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In the last two centuries, a high proportion of peatlands have been lost or severely degraded across the world. The value of peatlands is now well-recognised for biodiversity conservation, flood management, and carbon mitigation, with peatland restoration now central to many government policies for climate action. A challenge, however, is to determine 'natural' and 'disturbed' conditions of peatlands to establish realistic baselines for assessing degradation and setting restoration targets. This requires a tool or set of tools that can rapidly and reliably capture peatland condition across space and time. Our aim was to develop such a tool based on combined analysis of plant and testate amoebae; a group of shelled protists commonly used as indicators of ecological change in peatlands. The value of testate amoebae is well established in Northern Hemisphere Sphagnum-dominated peatlands; however, relatively little work has been undertaken for Southern Hemisphere peat forming systems. Here we provide the first assessment and comparison of the bioindicator value of testate amoebae and vascular plants in the context of Southern Hemisphere peatlands. Our results further demonstrate the unique ecohydrological dynamics at play in New Zealand peat forming systems that set them apart from Northern Hemisphere peatlands. Our results show that plant and testate amoeba communities provided valuable information on peatland condition at different scales, we found that testate amoebae tracked changes in the abiotic variables (depth to water table, pH, and conductivity) more closely than vascular plants. Our results further demonstrate that functional traits of testate amoebae showed promising relationships with disturbance. Amoeba test compression, aperture position and test size were linked to changes in hydrology driven by fluctuations in ground water tables; however, trait responses manifested differently in ombrotrophic and minerotrophic peatlands. Overall, testate amoebae provide a promising bioindicator for tracking degradation in New Zealand peatlands and a potential additional tool to assess peatland condition., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

The shells of testate amoebae are morphologically diverse and persistent in the environment. Accordingly, the examination of the morphology and composition of shells became a standard tool in ecological, palaeoecological, and evolutionary studies. However, so far the function of the shell remains poorly understood and, although based on limited evidence, the shell was considered as a defense mechanism. Based on recent evidence, we propose that the shell of arcellinid testate amoebae is a crucial component facilitating the amoebae's attack of large prey. Accordingly, the shell is not purely protective, but must be considered also as a weapon. This change in perspective opens up numerous new avenues in protistology and will lead to a substantial change in ecological, palaeoecological, and evolutionary research., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier GmbH.. All rights reserved.)

Extensive drainage of peatlands in north-west Europe for the purposes of afforestation for timber production and harvesting has altered the carbon balance and biodiversity value. Large-scale restoration projects aim to reinstate hydrological conditions to keep carbon locked up in the peat and to restart active peat growth. Testate amoebae are an informal grouping of well-studied protists in peatland environments and as microbial consumers play an important role in nutrient and carbon cycling. Using a space for time substitution approach, this study investigated the response of testate amoebae assemblages and vegetation composition after tree removal on a drained raised bog. There was a clear difference in microbial assemblages between open and a chronosequenceof restoration areas. Results suggest microbial recovery after rewetting is a slow process with plant composition showing a faster response than the microbial assemblage. Mixotrophic testate amoebae had not recovered seventeen years following plantation removal and the establishment of Sphagnum mosses in the wetter microforms. These results suggest that vegetation composition and Testate amoeba assemblages respond differently to environmental drivers at forest-to-bog restoration areas. Local physicochemical peat properties were a stronger driver of the testate assemblage compared with vegetation. Complete recovery of microbial assemblages may take place over decadal timescales., (Copyright © 2023 Elsevier GmbH. All rights reserved.)

Biological soil crusts (BSC) are associations of different macro and microorganisms and aggregated soil particles located on the surface of soils in many different habitats. BSC harbour a diverse and complex community of ciliates and testate amoebae. These phagotrophic protists play an important role in C and N recycling in soil ecosystems but have not been frequently studied in BSC. In this context, the effects of three increasing N inputs on ciliates and testate amoebae in crusts from a semi-arid Mediterranean ecosystem were evaluated. A field experiment with artificial N-deposition was designed to mimic the effects caused by anthropogenic N depositions. The results have shown that the protist populations of these semi-arid Mediterranean environments have lower species richness than other soil environments. The increase in N produces a net loss of diversity in the populations studied and shifts in the community structure. It has also been shown that some ciliates and testate amoebae, due to their population responses to increased N concentrations, could potentially be used as bio-indicators of N contamination in these BSCs., (Copyright © 2022 The Author(s). Published by Elsevier GmbH.. All rights reserved.)

This study provides new data on ecology of testate amoebae in the waterbodies of the Central Highlands and South-Central Coast regions of Vietnam. A total of 108 species and subspecies including six new records for Vietnam were identified. One new species Difflugia quangtrani sp. nov. was described. Difflugia, Arcella, and Centropyxis were the most species-rich genera, and Centropyxis aculeata was the most common species. The results of NMDS and ANOSIM analyses for the first time showed significant differences in composition of tropical freshwater testate amoeba communities within both various types of waterbodies (reservoir, river, and wetland) and biotopes (plankton and benthos). Average species richness per sample in different types of waterbodies was similar, while that of plankton was statistically higher than in benthos. The distance decay of similarity in tropical freshwater testate amoeba community of both plankton and benthos was observed for the first time indicating the importance of geographical distance in testacean species composition changes between samples. Redundancy analyses followed by the forward selection have determined elevation, pH, and dissolved oxygen as significant factors that affect tropical freshwater testacean community. More large-scale climatic and small-scale hydrological and hydrochemical variables should be included into further studies to find out most important factors determining structure of freshwater testacean assemblages., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier GmbH. All rights reserved.)

In the time of the global climate crisis, it is vital to protect and restore peatlands to maintain their functioning as carbon sinks. Otherwise, their transformations may trigger a shift to a carbon source state and further contribute to global warming. In this study, we focused on eutrophication, which resulted in the transition from rich fen to poor fen conditions on the Kazanie fen (central Greater Poland, western Poland Central Europe). The prior aim was to decipher how i) climate, ii) human, and iii) autogenic processes influenced the pathway of peatland changes in the last ca. 250 years. We applied a high-resolution palaeoecological analysis, based mainly on testate amoebae (TA) and plant macroremains. Our results imply that before ca. 1950 CE, dry shifts on the fen were generally climate-induced. Later, autogenic processes, human pressure and climate warming synergistically affected the fen, contributing to its transition to poor fen within ca. 30 years. Its establishment not only caused changes in vegetation but also altered TA taxonomic content and resulted in a lower diversity of TA. According to our research Microchlamyspatella is an incredibly sensitive testate amoeba that after ca. 200 years of presence, disappeared within 2 years due to changes in water and nutrient conditions. As a whole, our study provides a long-term background that is desired in modern conservation studies and might be used to define future restoration targets. It also confirms the already described negative consequences connected with unsustainable exploitation of nature., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Mariusz Lamentowicz reports financial support was provided by National Science Centre. Piotr Guzowski reports financial support was provided by Polish Ministry of Science and Higher Education., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Thecofilosea is a class in Cercozoa (Rhizaria) comprising mainly freshwater-inhabiting algivores. Recently, numerous isolates of thecofilosean amoebae have been cultured and were characterized by an integrated morphological and molecular approach. The captivating spine-bearing taxa in Thecofilosea were not yet molecularly characterized due to being very rare. There are only two known spine-bearing species, Pamphagus armatus and Lecythium spinosum, which were synonymized by Penard in 1902. Due to a morphological difference of those taxa, we discuss here that we disagree with this taxonomical act. We further isolated single cells of Pamphagus armatus directly from their habitat and successfully sequenced their SSU rDNA, which we subjected to phylogenetic analyses. We show that Pamphagus armatus branches within the Rhizaspididae (Tectofilosida, Thecofilosea). Accordingly, we transfer Pamphagus armatus and the assumingly closely related species Lecythium spinosum to Rhizaspis., (Copyright © 2021 Elsevier GmbH. All rights reserved.)

