Testate Amoeba Assemblages Research Articles

Environmental associations and the paleoecological significance of the genus Pyxidicula Ehrenberg,1838 and Pyxidicula muskegii sp. nov. in the Hudson and James Bay region peatlands, Canada

An environmental proxy routinely used in paleoecological studies of peatlands is testate amoebae, which are used to infer successional and hydrological shifts through time. However, since many species of protists globally remain undescribed, important ecological information about community assemblages and their interaction with environmental conditions in both the past and present has potential gaps. During the analysis of testate amoeba assemblages from peat cores across the Hudson and James Bay region of Canada, a testate amoeba that has not been formally described was discovered with high abundance in subfossil assemblages (up to 50%). We describe this new species, Pyxidicula muskegii sp. nov., using morphometric measurements of tests from these peat core records and demonstrate its environmental preferences using modern samples collected from the same region. The hemispheric shape and irregular areolar surface pattern on the test, along with its preference for lawns in both fens and bogs, support that P. muskegii is a new species. This species is also found in much lower relative abundance in modern samples (<3%) than in paleo-peat core records. This difference in modern and paleo-assemblage suggests that there is a taphonomic bias in their relative abundance with depth, which we attribute to their organic test that is less prone to decomposition. Therefore, it is critical to include rare taxa within future transfer function models to incorporate their environmental tolerances and improve model predictions.

Multi-scale beta-diversity patterns in testate amoeba communities: species turnover and nestedness along a latitudinal gradient.

The relationship between species diversity and spatial scale is a central topic in spatial community ecology. Latitudinal gradient is among the core mechanisms driving biodiversity distribution on most scales. Patterns of β-diversity along latitudinal gradient have been well studied for aboveground terrestrial and marine communities, whereas soil organisms remain poorly investigated in this regard. The West Siberian Plain is a good model to address diversity scale-dependence since the latitudinal gradient does not overlap with other possible factors such as elevational or maritime. Here, we collected 111 samples following hierarchical sampling (sub-zones, ecosystem types, microhabitat and replicate samples) and performed multi-scale partitioning of β-diversity of testate amoeba assemblages as a model of study. We found that among-ecosystem β-diversity is a leading scale in testate amoeba assemblages variation. Rare species determine β-diversity at all scale levels especially in the northern regions, where rare taxa almost exclusively accounted for the diversity at the ecosystem level. β-Diversity is generally dominated by the turnover component at all scales in lower latitudes, whereas nestedness prevailed at among-ecosystem scale in higher latitudes. These findings indicate that microbial assemblages in northern latitudes are spatially homogeneous and constrained by historical drivers at larger scales, whereas in southern regions, it is dominated by the turnover component both at the microhabitat and ecosystem scales and therefore determined by recent vegetation and environmental heterogeneity. Overall, we have provided the evidence for the existence of negative latitudinal gradient for among-ecosystem β-diversity but not for among-microhabitat and among-sample β-diversity for terrestrial testate amoeba communities.

Metalimnion as an ecotone in stratified freshwater lakes: A case study on benthic testate amoebae in Lake Valdayskoe

