Amoeba Communities Research Articles

Resilience of plant and testate amoeba communities after climatic and anthropogenic disturbances in a Baltic bog in Northern Poland: Implications for ecological restoration

This study explores the history of the development of Sphagnum communities in an ombrotrophic peatland – Bagno Kusowo – over the past 650 years, based on high-resolution plant macrofossil and testate amoebae analysis. Our research provided information related to the length of peatland existence and the characteristics of its natural/pristine state before the most recent human impacts. Changes in the Sphagnum communities before human impact could have resulted from climate cooling during the ‘Little Ice Age’ (LIA). In this cold and unstable hydrological period, among vascular plants, Eriophorum vaginatum and Baeothryon caespitosum dominated in the peatland vegetation. Peat-forming Sphagnum communities survived the drainage conducted during the 20th century at the Bagno Kusowo bog. We provide three important messages through this study: (1) testate amoebae reflect similar hydrological trends in two peat cores despite considerable microhabitat variability, (2) average long-term water level 10 cm below the surface should be a target for active bog conservation and (3) sites like Bagno Kusowo are extremely important to preserve the remains of pristine biodiversity (including genetic diversity of plants and protists) that was completely removed from most of the raised bogs in Europe due to human activities, for example, drainage.

Changes in Structure and Functioning of Protist (Testate Amoebae) Communities Due to Conversion of Lowland Rainforest into Rubber and Oil Palm Plantations.

Large areas of tropical rainforest are being converted to agricultural and plantation land uses, but little is known of biodiversity and ecological functioning under these replacement land uses. We investigated the effects of conversion of rainforest into jungle rubber, intensive rubber and oil palm plantations on testate amoebae, diverse and functionally important protists in litter and soil. Living testate amoebae species richness, density and biomass were all lower in replacement land uses than in rainforest, with the impact being more pronounced in litter than in soil. Similar abundances of species of high and low trophic level in rainforest suggest that trophic interactions are more balanced, with a high number of functionally redundant species, than in rubber and oil palm. In contrast, plantations had a low density of high trophic level species indicating losses of functions. This was particularly so in oil palm plantations. In addition, the relative density of species with siliceous shells was >50% lower in the litter layer of oil palm and rubber compared to rainforest and jungle rubber. This difference suggests that rainforest conversion changes biogenic silicon pools and increases silicon losses. Overall, the lower species richness, density and biomass in plantations than in rainforest, and the changes in the functional composition of the testate amoebae community, indicate detrimental effects of rainforest conversion on the structure and functioning of microbial food webs.

Loss of testate amoeba functional diversity with increasing frost intensity across a continental gradient reduces microbial activity in peatlands

Soil microbial communities significantly contribute to global fluxes of nutrients and carbon. Their response to climate change, including winter warming, is expected to modify these processes through direct effects on microbial functions due to osmotic stress, and changing temperature regimes. Using four European peatlands reflecting different frequencies of frost events, we show that peatland testate amoeba communities diverge among sites with different winter climates, and that this is reflected through contrasting functions. We found that exposure to harder soil frost promoted species β-diversity (species turnover) thus shifting the community composition of testate amoebae. In particular, we found that harder soil frost, and lower water-soluble phenolic compounds, induced functional turnover through the decrease of large species (−68%, >80μm) and the increase of small-bodied mixotrophic species (i.e. Archerella flavum; +79%). These results suggest that increased exposure to soil frost could be highly limiting for large species while smaller species are more resistant. Furthermore, we found that β-glucosidase enzymatic activity, in addition to soil temperature, strongly depended of the functional diversity of testate amoebae (R2=0.95, ANOVA). Changing winter conditions can therefore strongly impact peatland decomposition process, though it remains unclear if these changes are carried-over to the growing season.