With the effects of global warming becoming ever more obvious, biodiversity conservation is facing severe challenges. Currently, a deeper understanding the mechanisms of the effects of warming on sensitive species has become an important topic in aquatic biodiversity and ecological management. Our study first overcame the "challenge" for a sensitive indicator species (Netzelia tuberspinifera, an endemic testate amoeba species in East Asia) of culturing under laboratory conditions, and then explored its molecular response mechanisms to warming using transcriptomic analysis. Our data indicate that temperature mainly drove the geographical and seasonal variation of N. tuberspinifera populations. Transcriptomic results indicate that when the temperature is <25 °C, rising temperature triggers the biosynthesis of ribosomes; while the temperature is >25 °C, it triggers molecular processes related with cell division, test formation and general biomass increase. However, once the temperature exceeds 40 °C, N. tuberspinifera is unable to survive. Following from these results, the distribution of N. tuberspinifera might expand towards higher altitude or latitude regions under global warming. For the first time, our study showed direct evidence for sensitive protozoa species that presents a very narrow adaptation mechanism to local climate. Our work provides fundamental data for regional biodiversity conservation and scientific reference in subtropical and tropical waterbodies., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

New Zealand (NZ) is a well-known hotspot of biodiversity and endemism for macroscopic organisms, but its microbial diversity is comparatively poorly documented. We assembled all records on NZ testate amoebae published since the early 20th century and present a comprehensive taxonomic checklist for NZ. Testate amoebae are reported from six major habitat types across both the North and South Islands of NZ, but the sampling effort is ecologically and geographically biased in favour of wetlands and the South Island. As a result, 93% of all 128 morphotypes recorded in NZ occur in wetlands, 28% are restricted to the South Island, and diversity is greater at higher latitudes. Around 50% of morphotypes have a broad latitudinal distribution across the NZ mainland, whereas 15% have narrow latitudinal ranges. Future research should aim to broaden the geographical and ecological ranges. We predict that our list of NZ testate amoebae will expand substantially with future work, and that the latitudinal diversity gradient will be inverted. We also introduce an interactive, fully illustrated, online Lucid key for the rapid identification of NZ testate amoebae. As many morphospecies are cosmopolitan, this key provides a useful tool for testate amoebae identification in other parts of the world., (Copyright © 2021 Elsevier GmbH. All rights reserved.)

The policy and practice of ecological restoration and conservation in China obtained some remarkable results. For example, Sphagnum moss growing on abandoned farmland, which was peatland before agricultural use, has rapidly expanded the wetland area in SW China. Microorganisms such as testate amoebae are sensitive to environmental change and thus have been widely used as ecological indicators in various habitats. We analyzed differently aged Sphagnum growing plots on a Sphagnum growing farmland and natural Sphagnum plots in SW China to examine how Sphagnum-dwelling testate amoeba communities and corresponding protozoic silicon (Si) pools respond to ecological restoration practice. We found that abundance, taxon richness, and diversity of testate amoebae were higher in Sphagnum growing farmland plots compared to natural Sphagnum plots. Protozoic Si pools showed an increase with Sphagnum growing time representing increased Si accumulation by idiosomic testate amoeba shells. However, protozoic Si pools were negatively correlated with taxon richness and diversity of testate amoebae. Our results showed that (i) natural Sphagnum plots were not characterized by the expected higher biodiversity of testate amoebae compared to Sphagnum growing plots and (ii) consequently protozoic Si pool quantity in natural Sphagnum plots was less driven by biodiversity of testate amoebae than expected. We concluded our results to underline the value of (i) environmental restoration policy in general and (ii) testate amoeba communities and corresponding protozoic Si pools for Si cycling in restoration areas of peatlands in particular. Based on our results, we recommend a sustainable cultivation of Sphagnum moss and an additional establishment of protected areas, where no Sphagnum harvesting occurs. These protected Sphagnum areas might represent hot spots of undisturbed testate amoeba communities and corresponding protozoic Si pools and thus of microbial Si cycling., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature.)

Surface wetness of Yuanchi peatland in the Changbai Mountains were reconstructed by comprehensive analysis on plant residue, testate amoeba and humification, using the age-depth model established with AMS 14 C and 137 Cs dating methods. The response of surface wetness to climate change was addressed. Results showed that plant residues in the top 50 cm of peat sequence were dominated by mosses. Detrended correspondence analysis (DCA) of plant residue revealed that axis 1 of DCA biplot might represent mire surface wetness (MSW). MSW from 1962 to 2008 as indicated by axis 1 scores of DCA on plant residue were compared with depths to water table derived by testate amoebae-DWT transfer function and humification measurements, and the results showed that the trends of MSW reconstructed by three proxies were largely consistent. They were wetter MSW from 40-50 cm (1962 to 1975), 27-40 cm (fluctuating from wet to dry from 1975 to 1987), and 0-27 cm (drier from 1987 to 2008). Compared with instrumental data from nearby Erdao weather station, the reconstructed MSW was basically consistent with temperature change in this period. The decreases of MSW occurred when mean summer temperature and mean annual temperature were higher than long-term mean value. Our results suggest that the variability in MSW in the recent 46 years predominantly responded weakening of effective precipitation induced by increasing temperature.

Deep high-altitude mountain lakes can act as a natural laboratory, and have the potential to contribute ecological data for understanding the way natural climate and anthropogenic changes that can affect the ecosystems. We present a multi-proxy record from a sediment core from such a lake (Lake Lugu) in southwest China with emphasis on the changes in the testate amoebae community, along with sedimentological data (magnetic susceptibility, total organic carbon/TOC and total nitrogen/TN) over the last 2500 years. In total, 29 testate amoebae species belonging to eight genera (Arcella, Centropyxis, Cyphoderia, Difflugia, Netzelia, Phryganella, Pseudodifflugia and Zivkovicia) were identified. Three stages were clearly defined for the lake based on testate amoebae community. The first stage dated to about 500 BCE-800 CE, with the testate amoebae community dominated by Centropyxis and influenced by soil erosion. The second stage (about 800-1920 CE) was characterized by a gradual increase of TOC and TN and an abrupt shift from Centropyxis-dominated to Difflugia-dominated communities. The third stage (about 1920-2010 CE) showed the pronounced impact of environmental change, high proliferation of Difflugia and a strong influence of human activities. Our results suggest that the testate amoebae assemblages in this high-altitude mountain lake are sensitive paleoenvironmental indicators that can help to monitor alpine lake ecosystem change and model lake succession under changing climate and environment. The potential causes of changes in the testate amoebae species composition and three stages of Lake Lugu succession were soil erosion and pollutants. The soil erosion led to the inwash of terrestrial particles and few testate amoebae species into Lake Lugu showing the importance of stochastic processes. The nutrient enrichment from soil erosion generated disturbances in the environment and species competition that led to the proliferation of some species and disappearance of others through niche based deterministic processes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Testate amoebae are a widely-used tool for palaeohydrological reconstruction from peatlands. However, it has been observed that weak idiosomic siliceous tests (WISTs) are common in uppermost peats, but very rarely found as subfossils deeper in the peat profile. This taphonomic problem has been noted widely and it has been established that WISTs disaggregate and/or dissolve in the low pH condition of ombrotrophic peatlands. Here we investigate the effect of this taphonomic problem on water-table reconstructions from thirty European peatlands through the comparison of reconstructions based on all taxa and those with WISTs removed. In almost all cases the decomposition of WISTs does not introduce discernible bias to peatland water-table reconstructions. However, some discrepancy is apparent when large abundances of Corythion-Trinema type are present (9-12 cm deviation with 50-60% abundance of this particular taxon). We recommend that WISTs should be removed before carrying out water-table reconstructions, and that the minimum count of testate amoebae per sample should exclude WISTs to ensure the development of robust reconstructions., (Copyright © 2020 Elsevier GmbH. All rights reserved.)