Abstract Testate amoebae are widely used as bioindicators in the study of modern ecotopes and as proxies in palaeoecological reconstructions of lacustrine environments. The metalimnion with thermocline in stratified water bodies strongly affects the species structure of a number of aquatic animals and often plays a role as an ecotone for pelagic animals, but our knowledge on the influence of the metalinmion on benthic organisms, especially on testate amoebae, is still limited. This study aims to describe the influence of the metalimnion and its thermocline on benthic testate amoebae assemblages along a temperature gradient in the stratified freshwater Lake Valdayskoe. Twenty‐eight samples from nine sites were collected along the transect starting in the littoral zone, passing through a long metalimnion and its thermocline and finishing in the hypolimnion on the bottom slope. We identified four species assemblages, six non‐attributed samples and five morphotrait compositions in the transect, including those corresponding to the area inside the metalimnetic zone. We observed similarities in the transitions in benthic species assemblages, morphotype compositions, and species and morphotrait structures from shallow to deep water, and two shifts corresponded well with the upper and lower limnological boundaries of the metalimnion. The combination of the observed biological and hydrological characteristics suggests that the metalimnion plays a role of an ecotone between shallow and deep water in stratified freshwater lakes, and maintains the integrity and sustainability of benthic communities of testate amoebae. We explored a multivariate approach to demonstrate that the combination of highly abundant species and dominant morphotypes may be an efficient indicator of related environmental conditions. Thus, the high abundances of Cylindrifflugia acuminata, Centropyxis aculeata, Difflugia lacustris, D. linearis and C. discoides in combination with the dominance of elongate‐spiky and flattened‐spiky shells are closely related to the littoral zone with sandy sediments covered by many macrophytes. The combination of a high abundance of D. petricola and D. penardi, and the dominance of pyriform, necked and oval shells are closely related to deep depth. The studied species and morphotrait transition from littoral to deep water provides additional information about the morphological adaptations of testaceans, and about the processes of forming and maintaining benthic testate amoebae assemblages along the depth gradient. The described species and morphotrait assemblages related to specific water depths may be useful for palaeoreconstructions.

Hydroclimate Changes Based on Testate Amoebae in the Greater Khingan Mountains’ Peatland (NE China) during the Last Millennium

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.

Changes in Testate Amoeba Assemblages in a Series of Different Types of Aquatic and Terrestrial Habitats of Wetland and Forest Ecosystems

Changes in Testate Amoeba Assemblages in a Series of Different Types of Aquatic and Terrestrial Habitats of Wetland and Forest Ecosystems

Response of testate amoeba assemblages to peatland drain blocking

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.

Testate amoebae response and vegetation composition after plantation removal on a former raised bog

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.

First data on testate amoebae associated with the endemic cave bivalve Congeria jalzici Morton & Bilandžija, 2013 with a description of Psammonobiotus dinarica sp. nov.

Testate amoebae are phylogenetically a very diverse group of eukaryotic microorganisms. They can be found in marine and freshwater habitats and in soil. Some of these single-celled organisms inhabit both surface and cave habitats, but their diversity in caves has barely been explored. Recent studies in the Dinaric region imply that testate amoebae in caves show a high diversity. The aim of this study was to identify the alpha diversity of testate amoebae in the Lika region (Dinaric karst, Croatia) and to compare the habitats of different caves based on testate amoebae assemblages. In eight caves we found more than 40 testate amoebae taxa, including a new testate amoeba species, Psammonobiotus dinaricasp. nov. The greatest diversity of testate amoebae was found in Markov ponor (27 taxa). The Bray-Curtis Similarity Index showed that testate amoebae assemblages in caves inhabited by the endemic and endangered cave bivalve Congeria jalzici (Markov ponor, Dankov ponor and Dražice ponor) differ from caves not inhabited by this species. This differentiation is attributed to the impact of the sinking Lika river, which occasionally completely submerges these caves, creating specific habitats for eukaryotic microorganisms. This study contributes to our understanding of the diversity, biogeography and ecology of testate amoebae in caves, as well as providing further insight into the conditions that sustain populations of C. jalzici.

The Effects of Vegetation and the Environment on Testate Amoeba Assemblages in Sphagnum Peatlands in the Northern Caucasus Mountains

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.

CHANGES IN TESTATE AMOEBA ASSEMBLAGES IN A SERIES OF DIFFERENT-TYPE AQUATIC AND TERRESTRIAL HABITATS OF WETLAND AND FOREST ECOSYSTEMS

Patterns of changes in the species richness, abundance, community structure, and biomass of testate amoebae were studied in a series of different-type aquatic and terrestrial habitats along an interlake transect in the Tyumen Region. Altogether, 112 species and forms of testate amoebae, including subspecies, were identified. Micrographs of all species detected are given. The species Conicocassis pontiguasiformis (Beyens et al., 1986) Nasser and Anderson, 2015, previously described as an arctic endemic, was found in the south of Western Siberia for the first time. The species richness of testate amoeba assemblages is maximal in the periphyton. The highest values of species numbers and biomass were detected in the bottom detritus of the coastal part of a swamp lake. Testate amoeba assemblages in various habitats along the transect are divided into aquatic and terrestrial, according to the results of cluster and principal component analyses. The species composition of testate amoeba assemblages depended on substrate wetness, as well as the type of vegetation. The dominants in relative biomass were identified for aquatic, forest, and well-lit Sphagnum habitats.

