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Peatlands are susceptible not only to direct disturbance, but also to indirect changes in their surroundings, including land management. Changes in agricultural practices or forest management can significantly influence peatland functioning, for example, their trophic status or surface vegetation. Here, we investigate the effects of planned forestry on two Sphagnum -dominated peatlands in northern Poland’s Tuchola Forest. We use testate amoebae and compare them to available pollen and historical data to reconstruct past environmental conditions and assess anthropogenic pressure. The Tuchola Forest has undergone significant transformations as a result of human activities, notably during Prussia’s promotion of pine monoculture in the 19th century. We hypothesized that forest management activities and other related disturbances have led to wetland acidification and water table alterations. Our results show that these changes have had profound effects on both peatlands. Radiocarbon dating revealed a correlation between forest management practices and peatland dynamics. Quantitative reconstructions based on testate amoebae showed that, as a result of the introduced pine monoculture, both peatlands experienced rapid acidification (pH levels dropping from ca. 6.2 to 3.5) and water table lowering of over 15 cm. The predominance of pine monoculture has not only reduced biodiversity but also enhanced the susceptibility of the forest to fires and pest outbreaks, further affecting peatland conditions. These findings contribute to understanding of how historical land-use changes continue to influence present-day peatland dynamics, offering insights into restoration and conservation efforts in forested peatland landscapes.

The Quaternary glaciations profoundly shaped the biogeography of plants and animals, yet their impact on microbial eukaryotes remains largely unexplored. We tested the “genetic legacy of the Quaternary” (GLQ) paradigm in terrestrial protists using Arcellinida testate amoebae diversity distribution across the Iberian Peninsula, a well‐established glacial refugium. To do so, we compiled the most extensive Arcellinida metabarcoding dataset to date (ArKOI), including 615 samples from multiple continents and ecosystems. Our results showed that hotspots of intra‐OTU genetic diversity align with known Iberian refugia, supporting the concept of “refugia within refugia,” and displaying clear ecoregion‐specific climatic niches. Patterns of spatial clustering, niche breadth, and historical demographic reconstruction revealed repeated range contractions and expansions during the Pleistocene, mirroring those observed in macro‐organisms. These findings extend the GLQ paradigm to protists, highlighting shared historical and ecological processes across the eukaryotic tree of life and contributing to a unified theory of biogeographic responses to climatic change.

Climate change models point to a possible rise in air temperature, ranging from 2 °C to 4 °C. Global changes will therefore have a particularly pronounced effect on the functioning of shallow water bodies known as peat ponds, i.e., habitats formed after peat extraction in peatlands. However, the extent of this impact is still unknown. The main objective of the study was to determine the impact of water level and water physicochemical properties on the functioning of selected groups of aquatic organisms in peat ponds of different origins. The study was conducted in spring, summer and autumn of the years 2024 and 2025, in 10 peat ponds with different trophic status and typology, located in the Polesie National Park in eastern Poland. Considerable fluctuations in water levels, resulting from a scarcity of precipitation, accelerated the drying out and overgrowth of peat ponds, particularly the alkaline and acidic types. Within the zoocoenotic communities, a significant decline in the abundance of planktonic species and an increase in the abundance of littoral or periphytic species were recorded (F = 6.24, p < 0.015). Regarding trophic structure, an increase in the abundance of mixotrophic species and a decrease in the abundance of top-level predators were observed. Hydrological changes were reflected in an increase in species richness and abundance of communities of organisms with broad ecological tolerance (mainly ciliates), and a decrease in the number of species and abundance of planktonic crustaceans and macroinvertebrates. The RDA model explains over 84% of the total variability, indicating excellent model fit to the data and a strong correlation between environmental variables and species composition. Based on p values, water level, temperature, pH, and COD were selected as significant variables, with conductivity, O2, and Ptot demonstrating less statistical significance. Peat ponds ecosystems can serve as an excellent model system for studying the impact of intensifying climate change on the functioning of shallow water bodies.