Globally, lakes and reservoirs ecosystems are integral parts of ecological processes. Nevertheless, global warming is rapidly changing their function and sustainability, especially in the populated area of the northern hemisphere. Here we examined testate amoebae community and 10 environmental variables from 51 lakes and reservoirs across China and developed testate amoebae transfer functions for temperature based on both abundance- and biomass-datasets. A total of 169 testate amoebae taxa were identified. Our partial CCA analyses revealed that water temperature explained 5.15% (P = 0.006) and 5.57% (P = 0.008) of the total variance in testate amoebae abundance and biomass, respectively. The WA-PLS was the best model in abundance-based temperature transfer function (RMSEP = 2.87 °С, R 2  = 0.60), whereas the MAT proved to be the best model for biomass-based temperature transfer function (RMSEP = 3.34 °С, R 2  = 0.67). The application of all models should be carried out with suitable precautions. Our results suggested that freshwater testate amoebae could contribute to a better understanding of the ecological integrity and its vulnerability in inland aquatic environments., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

Methodological advances are essential for robust ecological research. Quantitative reconstructions of environmental conditions using testate amoebae rely on sound taxonomy. While the taxonomy of large species is relatively well resolved, this is not the case for most small taxa (typically <45 μm long). In New Zealand, peatlands contain a diversity of both cosmopolitan and characteristic large southern endemic taxa, but also have a high abundance of small taxa. The latter are often lumped into morphotypes reducing their value as ecological indicators. In this study, we demonstrate how (a) lumping small taxa versus splitting them into unique types, and (b) including or excluding them from community analysis influenced their ecological inference. We assessed testate amoeba composition in six peat bogs from New Zealand, three that were moderately-to-highly impacted, and three that were non-impacted. Environmental variables were measured at each sampling site and the surface testate amoeba community patterns and community-environment relationships compared. We found a clear division between impacted and non-impacted sites. Several distinct small taxa were more strongly related to water-table depth and conductivity, while the larger taxa were more correlated to pH. These results show that improved taxonomic resolution of small taxa can provide more informed environmental assessment., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

Paleoecological records suggest that growing season length and/or cloudiness may affect peatland carbon accumulation and testate amoeba-based environmental reconstructions, highlighting a need to understand how light intensity affects microbial communities. We shaded plots on two peatlands for two years to examine effects on testate amoeba communities, the relative abundance of mixotrophic and heterotrophic testate amoebae, transfer-function performance, and δ 13 C values of two species of mixotrophic testate amoebae. Surprisingly, relative abundance of mixotrophic species increased in shade, although compositional changes did not affect transfer-function performance. Shading did not affect δ 13 C values of Hyalosphenia papilio and Heleopera sphagni, which ranged from -23.5 to -19.6‰ and -23.2 to -19.2‰, respectively. These δ 13 C values were higher than those of potential food sources and lower than literature-derived values for Chlorella, the zoochlorellae inhabiting mixotrophic testate amoebae. δ 13 C values thus suggest that these mixotrophic species obtain some carbon from Chlorella, although coupled dietary and isotope studies are needed to quantify this contribution. More research is needed to assess impacts of light variability on peatland microbial communities; however, carbon sources are recorded by δ 13 C values of testate amoebae, indicating potential for studies of carbon cycling and how mixotrophy varies temporally and spatially., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

It is well established that in ombrotrophic bogs, water-table depth (WTD) is the primary environmental control on testate amoeba distribution. However, the environmental controls on testate amoebae in minerotrophic fens are less well known and successional change in their assemblages associated with fen-bog peatland development has been scarcely investigated. Here we investigate a peatland space-for-time sequence resulting from postglacial rebound on the west coast of Finland, to assess successional patterns in testate amoeba communities and their relationships with environmental variables during peatland development. Sample sites along a 10-km transect from coast to inland ranged from a recently emerged wet meadow to a mature bog. Environmental variables (e.g., peat thickness, carbon and nitrogen content, pH, WTD and vegetation) were measured alongside testate amoeba samples. Results showed that even though the distribution of testate amoebae was to some extent determined by the succession stage, many taxa had wide WTD and pH ranges. The primary environmental control for many taxa changed along the succession. In conclusion, the ecological constraints on testate amoebae in minerotrophic systems are more complex than in bogs. The detected patterns also complicate the use of testate amoebae as a primary proxy in palaeoecological reconstructions where fen-to-bog shifts occur., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

To date there have only been two studies using testate amoebae as palaeoecological indicators in tropical peatlands. Here we present a new ∼500-year testate amoeba record from San Jorge, a domed peatland in Peruvian Amazonia, which has a well-constrained vegetation history based on pollen analysis. We observe a major shift from Hyalosphenia subflava to Cryptodifflugia oviformis-dominated communities at ∼50 cm depth (c. AD 1760), which suggests a change to drier conditions in the peatland. The application of a statistical transfer function also suggests a deepening of the water table at this time. The transition in the microbial assemblage occurs at a time when pollen and geochemical data indicate drier conditions (reduced influence of river flooding), leading to an ecosystem switch to more ombrotrophic-like conditions in the peatland. Our work illustrates the potential of testate amoebae as important tools in tropical peatland palaeoecology, and the power of multiproxy approaches for understanding the long-term development of tropical peatlands., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

We investigated how the land-use change from rainforest into jungle rubber, intensive rubber and oil palm plantations affects decomposers and litter decomposition in Sumatra, Indonesia. Litterbags containing three litter types were placed into four land-use systems and harvested after 6 and 12 months. Litter mass loss and litter element concentrations were measured, and different microbial groups including bacteria, fungi and testate amoebae were studied. After 12 months 81, 65, 63 and 53% of litter exposed in rainforest, jungle rubber in oil palm and rubber plantations was decomposed. In addition to land use, litter decomposition varied strongly with litter type and short-term effects differed markedly from long-term effects. After 6 months, oil palm and rubber litter decomposed faster than rainforest litter, but after 12 months, decomposition of rainforest litter exceeded that of oil palm and rubber litter, reflecting adaptation of bacteria and fungi to decompose structural compounds in rainforest litter but not (or less) in rubber and oil palm litter. Bacterial and fungal community composition and testate amoeba species number and density varied strongly with litter type, but little with land use. However, community composition of testate amoebae was mainly affected by land use. Generally, changes in bacteria, fungi and testate amoebae were linked to changes in litter element concentrations, suggesting that element ratios of litter material as basal resource for the decomposer food web shape the structure of decomposer communities and decomposition processes via bottom-up forces. Overall, changing rainforest to monoculture plantations shifts the decomposer community structure and negatively affects litter decomposition.

Peatlands cover 3% of the earth's land surface but contain 30% of the world's soil carbon pool. Microbial communities constitute a crucial detrital food web for nutrient and carbon cycling in peatlands. Heterotrophic protozoans are considered top predators in the microbial food web; however, they are not yet well understood. In this study, we investigated seasonal dynamics in the community and the trophic structure of testate amoebae in four peatlands. Testate amoebae density and biomass in August were significantly higher than those in May and October. The highest density, 6.7 × 10 4 individual g -1 dry moss, was recorded in August 2014. The highest biomass, 7.7 × 10 2  μg C g -1 dry moss, was recorded in August 2013. Redundancy analyses showed that water-table depth was the most important factor, explaining over one third of the variance in fauna communities in all sampled seasons. High trophic position taxa dominated testate amoebae communities. The Shannon diversity index and community size structure index declined from August to October in 2013 and from May to October in 2014. These seasonal patterns of testate amoebae indicated the seasonal variations of the peatlands' microbial food web and are possibly related to the seasonal carbon dynamics in Northeast Chinese peatlands., (Copyright © 2018 Elsevier GmbH. All rights reserved.)