Abrupt ecological changes in the last 800 years inferred from a mountainous bog using testate amoebae traits and multi-proxy data

Mountainous peatlands of Western Sudetes are considered a unique habitat in Central Europe. The region contains one of the largest raised bog complexes in temperate Europe and is thus of great importance for biodiversity conservation. In this first high-resolution study from this region we use long-term ecological data to assess how these mountain wetland ecosystems responded to anthropogenic impacts and climate change. We used testate amoebae morphological traits, micro- and macroscopic charcoal, pollen and plant macrofossils to reconstruct the history of peatland development over 800 years, illustrating shifts in its development and fire dynamics. Five hydrological stages of peatland development were recognized. Testate amoebae morphological traits reflected several abrupt ecological changes linked to anthropogenic modifications of landscape openness. A shift towards mixotrophic taxa, linked to hydrological change or shrubs expansion and shading, preceded aperture position change, which was associated to dust input through surrounding deforestation and simultaneous water-table increase. Fire reconstruction revealed increasing burning together with intensifying human activity, including the expansion of a nearby settlement. This study confirms the potential of testate amoeba communities and the use of morpho-functional traits as indicators of ecological effects of land-use change over long-temporal scales.

Tree encroachment may lead to functionally-significant changes in peatland testate amoeba communities

Climate change is likely to cause increased tree recruitment on open peatlands but we currently have little idea what consequences this vegetation change may have below-ground. Here we use transects across forested to open bog ecotones at three Russian peatland complexes to assess potential changes in the most abundant group of peatland protists – the testate amoebae. We show that the testate amoeba communities of forested and open bog are markedly different with a very abrupt boundary at, or near, the vegetation ecotone. Changes along our transects suggest that tree encroachment may reduce the trophic level of testate amoeba communities and reduce the contribution of mixotrophic testate amoebae to primary production. Our study strongly suggests that increased tree recruitment on open peatlands will have important consequences for both microbial biodiversity and microbially-mediated ecosystem processes.

Testate amoebae as indicators of water quality and contamination in shallow lakes of the Middle and Lower Yangtze Plain

Testate amoebae are micro-organisms characterized by an agglutinated or autogenous shell enclosing the cytoplasm. Testate amoebae have been widely proposed as valuable bioindicators in a range of ecosystems (such as soils, peatlands and lakes). The use of testate amoebae as bioindicators of water quality in aquatic ecosystems is much less developed than for other microorganisms and previous research is geographically restricted. We investigated a large range of environmental variables and their relations to testate amoeba communities from 37 shallow lakes in the middle and lower Yangtze River Plain of China. Multiple factor analysis, redundancy analysis (RDA) and a forward-selection approach were used to explore the overall community structure and the links between the environmental variables and testate amoeba composition. Results showed that testate amoebae are widely distributed in most of the lakes despite often high levels of pollution. Our data highlight some links between water quality variables and testate amoeba communities. In particular, our results suggest that heavy metals have a role in shaping testate amoeba assemblage structure, although correlations are comparatively weak, perhaps due to lagged responses. Our results support previous suggestions that testate amoebae may be useful bioindicators in aquatic ecosystems but emphasize the need for an improved mechanistic understanding.

Testate Amoeba Communities of Epilithic Mosses and Lichens: New Data from Russia, Switzerland and Italy

The testate amoebae (TA) of many potential habitats around the world have been barely investigated but data on species presence and abundance is essential to answering big questions about microbial biogeography and the diversity of protist life. One such habitat lacking basic data is epilithic mosses and lichens with only a small number of samples analysed in previous studies and no systematic attempt to understand potential environmental controls. We use a large dataset (n = 81) from sites in Russia, Switzerland and Italy to demonstrate that testate amoebae in this habitat are both abundant and diverse. The community of our samples was dominated by ubiquitous taxa and differed between the northern (Russia) and southern (Switzerland and Italy) sites, perhaps due to differences in climate or air quality. Community composition, concentration and diversity were explained by moisture content but not by elevation above the ground surface and there were no significant differences between communities of mosses and lichens. Surprisingly our data showed a significant difference between communities of epiphytic and epilithic lichens in the same region sampled at the same time. Our study adds to the evidence that moisture availability is a critical factor in structuring testate amoeba communities across habitats and highlights the paucity of knowledge of TA in many environments.