Distribution of Soil Microbes in Urban Parks: An Effect of Under-Tree Crown and Hillside Position on Testate Amoeba Assemblages in Subtropics (Shenzhen, China)

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.

Testate amoebae assemblages from two tropical high-mountain lakes in central Mexico during the last ~60 years

Testate amoebae are bioindicators sensitive to environmental change, which show good preservation in sediments of low pH environments, such as high mountain lakes (LAM). The presence and diversity of testate amoebae were documented in surface sediments and sediment cores, dated with 210Pb, from the only 2 LAMs in Mexico (El Sol and La Luna), which have shown signs of recent human-induced changes. A total of 18 taxa were recorded and the main species observed in both lakes were Difflugia glans “glans” and D. globulosa. Specific richness and Shannon’s diversity index were higher in Lake El Sol than in the smaller, acidic and ultraoligotrophic Lake La Luna. The sediment cores recorded changes, during the last 20 to 25 years, in the composition of the testate amoebae communities (El Sol) and in their dominance (La Luna), as well as increased accumulation rate and concentrations of iron and organic carbon. These are signs of anthropogenic impact on the lakes, which should alert us to improve protection measures for these unique ecosystems, not only at the local (crater) level, but also with a more regional perspective.

First ecological analysis of lacustrine testate amoebae in Guatemala: A case study from the highland Lake Chichoj

Freshwater quality represents a central issue for human populations and the conservation of aquatic communities. In this sense, freshwater reservoirs, such as lakes, require proper management and monitoring plans to avoid their deterioration and pollution. Bioindicators, such as testate amoebae, are an excellent tool increasingly utilized for limnology and paleolimnology to assess the trophic status of lacustrine environments. However, despite their potential as bioindicators, the ecological research status of testate amoebae in Central American lakes remains poor. We conducted our research at highland Lake Chichoj, Alta Verapaz, Guatemala, which has become increasingly eutrophic since the 1980s. This study contributes to fill the knowledge gap about neotropical testate amoebae, parallel to testing their utility as bioindicators of lacustrine conditions. From a collection of 12 surface sediment samples (associated with different land uses), we found 19 testate amoebae taxa, and for the first time in Guatemala, we recorded Arcella megastoma, Arcella gibbosa, Cucurbitella tricuspis, Difflugia protaeiformis strain “acuminata”, Difflugia urceolata strain “elongata”, Lesquereusia spiralis, Lesquereusia modesta, and Mediolus corona. Our cluster analyses revealed three testate amoebae assemblages in connection to trophic conditions: 1) Stressed Conditions (SC), 2) Lowest Contamination Conditions (LC), and 3) Deep Transitional Conditions Assemblage (DT). After performing a transformation-based redundancy analysis (tb-RDA), we found total organic carbon as the only significant environmental parameter associated with testate amoebae assemblages (p<0.004). Our indicator species analysis (IndVal) confirms the eutrophic regime of Lake Chichoj in connection to the presence of Cucurbitella tricuspis and Centropyxis aculeata strain “aculeata” as indicators of nutrient enrichment and stressful conditions. The testate amoebae assemblages identified in Lake Chichoj represent a critical baseline for future studies of Guatemalan lakes, strengthening our understanding of the causal factors behind water quality in neotropical regions.