Testate amoebae are widely used in ecological and palaeoecological studies of peatlands, particularly as indicators of surface wetness. To ensure data are robust and comparable it is important to consider methodological factors which may affect results. One significant question which has not been directly addressed in previous studies is how sample size (expressed here as number of Sphagnum stems) affects data quality. In three contrasting locations in a Russian peatland we extracted samples of differing size, analysed testate amoebae and calculated a number of widely-used indices: species richness, Simpson diversity, compositional dissimilarity from the largest sample and transfer function predictions of water table depth. We found that there was a trend for larger samples to contain more species across the range of commonly-used sample sizes in ecological studies. Smaller samples sometimes failed to produce counts of testate amoebae often considered minimally adequate. It seems likely that analyses based on samples of different sizes may not produce consistent data. Decisions about sample size need to reflect trade-offs between logistics, data quality, spatial resolution and the disturbance involved in sample extraction. For most common ecological applications we suggest that samples of more than eight Sphagnum stems are likely to be desirable., (Copyright © 2017 Elsevier GmbH. All rights reserved.)

Testate amoeba-derived transfer functions are frequently used in peatland palaeohydrological studies and involve the development of training sets from surficial peats. However, within acrotelmic peats, considerable vertical variation in assemblage composition can occur, particularly along Sphagnum stems, which may limit the representation of the associated 'contemporary' testate amoeba samples as analogues for the peatland surface. This paper presents contiguous testate amoeba assemblage data from nine monoliths collected from different peatland microforms (hummock, hollow, lawn) in three Sphagnum dominated ombrotrophic peatlands in Ontario and Quebec, eastern Canada. The aim is to: (i) gain a greater understanding of the vertical distribution of xerophilous/hygrophilous taxa along Sphagnum stems; (ii) determine the vertical extent of live/encysted taxa along this gradient; and (iii) assess the significance of this distribution on surface sampling protocols. The results show that testate amoeba communities in the uppermost acrotelmic peat layers display considerable variability. This may reflect a complex interplay of abiotic and biotic controls, including moisture, temperature, light and other characteristics, food availability, and mineral particle availability for test construction. These findings underline the complexity of testate amoeba community structure and highlight the importance of analysing both living and dead Sphagnum stem sections when developing calibration sets., (Copyright © 2017 Elsevier GmbH. All rights reserved.)

Recent climate change on the Antarctic Peninsula is well documented [1-5], with warming, alongside increases in precipitation, wind strength, and melt season length [1, 6, 7], driving environmental change [8, 9]. However, meteorological records mostly began in the 1950s, and paleoenvironmental datasets that provide a longer-term context to recent climate change are limited in number and often from single sites [7] and/or discontinuous in time [10, 11]. Here we use moss bank cores from a 600-km transect from Green Island (65.3°S) to Elephant Island (61.1°S) as paleoclimate archives sensitive to regional temperature change, moderated by water availability and surface microclimate [12, 13]. Mosses grow slowly, but cold temperatures minimize decomposition, facilitating multi-proxy analysis of preserved peat [14]. Carbon isotope discrimination (Δ 13 C) in cellulose indicates the favorability of conditions for photosynthesis [15]. Testate amoebae are representative heterotrophs in peatlands [16-18], so their populations are an indicator of microbial productivity [14]. Moss growth and mass accumulation rates represent the balance between growth and decomposition [19]. Analyzing these proxies in five cores at three sites over 150 years reveals increased biological activity over the past ca. 50 years, in response to climate change. We identified significant changepoints in all sites and proxies, suggesting fundamental and widespread changes in the terrestrial biosphere. The regional sensitivity of moss growth to past temperature rises suggests that terrestrial ecosystems will alter rapidly under future warming, leading to major changes in the biology and landscape of this iconic region-an Antarctic greening to parallel well-established observations in the Arctic [20]., (Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Ecological studies of peatland testate amoebae are generally based on totals of 150 individuals per sample. However, the suitability of this standard has never been assessed for alkaline habitats such as spring fens. We explored the differences in testate amoeba diversity between Sphagnum and brown-moss microhabitats at a mire site with a highly diversified moss layer which reflects the small-scale heterogeneity in groundwater chemistry. Relationships between sampling efficiency and sample completeness were explored using individual-based species accumulation curves and the effort required to gain an extra species was assessed. Testate amoeba diversity differed substantially between microhabitats, with brown mosses hosting on average twice as many species and requiring greater shell totals to reach comparable sample analysis efficiency as for Sphagnum. Thus, for samples from alkaline conditions an increase in shell totals would be required and even an overall doubling up to 300 individuals might be considered for reliable community description. Our small-scale data are likely not robust enough to provide an ultimate solution for the optimization of shell totals. However, the results proved that testate amoebae communities from acidic and alkaline environments differ sharply in both species richness and composition and they might call for different methodological approaches., (Copyright © 2017 Elsevier GmbH. All rights reserved.)

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 125cm, 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., (Copyright © 2015 Elsevier GmbH. All rights reserved.)

Testate amoebae are a polyphyletic assemblage of at least three major, unrelated taxonomic groups of unicellular amoeboid eukaryotes exhibiting a test. The focus on testate amoebae in scientific research has greatly increased in the past 20 years: from an average of about 5 papers a year in the mid-1990s to the current rate of more than 50 papers published yearly. The application range of these organisms is rapidly expanding as well: from the traditional fields of environmental monitoring and paleoecology, to forensic sciences and ecotoxicology studies. These developments are nevertheless strongly dependent on reliable taxonomy and nomenclature. However, scientometric data reveal that despite an ever-increasing necessity for the use of names (the product of taxonomy), the corresponding effort has not been achieved for improving testate amoebae systematics. As a consequence, inaccurate taxonomy yields to misinterpretations in the diversity of the organisms and to potentially incorrect conclusions. These and related problems are discussed in this study, highlighting the outcome of poor taxonomic expertise in accurate classification and phylogeny of testate amoebae, and the consequences derived from it. Additionally, this study is aimed to discuss the current status of testate amoebae classification, and to present all nomenclature and taxonomic changes in higher and lower taxonomic levels of testate amoebae, as a result of recent molecular reconstructions. Finally, we conclude with a list of the needs and suggestions toward a unified and modernized taxonomy of testate amoebae., (Copyright © 2016 Elsevier GmbH. All rights reserved.)

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., (Copyright © 2016 Elsevier GmbH. All rights reserved.)

Arcellacea (testate lobose amoebae) are important lacustrine environmental indicators that have been used in paleoclimatic reconstructions, assessing the effectiveness of mine tailings pond reclamation projects and for studying the effects of land use change in rural, industrial and urban settings. Recognition of ecophenotypically significant infra-specific 'strains' within arcellacean assemblages has the potential to enhance the utility of the group in characterizing contemporary and paleoenvironments. We present a novel approach which employs statistical tools to investigate the environmental and taxonomic significance of proposed strains. We test this approach on two identified strains: Difflugia protaeiformis Lamarck strain 'acuminata' (DPA), characterized by fine grained agglutination, and Difflugia protaeiformis Lamarck strain 'claviformis' (DPC), characterized by coarse grained agglutination. Redundancy analysis indicated that both organisms are associated with similar environmental variables. No relationship was observed between substrate particle size and abundance of DPC, indicating that DPC has a size preference for xenosomes during test construction. Thus DPC should not be designated as a distinct strain but rather form a species complex with DPA. This study elucidates the need to justify the designation of strains based on their autecology in addition to morphological stability., (Copyright © 2014 Elsevier GmbH. All rights reserved.)