A legacy of human‐induced ecosystem changes: spatial processes drive the taxonomic and functional diversities of testate amoebae in Sphagnum peatlands of the Galápagos

AbstractAimOur aims were to compare the composition of testate amoeba (TA) communities from Santa Cruz Island, Galápagos Archipelago, which are likely in existence only as a result of anthropogenic habitat transformation, with similar naturally occurring communities from northern and southern continental peatlands. Additionally, we aimed at assessing the importance of niche‐based and dispersal‐based processes in determining community composition and taxonomic and functional diversity.LocationThe humid highlands of the central island of Santa Cruz, Galápagos Archipelago.MethodsWe survey the alpha, beta and gamma taxonomic and functional diversities of TA, and the changes in functional traits along a gradient of wet to dry habitats. We compare the TA community composition, abundance and frequency recorded in the insular peatlands with that recorded in continental peatlands of Northern and Southern Hemispheres. We use generalized linear models to determine how environmental conditions influence taxonomic and functional diversity as well as the mean values of functional traits within communities. We finally apply variance partitioning to assess the relative importance of niche‐ and dispersal‐based processes in determining community composition.ResultsTA communities in Santa Cruz Island were different from their Northern Hemisphere and South American counterparts with most genera considered as characteristic for Northern Hemisphere and South American Sphagnum peatlands missing or very rare in the Galápagos. Functional traits were most correlated with elevation and site topography and alpha functional diversity to the type of material sampled and site topography. Community composition was more strongly correlated with spatial variables than with environmental ones.Main conclusionsTA communities of the Sphagnum peatlands of Santa Cruz Island and the mechanisms shaping these communities contrast with Northern Hemisphere and South American peatlands. Soil moisture was not a strong predictor of community composition most likely because rainfall and clouds provide sufficient moisture. Dispersal limitation was more important than environmental filtering because of the isolation of the insular peatlands from continental ones and the young ecological history of these ecosystems.

Use of functional diversity to assess determinant assembly processes of testate amoebae community

Functional diversity is among the main components of biodiversity, by quantifying the characteristics of organisms and by investigating which assembly processes prevail in the organisation of communities. The objective of this study was to assess the functional diversity of testate amoebae in floodplains, verifying whether the determinant assembly process of the community is related to environmental filters or the limiting similarity. We tested the hypothesis that the functional diversity of the testate amoebae would be lower than randomly expected in the hydrological periods, influenced by environmental filters. In addition, the functional diversity of the testate amoebae was expected to be strongly influenced by variables related to the productivity of the environments, since the food resources are the most important environmental factors in the assembly of testate amoeba communities. Sampling was carried out quarterly between 2002 and 2011 on the surface of the pelagic zone in six floodplain environments. Results showed that the values were lower than randomly expected according to the functional diversity indices. In addition, the functional diversity was predicted by the environmental variables related to the productivity of the environments according to multiple regression analyses. Our results highlight that functional diversity was mainly influenced by the environmental filters. The limiting similarity and neutral processes could not be totally discarded, and the three mechanisms of community assembly can occur. The environmental filters were linked to productivity and consequently to food resources, which are determinant in the assembly of the testate amoebae community, corroborating our predicted hypothesis.

Molecular and Morphological Snapshot Characterisation of the Protist Communities in Contrasting Alpine Glacier Forefields

Phagotrophic protist diversity in oligotrophic soils such as alpine glacier forefields is still poorly studied. Combining morphologic observations with molecular-based analyses, we assessed the diversity of major phagotrophic protist groups in two contrasting glacier forefields in the Swiss Alps (Tiefen glacier forefield, siliceous bedrock, and Wildstrubel glacier forefield, calcareous bedrock), at sites differing in soil development. Ciliates and heterotrophic flagellates could be detected with both approaches, while amoebae could be observed only microscopically. Soils from Tiefen and Wildstrubel glacier forefields harboured distinctly different ciliate, flagellate and amoebae communities. The ciliate clone libraries from the Tiefen glacier forefield were dominated by Oligohymenophorea-related sequences while those from the Wildstrubel glacier forefield were dominated by Spirotrichea-related sequences. Testate amoebae morphospecies of the genera Corythion , Cryptodifflugia , Euglypha and Tracheleuglypha were restricted to the Tiefen glacier forefield, while Centropyxis and Trinema to the Wildstrubel one. No ciliate sequences and only a few ciliate and testate amoebae morphospecies could be retrieved from unvegetated soils of both glacier forefields. The ciliate and testate amoebae community detected at unvegetated sites were a subset of the community developed at vegetated sites. Overall, our results suggest that alpine glacier forefields are colonised by a diverse community of phagotrophic protists which seems to be shaped by bedrock geology and vegetation cover.

