Search Results (19)

The paper presents the results of a microfossil study of Holocene sediments in the Yana River flow zone in the southeastern part of the Laptev Sea. A rich diatom flora (242 species and intraspecific taxa, of which 177 species are freshwater) was revealed; additionally, five species of marine tintinnids (planktonic ciliates) and 15 species of freshwater testate amoebae (testacean) were discovered for the first time in the sea sediments. Three assemblages of microfossils reflecting the phases of environmental changes during the Holocene transgression are distinguished in the studied sediments of core LV83-32. Assemblage 1 was formed under terrestrial conditions (assemblage of diatoms Eunotia-Pinnularia and testacean Difflugia-Cylindrifflugia-Centropyxis), assemblage 2 in the zone of mixing of sea and fresh waters (assemblages of diatoms Cyclotella striata-Aulacoseira, Thalassiosira hyperborea-Chaetoceros and T. hyperborea-Aulacoseira, testacean Cyclopyxis kahli, tintinnids Tintinnopsis fimbriata), and assemblage 3 reflects modern conditions in the inner shelf of the Laptev Sea under the strong influence of river runoff (assemblage of diatoms T. hyperborea-Aulacoseira-M. arctica and tintinnids Tintinnopsis ventricosoides). Changes in the natural environment in the coastal part of the Laptev Sea shelf during the Holocene, established by microfossil assemblages, are confirmed by geochemical data. Full article

Rivers are crucial hydrological cycle components, supporting ecosystems and human activities. Managing and protecting river water quality is essential. Diatoms, microscopic algae, are widespread and sensitive to changes in water quality, making them effective bioindicators. This study focused on the Kuils River in the Western Cape, South Africa, where diatom sampling was conducted at four sites. Their communities are affected by different physicochemical parameters, such as changes in pH, salinisation, eutrophication, and organic enrichment. A total of 98 diatom species were identified. The Omnidia software was used to calculate the Generic Diatom Index, Specific Pollution Index, and Trophic Diatom Index. Historical physicochemical data such as pH, chemical oxygen demand, and phosphorus were obtained from the Department of Water and Sanitation between 2019 and 2021 and were used to provide a reference for comparing diatoms. The results showed clear signs of pollution, as shifts in diatom species composition were observed. Pollution-tolerant species such as the Nitzschia palea (Kützing) W Smith 1856, Navicula viridula (Kützing) Ehrenberg 1838, Eunotia bilunaris (Ehrenberg) Schaarschmidt 1880, and Ulnaria ulna (Nitzsch) Compère 2001 dominated, while less pollution-tolerant species like Gomphonema parvulum f.saprophilum Lange-Bertalot and E. Reichardt 1993 and Stephanocylus meneghinianus (Kutzing) Kulikovskiy, Genkal, and Kociolek 2022 were less abundant. Both diatom indices and physicochemical data indicated poor water quality in the Kuils River. The study concludes that diatoms are a valuable tool for biomonitoring river water quality and recommends their use alongside traditional physicochemical methods for future assessments of river systems. Full article

The altitude of the habitat is one of the important regulators of species survival. Kaçkar Mountains National Park is located in the Eastern Black Sea region of Turkey. This is the first study on the benthic diatom flora of the high mountain lakes in Kaçkar Mountains National Park, which is situated between 2782 and 3075 m a.s.l. A total of 84 diatom species were identified from benthic communities of 15 habitats in summer (19 July, 28 August) and autumn (10 September) months of 2020. The genus Pinnularia (thirteen species) formed the basis of the taxonomic list, followed by Eunotia (five species), Navicula (five species), and Frustulia (four species) genera, respectively. The waters in all the studied lakes were fresh, low-saline, with low-alkaline or circumneutral pH and organically uncontaminated, as evidenced by prevailed bioindicator groups. Statistical methods and comparative floristic results confirm the role of the lake altitude for the diatom species distribution. The species richness of the studied lakes was higher in lakes with lower altitudes. The statistical approach also revealed the potential for an increase in the number of species in high mountain lakes if the study of the diatom flora of the Kachkar Mountains National Park is continued and the species composition of the lakes is replenished. Further studies will be needed to continue exploring this pattern. To protect studied high mountain lakes, their ecological conditions must be constantly monitored in the Kaçkar Mountains National Park. Full article