Estimation of the post-mortem interval (PMI, the time interval between death and recovery of a body) can be crucial in solving criminal cases. Today minimum PMI calculations rely mainly on medical and entomological evidence. However, beyond 4-6 weeks even entomological methods become less accurate. Thus additional tools are needed. Cadaveric fluids released by decomposing cadavers modify the soil environment and thus impact soil organisms, which may thus be used to estimate the PMI. Although the response of bacteria or fungi to the presence of a corpse has been studied, to the best of our knowledge nothing is known about other soil organisms. Testate amoebae, a group of shelled protozoa, are sensitive bioindicators of soil physico-chemical and micro-climatic conditions and are therefore good potential PMI indicators. We investigated the response of testate amoebae to three decomposing pig cadavers, and compared the pattern to two controls each, bare soils and fake cadavers, in a beach-oak forest near Neuchâtel, Switzerland. Forest litter samples collected in the three treatments over 10 months were analysed by microscopy. The pig treatment significantly impacted the testate amoeba community: after 22 and 33 days no living amoeba remained underneath the pig cadavers. Communities subsequently recovered but 10 months after the beginning of the experiment recovery was not complete. The fake cadavers also influenced the testate amoeba communities by altering the soil microclimate during a dry hot period, but less than the cadavers. These results confirm the sensitivity of soil testate amoebae to micro-climatic conditions and show that they respond fast to the presence of cadavers - and that this effect although decreasing over time lasts for months, possibly several years. This study therefore confirms that soil protozoa could potentially be useful as forensic indicators, especially in cases with a longer PMI., (Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.)

The driving force of climate change in the monsoon margin is complex, making it a key area for regional and global climate change research. Palaeohydrological studies in the monsoon margin have increased the resolution of research in the long term, transitioning from qualitative to quantitative studies to comprehend climate change processes, patterns, and mechanisms. Testate amoebae (TA) in peat sediments are used as a proxy indicator organism for quantitative reconstruction of palaeohydrology. Thus, their community changes are directly related to precipitation, and widely used to reconstruct the patterns of summer precipitation globally. We investigated TA species and reconstructed palaeohydrological changes in the Greater Khingan Mountains' Hongtu (HT) peatland, located in the East Asian Summer Monsoon (EASM) margin. The result showed that the most abundant TA species were Assulina muscorum (12.4 ± 5.0%) and Nebela tincta (8.9 ± 4.9%) in the HT peat core. The increase in dry indicator species (e.g., A. muscorum and Alabasta militaris) indicated a drying pattern in the HT peatland since 150 cal yr BP. Principal component analysis (PCA) explained 47.6% of the variation in the selected TA assemblages. During 400 to 250 cal yr BP, PCA axis 1 scores ranged from 0.2 to −1.3 (reflecting a drier climate), associating with the Little Ice Age. The paleohydrology of the northern part of the Greater Khingan Mountains was mainly controlled by the EASM, which was associated with changes in North Atlantic Sea surface temperature and solar radiative forcing. The apparent drying pattern may be the result of the gradual intensification of anthropogenic activities and the increase in EASM intensity. [ABSTRACT FROM AUTHOR]

Peatlands represent globally important habitats and carbon stores. However, human impacts and climate change leave peatlands with a substantial management challenge. Degradation of peatland habitats and their hydrological integrity is increasingly counteracted through the rehabilitation of peatlands including re-wetting and drain blocking. Research into how such management interventions affect peatland microbial assemblages is limited. Here, we investigate the response of testate amoebae (established unicellular amoeboid protist indicators of hydrological conditions in peatlands) to drain blocking on three small lowland raised bogs in Northern Ireland, UK. We sampled Sphagnum adjacent to areas of focused flow near sites of damming in addition to control sites away from dam blocking. These restoration measures show complex but meaningful results after restoration. We observe several key developments following dam blocking: (i) species diversity increases; (ii) unambiguous wet indicator taxa appear in increasing abundance at dammed sites; (iii) and transfer-function reconstructed water-table depths show wetter conditions in the dammed sites. These findings imply wetter conditions after restoration, where routine monitoring presented no clear trend in water-table depths. We found no statistically significant assemblage-level response to experimental or environmental variables, which may be related to antecedent conditions and significant periods of drought during the study period. Thus, caution is advised when utilising testate amoebae for bioindication until their assemblage-level response to restoration is better understood. Nevertheless, this study emphasises the potential of an indicator-taxa based approach to applying testate amoebae as contemporary bioindicators of peatland restoration—particularly on short-term timescales immediately following restoration. [ABSTRACT FROM AUTHOR]

Testate amoebae are unicellular eukaryotic organisms covered with an external skeleton called a shell. They are an important component of many terrestrial ecosystems, especially peatlands, where they can be preserved in peat deposits and used as a proxy of surface wetness in paleoecological reconstructions. Here, we represent a database from a vast but poorly studied region of the Western Siberia Lowland containing information on TA occurrences in relation to substrate moisture and WTD. The dataset includes 88 species from 32 genera, with 2181 incidences and 21,562 counted individuals. All samples were collected in oligotrophic peatlands and prepared using the method of wet sieving with a subsequent sedimentation of aqueous suspensions. This database contributes to the understanding of the distribution of testate amoebae and can be further used in large-scale investigations. Dataset: https://doi.org/10.15468/avvq78. Dataset License: CC-BY 4.0 [ABSTRACT FROM AUTHOR]

The paper describes a dataset, comprising 236 surface moss samples and 143 testate amoeba taxa. The samples were collected in 11 Sphagnum-dominated bogs during frost-free seasons of 2004, 2007, 2009, 2017, and 2022. For the whole dataset, the sampling effort was sufficient in terms of observed species richness (143 species in total), though a regional species pool is deemed to be discovered incompletely (143 species is its lower 95 % confidence limit using Chao's estimator). The local community composition demonstrated high heterogeneity in a reduced ordination space. It supports the opinion that the high versatility of bog ecosystems should be taken into account during ecological studies. Dataset:  https://doi.org/10.15468/mnapsy. Dataset License: CC-BY 4.0 [ABSTRACT FROM AUTHOR]

Understanding the interactions among the functional groups of living organisms within ecosystems is a main challenge in ecology. This question is particularly important in relation to the interactions between the above- and below-ground components of terrestrial ecosystems. We investigated the effects of macro- (geographic position and mire size) and micro-environmental (pH, water table depth, water mineralization and temperature) characteristics and vegetation composition (both vascular plants and bryophytes) on the species structure of testate amoeba assemblages in eight Sphagnum-dominated mires across the Northern Caucasus Mountains (Russia). In total, 97 testate amoeba species from 34 genera were identified. A multiple factor analysis indicated the strongest relationships between the species structure of the testate amoeba assemblages and the local vegetation, especially bryophytes, whereas the interaction with the micro-environmental characteristics was the weakest. Among the micro-environmental data, the strongest effects on the species composition of all the assemblages were detected for the pH followed by the water table depth and water temperature. The variance partitioning of the species structure of the testate amoeba assemblages in response to the abiotic and biotic data indicated that most of the variance was related to the bryophyte and vascular plant assemblages, whereas the contribution of the environmental data was lower. Moreover, most of the effects were highly related to each other, so that the proportion of the jointly explained variation was high, whereas the individual effects were much lower. [ABSTRACT FROM AUTHOR]