Effect of daily variation on the seasonality of testate amoebae community structure in different environments of a Neotropical floodplain

<p>Ecological communities are constantly restructuring in the short and long term in response to population dynamics and environmental variables. This study evaluated the structure of arcellinid and euglyphid testate amoebae planktonic communities in three environments of the Upper Paraná River basin, Brazil. We hypothesised that the community structure of testate amoebae is differentially influenced by environmental conditions, mainly in isolated lentic ecosystems, due the effect of the low-water period. In addition, we predicted that the response of testate amoeba communities to environmental changes is also affected by the distinct hydrodynamic characteristics of the environment. Plankton were sampled in the low- and high-water periods, and physical and chemical variables were calculated for each site. In order to evaluate the influence of environmental conditions on the variation in testate amoebae community structure over time, a time-lag analytical approach was used and significance was estimated using a Mantel test. A Kendall test coefficient was used to estimate the maintenance of species abundance on each day when sampling was carried out and for each water body. A redundancy analysis was also performed to assess the responses of testate amoeba communities to environmental change in the three studied environments. Bray–Curtis dissimilarity indices were calculated for the testate amoeba communities and the significance of the differences between communities was estimated using a Mantel test. Seventy-five taxa belonging to six families were identified. Environmental conditions influenced the richness, abundance, and dominance pattern of the testate amoebae communities, and distinct hydrodynamic characteristics of the environments affected the establishment of community structure.</p>

<b>Testate amoebae (Protozoa Rhizopoda) in two biotopes of Ubatiba stream, Maricá, Rio de Janeiro State

Four samplings were carried out during the dry and rainy seasons in 2014, in two biotopes (plankton and aquatic macrophytes) to assess the composition and species richness of testate amoebae community in a coastal stream in the state of Rio de Janeiro, Brazil. Results showed great representation of Difflugiidae, Centropyxidae, Lesquereusiidae and Arcellidae families. Higher richness was observed in the plankton samples and higher densities of testate amoebae were reported among the aquatic vegetation during the dry season. Current investigation is a pioneer study conducted in the Ubatiba stream. Further researches on these protists, especially in Rio de Janeiro, should be undertaken.

Testing peatland water-table depth transfer functions using high-resolution hydrological monitoring data

Transfer functions are now commonly used to reconstruct past environmental variability from palaeoecological data. However, such approaches need to be critically appraised. Testate amoeba-based transfer functions are an established method for the quantitative reconstruction of past water-table variations in peatlands, and have been applied to research questions in palaeoclimatology, peatland ecohydrology and archaeology. We analysed automatically-logged peatland water-table data from dipwells located in England, Wales and Finland and a suite of three year, one year and summer water-table statistics were calculated from each location. Surface moss samples were extracted from beside each dipwell and the testate amoebae community composition was determined. Two published transfer functions were applied to the testate-amoeba data for prediction of water-table depth (England and Europe). Our results show that estimated water-table depths based on the testate amoeba community reflect directional changes, but that they are poor representations of the real mean or median water-table magnitudes for the study sites. We suggest that although testate amoeba-based reconstructions can be used to identify past shifts in peat hydrology, they cannot currently be used to establish precise hydrological baselines such as those needed to inform management and restoration of peatlands. One approach to avoid confusion with contemporary water-table determinations is to use residuals or standardised values for peatland water-table reconstructions. We contend that our test of transfer functions against independent instrumental data sets may be more powerful than relying on statistical testing alone.

Shifts in soil testate amoeba communities associated with forest diversification.