In mountain regions, biological soil crusts (BSCs) provide essential ecological services by being involved in primary production and nitrogen fixation. Eukaryotic algae and cyanobacteria are important photosynthetic components of these unique cryptogamic communities. Here, we present an overview of the eukaryotic and prokaryotic diversity of such phototrophs in BSCs in the mountain tundra of the northern Ural Mountains. Such assessment is based on morphological surveys and the first metabarcoding analysis in the region. In total, 166 taxa of Cyanobacteria and 256 eukaryotic algae (including Euglenophyta, Ochrophyta, Dinophyta, Bacillariophyta, Chlorophyta, and Charophyta) were identified. For the first time, 86 taxa new to the BSCs of the high-mountain belt of the region were discovered. Considering species composition, Cyanobacteria and Chlorophyta are the most abundant taxa in all the analyzed BSCs. The genera Nostoc, Coccomyxa, Chlamydomonas, Leptolyngbya, Stenomitos, Pycnacronema, Stigonema, and Eunotia had the highest number of taxonomic units. These groups shape the structure, function, and ecology of the BSC communities in the studied region. Our results show that BSCs in the tundras of the Ural Mountains have a high active and passive biodiversity of terrestrial cyanobacteria and algae. Both implemented methods resulted in similar results with a comparable number of algae and cyanobacteria species per sample. Metabarcoding could be implemented in future in the region to accurately screen photosynthetic organisms in BSCs. Full article

Climate change and human activities may alter the structure and function of boreal peatlands by warming waters and changing their hydrology. Diatoms can be used to assess or track these changes. However, effective biomonitoring requires consistent, reliable identification. To address this need, this study developed a diatom voucher flora of species found across a boreal fen gradient (e.g., vegetation) in interior Alaskan peatlands. Composite diatom samples were collected bi-weekly from three peatland complexes over the 2017 summer. The morphological range of each taxon was imaged. The fens contained 184 taxa across 38 genera. Eunotia (45), Gomphonema (23), and Pinnularia (20) commonly occurred in each peatland. Tabellaria was common in the rich and moderate fen but sparse in the poor fen. Eunotia showed the opposite trend. Approximately 11% of species are potentially novel and 25% percent matched those at risk or declining in status on the diatom Red List (developed in Germany), highlighting the conservation value of boreal wetlands. This voucher flora expands knowledge of regional diatom biodiversity and provides updated, verifiable taxonomic information for inland Alaskan diatoms, building on Foged’s 1981 treatment. This flora strengthens the potential to effectively track changes in boreal waterways sensitive to climate change and anthropogenic stressors. Full article

Incorporating diatoms species and their autecology from reference stream conditions is essential for improving the accuracy of North American diatom bioassessments. This study documents a voucher flora and physicochemical conditions of Upper Three Runs Creek (UTRC), a tributary to the Savannah River that has been protected from heavy human activity for the last 50 years. The algae of UTRC and its watershed have been monitored continuously during this time by the Academy of Natural Sciences in Philadelphia to detect potential impacts from the Savannah River Site and Plant Vogtle. Standard protocols were used to sample and denote substrate types and preferences and to estimate relative abundances of diatom species. Data from artificial substrates (diatometers) were compared to composite samples. Phenotypic plasticity of taxa from Gomphonema parvulum, Eunotia incisa, and Tabellaria flocculosa sensu lato species complexes were considered in biodiversity metrics. We provide documentation of these separations. A total of 297 species/operational taxonomic units (OTUs) were recorded. For 2018 samples, Eunotia rhomboidea accounted for 8.3% for separated taxa methods and G. parvulum sensu lato (16.2%) dominated for combined taxa methods. Luticola goeppertiana (5.4%) was the most abundant taxon in the 1956 samples. The 1956 composite samples species richness means were greater and significantly greater than those for other sample types (ANOVA, df = 3, p = 0.004). The recounted 1956 composite samples had the highest species richness (153) followed by the left diatometer (129). At the same location, the right and left diatometers were not similar. Both methods (diatometers and composite sampling) are useful when assessing species richness. Diatom community composition indicated an acidic and highly oxygenated environment. Full article

