trophic levels [14, 22, 23, 24]. Ciliates can also be used as indicators of the purity of rivers and lakes [22, 24]. Studies on the structure of psammonic ciliates are usually fragmentary. So far, only one paper on those protozoa in the psammolittoral of a eutrophic lake (Lake Mikolajskie) has been published in Poland [14]. World literature includes a few publications describing ciliates in the psammon of the Caspian Sea [1], the White Sea [18, 19, 20] and Lakes: Kinneret [17], Tanganika [4] and Baikal [27]. According to Wiszniewski [32], "hydropsammon is the main of development of zoopsammon; however it cannot be recognised as a transitional stage between aquatic life and life on the beach. The is specific in all aspects". Therefore, the psammolittoral may constitute a type of ecotone, i.e. a transitional between adjacent ecological systems. Currently, the term is understood much more widely as a transitional between adjacent ecological systems, with unique features determined by the space and time scale, and distinct interactions between the systems [12]. Contact between water and land results in development of a new species structure within its , and in intensification of ecological processes in comparison to adjacent environments [26, 10]. Therefore, assemblages of psammonic ciliates should also show certain species diversity and abundance in the water/land transitional . Studies on the structure of ciliates in aquatic ecosystems indicate strong correlations between numbers of those organisms and physical and chemical water parameters [14, 21, 22, 23]. The most numerous positive correlations were recorded between numbers of ciliates and chlorophyll a, TOC, and Ptot in water. This suggests a distinct relation of abundance of the microorganisms to nutrient concentrations in the lake waters. High horizontal variability of physical and chemical water parameters within the psammolittoral (, higroarenal, hydroarenal) suggests that a similar pattern should be observed in the species richness and abundance of psammonic ciliates. Scarce information on horizontal distribution of psammonic ciliates led to undertake studies on that group of microorganisms. The main objective of the study was to determine the number of taxa and abundances of psammonic ciliates in lakes of different trophic status. The effect of selected physical and chemical water parameters on development of that microorganisms was also analysed. STUDY AREA Two lakes of Lczna-Wlodawa Lakeland (eastern Poland, 51º N, 23º E) (Fig. 1) were selected: mesotrophic Lake Piaseczno (area 84.7 ha, maximum depth 38.8 m) with well developed sandy psammolittoral, and eutrophic Lake Sumin (area 91.5 ha, maximum depth 6.5 m) with well developed psammolittoral [29]. In the eulittoral of Lake Piaseczno the emergent vegetation is very scarce (Carex arenaria L., Phragmites australis (Cav.)Trin. ex Steud) and the submerged macrophytes, Lczna-Wlodawa Lakeland Fig. 1. Location of study area such as Myriophyllum alternifolium DC. and Ceratophyllum demersum L. dominate. In Lake Sumin well developed belts of emergent (Phragmites australis (Car.), Trinex stend and Typhalatifolia L.) and submerged (Myriophyllum spicatum) dominate in littoral [15]. In Lake Piaseczno samples were taken in the North-East coast whereas in Lake Sumin in the South-East coast. METHODS Ciliates were collected in spring, summer and autumn in 2010. The samples of psammon were taken from three s of arenal: - exposed sand, 1 m of shoreline; higroarenal - at the shoreline; hydroarenal - under water, 1 m from the shoreline. The samples were collected with a plastic sharp-edged tube, 60 mm in diameter at four points of each . The samples were taken to the depth of 2 cm. From each 12 samples were collected in each each sample was analysed at the depth of 2 cm (Fig. 2). Each sample was shaken with saline solution and then condensed by filtering through a mesh net and fixed immediately with Lugol's solution (0.2% final concentration). Ciliate density was calculated per 1 cm3 of sand. Observation of life samples was used for the taxonomic identification. Species identification was based on Foissner and Berger [9]. Ciliate biomass was estimated by multiplying the numerical abundance by the mean cell volume calculated from direct volume measurements using appropriate geometric formulas. Therefore, the calculated cell volume was divided by a correcting factor of 0.4 [13]. Each time the following physical and chemical parameters: pH, conductivity, temperature, total organic carbon (TOC), total