Most eukaryotic microbial biodiversity is undescribed, and most species might be morphologically indistinguishable. Notable exceptions are so-called flagship species which are highly conspicuous and can therefore be used to address biogeographical questions. Here we describe Hyalosphenia papilio subsp. paynei, an arcellinid testate amoeba (Amoebozoa; Arcellinida; Hyalospheniidae) from wet hollows in two Sphagnum peatlands, one in Wales and one in Ireland. Phylogenetic analysis based on Cytochrome C oxidase subunit I (COI) sequencing places it within the lineage A of the H. papilio complex, but it differs from all 13 known H. papilio genetic lineages by its very distinctive, wider than long, morphology. The fact that such a conspicuous taxon was never reported in hundreds of studies published on Holarctic Sphagnum peatlands since Leidy's description of H. papilio in 1874 suggests that this subspecies has not dispersed and survived beyond Britain and Ireland. Furthermore its genetic similarity to H. papilio s. str. suggests that it has recently evolved. The discovery of this new taxon calls for a more detailed analysis of the morphological, ecological and molecular diversity of the H. papilio species complex. [ABSTRACT FROM AUTHOR]

The Hudson Bay Lowlands (HBL) stores a significant proportion of the northern peatland carbon pool, and constraints on the factors controlling local‐scale variation are needed to better predict soil carbon stocks. We investigated two treed peatland sites, a fen and a bog, to understand how local ecohydrological factors impacted long‐term carbon storage. Ecohydrological conditions were reconstructed using quantitative water table depth reconstructions from testate amoebae (TA) and broad peat type classifications. We also linked these factors and carbon storage to changes in TA community structure through the investigation of morphological and functional traits. Both sites have high rates of peat vertical accretion during the warmer Middle Holocene. A shift to a drier, Sphagnum‐dominated habitat after 7400 cal a bp at the bog site, however, led to lower apparent carbon accumulation rates (aCARs) than at the fen site. aCARs decreased with the transition to a cooler Late Holocene climate at both sites. Both sites have higher total carbon masses (kg m−2) than other more open and younger HBL localities, demonstrating the potential importance of treed peatlands in regional carbon storage. Shifts in the frequency of TA traits corresponded to changing ecohydrological conditions and provided insights into the role of TA in carbon storage. [ABSTRACT FROM AUTHOR]

Testate amoebae (TA) are important components of soil ecosystems, where they play an essential role in belowground food webs. In this study, we examined species composition, diversity, and structure of TA assemblages in soils beneath tree crowns (microscale) at three slope positions (mesoscale) in subtropical urban parks in Shenzhen, China. Forty-two species of TA belonging to 18 genera were identified in 81 samples. TA assemblages were the most diverse and abundant in the center of the tree crown comparing with other under-tree habitats. Foot of the hills harbored higher TA abundance and diversity comparing with upper locations along the hillslopes. The distribution of TA was mostly driven by under-crown and hillside positions but not by elementary environmental conditions such as pH, moisture content and thickness of leaf litter layer. None of later factors were sufficient in shaping TA assemblage composition. The findings of our study suggest that in regional studies of soil microbial eukaryotes both micro- (i.e., under-crown) and mesoscale (i.e., the slope position) heterogeneity should be considered. [ABSTRACT FROM AUTHOR]

Testate amoebae are widely used in palaeoecological studies as indicators (proxies) of environmental conditions in mires and freshwater ecosystems. The goal of this work was to identify patterns in the dynamics of the species composition of testate amoeba assemblages during a "waterbody–mire" succession. This study was performed using multiproxy analysis of the deposits in Mochulya Bog, Kaluga oblast, European Russia. To explain changes in the species composition of testate amoebae, we used data on the plant macrofossil composition, peat humification, and the loss on ignition, together with the results of radiocarbon dating and pollen analysis. The deposit was formed by the sediments of the waterbody, with rich fen and poor fen. The age at the base of the deposits was 4100 cal. yr. BP. Changes in the species composition of testate amoeba assemblages were largely determined by local vegetation, especially Sphagnum mosses, which significantly transform the environment. The transformation of the waterbody into a rich fen may have most likely occurred as a result of climatic (allogeneic) factors: short-term drying and wildfires that might have led to the overgrowth of the shore. The transformation of the rich fen to a poor fen could have been related to the effects of both autogenic (accumulation of the deposits) and allogeneic factors (decrease in human activity in the adjacent area). [ABSTRACT FROM AUTHOR]

Peatland complexes in the humid highlands of Hawai'i are vital refuges of biodiversity and freshwater resources. Hawaiian peat deposits are also rare repositories of terrestrial ecosystem archives located in an otherwise vast expanse of ocean. We investigated the potential for researching the paleohydrological history of Hawaiian montane peatlands on Kohala, Hawai'i Island through analyses of testate amoebae and Cladocera. Surface peat was collected from a variety of ecohydrological habitats (from water pools to hummocks) and analyzed for modern testate amoeba and cladoceran species relative abundance. We identified 54 morphotype taxa from 21 genera of testate amoebae, 4 taxa and genera of littoral Cladocera, and the common peat rotifer Habrotrocha angusticollis. Testate amoeba diversity and morphotype occurrence mirrored observations from many high-latitude peatland studies. Constrained and unconstrained ordinations support the hypothesis that surface moisture, measured as water-table depth, is an important control on the distribution of testate amoebae and Cladocera in Hawaiian peatlands. Transfer functions relying on weighted-averaging and modern analogs were developed to predict water-table depths from species relative abundance data, and these perform well under leave-one-site-out cross-validation: RMSEP = 9.75–10.3 cm, R2 = 0.56–0.62. Including cladoceran abundance data in the calibration dataset produced modest model improvement: RMSEP = 1–8% and R2 = 2–13%. A weighted-average partial-least-squares transfer function was applied to microfossil assemblages from a 0.5 m-long peat core with a 210Pb decay chronology anchored by ten existing measurements of 210Pb activity and a Bayesian statistical framework. Microfossils were well-preserved in the peat core. The water-table depth optima of an abundant down-core taxa, Hyalosphenia subflava, is not precisely constrained in the calibration data set, but estimates match those of other tropical studies. A reconstruction of water-table depth indicates dry early nineteenth-century conditions, wet conditions in the late 19th to early twentieth centuries, followed by progressive drying for much of the twentieth-century. Testate amoeba composition appears to have been sensitive to severe drought in recent decades. The results signal that assemblages of testate amoebae and Cladocera are useful proxies of Hawaiian peatland paleohydrology and should be considered alongside other archives of Hawaiian environmental history. [ABSTRACT FROM AUTHOR]

We present a ~ 40–year record of environmental change in the Swan Oxbow, Yangtze River, China, inferred from testate amoeba and sedimentary pigment data, combined with remote sensing and analysis of local socio–economic growth. These data indicate there were several distinct phases of aquatic conditions linked to human activities in the region: (1) Between ca. AD 1970 and 1984, there may have been some exchange of water and organic matter between the Swan Oxbow and the main river channel, following initial hydrologic disconnection in 1972. The lake area was relatively large in the early phase after the oxbow first formed, and the trophic state generally increased during that time frame, (2) From ca. AD 1984 to 1992, the lake area was about a third smaller in size, while the human population and GDP increased about 10% and 10x, respectively, compared to values in 1975. The nutrient status (inferred from testate amoeba and pigment data) increased, owing to the greater discharge of nutrients and separation of the Swan Oxbow from the main Yangtze River, which reduced water supply and increased sedimentation in the oxbow, (3) From ca. AD 1992 to 2003, the lake continued to diminish in size, to an area < 20 km2, except in 1998, when a major flood occurred. The testate amoeba and pigment data suggest that water quality had improved by that time, which probably reflects efforts to control agricultural and industrial activities, including establishment of two national reserves in 1992 and 1993, created to protect the rare Père David's deer (Elaphurus davidianus) and the freshwater Baiji dolphin (Neophocaena phocaenoides asiaeorientalis), (4) From ca. AD 2003 to 2005, the water area remained relatively unchanged, owing to construction of a dam following the 1998 flood. Occurrence of testate amoeba species Difflugia biwae and D. tuberspinifera, however, indicates that water pollution and eutrophication had been controlled in Swan Oxbow. The Swan Oxbow yielded important information about the effects of environmental protection and restoration in the middle reaches of the Yangtze River. [ABSTRACT FROM AUTHOR]

