Influence of Environmental Heterogeneity on the Structure of Testate Amoebae (Protozoa,Rhizopoda) Assemblages in the Plankton of the Upper Paraná River Floodplain,Brazil

In freshwater environments, testate amoebae are usually found associated with macrophytes and sediments and many studies have suggested that their occurrence in plankton samples is accidental. This implies that predictable patterns detected in planktonic assemblages should not be observed in testate amoebae assemblages. This hypothesis was tested in this study. Plankton samples were collected from different environments in the Upper Paraná River floodplain. Results show that patterns in species composition and abundance of testate amoebae are predictable, and that dominant species tend to present characteristic shell morphology in hydrologically different environments. We suggest that testate amoebae must be routinely included in plankton ecology studies, at least in floodplain environments.     

The Temporal Asynchrony of Planktonic Cladocerans Population at Different Environments of the Upper Paraná River Floodplain

The aim of this study was to investigate the existence of synchronic fluctuation patterns in cladoceran populations of the Upper Paraná River floodplain. The following hypothesis were tested: (i) the populations of a given species present the same fluctuation pattern in abundance for different environments and (ii) synchrony is higher when we consider subsets of neighboring environments or those belonging to the same category (e.g., lagoons, rivers). Samplings were performed every three months from February 2000 to November 2002 at 11 sites. To evaluate spatial synchrony, the intraclass correlation coefficient was used. The results showed no significant correlation for the most abundant species, meaning that fluctuation patterns of planktonic cladocerans were asynchronous. Asynchrony indicated that the influence of floods and regional climatic factors was not strong enough to synchronize the populations, suggesting that local factors were more important than regional effects in determining zooplankton abundance patterns. The implications of these results are that the observations from a single environment cannot be extrapolated to other environments in a manner that would allow its use as a sentinel site. This means that a monitoring program for floodplain systems, or at least for the Paraná River floodplain, has to comprise greater spatial extents. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Environmental factors exert predominant effects on testate amoeba metacommunities during droughts in floodplains

Metacommunities have been evaluated as models for the relative importance of environmental and spatial processes in assembling ecological communities. Here, we tested the hypothesis that different hydrological periods (drought and flooding) influence the environmental associations of planktonic testate amoeba metacommunities. We predicted that environmental factors would exert the strongest effects on species dispersal under drought, but that they would be less significant during flooding. Testate amoebae were sampled during drought and flooding, from 72 lakes in four Brazilian floodplains (Amazonian, Araguaia, Pantanal and Paraná). Partial redundancy analysis indicated that only environmental factors were significant; they were significant in all floodplain lakes during the drought. Only the Paraná floodplain had significant results for environmental factors during both hydrological periods. Spatial factors did not contribute significantly to any of the metacommunities. The depth, pH and variables related to environmental productivity were identified as major predictors in the assembly of testate amoeba communities. Our results highlight that different hydrological periods vary in their relative importance in environmental and spatial processes. The species‐sorting model was predominant during drought, while stochastic processes prevailed during flooding in all but the Paraná floodplain. In the Paraná floodplain, the construction of dams could potentially alter the effects of environmental and spatial factors on the dispersal of planktonic testate amoebae. The pH and the environmental productivity factors were largely responsible for species selection and the structuring of the planktonic testate amoebae metacommunities in Brazilian floodplains.     

Testate Amoebae (Rhizopodea-Sarcodina) from Zooplankton of the High Paraná River Floodplain,State of Mato Grosso do Sul,Brazil: I. Families Arcellidae and Centropyxidae

A first contribution towards the taxonomy of testate amoebae (Rhizopodea – Sarcodina) recorded in planktonic samples of lotic and lentic environments in the high Paraná River Floodplain in the States of Paraná and Mato Grosso do Sul, Brazil, is provided. Twenty-four taxa belonging to the families Arcellidae and Centropyxidae were identified, described and sketched. Among the taxa, A. vulgaris f. undulata, A. vulgaris var. penardi, A. mitrata var. spectabilis, A. nordestina and Centropyxis aculeata var. tropica represent new occurrences in Brazil.     