phosphorus (Ptot), P-PO4, N-NO3, N-NH4 and chlorophyll a were examined in three sites: (interstitial water), higroarenal and hydroarenal (water above the ground). Temperature, conductivity and pH were determined in situ using the multiparameter sensor 556 MPS (Envag). TOC was determined using the PASTEL UV, and the other parameters were analyzed in laboratory, according to Hermanowicz et al. [11]. Chlorophyll a was determined by the spectrophotometric analysis of alcohol extracts of the algae retained on polycarbonate filters. Fig. 2. The outline of beach ­ littoral with sampling station (I, II, III, IV) The biodiversity index, expressed as the Shannon-Wiener index, was calculated using the formula [16]: H '= - S i =1 pi ln pi (1) were: ni- the number of individuals of i species; the abundance of I species, S - the number of species (species richness), N - the total number of individuals, pi - the relative abundance of each species, calculated as the proportion of individuals of a given species n to the total number of individuals in the community: Ni . The frequency of particular taxa was calculated as the percentage of collected samples in which the species occurs. All the species found were classified into the four groups: very constant species (occurring in 61­100 percent of the samples), constant species (occurring in 41­60 percent), accidental species (occurring in 21­40 percent of the samples), accessory species (occurring in less than 20 percent of the samples) [31]. The index of similarity between assemblages was calculated using the Jaccard formula: JI = S ab S a + S b - S ab (2) were: Sa - abundance taxa in assemblage a, Sb - abundance taxa in assemblage b, Sab - abundance taxa in assemblage a and b. Statistical analyses of results were carried out using the STATISTICA 7.0 software. The differences between samplings were analyzed using T-Student test. Pearson correlation coefficients were calculated between pairs of variables in order to determine the relationship between ciliates and physical and chemical parameters. RESULTS Physical and chemical parameters Irrespective of the lake's trophic status and the analysed, neither water temperature, pH, nor chlorophyll a concentration differed significantly (Table 1). Table 1. Physical and chemical characteristic of the psammon water of investigated lakes (* average and ** range) Lake/ / 91.3 86-101 0.394 0.083-0.578 0.293 0.058-0.710 0.070 0.005-0.190 0.096 0.019-0.23 8.6 4.6-12.1 Temp. pH Conductivity S·cm-1 N-NH4 mgN·dm-3 N-NO3 mgN·dm-3 PO4 mgPO4·dm-3 Ptot mgP·dm-3 TOC mgC·dm-3 Chlorophyll a g·l-1 32.76 11.21-73.90 *19.34 **14.83-25.00 6.77 6.68-6.86 Piaseczno *20.15 **16.80-27.44 7.13 6.74-7.50 76.0 62-89 0.423 0.015-0.94 0.326 0.065-0.840 0.049 0.001-0.140 0.175 0.025-0.390 9.2 4.0-17.8 23.40 3.44-53.07 hydroarenal higroarenal *20.19 **16.33-26.74 7.47 6.60-8.60 111.7 90-137 0.111 0.010-0.275 0.280 0.054-0.630 0.035 0.002-0.100 0.153 0.015-0.150 4.2 3.0-5.9 25.91 13.40-50.42 *17.98 **13.25-21.00 8.33 7.2710.75 395.0 273-477 1.131 0.675-1.650 0.620 0.211-1.320 384.7 361-412 0.362 0.246-0.430 0.334 0.102-0.750 0.282 0.049-0.730 0.254 0.195-0.289 31.2 16.4-55.5 26.71 18.75-40.46 Sumin *19.20 **15.27-24.58 7.37 7.24-7.63 0.028 0.001-0.080 0.337 0.029-0.870 15.2 14.6-16.4 26.31 20.26-32.97 hydroarenal higroarenal *19.08 **15.35-24.78 7.33 7.14-7.70 417.7 403-427 0.342 0.199-0.420 0.366 0.087-0.860 0.005 0.001-0.010 0.062 0.016-0.101 14.8 13.4-16.4 23.79 17.38-29.86 Conductivity, N-NO3, N-NH4, Ptot, and TOC, in turn, reached their highest values in eutrophic Lake Sumin. The tendency was particularly distinct in the eu- and higroarenal s. In mesotrophic Lake Piaseczno, conductivity reached from 62 S cm-1 in the higroarenal to 137 S cm-1 in the hydroarenal. P-PO4 concentrations reached the highest values in the in both lakes (Sumin ­ 0.289 mg PO4 dm-3, Piaseczno ­ 0.190 mg PO4 dm-3). The highest content of TOC was noted in the of the eutrophic lake (55.5 mgC dm-3), and the lowest in the hydroarenal of the mesotrophic lake (3.0 mgC dm-3). The highest total phosphorus concentrations were recorded in the higroarenal of eutrophic lake (0.87 mgP dm-3), and the lowest in the hydroarenal (0.015 mgP dm-3) of the mesotrophic lake (Table 1). Taxonomic composition and species frequency In the lakes studied, a total of 53 ciliate taxa were recorded; in the eutrophic lake ­ 44 taxa, and in the mesotrophic lake ­ 35 ciliate taxa (Table 2). Species diversity was highly varied between the studied s. In the eutrophic lake, the highest number