Abstract
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
1. Summary
Testate amoebae (TA) are a large polyphyletic group of microorganisms with a complicated systematic position that regularly renews [1,2,3]. They are characterized by the presence of a rigid external cell cover called a shell. Over the past 200 years of investigations, about 2000 species have been described. Most of them are freshwater, but they are widely observed in almost all types of terrestrial ecosystems [4].
TA are the most abundant and diverse component of microbial communities in peatlands [5] and can constitute up to 50% of the total microbial biomass [6]. They include bacterivorous, mixotrophic and even predatory organisms and might form complex multilevel trophic chains [7]. TA are characterized by a unique set of features such as a worldwide distribution, diverse and decay-resistant shells, high sensitivity and quick responses to environmental changes that make them useful bioindicators of past and present conditions [8,9]. The most important environmental factor affects the species structure of TA assemblages is substrate moisture, as has been demonstrated in numerous studies [10,11,12,13]. In particular, the surface moisture in mire ecosystems greatly depends on the water table depth (WTD), which varies along the microtopography determining TA distribution [14,15]. Therefore, the provided dataset contains information on TA occurrences in relation to substrate moisture and WTD.
Boreal peatlands are widely distributed in Northern America, Northern Europe and Western Siberia. However, the study of the distribution of testate amoebae in these regions is extremely uneven. For example, the vast Siberian regions remain a blank spot on the map [16,17,18,19,20,21,22]. This dataset description is based on testate amoebae data published in Mazei et al., 2017 [23]. Thus, the main aim of this contribution is to provide a dataset on the distribution of testate amoebae in relation to surface wetness and related characteristics in peatlands in the Western Siberia Lowland (WSL).
2. Data Description
2.1. Dataset Description
The dataset is organized according to GBIF requirements for “Occurrence Data” type [24], and it follows Darwin Core standard of Biodiversity Information Standards (historical “TDWG”—Taxonomic Databases Working Group) and uses terms of “Occurrence” [25]. In the dataset, each observation includes basic information on the location (latitude/longitude), date of observation, name of the observer, substrate moisture and a comment on the sampling point location (microtopography of the sampling point). The coordinates were determined in situ using a GPS device (Table 1).
Table 1.
Description of the dataset.
2.2. Species Diversity and Community Structure in the Dataset
The dataset presents information on 88 species of testate amoebae belonging to 14 families except for incertae sedis and 32 genera found in the WSL (Tyumen region and Yamalo-Nenets Autonomous okrug) (Table 2). The total number of occurrences was 2181 (localization of an individual of the same species, as well as the total number of samples reviewed), and the number of counted individuals was 21,562. The most diverse families in terms of genus number were Hyalospheniidae (6), Centropyxidae (4) and incertae sedis (5—genera Ellipsopyxis, Paraquadrula, Physochila, Tracheleuglypha and Trigonopyxis). The greatest number of species were observed in the families Euglyphidae (16), Centropyxidae (15) and Hyalospheniidae (11).
Table 2.
Species diversity of testate amoeba families in the dataset.
The most abundant species in the Western Siberia peatlands is Trinema lineare (25.4% of the total individual counts). The following species are also abundant and constitute more than 1%: Corythion dubium (7.26%), Assulina muscorum (6.46%), Euglypha laevis (5.59%), Centropyxis aerophila (5.29%), Trinema enchelys (3.89%), Phryganella hemisphaerica (3.41%), Trinema complanatum (2.98%), Euglypha rotunda (2.53%), Nebela tincta (2.32%), Lesquereusia epistomium (1.93%), Centropyxis aerophila sphangicola (1.84%), Corythion orbicularis (1.70%), Cryptodifflugia oviformis (1.70%), Cyclopyxis arcelloides (1.54%), Assulina seminulum (1.47%), Bullinularia indica (1.37%), Euglypha tuberculata (1.32%), Euglypha strigosa glabra (1.3%), Arcella rotundata (1.28%), Trigonopyxis arcula (1.16%), Archerella flavum (1.09%) and Centropyxis orbicularis (1.02%). The other 66 species (Table 3) were less abundant than 1% of the total counts. T. lineare is the most common species (found in 94% of all sampling points). The following species have been encountered in more than 20% of samples: A. muscorum (83%), E. laevis (74%), C. dubium (66%), C. aerophila (52%), T. complanatum (52%), E. tuberculata (51%), P. hemisphaerica (50%), T. enchelys (50%), E. strigosa glabra (48%), C. orbicularis (46%), B. indica (46%), N. tincta (36%), C. oviformis (32%), Euglypha strigosa (32%), A. flavum (31%), T. arcula (29%), Galeripora catinus (29%), Euglypha compressa (29%), A. seminulum (28%), E. rotunda (26%), C. aerophila sphangicola (26%), Galeripora arenaria (22%), Euglypha ciliata (22%), Alabasta militaris (20%), Nebela collaris (20%). Centropyxis sylvatica minor, Paraquadrula irregularis, Arcella megastoma, Centropyxis constricta, Euglypha compressa glabra, Padaungiella lageniformis, Padaungiella wailesi, Plagiopyxis minuta, Planocarina marginata, Sphenoderia lenta and Trinema grandis were found in a single sample and are therefore considered rare. The other 52 species were found in less than 20% but more than 1% of samples.
Table 3.
Abundance (in %) and occurrences (samples) per study area of testate amoeba species from the dataset. Species names are listed in alphabetical order; study area codes are described in the Methods section. ab.—abundance; occ.—number of occurrences.
