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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.

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.

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.

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.

Over the last 300 years, many European forests have been progressively modified toward monoculture ecosystems, with preference given to coniferous forests. These forests, often dominated by Scots pine (Pinus sylvestris), are currently impacted by various disturbance factors, e.g., more frequent windthrows, droughts, fires and insect infestations. Peatlands located in these monocultures are also significantly impacted, enhancing their vulnerability to drying and burning. Here, we investigate how the functioning of a Sphagnum-dominated peatland has changed during the last ca. 700 years along with the introduction of new forest management strategies–modification of a mixed-forest complex into a Scots pine monoculture. Multi-proxy, high-resolution palaeoecological analyses include AMS radiocarbon dating, pollen and spores, plant macrofossils, testate amoebae and historical data. Direct peatland fire disturbance was reconstructed using a wide range of charcoal analyses: charcoal counts and morphological types to reconstruct past fire activity, and Raman spectroscopy to reconstruct past fire intensity. The results obtained confirm that introduction of new management techniques impacted the functioning of the peatland, leading to critical transitions in vegetation composition and hydrology. Detailed analyses of a distinct charcoal layer present in the peat show that increased fire activity as recorded by charcoal accumulation does not necessarily equate to burning intensity. Therefore, we recommend the use of charcoal-derived wildfire intensity reconstructions in tandem with charcoal abundance studies.

THÀNH PHẦN LOÀI TRÙNG CHÂN GIẢ CÓ VỎ TẠI HỒ CHỨA SUỐI SIM, KHÁNH HÒA, VIỆT NAMThành phần loài trùng chân giả có vỏ tại hồ chứa Suối Sim (tỉnh Khánh Hòa, Việt Nam) lần đầu tiên được tiến hành nghiên cứu. 46 loài, thứ và dạng trùng chân giả có vỏ thuộc 4 họ và 7 giống đã được phân loại từ các mẫu nước và nền đáy. Số lượng loài trùng chân giả có vỏ dạng phù du cao hơn rõ rệt số lượng loài trùng chân giả có vỏ dạng sống đáy. Đa dạng loài của giống Difflugia là cao nhất với 24 taxa. Các loài Centropyxis aculeata, Difflugia corona, Difflugia elegans, Difflugia elegans angustata, Difflugia lobostoma, Difflugia sp.2 và Lesquereusia spiralis là những loài thường gặp trong số các loài trùng chân giả có vỏ dạng phù du. Đồng thời, Centropyxis aculeata và Difflugia corona cũng phổ biến trong nền đáy. Trong nghiên cứu này, một số loài hiếm gặp và một số loài mới đối với Việt Nam đã được phát hiện. Những nghiên cứu tiếp theo cần được tiến hành để tìm ra thêm các loài trùng chân giả có vỏ trong hồ chứa này.

The distribution of diversity in function of climate has been largely studied in plants and animals, leading to a large body of literature on macroecological rules applied to large geographic scales. However, the applicability of these rules to microbes has almost never been tested at local scales. Arcellinida are a diverse group of protists known to be narrow ecological specialists and constitute therefore an excellent group to test general rules validated on “macrobes”, like the water-energy balance that stipulates that biodiversity peaks with humidity and temperature. In order to test that hypothesis, we collected 122 samples from four cedar forests situated along an elevation gradient in Lebanon, spanning different local climates. We evaluated their diversity using an Arcellinida-specific metabarcoding approach based on the cytochrome oxidase subunit I gene. Our study shows that Arcellinida richness and phylogenetic diversity follow a unimodal distribution, peaking at mid-elevations. β-diversity was chiefly the product of turnover, illustrating the high spatial heterogeneity of the forests. Precipitation and actual evapotranspiration were identified as key drivers of diversity, thus supporting the water-energy balance hypothesis. Communities situated at higher or lower elevation were, to a large extent, subsets of more diverse mid-elevation assemblages, which designates the latter as biodiversity sources. These results suggest that, under the increasing aridification of the Middle East due to climate change, Arcellinida communities will lose diversity and will undergo a process of homogenisation, with possible consequences on ecosystem functioning.

No previous literature has documented testate amoebae living on moss in the Nagi Bird Sanctuary, a designated Ramsar site in Bihar. Therefore, this investigation became the first study to explore testate amoebae species diversity in this important wetland. Testate amoebae are excellent environmental bioindicators, and single-celled microorganisms with external shells and are free-living. The present study is based on the moss samples collected from the Nagi Bird Sanctuary resulted in 16 testate amoebae species from 6 genera and 6 families. This research expands the existing understanding about testate amoeba species and distribution patterns at Ramsar sites in India as well as general ecological knowledge for future surveys and conservation efforts, especially for wetlands.