Biodiversity of testate amoebae (Arcellinida and Euglyphida) in different habitats of a lake in the Upper Paraná River floodplain

This study aimed to investigate the testate amoebae (Arcellinida and Eugliphida) species diversity in plankton, macrophytes and aquatic sediment samples from a shallow lake of the Upper Paraná River floodplain. Samples were carried out from April 2007 to March 2008. We recorded 89 taxa, belonging to 10 families. Eighty-two taxa were found in the aquatic sediment, 71 in the macrophytes and 53 in the plankton. Highest values of alpha diversity were observed in the aquatic sediment. Although the plankton had the highest number of accidental species, accessory and constant species were also observed in this habitat. Most of the species classified as constant for the plankton belonged to the genus Arcella. Most of the constant species in the macrophytes and aquatic sediment belonged to the genus Difflugia. This study supports the idea that the presence of these protists in the plankton should not be attributed only to stochastic processes because (i) the species diversity recorded in this habitat was remarkably high in relation to the total biodiversity of the lake, and (ii) we also recorded frequent and constant species in the plankton.     

Testate amoebae community structure in the moss biotopes of streams

The specific composition and community structure of testate amoebae in the moss biotopes of streams were studied in the Sura River basin (Middle Volga region). Twenty-nine species and forms were identified. The eurybiont species Trinema enchelys, Euglypha ciliata glabra, Centropyxis aerophila, Tracheleuglypha dentata, Crythion dubium, Centropyxis cassis, Trinema complanatum, and Trinema lineare are dominant. The species richness varies from 2 to 11 species per sample, the abundance is 100 to 4000 ind./g of absolutely dry moss. The degree of forest covering in the basin, hydrochemical peculiarities (the amount of biogenic elements and water hardness) of streams, the size of streams, and environmental contamination are possible factors that determine the specific character of the composition and structure of testate amoebae communities.     

Testate amoebae and tintinnids as spatial and seasonal indicators in the intertidal margins of Guadiana Estuary (southeastern Portugal)

The present study gathers pioneering taxonomical and community data on testate amoebae and agglutinated tintinnids, analyzing their seasonal and spatial distribution patterns in the mesotidal system of the Guadiana Estuary, southeastern Portugal. To evaluate both groups’ potential as bioindicators in climate monitoring and paleoenvironmental reconstructions, their abundance, diversity and living proportions were compared to elevation in relation to mean sea-level, marine influence and to periods of elevated water levels. The distributions of testate amoebae and tintinnid total assemblages were also related to major physicochemical variables by means of multivariate analysis.From 49 surface sediment samples collected in winter and summer 2010, 17 species (25 strains) of testate amoebae were identified (in the 63 μm fraction). The Centropyxidae, mainly represented by Centropyxis aculeata, Centropyxis arcula and Centropyxis constricta, had the greatest density (71% of total individuals), while the Difflugidae represented the most species (82% of total species). Higher diversities and densities were observed in winter in the upper estuary, where salinity is negligible, and in the middle estuary where they are concentrated at the lower levels of the intertidal zone. Few or no individuals were observed in the highest marsh zones. In winter, dead testate amoebae were dominant, with empty tests accumulating in the sediments from post-mortem transport by high river discharge. In summer, an increase in the living fraction is observed, with living testate amoebae along the entire estuary, which could indicate that some species are able to live in the lower reaches of the estuary.Along with the testate amoebae, two species of agglutinated tintinnids (>63 μm), Stenosemella ventricosa and Tintinnopsis cf. lata, were abundant in the sediments. Their highest abundances were observed in summer. Living individuals were only recorded in summer, mainly in the vicinities of freshwater and sewage outflows, where elevated nutrient concentrations may be expected.The present study demonstrates that both testate amoebae and tintinnids have well defined patterns in their temporal and spatial distribution, offering high bioindicator potential in environmental/climate monitoring studies as well as in paleoenvironmental reconstructions.     

Testate amoebae community pattern in different types of boundary structures at the water-land contact zone

The patterns of changes in the species richness, abundance, species composition, and species structure of the testate amoebae community along six different types of water-land boundaries in the Medveditsa River (Don river Basin) were studied, namely, a new boundary, terrigenous and reogeneous edges, reogeneous and terrigenous hemiecotones, and the full ecotone. The testate amoebae communities are divided into terrestrial and aquatic variants for all types of boundaries. Hydrophilic species of the genera Arcella, Diffugia, Cyphoderia, and Pseudodifflugia dominate in the aquatic types of communities while pedobiont and eurybiont groups from the genera Centropyxis, Euglypha, Plagiopyxis, and Trinema are characteristic of the terrestrial communities. A decrease in the abundance and species richness of testate amoebae in the boundary zones was detected.     