We studied changes of testate amoeba communities associated with the conversion of spruce monocultures into mixed beech-fir-spruce forests in the Southern Black Forest Mountains (Germany). In this region, forest conversion is characterized by a gradual development of beech undergrowth within thinned spruce tree stands leading to multiple age continuous cover forests with a diversified litter layer. Strong shifts in the abundance of testate amoeba observed in intermediate stages levelled off to monoculture conditions again after the final stage of the conversion process had been reached. The average number of species per conversion stage (i.e., local richness) did not respond strongly to forest conversion, but the total number of species (i.e., regional richness) was considerably higher in the initial stage than in the mixed forests, due to the large number of hygrophilous species inhabiting spruce monocultures. Functional diversity of the testate amoeba community, however, significantly increased during the conversion process. This shift was closely associated with improved C and N availability as well as higher niche diversity in the continuous cover stands. Lower soil acidity in these forests coincided with a higher relative abundance of eurytopic species. Our results suggest that testate amoeba communities are much more affected by physicochemical properties of the soil than directly by litter diversity.

Diversity and community ecology of forest epiphyte testate amoebae from European Russia

Testate amoebae are an abundant group of microorganisms which make a significant contribution to the diversity of protist life. Most of the world's potential habitats for testate amoebae have been barely studied and when such places are investigated they frequently reveal novel communities and species. Here we consider the testate amoeba communities associated with boreal forest epiphytes (mosses and lichens); an environment which we argue has been under-researched. We present a dataset of 165 samples from four regions of western Russia and analyse these data in relation to micro-habitat position and selected environmental data. The testate amoebae of epiphytes are abundant but dominated by ubiquitous species. We show that there are trends toward a lower species richness and test concentration with greater elevation on the trunk and in lichens compared to mosses. There are considerable differences in community composition between sampling regions. Of all measured environmental variables only moisture content showed a significant relationship with testate amoeba community structure. Our data highlight how little is known about testate amoeba communities of this habitat and call for greater research efforts, particularly in less-studied regions and biomes.

Comparative ecology of vascular plant, bryophyte and testate amoeba communities in four Sphagnum peatlands along an altitudinal gradient in Switzerland

Monitoring tools are needed to assess changes in peatland biotic communities and ecosystem functions in response to on-going climate and other environmental changes. Although the responses of soil organisms and plants to ecological gradients and perturbations do not always correlate, peatland monitoring is mainly based on vegetation surveys. Testate amoebae, a group of protists, are important contributors to carbon and nitrogen cycling in organic soils and are useful bioindicators in peatland ecology and paleoecology. There is however little comparative data on the value of testate amoebae, vascular plants and bryophytes as bioindicators of micro-environmental gradients in peatlands.We compared the relationships of testate amoebae, bryophytes, and vascular plants with soil temperature, water table depth, micro-habitats and the carbon and nitrogen content of Sphagnum mosses in four peatlands along a 1300m altitudinal gradient in Switzerland. We used the full diversity of vascular plants and bryophyte but only a selection of ten easily identifiable testate amoeba morpho-taxa (i.e. species or species-complexes).Indirect and direct gradient ordinations, multiple factor analysis (MFA) and transfer function models for inferring water table depth showed that a selection of ten testate amoeba taxa are more powerful (% variance explained in RDA) and accurate (discrimination among habitats) indicators of local conditions (micro-habitat type, water table depth and Sphagnum C/N ratio) than the vegetation (vascular plants and bryophytes either individually or combined and considering the full diversity).Our study showed that a limited list of ten easily identifiable testate amoeba taxa have higher bioindication value than the full bryophytes and vascular plants. Furthermore, testate amoebae can be analyzed on samples collected at any season (accessibility allowing and if precise sampling sites are well marked) – a clear advantage for biomonitoring and can be used to infer past changes from the peat record at the same taxonomic resolution. This simple approach could therefore be very useful for biomonitoring of peatlands.