Peat cores from boreal bog and fen sites in the Hudson Bay Lowlands of Northern Ontario, Canada, were analysed to calculate Holocene carbon accumulation rates, and to show how testate amoeba taxonomic assemblages, inferred depths to water table, and four morpho-traits that may be linked to function (mixotrophy, aperture size, aperture position, and biovolume) changed since peatland initiation. Carbon accumulation rates were on average higher for the Holocene in the fen record (19.4 g C m−2 yr−1) in comparison with the bog record (15.7 g C m−2 yr−1), which underwent a fen-to-bog transition around 6900 cal yr BP. Changes in rates of carbon accumulation were most strongly driven by changes in rates of peat vertical accretion, with more rapid rates in the fen record. Carbon accumulation rates were highest following peatland initiation when reconstructed water tables were highest, and in the late Holocene, when water table positions were variable. Taxa with larger biovolumes and apertures were generally more abundant when reconstructed water tables were higher, most notably following peatland initiation. Mixotrophic taxa were more prevalent in drier conditions and in the bog record. Changing frequencies of morpho-traits suggest that testate amoebae may occupy a higher trophic position in the microbial food web during wetter periods, signaling the possibility of internal feedbacks between peatland ecohydrology and critical ecosystem functions including long-term carbon accumulation. [ABSTRACT FROM AUTHOR]

Microbial diversity is known to be huge but remains only partly documented. Testate amoebae are a relatively well studied group or free-living protists that build morphologically characteristic shells on which the taxonomy of this group is mainly based. Among testate amoebae, the Hyalospheniformes are especially well documented and are a model group for microbial biogeography. Here we describe a new species of genus Certesella from Sphagnum mosses and forest litter samples collected in the Dominican Republic and Chile. We name this species Certesella larai to honour our esteemed colleague Enrique Lara. This species bears two large pores connected by tube, which are characteristic of the genera Porosia and Certesella. The new species fits best in the latter genus given the presence of a distinct, sometimes denticulated, neck with a bulge that is absent in genus Porosia but occurs in Certesella. Its elongated shape (length/breadth ratio 2.03-2.58) only overlaps with C. certesi, which is distinguishable by the presence of a distinct longitudinal groove in the neck region that is absent from the new species. Interestingly most specimens lacked the internal teeth which are usually present in members of genus Certesella. As such, while the morphology of C. larai strongly suggests a belonging to genus Certesella, molecular analyses are still required to confirm its phylogenetic position, clarify the relationships among all species in genera Porosia and Certesella and the definition and validity of these two genera. The presence of this new species in two rather distant regions - Caribbean and central Chile - suggests it is likely widespread, but possibly rare. However, this perception may be due to a sampling bias in favour of Sphagnum mosses and wet and organic-rich habitats. This illustrates the need for a more systematic sampling effort to document the full and mostly unknown taxonomic diversity of soil protists. [ABSTRACT FROM AUTHOR]

In this study, we compared new testate amoeba records produced by the conventional water-based wet-sieving method to testate amoeba data from previous palynological analyses of two Holocene peat profiles from British Columbia, Canada. We used 132 paired samples from the same peat cores to compare the composition of testate amoeba assemblages between the two methods and evaluate the potential of palynological testate amoeba records as quantitative paleohydrological proxies in peatlands. Our results suggest that the palynological treatments (acetolysis, 10% KOH and 150 µm sieving) substantially reduce test concentrations, diversity and richness in most pollen-slide samples. The smaller sieve size used in the palynological treatment (i.e. 150 µm) removed only a small fraction of the total tests, but could introduce a species-specific bias in assemblage composition. However, major shifts between wet and dry conditions, as shown by the water table depth (WTD) reconstructions using wet-sieved samples, were relatively well captured by the palynological datasets in most instances. The palynological assemblages with counts of >50 tests (n = 30) provided WTD estimates similar to those inferred from the wet-sieved samples as the most dominant hydrophilous and xerophilous taxa were relatively well represented in the pollen-slide samples in the two studied peat cores. Testate amoeba data from pollen slides can provide useful paleohydrological information particularly when combined with other paleoenvironmental proxies. Nonetheless, if the goal is to generate quantitative paleohydrological reconstructions, we recommend that testate amoeba analyses be conducted using the wet-sieving method, as testate amoeba concentrations, diversity and richness are typically much lower in samples prepared with palynological treatments. [ABSTRACT FROM AUTHOR]

Testate amoebae are an irreplaceable key component of microbial communities in many aquatic and soil ecosystems and well known as useful bioindicators. In the present work, testate amoebae compositions in different-type biotopes of freshwater waterbodies of North Vietnam were investigated for the first time. A total of 80 species and subspecies belonging to 12 genera and 8 families were identified from 105 samples collected in Suoi Hai, Xuan Khanh, Cam Quy, Ho Ba reservoirs, and Van Long wetland. Difflugia acutissima, D. brychtai, D. distenda, D. elegans teres, D. glans, and Awerintzewia cyclostoma were new records for Vietnam. Centropyxis aculeata, D. schurmanni, and D. elegans were the most common species in all types of biotopes including plankton, benthos, and periphyton. The results of two-way ANOVA showed statistically significant interaction effects of waterbodies and the type of biotopes on testate amoebae species richness per sample (p < 0.05). The simple effects analysis was performed to compare species richness per sample within studied waterbodies concerning the type of biotope and vice versa. A statistically significant difference (p < 0.001) in testacean mean species richness per sample was observed between aquatic macrophytes in periphytonic biotope. The results of NMDS and ANOSIM analyses showed statistically significant difference in the testate amoeba communities between studied waterbodies (ANOSIM r = 0.16, p < 0.001) and biotopes (ANOSIM r = 0.29, p < 0.001). The indicator value of species (p < 0.05) selected 17 indicator species including one for plankton, one for benthos, and 15 for periphyton. These findings provide new useful information for further paleoenvironmental researches using testate amoebae as bioindicators. [ABSTRACT FROM AUTHOR]

Testate amoebae are a highly diverse and polyphyletic group of heterotrophic, free-living amoeboid protists that consist of a single cell enclosed within a shell, or test. These organisms inhabit a broad range of habitats, including lakes, ponds, rivers, bogs, wetlands, and peatlands, where they prey on bacteria, algae, other protists, and in some cases small micrometazoans. One group of testate amoebae produce the test out of overlapping siliceous plates that are formed individually within the cell and then secreted and glued together to make an organized shell. Upon amoebae death, the siliceous plates can accumulate in lake sediments and become part of the fossil record. The goals of the current study were to document the concentrations of siliceous plate morphotypes in waterbodies along the east coast of North America, examine distributional patterns, and determine the relationships between environmental variables and abundances of plates. Seven siliceous plate morphotypes representing remains of testate amoebae belonging largely to the Order Euglyphida were enumerated in surface sediments from 125 waterbodies situated from North Carolina, USA, to Newfoundland, Canada. Circular-shaped plates were the most widely distributed morphotype, found in 95% of the waterbodies, and along with oval-shaped plates, they accounted for 75% of all specimens enumerated. Other plate morphotypes, including quadrangular, rectangular, rhomboidal, and scutiform, were also common, and all morphotypes exhibited distinctive distribution patterns. We used best subset regression to evaluate the relationships between environmental variables and the concentration of plates/dry mass of sediment and to assess differences among sites. Water depth and pH were consistently shown to explain the most variation in testate plate abundance. Concentrations of potassium and sulfate were of lesser importance. Higher concentrations of siliceous plates were found in shallow and acidic waterbodies, indicating the possibility of reconstructing estimates of these 2 variables in ancient waterbodies. [ABSTRACT FROM AUTHOR]