of taxa occurred in summer in the hydroarenal (23 taxa), and the lowest number of taxa (4 taxa) was observed in the higroarenal in autumn. In the mesotrophic lake, in turn, a considerable increase in the number of psammonic ciliate taxa occurred in autumn in the higroarenal , where 14 taxa of the protozoa were identified, and the lowest number of taxa (5 taxa) was observed in spring and summer. The highest species similarity in the eutrophic lake, expressed by the Jaccard index, occurred between the hydroarenal and higroarenal s. In the mesotrophic lake, the index was the highest between the hydro- and s (Table 3). The analysis of species frequency revealed one constant species in Lake Sumin, i.e., Codonella cratera. In Lake Piaseczno, no constant species were determined. Accessory species were recorded in each of the lakes - in Lake Sumin: Cyclidium glaucoma, Paramecium sp., Brachonella spiralis, Euplotes sp; and in Lake Piaseczno: Cyclidium glaucoma, Paramecium sp., Glaucoma sp. The remaining species were classified as random. Irrespective of the lake tropic status, within the and higroarenal, constant taxa were Paramecium sp. and Codonella cratera. In the hydroarenal, Cyclidium glaucoma reached the highest frequency. The highest numbers of psammonic ciliates were determined in eutrophic Lake Sumin (516 ind. cm-3). In mesotrophic Lake Piaseczno, densities were even twice lower, and amounted to 191 ind. cm-3. In the zonal distribution the highest density of those microorganisms in Lake Sumin was observed in spring in the hydroarenal. The lowest numbers in the lake were recorded in the higroarenal in autumn (Fig. 3). In the mesotrophic lake, the highest abundance was observed in spring in the ­ 280 ind. cm-3, and the lowest in the hydroarenal ­ 98 ind. cm-3. Differences in protozoa biomasses were also distinctive, both between the s and lakes (Fig. 4). The average ciliate biomass in Lake Sumin amounted to 73.39 g cm-3, and in Lake Piaseczno to 27.65 g cm-3. The t-student analysis (level of significance p = 0.05) of numbers of ciliates between individual s revealed no significant differences in numbers of the organisms between s in individual lakes. The highest biomass was recorded in summer in the hydroarenal in Lake Sumin (240 g cm-3), and the lowest in autumn in the higroarenal (5.12 g cm-3). In Lake Piaseczno, the highest biomass occurred in spring in the hydroarenal (51.46 g cm-3), and the lowest within the same Table 2. Taxonomic composition of psammonic ciliates of three s in investigated lakes (Eu-, Hi-higroarenal, Hy-hydroarenal) Autumn Hi Lake Sumin Hy Taxa + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Colpodea Colpoda sp. Cyrtrophorida Trochilia minuta (Roux) Pseudochilodonopsis sp. Gymnostomatida Lagynophyra acuminata (Kahl) Mesodinum pulex (Clap. & Lach.) Tracheophyllum sp. Spatidium spatula (Dujardin) Heterotrichida Blepharisma sp. Brachonella spiralis (Smith) Hymenostomatida Colpidium sp. Colpidium colpoda (Losana) Colpidium kleini (Foissner) Dexiostoma campylum (Stokes) Table 2. Taxonomic composition of psammonic ciliates of three s in investigated lakes (Eu-, Hi-higroarenal, Hy-hydroarenal) ­ continuation Taxa + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Dexiotricha granulosa (Kent) Dexiotrichides centralis (Stokes) Frontonia sp. Frontonia angusta (Kahl) Frontonia atra (Ehrenberg) Frontonia leucas (Ehrenberg) Glaucoma sp. Glaucoma reniforme (Schewiakoff) Lembadion sp. Lembadion bullinum (Müller) Lembadion lucens (Maskell) Paracolpidium truncatum (Stokes) Paramecium sp. Paramecium bursaria (Ehrenberg) Paramecium putrinum (Claparede) Sathrophilus muscorum (Kahl) Stokesia vernalis (Werich) Tetrahymena sp. Table 2. Taxonomic composition of psammonic ciliates of three s in investigated lakes (Eu-, Hi-higroarenal, Hy-hydroarenal) ­ continuation Taxa + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + Uronema nigricans (Müller) Unindetified Hymenostomata Hypotrichida Aspidisca cicada (Müller) Euplotes sp Euplotes affinis (Dujardin) Euplotes moebiusi (Kahl) Holosticha kessleri (Wrzeniowski) Holostichia monilata (Kahl) Oxytrichia similis (Engelmann) Unindentified Hypotrichia Loxodes Loxodes sp. Nassulida Chilodontopsis sp. Oligotrichida Codonella cratera (Leidy) Strombilidium humile (Penard) Table 2. Taxonomic composition of psammonic ciliates of three s in investigated lakes (Eu-, Hi-higroarenal, Hy-hydroarenal) ­ continuation Taxa + + + + + + + + + + + + + + + + + + + + + + + + + + + + + 12 11 5 6 5 5 6 14 10 12 13 10 14 9 23 15 4 8 + + + + Odontostomatida