A total of 413 diatom taxa were known for aquatic habitats of the Lena Delta Nature Reserve. We identified 385 taxa in 14 small tundra lakes near the reserve that significantly enriched the diatom diversity of the region (666 taxa including definitions to the genus level). Thus, the species composition of diatoms in the reserve and adjacent territories was increased by 278 species. We showed that the species of the genera Pinnularia (57) and Eunotia (51) have predominance at the family and generic levels. The index of intraspecific variability Ssp./Sp. for the lakes of the reserve was 1.11, and that for the lakes of the Tiksi region 1.14, which is typical for high-latitude and high-mountain communities. The number of rare or endangered species varied in different lakes from 1 to 10, totaling 42 species for the entire study area. Bioindication has shown that potentially threatened species prefer moderate temperatures, and slightly acidic or neutral environments free from organic pollution. A comparative analysis of the species composition of diatoms in the vicinity of the Lena Delta and other northern water bodies of Yakutia and the Arctic Islands showed that the species composition of each lake in the Arctic has a discernably different species distribution. The indicator characteristics show a certain response of the species composition of diatoms to changes in salinity, pH, and organic pollution. Regularities in the spatial distribution of diatoms in the study area were revealed in connection with the environmental variables of their habitat. Statistical mapping of diatom diversity data and bioindicators revealed a pronounced response to point pollution, and also let us assume the influence of summer northeast winds on species composition of the studied lake communities. We suggest that the high diversity inherent in the diatom lakes of the Tiksi coastal zone, which can even be updated in further studies, can be considered as a property of coastal biota inherent in ecotones. Since it is in the coastal Tiksi region that a surge in the number of species is observed, this region can be considered not only an ecotone, but also a hotspot of diatom diversity. The results of the study are important for developing the basis for monitoring biodiversity under the conditions of anthropogenic and climatic changes in the Arctic. Full article

Data about the ecotonic diatom communities of the Kamchatka Peninsula, a unique territory with strong volcanic activity, are very limited. We aimed to investigate diatom algae of the ecotones in the southeastern part of Kamchatka, including the Paratunka river valley, at the foot of the Vachkazhets volcano, and the bank of the Bystraya river. In total, 55 taxa were identified. The most diverse were the flora of the Paratunka river, with 31 taxa. Near the Bystraya river, 26 taxa were identified. Near the Vachkazhets volcano, 18 taxa were identified. Fragilariforma virescens, Planothidium lanceolatum, Pinnularia cf. subcapitata, Halamphora normanii, Nitzschia palea, and Eunotia exigua were the dominant species in the studied ecosystems, with the maximum abundance score. Pinnularia cf. subcapitata and Planothidium lanceolatum were found in all ecotones. In the studied habitats, small indifferent alkaliphilic cosmopolitan species prevailed. Our study revealed that the diatom species composition of the Kamchatka ecotones reflects their adaptability to survive in the extreme conditions of volcanic substrates. The results contribute to our knowledge of the ecology and biogeography of a number of diatom taxa. Full article

Despite the reported allelopathic nature of the Eucalyptus genus, eucalypt leachates have unknown effects on the trophic base of stream green food webs. Eucalypt plantations have increased worldwide, including riparian ecosystems. We aimed to test whether short-term eucalypt leachates might alter water chemistry, periphytic algal biomass and diatoms, and herbivorous invertebrates’ (i.e., scrapers). We studied two oligotrophic and well-preserved headwaters from NW Spain. The experiment followed a before-after control-impact paired (BACIp) design, with weekly sampling before and after eucalypt leaves addition to streams. In the stream with lower discharge, the eucalypt treatments seemed to affect increases in biomass accrual (Chl-a) and diatom assemblages, disfavouring sensitive species (e.g., Eunotia minor and Achnanthidium pyrenaicum). Therefore, the ecological status was reduced from high to good. In the stream with higher discharge, invertebrate assemblages changed with scrapers having their abundances modified in comparison with the control (e.g., Habrophlebia sp. and Elmidae). Results suggest that eucalypt leaves leachates exert toxic effects on periphyton and on diatom and invertebrate assemblages, and this effect might be mediated by discharge. Alterations at the base of stream food webs may compromise their good ecological status. Further studies are necessary to identify whether this toxicity is due to allelopathic processes. Full article

The benthic diatom assemblages of the glacier Avusor Great Lake and Koçdüzü Great Lake were investigated in August 2019. A total of 71 diatom species belonging to 34 genera were determined in the samples, 49 species from Avusor Great Lake and 37 from Koçdüzü Great Lake. Only 15 diatom species were common to both lakes. Total floristic similarity between the neighbouring lakes was only 21.12%. Genera with the highest number of species were Eunotia (8), Gomphonema (6), Pinnularia (6), Navicula (5) and Aulacoseira (4). The diatom flora of both lakes was formed by cosmopolitan species with a large influence from species in alpine and subalpine area. A comparison of the diatom assemblages of the investigated lakes showed differences in both relative abundance and species present in the individual lakes. Bioindicative analysis showed that the water of Koçdüzü Great Lake is more alkaline and less saturated with organic substances than Avusor Great Lake. In both lakes, the communities are composed of species adapted to living in the benthos of fresh waters of moderate temperature well enriched with oxygen. In both lakes, the water quality was Class 2 with a saprobity index of S = 1.08 in Avusor Great Lake and 0.97 in Koçdüzü Great Lake, but their communities were composed of species with both oligotrophic and mesotrophic status. Statistical comparison of the species composition of studied lakes with other high mountain lakes and the lakes in northern Turkey revealed the role of altitude as the main factor in the formation of diatom floras. Full article