Productivity gradient affects the temporal dynamics of testate amoebae in a neotropical floodplain

Testate amoeba communities are influenced by temporal variation in the productivity levels in the environment, and may be used as an indicator group for these changing conditions. Here, we analysed the effect of temporal variation in the levels of productivity variables on testate amoeba community of the upper Paraná River floodplain. We evaluated the hypothesis that the frequency and abundance of the testate amoeba community change along an environmental gradient, with different taxa establishing at different points along the gradient in response to changes in the levels of productivity variables. We predicted that the number of species would increase and decrease at points associated with higher and lower levels of productivity variables, respectively. Testate amoeba species were sampled quarterly between 2000 and 2012 from six lakes in the upper Paraná River floodplain, Brazil. We recorded 110 species belonging to 11 families. Threshold Indicator Taxa Analysis identified positive and negative significant shift points in response to the concentration of chlorophyll-a, total nitrogen, and total phosphorus on the frequency and abundance of the testate amoeba community. Our results indicated that change intervals in the levels of productivity variables were associated with the establishment of different taxa. The main bioindicator species of productivity were Difflugia acuminata, D. amphoralis, D. helvetica multilobata, D. kempny, D. lobostoma multilobata, D. parva, D. schurmanni, D. ventricosa, and Lesquereusia ovalis. These species were linked to the increase and decrease in the levels of productivity, confirming the ecological importance of the role of these organisms as bioindicators in aquatic ecosystems.     

Distribution of soil-inhabiting testate amoebae along a mountain slope (Baikal Lake region, Khamar-Daban ridge, Cherskii peak)

The specific composition and distribution of soil-inhabiting testate amoebae along the Cherskii peak slope (Khamar-Daban mountain ridge, Lake Baikal region) were studied within the altitude range from 1000 to 1570 m above sea level according to the changes in biogeocenoses from birch-aspen to cedar-fir forests to cedar-fir-bush forest-tundra. One-hundred-four taxa were identified. The most common species are ubiquits with a wide geographical distribution: Trinema lineare, Euglypha levis, Euglypha rotunda, Trinema enchelys, Phryganella acropodia, Tracheleuglypha dentata, Assulina muscorum, Trinema complanatum, and Centropyxis aerophila. The species richness varies from 12 to 40 species per sample, and the abundance varies from 500 to 120000 ind. per gram of absolutely dry soil. The spatial heterogeneity of the specific composition grows with altitude, and the community composition changes. The absence of a common pattern in the cenotic changes in the communities of testate amoebae in Western Europe and the Lake Baikal region is discussed.     

Palaeoecology of testate amoebae in a tropical peatland

We present the first detailed analysis of subfossil testate amoebae from a tropical peatland. Testate amoebae were analysed in a 4-m peat core from western Amazonia (Peru) and a transfer function developed from the site was applied to reconstruct changes in water table over the past ca. 8,000 years. Testate amoebae were in very low abundance in the core, especially in the lower 125 cm, due to a combination of poor preservation and obscuration by other organic matter. A modified preparation method enabled at least 50 testate amoebae to be counted in each core sample. The most abundant taxa preserved include Centropyxis aculeata, Hyalosphenia subflava, Phryganella acropodia and Trigonopyxis arcula. Centropyxis aculeata, an unambiguous wet indicator, is variably present and indicates several phases of near-surface water table. Our work shows that even degraded, low-abundance assemblages of testate amoebae can provide useful information regarding the long-term ecohydrological developmental history of tropical peatlands.     

Diverse fossil amoebae in German Mesozoic amber

Fossil amoebae are very rare, although their evolutionary history extends back into the Proterozoic. The Cenomanian amber of Schliersee (southern Germany) is very rich in micro-organisms and contains the highest diversity of fossil freshwater rhizopods (Gymnamoebia and Testacealobosia) yet discovered. Altogether seven testate amoebae and one gymnamoebian species are recorded from this Mesozoic amber. The four newly discovered taxa described in this paper can be assigned to the extant species Centropyxis delicatula , Centropyxis hirsuta , Phryganella acropodia and Phryganella paradoxa . Over 200 individuals of Phryganella paradoxa are preserved. Together with their syninclusions, the amoebae are species of limnetic or limnetic–terrestrial microcoenoses. The presence of 100-myr-old fossils with extant representatives suggests evolutionary stasis of these freshwater amoebae. However, not all modern testacean families have been recorded from Mesozoic limnetic habitats. Our experimental studies verify that naked and testate amoebae can be embedded in resins.     