Unindentified Odontostomatida Peritrichida Vorticella sp. Pleurostomatida Acineria sp. Acineria incurvata (Dujardin) Litonotus sp. Litonotus lamella (Müller) Prostomatida Holophyra sp. Holophrya discolor (Ehrenberg) Scuticociliatida Cinetochilum margaritaceum (Ehrenberg) Cyclidium glaucoma (Müller) Suctoria Actineta sp. Total number of taxa: 53 Table 3. Pearson correlation between ciliate density and physical and chemical factors of investigated lakes (p 0.05) Variables Density Lake Piaseczno Higroarenal Hydroarenal -0.32 n.s. 0.31 -0.31 0.50 n.s. 0.31 0.29 n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s. -0.31 n.s. n.s. 0.40 0.40 n.s. 0.28 -0.27 2500 2000 Higroarenal Hydroarenal Lake Sumin Higroarenal 0.51 0.29 0.58 0.49 0.50 0.54 0.49 0.31 Hydroarenal -0.45 0.43 0.28 -0.51 -0.58 0.63 -0.63 -0.74 pH Conductivity N-NH4 N-NO3 P-PO4 Ptot TOC Chlorophyll a n.s. n.s. n.s. n.s. n.s. n.s. n.s. -0.29 Cialiate density (ind.·cm ) -3 0 Spring -500 Summer Lake Piaseczno Autumn Spring Summer Lake Sumin Autumn -1000 Fig. 3. Density of psammonic ciliates in investigated lakes (± standard deviation) in autumn (11.93 g cm-3). The statistical significance analysis for biomass between s and lakes revealed no significant discrepancy between the values compared. Irrespective of the lake's trophic status, Hymenostomata reached the highest participation in total numbers (from 13 to 95% of total numbers of ciliates) (Fig. 5). Irrespective of the , the eulittoral was dominated by Hymenostomata. In the two remaining s, participation of Oligotrichida (from < 1% to 40%) and Hypotrichida (from < 1% to 35%) increased. In the mesotrophic lake, participation of Scuticociliatida increased from 1% in spring to 60% in autumn. Relationship between psammonic ciliates and physical and chemical factors Total numbers of psammonic ciliates correlated positively with all of the physical and chemical water parameters analysed in the hydroarenal . The lowest correlation was Higroarenal Hydroarenal Biomass ( g·cm-3) 0 Spring -200 Summer Lake Piaseczno Autumn Spring Summer Lake Sumin Autumn -400 Fig. 4. Biomass of psammonic ciliates in investigated lakes (± standard deviation) 100% 80% 60% 40% 20% 0% Summer Summer Summer Summer Summer Summer Autumn Autumn Autumn Autumn Autumn Autumn Spring Spring Spring Spring Spring Spring Others Scuticociliatida Prostomatida Pleurostomatida Oligotrichida Hypotrichida Hymenostomatida Heterotrichidia Higroarenal Lake Piaseczno Hydroarenal Higroarenal Lake Sumin Hydroarenal Fig. 5. Domination structure of psammonic Ciliata orders in psammolittoral of investigated lakes (% of total numbers) determined between the numbers of ciliates and conductivity (r = 0.29, p = 0.05), and the highest between the numbers of ciliates and N-NH4 concentration in water (r = 0.58, p = 0.05). In the eutrophic lake, the characterised by the strongest correlations between the physical and chemical factors analysed and ciliate numbers was the hydroarenal. In the mesotrophic lake, a significant correlation was observed in the hydroarenal between N-NO3 concentration and ciliate numbers (r = 0.50, p = 0.05) (Table 4). DISCUSSION The number of psammonic ciliate taxa (53 taxa) in the lakes studied was similar to that determined in the hydroarenal of eutrophic Lake Mikolajskie in Mazury Lakeland (56 taxa) [14] and above 3 times higher than values observed by Madoni [16] in the psammolittoral of Lake Kinneret (Israel) (16 taxa). Such differences may result from local climatic conditions (rain, fluctuation, wind) [7]. Also Wiszniewski [33] mentioned the effect of atmospheric conditions and anthropopressure as the main reasons for the variability of taxonomic composition of psammonic organisms, even in the diurnal cycle. Table 4. Jaccard similarity coefficient value for the analyzed Lake Piaseczno /Higroarenal Higroarenal/Hydroarenal Hydroarenal/ Lake Sumin /Higroarenal Higroarenal/Hydroarenal Hydroarenal/ Spring 0.15 0.21 0.23 0.47 0.53 0.47 Summer 0.22 0.00 0.38 0.21 0.14 0.23 Autumn 0.13 0.22 0.23 0.12 0.20 0.28 The factors are often difficult to measure or distinguish, due to their specificity and simultaneous occurrence. The average numbers of psammonic ciliates in the eutrophic lake Sumin (266-703 ind. cm-3) were similar to those recorded in the eutrophic lake Mikolajskie [14]. In the psammolittoral of Lake Kinneret, the average numbers of ciliates amounted to 378 ind. cm-3 [17]. The available literature provides no information on the dynamics of al changes in the abundance of psammonic ciliates. Studies