Testate amoebae are known among the proxies for paleolimnological investigations but, despite their recognized importance and recent findings, they have not been sufficiently studied in alpine lakes, particularly in Europe. The present study analyzes fossil testate amoeba assemblages from the Upper Balma Lake (2216 m a.s.l., Western Alps, Italy) to reconstruct ecological changes over the past 1200 years. 21 species belonging to 5 genera were identified, with Centropyxis and Difflugia being the most abundant. Multivariate statistical analyses, combined with sedimentological and geochemical data, revealed five paleoenvironmental phases corresponding to known climatic events, including the Medieval Climate Anomaly, the Little Ice Age, and the Recent Warming period. Assemblage composition and diversity were related to grain size variations, nutrient input, and trace element concentrations (e.g., As, Mn, Mo) and periods of climatic stability were associated with higher biodiversity, while cold or disturbed intervals, marked by floods or sediment reworking, resulted in reduced abundances and diversity. In recent decades, a decline was observed for the genus Centropyxis , possibly indicating reduced oxygenation and changes in contaminant levels. Comparative analysis with the Lower Balma Lake, located downstream in the same area, highlighted the influence of morphological/hydrological differences between lakes on species distributions. The findings underscore the value of testate amoebae as sensitive bioindicators and their applicability in paleoecological reconstructions of alpine lakes. This study contributes to understanding long-term ecological responses to climate change and provides insights into flood regime variability in high-mountain environments.

Non-pollen palynomorphs (NPPs) are important ecological indicators and are increasingly used in the study of Arctic ice-wedge polygon mires in Siberia. This paper provides an overview of NPPs found in high-spatial-resolution (1 m sample distance) surface samples along transects crossing various polygon microtopographical elements, and in high-temporal-resolution (sample distance 0.5 cm) contiguous samples in peat profiles. Whereas algal palynomorphs - of e.g. Botryococcus, Pediastrum, and various Zygnemataceae - show a distinct presence in open water settings, testate amoebae tests - of Arcella, Assulina, and Amphitrema flavum - are typical for dry peatland settings such as polygon rims. Various other NPPs were encountered including types not yet described. The latter have been denominated using morphological terms to facilitate future identification. These types are often typical for distinct polygon microhabitats and thus have indicator values that allow the reconstruction of past ecological settings without knowing the taxa that produce them.

Inland saline lakes are dynamic environments with fluctuating salinity levels, sometimes reaching values higher than those of seawater. Their abiotic conditions are often extreme and more unpredictable than in marine systems, which could imply lower biotic pressures. This could have allowed nonmarine organisms to cross the salinity barrier and subsequently specialize and diversify there. Alternatively, inland saline lakes could host generalist species that are also found in other environments. In order to answer this question, we focused on a group of protists characterized by their narrow ecological tolerance, Arcellinida testate amoebae. We studied their diversity using a metabarcoding approach in different thalassic and athalassic saline systems from Spain and Chile. The majority of operational taxonomic units (OTUs) were exclusive to athalassohaline systems. Three clades included most diversity in athalassohaline systems, in addition to several specific colonization events. Inland saline systems have been colonized by freshwater species, which diversified there, turning these athalassohaline environments into hotspots of specialized Arcellinida biodiversity.

Many UK blanket bog peatlands are degraded due to historical management including drainage, leading to reduced biodiversity, carbon sequestration and water storage. Currently, much restoration efforts including rewetting and revegetation strategies are being deployed aiming to restore habitats towards intact and ecohydrologically functioning ecosystems. However, it remains unclear how these efforts affect the key microbial consumers, testate amoebae (TA), especially their functional traits, and whether TA can be used as a generic tool to monitor the long-term hydrological restoration success. This study compared TA communities and their key functional traits at one intact and three near-intact sites versus three modified blanket bog sites with different habitat conditions (i.e., least modified, post-restoration, and degraded) to assess their environmental responses, bioindicator potential and explore their possible functional contribution to ecosystems in the process of recovery. The results showed: 1) TA community composition gradually changes from degraded to intact sites in both Sphagnum and surface peat, with distinct dominant TA species in each; 2) soil moisture, Sphagnum cover, and phosphorus content strongly relate to TA composition; 3) Hyalosphenia subflava and Corythion dubium indicate dry conditions, while Archerella flavum and Amphitrema wrightianum are indicators of wet conditions; 4) significantly higher community-weighted mean values of TA traits (biovolume, aperture width, siliceous tests) in surface peat at the least modified areas suggest TA's strong role in carbon and silica cycling following rewetting. Our findings support TA as bioindicators for tracking habitat hydrological conditions and restoration progress in blanket bogs, effectively linking community composition to ecosystem functions.