Testate Amoebae from a Cretaceous Forest Floor Microbiocoenosis of France

ABSTRACT. Amber‐preserved shells of testate amoebae often provide as many diagnostic features as the tests of modern taxa. Most of these well‐preserved microfossils are morphologically assignable to modern species indicating either evolutionary stasis or convergent evolution. Here we describe two Lower Cretaceous testate amoebae that are clearly distinguishable from modern species. Centropyxis perforata n. sp. and Leptochlamys galippei n. sp. possessed perforate shells that were previously unknown in these genera. They are preserved in highly fossiliferous amber pieces from the Upper Albian (ca. 100 million years old) of Archingeay/Les Nouillers (Charente‐Maritime, southwestern France). Syninclusions of soil and litter dwelling arthropods and microorganisms indicate a limnetic‐terrestrial microhabitat at the floor of a coastal conifer forest.     

Diversity and community patterns of testate amoebae in Bau Sen and Bau Trang lakes in Binh Thuan Province,Vietnam

The species composition and distribution of testate amoebae in Bau Sen and Bau Trang lakes (Binh Thuan Province, Vietnam) were investigated. Fifty-three species, varieties and forms have been identified from the water column and sediments. Twenty-seven species, varieties and forms from the genera Arcella, Centropyxis, Cyclopyxis, Difflugia and Pyxidicula were found in Vietnam for the first time. The updated list of testate amoebae in Vietnam now includes 286 taxa. The genera Arcella, Centropyxis and Difflugia are characterized by the highest frequency of occurrence. The species diversity of Arcella, Centropyxis, Difflugia was the highest. Centropyxis aculeata, Arcella discoides, Difflugia schurmanni, Netzelia oviformis and Difflugia limnetica were the most common species. Many species have shown restricted distribution, some species have been found only in one lake and not been found in another lake. The number of observed species, varieties, and forms in each lake is 34. The average number of the species per sample on the shores of the lakes subjected to human agricultural activity was significantly higher than in the samples from the shores of the lakes with less anthropogenic disturbance. The curves of “cumulative species number vs. sampling effort” are well fitted by equations S = 7.60 N ^0.69 for Bau Sen lake and S = 12.52 N ^0.46 for Bau Trang. The curves are unsaturated, which indicates that more intensive investigations of testate amoebae should be expected to reveal more species.     

The Impact of Simulated Sulfate Deposition on Peatland Testate Amoebae

Peatlands subjected to sulfate deposition have been shown to produce less methane, believed to be due to competitive exclusion of methanogenic archaea by sulfate-reducing bacteria. Here, we address whether sulfate deposition produces impacts on a higher microbial group, the testate amoebae. Sodium sulfate was applied to experimental plots on a Scottish peatland and samples extracted after a period of more than 10 years. Impacts on testate amoebae were tested using redundancy analysis and Mann–Whitney tests. Results showed statistically significant impacts on amoebae communities particularly noted by decreased abundance of Trinema lineare, Corythion dubium, and Euglypha rotunda. As the species most reduced in abundance are all small bacterivores we suggest that our results support the hypothesis of a shift in dominant prokaryotes, although other explanations are possible. Our results demonstrate the sensitivity of peatland microbial communities to sulfate deposition and suggest sulfate may be a potentially important secondary control on testate amoebae communities.     

Testate amoebae communities from aquatic habitats in the Arctic

Summary Forty taxa of testate amoebae were found in 15 aquatic samples collected in East Greenland (Angmasssalik Region), Jan Mayen and N.W. Spitsbergen. The number of species per sample is rather small, and the contribution of strictly aquatic species to the fauna is limited. A geographical shift in the importance of some genera can be demonstrated. Centropyxis aerophila and Paraquadrula irregularis are two of the most frequent species. The first-named is characteristic for acidoligotrophic waters, while the latter belongs to an alkaline-mesotrophic community. A third community is named after the commonest species, Trinema lineare. It seems to prefer a somewhat intermediate type of water.     