The Effects of Sampling Depth on Benthic Testate Amoeba Assemblages in Freshwater Lakes: A Case Study in Lake Valdayskoe (the East European Plain)

Testate amoebae are widely used as proxies in paleoecological reconstructions of lacustrine environments; however, our knowledge on their distribution along depth gradients are limited. This study investigates the distribution of benthic testate amoebae along a sampling depth gradient (0 to 57 m) and related environmental characteristics in Lake Valdayskoe, Russia. In total, 101 species belonging to twenty-one genera were identified. Four types of testate amoeba assemblages (littoral, sublittoral, bottom slope and profundal) were distinguished that corresponded well to the bottom zones of the lake. The results of redundancy analysis indicated that sampling depth, temperature, pH and bottom inclination significantly explained 40.2% of the total variance in the species composition. Temperature and sampling depth had the largest individual contributions of 19.2 and 7.4% (p < 0.001), respectively. The minimal values of species diversity were observed on the littoral and at the lower boundary of the thermocline. We estimated depth optima and ranges for the species with high occurrences and distinguish stenobathic and eurybathic species. These data might improve the interpretations of paleoecological records of subfossil testate amoeba assemblages in lacustrine surface sediments and serve as basis for the development of a transfer function for reconstruction of lake depths.

Distribution of soil microbes in urban parks: an effect of under-tree crown and hillside position on testate amoeba assemblages in subtropics (Shenzhen, China)

Distribution of soil microbes in urban parks: an effect of under-tree crown and hillside position on testate amoeba assemblages in subtropics (Shenzhen, China)

Foraminifera and testate amoebae morphogroup analysis and biofacies of the Upper Cretaceous (Turonian) Ferron-Notom Delta, Utah, USA

Morphogroup and biofacies analyses were conducted on strata of the Upper Cretaceous (Turonian) Ferron-Notom delta, Central Utah, USA. This study investigates associations between ancient deltaic environments and foraminiferal and testate amoebae assemblages with an assessment of their ecological zonation based on their extant Holocene counterparts. Sixty-six hand samples of mudstone were collected from the three outcrops (Caineville North, Blue Hills, and Steamboat) along strike and dip profiles. Morphological analysis showed four morphogroups with eleven morphotypes of foraminifera and testate amoebae reflecting relationships between test morphology and depositional environment. Morphotypes were used to define the main biofacies of the study sections using cluster analysis. Due to a possible fossilization biases with the calcareous foraminiferal fraction, the biodiversity index is only used as relative measure in defining biofacies. Despite this possible taphonomic bias, the agglutinated foraminifera and testate amoebae morphogroups show plausible trends of salinity both among the outcrops and stratigraphically within each outcrop. The Blue Hills outcrop represents the most landward and thus the lowest salinity environment (tidally-influenced backwater), Steamboat is more coast proximal with a slightly higher salinity found in the delta front and the fluvial/estuarine environment, while the Caineville North outcrop represents the most coast proximal with the highest salinity of the prodelta/delta front and fluvial/estuarine environment. It appears that landward and coastward transport of tests led to a taphonomic bias. Nonetheless, the assemblages provide useful information that correlates with previously documented, lithofacies data. A salinity index, which is a ratio of trochospiral taxa versus testate amoebae taxa, provides a useful measure of coastal proximity that matches lithofacies trends. In addition, an Organic Matter (OM) index, which is the ratio of bolivinid-type taxa versus trochospiral taxa shows relationships with original probable OM content of the sediment inferred from the lithofacies and the plant macrofossils.

Testate Amoeba and Chironomid assemblages from Balma Lake (Piedmont, Italy): a multi-proxy record to identifying recent climate and environmental changes in alpine areas

Alpine lakes are well known as “environmental sentinels”, which are sensitive to anthropogenic impacts, and paleoecological studies provide useful information regarding the effects of local and global changes. In the present study we investigate, for the first time, the temporal variations in testate amoeba assemblages in relation to environmental factors and anthropogenic impacts in a high-altitude lake located in the Italian Alps (Balma Lake, Piedmont, Italy). The testate amoebae are well-suited as bioindicators and have been employed to reconstruct past climate and environmental changes from lake sediments. However, these organisms have not been thoroughly studied in alpine lakes, especially in Europe. We detected significant changes in testate amoeba assemblages along an alpine lake sedimentary profile over the last 2000 years. These changes were mainly associated with variations of trace elements, nutrients, and grain size. Moreover, five different time periods were identified and related to pluvial/drought events of the last 2000 years and to the “Late Antique Little Ice Age” (LALIA). Alpine lakes are originally fishless and fish introductions for recreational purposes could cause important changes in these ecosystems. However, the introduction of brook trout in Balma Lake during the 1970s seems to have had little influence on testate amoeba assemblages. The present work provides new insights for the evaluation of temporal changes in testate amoebae through paleoecological investigations. Similarly, the comparison of testate amoeba and chironomid proxies offered an important tool for analyzing recent climatic and environmental changes in alpine lakes (in lacustrine environments), especially for the European Alps.