Restoring degraded peatlands is vital for sustaining their capacity as carbon sinks and long-term carbon stores. Microbial assemblages serve as valuable indicators for monitoring environmental change and assessing the success of ecosystem restoration efforts. Testate amoebae are a group of unicellular shelled protists that are commonly used for Holocene palaeohydrological reconstruction in peatlands. While progress is being made, the use of testate amoebae for biomonitoring in peatland restoration is still in its early stages. The aim of this study is to assess testate amoebae response to restoration measures (drain blocking) across three lowland raised bogs in Northern Ireland. To accomplish this, Sphagnum samples were collected from each site using a before-after control-impact (BACI) experimental design. After peatland drainage ditches were blocked, subtle yet significant responses in testate amoebae were observed: (1) key unambiguous wet-indicator taxa became more abundant in samples adjacent to blocked dams; (2) a widespread increase in the abundance of taxa with sub-spherical tests was observed, most notably in samples near to blocked drains. The findings of this study demonstrate the reliable response of testate amoebae to wetter conditions across all sites after restoration. Functional trait analysis paired with an indicator-taxa based approach, demonstrate the value of testate amoebae as contemporary bioindicators for tracking peatland restoration success, even when detailed hydrological monitoring data is not available. However, testate amoebae should be used with some degree of caution for peatland biomonitoring until long-term assemblage-level response to restoration is better understood.

Arcella is a genus of testate amoebae with a radially symmetrical shell composed of secreted material arranged in hexagonal units. Within the genus, species are distinguished by the morphology and dimensions of the shell. We describe a new species, Arcella prismatica sp. nov., discovered in a brown-water lake in the Mer Bleue Bog Conservation Area, a protected wetland in the city of Ottawa, Ontario, Canada. Specimens of the same morphotype have also been found in a subarctic peatland on the James Bay coast, near the village of Chisasibi, Quebec, Canada. The species has a polyhedral shell with a relatively flat dorsal surface and an irregularly crenulated aperture, a combination of characters not found in other members of the genus. The discovery of a novel and evidently widely distributed Arcella within the limits of a populous North American city is a reminder that the diversity of microbial eukaryotes is still poorly understood. Further exploration of undersampled peatland habitats can be expected to reveal new organisms and new relationships among known species.

The problem of increasing salinity and mineralization in natural and artificial freshwater bodies with climate warming is very relevant nowadays, as it leads to changes in the species composition of planktonic organisms. Testate amoebae are one of the responsive bioindicators that are sensitive to even minor changes in environmental conditions. In this study, a comparative analysis of the species diversity of planktonic testate amoebae was carried out in a number of lakes in the forest–steppe and forest–swamp natural zones of Western Siberia using microscopy and metabarcoding. One new species, Pseudodifflugia siemensmai sp. nov., was described. The detection frequency and the number of reads of amplicon sequence variants of potentially pathogenic testate amoebae belonging to the genera Rhogostoma and Fisculla were higher in forest–steppe lakes. Universal eukaryotic primers for the 18S rRNA gene are well suited for identifying testate amoebae from the supergroup Cercozoa but are practically not applicable for identifying Amoebozoa testaceans. The plankton of the lakes with the highest mineralization and salinity was characterized by the most specific species composition. These results should be taken into account when predicting changes in aquatic communities with further climate warming, which may also be associated with an increase in the occurrence of pathogenic testaceans that pose biosafety threats.