3. Methods
3.1. Study Area
The materials for the study were collected in six study areas along the latitudinal gradient at the WSL (Figure 1) in July 2008 and June 2009. All sampling sites were represented by various types of mire ecosystems located in the geographical range of 58° to 66° N and 68° to 79° E.
Figure 1.
Map of the study areas. Numbers are study areas described in Methods.
Study area 1 (N 58.79°, E 68.79°) is located on the east bank of the Irtysh River and was represented by two mires. Both of them are forested peatlands (‘ryam’) with Pinus sibirica or Betula sp. in the tree stand. The shrub cover is dominated by Rhododendron tomentosum and Rubus chamaemorus; the moss layer is formed by Sphagnum species, Pleurozium schreberi, Dicranum spp., Cladonia lichens, Hylocomnium splendens and Polytrichum commune.
Study area 2 (N 58.23°, E 68.22°) is located further south on the east bank of the Irtysh River and is represented by two mires. The vegetation cover is similar to the previous study site, with a denser Betula sp. canopy, the presence of Rhododendron tomentosum with Andromeda polifolia and sedges and a moss cover primarily formed by Sphagnum mosses.
Study area 3 (N 66.4°, E 79.02°) is located in the far north of the WSL, near the eastern bank of the Pur River. This site is an open tundra peatland with low vegetation of Betula nana, Rhododendron tomentosum and Oxycoccus palustris underlined by Sphagnum, Cladonia and Pleurozium schreberi.
Study area 4 (N 65.58°, E 77.58°) is located to the west of the Pur River in the vicinity of the town of Urengoi. It includes three sites: (1) an open permafrost peatland with Betula nana, Salix, Rhododendron tomentosum, Rubus chamaemorus and Sphagnum species and brown mosses including Polytrichum strictum and Polytrichum commune; (2) a lake-margin mat with dominated Eriophorum spp. with Andromeda polifolia and Rhododendron tomentosum and Sphagnum in the moss cover; (3) a shrub-dominated peatland with Betula, Salix, sedges, Polytrichum commune and Sphagnum.
Study area 5 (N 60.12°, E 71.50°) is in the middle taiga zone in the center of the WSL, south of the River Ob. The petaland is covered by Pinus sylvestris, Rhododendron tomentosum, Chamaedaphne calyculata, Rubus chamaemorus and Sphagnum.
Four sites were chosen in Study area 6 (N 58.23°, E 68.22°) on the east bank of the Irtysh River in the vicinity of the town of Tobolsk. Two of the peatlands are ‘ryams’ with Pinus, abundant Rhododendron tomentosum and Andromeda polifolia among shrubs and Pleurozium schreberi and sparse Sphagnum mosses. Two other peatlands are sedge-dominated, with an extensive cover of Carex species, Oxycoccus palustris, Sphagnum mosses and rare Betula trees.
3.2. Sample Collection and Treatment
Samples for the study were collected in an attempt to cover the diversity of habitat types in each study site, taking into account the microtopography of peatland, i.e., hummocks, lawns and hollows. The sampled substrates represented either mosses (if present) or plant litter (if mosses are not dominant or absent) of approximately 5 cm depth and 25 cm3 volume. Each sample was carefully removed and immediately placed in sealed plastic bags to avoid contamination and moisture loss. Further, it was refrigerated as soon as possible at 5 °C until laboratory processing and analyses to avoid major post-sampling changes in the community structure [26]. WTD was measured in situ during fieldwork. Holes for WTD were made at the sampling point and settled for 30 minutes before the measurement using a ruler.
Samples were divided into two parts in the laboratory. One of them was used for testate amoebae extraction following the method based on suspension in water, physical agitation and subsequent sedimentation described by Mazei et al. (2011) [17]. Samples (1 cm3) were soaked in water for 24 hours, stirred for 30 minutes and filtered through a 500 μm mesh. The suspension was left to settle for the other 24 hours and the supernatant was decanted off. No back-filtering step was used as this leads to the loss of small taxa and a relatively large mesh size (500 μm) was used to retain the largest tests [20,27]. Samples were examined using a light microscope and shells were identified to the highest possible taxonomic resolution at 400× and 200× magnification using Mazei and Tsyganov (2006) until a minimum count of 150 shells in each sample [28]. The taxonomic classification at the genus level is based on the revisions of Kosakyan et al. (2016a, b) [2] as summarized in Tsyganov et al. (2016) [29], González-Miguéns et al. (2021) [3] and González-Miguéns et al. (2022) [30].
Moisture content was determined from the other part of the sample. Wet subsamples were weighed and placed in an oven at 105 °C for eight hours. Further, samples were cooled in the desiccator to room temperature and then weighed again. Percentage moisture was calculated based on the difference between the wet and dry sample weights.
Author Contributions
Conceptualization and methodology—Y.M.; Fieldwork—Y.M., N.M., A.T., V.C. and K.B.; Microscopy—V.C., S.Y. and K.B.; database construction—X.G., J.S., B.Y., D.S., N.S. and A.E.; writing—original draft preparation, D.S. and K.B.; writing—review and editing, A.E., A.T., N.K. and Y.M. All authors have read and agreed to the published version of the manuscript.
Funding
The work was supported by the Shenzhen Natural Science Foundation: 20200828181231001 and Russian Science Foundation (19-14-00102).
Informed Consent Statement
Not applicable.
Data Availability Statement
The data presented in this study are openly available in GBIF at https://doi.org/10.15468/avvq78. accessed on 15 July 2020.
Conflicts of Interest
The authors declare no conflict of interest.
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