Local factors affecting the testate amoeba community (Protozoa: Arcellinida; Euglyphida) in a neotropical floodplain

The objective of this study was to evaluate the possible influential factors on the patterns of temporal distribution of testate amoebae (Protozoa: Arcellinida and Euglyphida) in plankton environments connected to a main river in a Neotropical floodplain. In this context, we hypothesised that the local factors would be the main structural factors for the testate amoebae. Samplings during two hydrological periods were conducted along a longitudinal axis of three environments for aquatic macrophytes, at the edge of the banks. The highest mean values of the richness, diversity and density were recorded for the high water period. Our results suggested that local factors influence the distribution of testate amoebae. These environments were significantly affected by the hydrological regime, where the main structural factors for testate amoebae were the environmental variables, supporting the predicted hypothesis.

Ecology of testate amoebae (Protists) in mosses: distribution and relation of species assemblages with environmental parameters (King George Island, Antarctica)

Microbial communities living in mosses are known to constitute early indicators of ecosystem disturbances, but little is known about their response to environmental factors in the Antarctic area. This paper presents the first major study on testate amoebae from different species of mosses occurring on King George Island (Antarctica). The objective of the study was to investigate the structure and spatial distribution of moss-dwelling testate amoebae communities and to identify the environmental factors determining the structure of their assemblages. Additionally, we compared moss-dwelling testate amoebae communities on King George Island with other isolated islands of the Antarctic. Samples were collected from different species of mosses (Polytrichastrum alpinum, Sanionia georgico-uncinata, Sanionia uncinata, and Brachythecium austrosalebrosum). Sampling was carried out three times from 17 January to 24 February 2012. The species richness and abundance of protozoa differed significantly between the stations studied with the lowest count found in Polytrichastrum and the highest in Sanionia. The total population of testate amoebae was dominated by small taxa recognised as cosmopolitan, also recorded on other islands of the maritime Antarctic. The RDA analysis showed that all variables together accounted for 84.5 % of the total variance. However, variables that significantly explained the variance in testate amoebae communities were moisture, temperature, pH, and dissolved oxygen. Further research is required to explain the impact of biotic factors influencing the presence of testate amoebae, including the abundance of bacteria, microalgae, and small metazoa.

A natural experiment suggests little direct temperature forcing of the peatland palaeoclimate record

ABSTRACTAn important uncertainty in the interpretation of peat‐based Holocene climate reconstructions is what aspect of climate is recorded. Testate amoeba palaeoecological records have generally been interpreted in terms of water table depth but an increasing weight of experimental evidence shows that testate amoeba communities may respond to temperature independent of hydrological variability. In most ombrotrophic peatlands, variability in water table depth is driven by a combination of both temperature and precipitation, making it difficult to isolate any direct forcing by temperature. An unusual peatland ecosystem in which water tables are extremely stable offers an approach to this question. If testate amoeba communities show variability through time in these percolation bogs this implies a direct influence of temperature. This study presents a late Holocene testate amoeba record from the Imnati percolation bog in western Georgia. Below a phase of recent eutrophication results show essentially no variability in testate amoeba community composition or inferred water table depth through more than 4 m of peat representing over 2000 years. It is improbable that there has been no temperature variability over this period and the data therefore imply that direct temperature forcing of the palaeoecological record is minimal, at least for this region and time‐scale.

Seasonal changes in Sphagnum peatland testate amoeba communities along a hydrological gradient

Testate amoebae are an abundant and functionally important group of protists in peatlands, but little is known about the seasonal patterns of their communities. We investigated the relationships between testate amoeba diversity and community structure and water table depth and light conditions (shading vs. insolation) in a Sphagnum peatland in Northern Poland (Linje mire) in spring and summer 2010. We monitored the water table at five sites across the peatland and collected Sphagnum samples in lawn and hummock micro-sites around each piezometer, in spring (3 May) and mid-summer (6 August) 2010. Water table differed significantly between micro-sites and seasons (Kruskal–Wallis test, p=0.001). The community structure of testate amoebae differed significantly between spring and summer in both hummock and lawn micro-sites. We recorded a small, but significant drop in Shannon diversity, between spring and summer (1.76 vs. 1.72). Strongest correlations were found between testate amoeba communities and water table lowering and light conditions. The relative abundance of mixotrophic species Hyalosphenia papilio, Archerella flavum and of Euglypha ciliata was higher in the summer.