by Pennak [28] revealed that psammonic organisms show high al variability. Their numbers decrease significantly in autumn, and increase in spring and summer. A similar pattern was observed in the present research. In the lakes studied, a moderate effect (depending on the analysed) of a number of physical and chemical factors on protozoa occurrence was recorded. The influence of food abundance seems to be more significant (correlation between numbers of ciliates and chlorophyll a concentration). Studies by Czerna [3] revealed substantial abundance of psammonic algae in the lakes studied. Significant correlations between numbers of psammonic ciliates and nutrient concentration in the eutrophic Lake Sumin also suggest a considerable importance of the food source for the occurrence of ciliates. Both TOC and nutrients influence bacteria abundance. Therefore, they may have direct impact on the occurrence of protozoa, feeding on bacteria [22]. The trophic structure of ciliates was dominated by omnivorous and bacteriovorous species, which is in accordance with data from the eutrophic lake [14]. The psammolittoral is a variable environment, and according to Schmid-Aray [30], it is suitable for organisms with the ability of fast population growth and wide ecological tolerance. Therefore, it seems that sand is an environment adequate for organisms easily adapting to changes in environmental conditions. Moreover, ciliates may play a significant role in phosphorus regeneration, which should also result in an increase in abundance of algae and bacteria. The process may be largely influenced by the participation of small ciliate taxa, due to their high metabolic activity and fast generation. They are able to provide much more phosphorus than organisms of higher trophic levels [7]. The edge effect also seems to have a significant impact on the organisms analysed. The distribution of numbers and biomass between individual s and s suggests a substantial influence of rapid changes of environmental conditions on the occurrence of protozoa. A high water level in spring could also favour an increase in numbers of protozoa. The psammolittoral in the included large amounts of decomposing plant remains which could condition the occurrence of bacteria constituting the main sustenance of ciliates. Irrespective of the lake trophic status, Hymenostomata reached a significant dominance. However, their participation changed depending on the and analysed. This group (mainly taxa: Paramecium sp., Glaucoma sp., and Uronema nigricans) also prevailed in the hydroarenal of the eutrophic lake in Mazurian Lakeland [14]. In the psammon of Lake Kinneret, in turn, Pleuronema sp. predominated [17]. Typical (exclusive) taxa inhabiting only one of the s analysed were species Colpidium kleini and Frontonia atra, occurring only in the higroarenal. Both species are categorised as benthic species. Colpidium kleini is bacteriovorous, and Frontonia atra prefers diatoms [9]. The analysis of the correlation between physical and chemical water parameters and numbers of ciliates reveals a variable relation between those values. In the hydro- and higroarenal of the eutrophic lake, a strong correlation between chemical parameters and numbers of the studied group of microorganisms was recorded. In the mesotrophic lake, a weak correlation occurred only between numbers of ciliates and nitrogen concentration. In the of both lakes, no correlations between chlorophyll a concentration and numbers of ciliates were observed, which is in accordance with results from the eutrophic lake [14]. The study confirms the presumption that psammon is a structure subject to continuous transformation. It also proves the thesis of higher concentrations of microorganisms in lakes of higher trophy, which is probably related to food availability. It seems that the factor has a crucial impact on the differences observed between the meso- and eutrophic lakes. Within the , no significant correlations between physical and chemical water parameters and numbers of ciliates were determined. In the remaining s, positive correlations were observed, whereas the most numerous significant correlations occurred in the eutrophic lake. However, with the aim of clarifying the understanding of the role of factors conditioning the presence of psammonic ciliates, in future research it is necessary to explain the biotic factors such as the abundance of bacteria and flagellates, among others.

Journal

Archives of Environmental Protectionde Gruyter

Published: Jan 1, 2012

References