Relationship Between Testate Amoeba (Protist) Communities and Atmospheric Heavy Metals Accumulated in <Emphasis Type="Italic">Barbula indica</Emphasis> (Bryophyta) in Vietnam

We studied the relationships between testate amoeba communities and heavy metal (Pb, Cd, Zn, Ni, Cu, Mn, and Fe) concentrations in the moss Barbula indica sampled at 29 sites in and around the city of Hanoi (Vietnam). Our first approach was to compare the heavy metal concentrations and testate amoeba variables between the city (zone 1) and the surrounding (zone 2). Mean moss concentrations of Pb, Cd, Zn, Ni, and Cu were significantly higher and testate amoeba species richness and abundance were significantly lower in zone 1 and the abundance of eight taxa differed significantly between the two zones. We then studied the correlation between heavy metals and testate amoebae. Species richness and abundance were correlated negatively to Pb concentration. Shannon H′ was negatively correlated to both Pb and Cd. The abundance of several species was negatively correlated with Pb, Cd, Zn, and Ni; however, at the community level, Pb emerged as the only significant variable in a redundancy analysis. Our results suggest that testate amoebae are sensitive to and may be good bioindicators for heavy metal pollution, especially lead. Further research is needed to understand the causal relationships underlying the observed patterns.     

Community size structure of zooplanktonic assemblages in three lakes on the upper River Paraná floodplain, PR-MS, Brazil

Abundance and body size of zooplanktonic organisms, testate amoebae, rotifers, cladocerans and copepods from the littoral and pelagic regions of three lakes were analyzed in February and August 2000. The lakes belong to three different river systems (Baía, Ivinhema and Paraná rivers) of the upper River Paraná floodplain. It was expected that average body size was different in space (regions of the lake and limnological characteristics) and time (summer and winter) because the variation of depth, pH, oxygen dissolved, chlorophyll-a and water temperature of each lake. Zooplankton community was represented by 119 species. Sorensen's coefficient showed that the three communities were similar. Larger organisms were found in the lakes' pelagic region, and seasonally larger individuals were registered in the winter and smaller individuals in the summer. The relationship between body size and density was slight, positively significant. The body size frequency distribution was bi-modal. ANOVA results showed a significant influence of the interaction of the littoral and pelagic regions, lakes, and seasons in the body size of zooplankton organisms. Spatial and temporal changes of the community size structure of zooplanktonic assemblages were related to the food resource (microbial-loop or herbivore chain), species habitat preference and life strategies (growth and reproduction).     

Ecology of terrestrial testate amoebae assemblages from coastal Lowlands on Devon Island (NWT,Canadian Arctic)

Summary Fifty-seven taxa belonging to 17 genera of testate rhizopods were recorded in samples of mosses, soils and lichens, collected from the Truelove and Sparbo Hardy Lowlands on the high arctic Devon Island (NWT, Canada). Different groups of habitats are characterized by particular assemblages of Testacea species, with the quantity and quality of the available water as important ecological parameters. The Assulina muscorum-Corythion dubium assemblage characterizes the most dry and acidic moss habitats, while the Paraquadrula irregularis assemblage is to be found in wet and rather neutral habitats. The sedge moss meadows with their more moderately coarse textured and poorly drained soils, bear a Plagiopyxis callida-Plagiopyxis declivis soil-dwelling testate amoebae assemblage. The Centropyxis minuta assemblage lives in the most coarsely textured soils. pH seems to play a subordinate role, not only in the mosses but also in the soils. Multivariate methods (cluster analysis and CANOCO) have been used to separate these different assemblages.     

Testate amoebae taxonomy and trait diversity are coupled along an openness and wetness gradient in pine-dominated Baltic bogs

Sphagnum peatlands host a high abundance of protists, especially testate amoebae. Here, we designed a study to investigate the functional diversity of testate amoebae in relation to wetness and forest cover in Baltic bogs. We provided new data on the influence of openness/wetness gradient on testate amoebae communities, showing significant differences in selected testate amoebae (TA) traits. Three key messages emerged from our investigations: 1) we recorded an effect of peatland surface openness on testate amoebae functional traits that led us to accept the hypothesis that TA traits differ according to light intensity and hydrology. Mixotrophic species were recorded in high relative abundance in open plots, whereas they were nearly absent in forested sites; 2) we revealed a hydrological threshold for the occurrence of mixotrophic testate amoebae that might be very important in terms of peatland functioning and carbon sink vs. source context; and 3) mixotrophic species with organic tests were nearly absent in forested sites that were dominated by heterotrophic species with agglutinated or idiosomic tests. An important message from this study is that taxonomy of TA rather indicates the hydrological gradient whereas traits of mixotrophs the openness gradient.