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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.

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.

Peatlands are globally-important carbon sinks at risk of degradation from climate change and direct human impacts, including drainage and burning. Peat accumulates when there is a positive mass balance between plant productivity inputs and litter/peat decomposition losses. However, the factors influencing the rate of peat accumulation over time are still poorly understood. We examine apparent peat accumulation rates (aPAR) during the last two millennia from 28 well-dated, intact European peatlands and find a range of between 0.005 and 0.448 cm yr^-1 (mean = 0.118 cm yr^-1). Our work provides important context for the commonplace assertion that European peatlands accumulate at ~0.1 cm per year. The highest aPAR values are found in the Scandinavian and Baltic regions, in contrast to Britain, Ireland, and Continental Europe. We find that summer temperature is a significant climatic control on aPAR across our European sites. Furthermore, a significant relationship is observed between aPAR and water-table depth (reconstructed from testate-amoeba subfossils), suggesting that higher aPAR levels are often associated with wetter conditions. We also note that the highest values of aPAR are found when the water table is within 5–10 cm of the peatland surface. aPAR is generally low when water table depths are < 0 cm (standing water) or > 25 cm, which may relate to a decrease in plant productivity and increased decomposition losses, respectively. Model fitting indicates that the optimal water table depth (WTD) for maximum aPAR is ~10 cm. Our study suggests that, in some European peatlands, higher summer temperatures may enhance growth rates, but only if a sufficiently high water table is maintained. In addition, our findings corroborate contemporary observational and experimental studies that have suggested an average water-table depth of ~10 cm is optimal to enable rapid peat growth and therefore carbon sequestration in the long term. This has important implications for peatland restoration and rewetting strategies, in global efforts to mitigate climate change.

Testate amoebae are a valuable group of species for biogeographic research. Current knowledge about the distribution of testate amoebae in the aquatic habitats Arctic is incomplete. In this study, we present the first report on testate amoebae from ponds of eastern part of Chukotka in the Arctic. Testate amoebae were studied in 11 ponds on the coast of Anadyr Bay of the Bering Sea. We identified 46 species belonging to 15 genera, among which Difflugia lobostoma, Netzelia gramen, and Cucurbitella mespiliformis were found in Arctic for the first time. Most common genera in ponds were Difflugia, Centropyxis, and Arcella. This genera structure is similar to that in lacustrine in the temperate climatic zone, but differed from genera structure described in Devon Island, Greenland, and Spitsbergen. Species structure of assemblages differed from that in both aquatic habitats from temperate zone and in other Arctic aquatic habitats. These results are consistent with the concept of a regionalized distribution of testate amoebae in the Arctic and provide new information on the species and genus distribution and species structure of testate amoebae communities from aquatic habitats in the Arctic.

Research on testate amoebae goes back to the early 19th century, more precisely the year 1815 when Leclerc (or Le Clerc) described the genus Difflugia , which he presented as a “new type of amorphous polyp” (Leclerc, 1815). Since then the pace of publication was uneven but some very significant early works such as the seminal works of Leidy, Penard, and Cash, Hopkinson and Wailes paved the way to future research (Penard, 1890, Penard, 1902, Penard, 1911, Leidy, 1879, Cash et al., 1905-1921). These early studies focused on describing the diversity of testate amoebae but also included discussions (or speculations) about their geographical distribution and ecology. The lives and scientific careers of Leidy and Penard were nicely described by Corliss who had the privilege of meeting Penard towards the end of his long life (Corliss, 2001).

Carbon storage capacity of peat deposits in permafrost mires is highly sensitive to climate change which effects might be strongly mediated by mire moisture and permafrost. Thus, it is essential to develop appropriate indicator tools of hydrological regime which can be used for monitoring present and past conditions in these mires. We use testate amoebae to investigate their indicator value to water table depth (WTD) and substrate water content (SWC) and to develop transfer functions for quantitative reconstructions of these environmental characteristics in the permafrost mires on the Central Siberian Plateau. In many cased, direct measurement of WTD in permafrost mires are not possible due to the presence of ice, so that SWC can be used as an alternative characteristic. Overall, 330 surface samples were collected in five study regions together with the corresponding environmental measurements. We find that testate amoebae form diverse assemblages with the species structure strongly controlled by WTD and SWC. We developed two testate amoeba-based transfer functions to reconstruct these characteristics based on Modern Analogue Technique which were assessed using leave-one-out and bootstrap cross-validation. We find that both transfer functions have good predictive power (for WTD: RMSEP = 6.8–7.6 cm, R2 = 0.54, for SWC: RMSEP = 2.0–2.3 %, R2 = 0.74–0.76). The ecological preferences of the majority of testate amoebae were similar to those reported by the studies in lower-latitudes, although some hydrophilic taxa were observed in the drier end of the surface wetness gradient. These data represent an important source for improvement of quantitative reconstructions based on subfossil testate amoebae in permafrost mires.

Despite of the rapid advancements in genomic tools over the past decade, genomic data remains limited for many protists, with some taxonomic groups lacking it entirely. One such group is testate amoebae, a group of shelled amoeboid protists known to have a long fossil record. Indeed, for some of them (i.e., arcellinid testate amoebae) the evolutionary roots trace back approximately 730 million years. Beyond their fascinating evolutionary history, these organisms are highly valued for their diverse applications across various research fields, including paleoecology, environmental monitoring, ecotoxicology, microbial community ecology, endosymbiont studies, and more. Consequently, their genomic data harbors significant potential for yielding crucial insights within the contexts of evolution, ecology, and climate change, while also offering opportunities for exploration from both biotechnological and functional perspectives. This short communication gives an overview of possible research directions for testate amoebae based on molecular data and outlining innovative techniques that have the potential to elevate testate amoebae research to a new next level.