Distribution of soil testate amoeba assemblages along an elevation gradient on Mount Fuji (Japan)

Elevation gradients have been useful to study distributional patterns of soil organisms since the time of Humboldt but only recently these patterns have been studied for soil microorganisms. Here we report the results on species diversity and composition of soil- and moss-dwelling testate amoeba assemblages along a 1400 m elevation gradient (904–2377 m a.s.l.) on Mount Fuji (Japan) from temperate forest to alpine vegetation. In total, 95 testate amoeba taxa belonging to 29 genera were identified. The core of testate amoeba assemblages was formed by ubiquitous species such as Trinema lineare, Euglypha laevis, Cryptodifflugia oviformis, and Trinema complanatum. However, several taxa with limited geographic distribution were also observed (e.g., Centropyxis latideflandriana, C. stenodeflandriana, Plagiopyxis cf. barrosi, Heleopera rectangularis, and Distomatopyxis couillardi). Species diversity indices (species richness and Shannon’s index) were characterised by bell-shaped patterns peaking at ∼ 1700 m in the subalpine mixed conifer-deciduous forest. The species composition of testate amoeba assemblages was best explained by the vegetation types which accounted for 12.3% of the total variation. Overall, these findings indicate that elevation effects on species composition of testate amoeba assemblages are strongly mediated by vegetation.

Dynamics of the Species Structure of Testate Amoeba Assemblages in a Waterbody-to-Mire Succession in the Holocene: A Case Study of Mochulya Bog, Kaluga Oblast, Russia

Dynamics of the Species Structure of Testate Amoeba Assemblages in a Waterbody-to-Mire Succession in the Holocene: A Case Study of Mochulya Bog, Kaluga Oblast, Russia

Responses of testate amoebae assemblages (Amoebozoa: Arcellinida) to recent volcanic eruptions, inferred from the sediment record in Laguna Verde, southern Patagonia, Argentina

There is little knowledge about testate amoebae in lakes and their responses to volcanic eruptions. To address this knowledge gap, we studied the paleoecology of these protists in a sediment record from Laguna Verde, a lake located east of the southern Patagonian Ice Field, in Santa Cruz Province, Argentina. The lake is under the influence of volcanic eruptions from Lautaro Volcano, Chile, ~ 42 km WNW of Laguna Verde. We evaluated the response of 11 testate amoeba morphospecies in the lake to the last four Lautaro eruptions, using a 61-cm sediment core. Calcium (Ca), a major element of volcanic ash, was the most important variable explaining testate amoeba variability in the three zones determined by detretended correspondence analysis. We identified four declines in testate amoeba abundance and diversity associated with tephra deposition. Poisson regression analysis revealed that Difflugia immanata, D. bidens, and D. glans strain “glans” decrease after deposition of tephra layers. In contrast, Centropyxis constricta strain “constricta,” C. aculeata strain “aculeata” and Zivkovicia compressa respond positively to ash deposition. Our findings suggest a high resilience of testate amoebae to stochastic events such as volcanism because the same assemblage (D. immanata, D. bidens, and D. glans strain “glans”) inhabited the lake before and after the ashfalls. Nevertheless, several volcanic eruptions during the last ~ 300 years may have weakened this resilience and had a long-term effect on community diversity. Multivariate analysis showed that potassium (K) plays a significant role in shaping assemblage composition. Because of the low K content of the Lautaro tephra, we infer that higher potassium concentrations in sediments are not related with volcanic events, but rather, are associated with terrestrial input. Future studies, however, will be needed to identify the source of K in the sediment record and its relationship with testate amoebae assemblages. Our study demonstrates the potential for using lacustrine testate amoebae as environmental proxies, and illustrates the direct effects of volcanic ash deposition on their assemblage composition, diversity and distribution in southern Patagonia.