The Arctic is experiencing substantial warming with possibly large consequences for global climate when its large soil carbon stocks are mobilized. Yet the functioning of permafrost peatlands, which contain considerable amounts of carbon, is still not fully understood. Palaeoecological studies may contribute to unravelling this functioning but require actuo-ecological calibration of the environmental proxies used. Testate amoebae may be valuable proxies for palaeoecological reconstruction, but indeed still large gaps exist regarding their present-day distribution in Arctic peatlands. This study presents the distribution of testate amoebae taxa with high (1 m) spatial resolution along a transect crossing an Arctic ice-wedge polygon mire. Whereas the polygon ridges are characterised by taxa that are known to be typical of dry environments or hydrologically indifferent, the low-lying wet settings show a mixture of wet- and dry-living taxa, indicating seasonally rapidly changing conditions. High testate amoebae concentrations were only found on the dry polygon ridges. Archerella flavum occurs in various moss species in drier polygon settings, in contrast to temperate regions where the species is exclusively known from wet sites with Sphagnum, which probably relates to the special moisture conditions associated with permafrost. To compare the results of full testate amoebae analysis with those of palynology, each surface sample was split into two parts and prepared and analysed following standard testate amoebae analysis and palynological methods, respectively. Clear differences in qualitative content were found and can be attributed to the different preparation methods and to possible small (a few cm) differences in sample location. Nevertheless, the indicative value of testate amoebae found in pollen samples adds importantly to the ecological inference of palynological studies. Overall testate amoebae research is very valuable for the recognition of past ecological settings and the accurate reconstruction of past hydrological regimes in Arctic mires. Considerably more research is, however, necessary to cover the total (ecological) diversity of testate amoebae populations in NE Siberia. [ABSTRACT FROM AUTHOR]

Although the use of sub-fossil testate amoebae as a proxy for raised bog hydrology in Holocene paleoecological studies is well-established, some detailed aspects of species-environment relationships remain under-researched. One such issue is the effect of bog surface microtopography on the climatic sensitivity of testate amoeba communities. Although it has been suggested that some microforms—especially hummocks—may be less sensitive to climatic forcing than others, this has rarely been objectively tested. To investigate this, subfossil testate amoebae assemblages have been examined in a series of shallow cores collected along a hummock-lawn-hollow transect from a bog in central Ireland and the resulting reconstructed water table records, dated using 210Pb, have been compared with instrumental weather data. Testate amoebae communities in the hollow microform were found to be significantly less diverse than those in the hummock and lawn, and both the hummock and lawn showed statistically significant correlations with instrumental temperature and precipitation data. Therefore, whilst the suggestion that paleoecological investigations should target intermediate bog microforms remains sound, the notion that hummock-based testate amoebae hydrological data are climatically-insensitive is challenged. [ABSTRACT FROM AUTHOR]

In this article, we examined the indicative value of a relationship between two non-pollen palynomorphs (NPPs), fungal HdV-10, related to the presence of Calluna vulgaris, and HdV-31A, which is testate amoeba – Archerella flavum. Both are frequently present on slides designated for pollen analysis, prepared from Sphagnum peat. We analysed three profiles from three extensive ombrotrophic peatlands in northern Poland, in which the content of testate amoebae (TA) was examined and TA-inferred depth to the water table (DWT) was reconstructed. The new analysis of palynological samples regarding NPPs revealed that strong increases in HdV-10 content were mostly simultaneous to HdV-31A declines. However, the relations between both types were not statistically significant. The rapid increases in HdV-10, despite the fact that this type of conidiospores is related to drier habitats on peatlands, were tentatively interpreted as an indicator of rapid rises in the water table level which, in consequence, might have stimulated the production of these spores by fungi. In addition, a negative correlation between HdV-31A and Arcella discoides and positive one, but weaker, in case of HdV-10 (attributed by some authors to species Trichocladium opacum (Corda) S Hughes) and A. discoides show a link between mutual fluctuations of both NPPs and hydrological instabilities on peatland. The Bagno Kusowo bog, the westernmost peatland subjected to the study, displayed an intriguing agreement between the presence of peat sections with strong increases in HdV-10 and cold climate events affecting Europe. Our study reveals that counting even a limited number of NPP types during the standard pollen analysis of Sphagnum peat may support the interpretation of results, especially, in cases when the investigation lacks testate amoeba analysis. When the reconstruction of TA-inferred DWT is provided, it may introduce additional information about the patterns of hydrological dynamics. [ABSTRACT FROM AUTHOR]

Thecofilosea is a class in Cercozoa (Rhizaria) comprising mainly freshwater‐inhabiting algivores. Recently, numerous isolates of thecofilosean amoebae have been cultured and were characterized by an integrated morphological and molecular approach. As attempts to establish a culture of Lecythium mutabilis repeatedly failed, it was not yet investigated by molecular means. We isolated single cells of L. mutabilis directly from their habitat and successfully sequenced the V4 region of their SSU rDNA. Phylogenetic analyses showed that L. mutabilis is not directly related to the genus Lecythium and instead branches within the Fiscullidae (Tectofilosida, Thecofilosea). Accordingly, we transfer the species L. mutabilis to a novel genus Omnivora gen. nov. [ABSTRACT FROM AUTHOR]

We evaluated the feasibility of using testate amoebae to infer the quantitative paleohydrology of ombrotrophic mires during their early stages (fen and fen-bog transition) of development. Two transfer functions, one derived from ombrotrophic and the other from minerotrophic mires, were applied to a peat core from an ombrotrophic mire in a taiga region of west Siberia. An ombrotrophic transfer function was applied to the bog stage of mire development. In contrast, ombrotrophic and minerotrophic transfer functions were applied independently to infer water table depth in the fen and fen-bog transition stages. Results of the two approaches for calculating water table depth during the fen and fen-bog transition stages differed by as much as 38 cm for the same peat sample. The main reason for this discrepancy is presence of testate amoeba taxa (e.g. Centropyxis aculeata, Cyclopyxis eurystoma, Cyclopyxis eurystoma v. parvula) in the peat that inhabit both modern ombrotrophic and minerotrophic mires, but differ substantially, in cases by > 20 cm, in terms of their water table depth optima in the ombrotrophic and minerotrophic mire calibration data sets. This difference in inferred water table depth also stems, to a lesser degree, from the fact that the ombrotrophic mire model does not include taxa that inhabited exclusively minerotrophic mires in the fen and fen-bog transition stages. Given these findings, we propose that different models be used for different stages of development, to reconstruct past water table depth in ombrotrophic mires. We recommend use of a model based solely on the ombrotrophic mire data set for the bog stage, and application of a second model based on the minerotrophic mire data set, for the fen and fen-bog transition stages. Application of an ombrotrophic model to the early stages of bog development can yield erroneous paleohydrological reconstructions. [ABSTRACT FROM AUTHOR]