Myristica swamps are one of the rarest wetland ecosystems within the sub-tropical evergreen forests of the Western Ghats, India. As their name indicates, they harbor trees belonging to the ancient family Myristicaceae. Due to the waterlogged conditions and high humic decomposition, these swamps are acidic, harbor rare and endemic biotas, and provide ecosystem services to humans. Monitoring this rare ecosystem is crucial because the swamps that once formed a large hydrological network across the Western Ghats are now confined to isolated patches due to human disturbance such as agricultural interventions, roads, and dam construction. Due to the change in land use, there is also a drastic change in water chemistry and associated biodiversity. Biomonitoring is more precise than physical and chemical monitoring. So, the current study aimed to undertake a comprehensive analysis of the physical, chemical, and biological assessment of these swamps. The diatom assemblages are strongly affected by water chemistry and serve as a powerful indicator of environmental changes in the freshwater aquatic systems. However, there is no information on diatom assemblages in these swamps, and the present study aimed to determine the diatom assemblage structure in the Myristica swamps and their response to changing water quality. Diatom samples were taken at 17 different swamps across the central Western Ghats, and a set of environmental parameters was evaluated. Analysis revealed a total of 91 species of diatoms belonging to 27 genera across the 17 sites, from which 44 diatom species showed restricted distribution to this unique environment. Overall, the dominant diatom genera inside the swamps included, Navicula (19.8%), Gomphonema (16%), Eunotia (13.3%), Ulnaria (9.4%), Achnanthidium (8%), Frustulia (6.2%), Planothidium (5.2%), and Brachysira (2.8%). High diatom species richness was observed in the swamps having less anthropogenic disturbance, and diatom assemblage composition was primarily determined by dissolved oxygen, pH, and conductivity. The significant number of geographically restricted taxa in this study points towards our limited understanding of this tropical biome and calls for a dire need for more studies from here, not only to improve our knowledge concerning the diversity, ecology, and biogeography of these diatoms but to further encourage their use in applied (paleo) environmental sciences. Our results indicate that diatoms can prove useful environmental indicators even in harsh environments like swamps and can be a potential tool for assessing ecological and climatic change. Full article

A number of pennate diatom genera typically have teratogenic deformations of their siliceous frustules due to the effects of environmental stress, such as high concentrations of heavy metals and low pH. However, the quantitative assessment of these deformations has rarely been applied. One species in which aberrations have frequently been reported is Eunotia bilunaris, which typically has bilaterally symmetric frustules with dorso-ventral differentiation. In this study, we aimed to illustrate the geometric morphometric analysis of symmetry as a tool for assessing the severity of teratogenic deformations. These were quantified by Procrustes superimposition of equidistant points placed along the valvar outlines in pairs of configurations based on their bilateral reflection symmetry. The shape deformations were mostly confined to central parts of the ventral outlines and were captured both by the symmetric and asymmetric subspaces of the variation. The amount of bilateral asymmetry in individual cells was negatively related to frustule size via the allometric power law relationship, illustrating that asymmetry increased in the asexual diminution series. The presented analysis provides a framework for the quantitative assessment of frustule deformations in eunotioid diatoms that can be used for the comparative scoring of teratogenic deviations among cells, populations, or species. Full article

Using light (LM, including plastid characterization on fresh material) and scanning electron microscopy (SEM), as well as a thorough morphological, physical, chemical, and biological characterization of the habitats, the present study aims at describing three species new to science. They belong to the genera Eunotia Ehrenb., Planothidium Round and L. Bukht., and Delicatophycus M.J. Wynne, and were found in two contrasting spring types in the northern Apennines. The three new species described differ morphologically from the most similar species by: less dense striae and areolae, and the absence of a ridge at the valve face-mantle transition (SEM feature) [Eunotia crassiminor Lange-Bert. et Cantonati sp. nov.; closest established species: Eunotia minor (Kütz.) Grunow]; narrower and shorter cells [Planothidium angustilanceolatum Lange-Bert. et Cantonati sp. nov.; most similar species: Planothidium lanceolatum (Bréb. ex Kütz.) Lange-Bert.]; barely-dorsiventral symmetry, set off ends, and lower density of the central dorsal striae [Delicatophycus crassiminutus Lange-Bert. et Cantonati sp. nov.; most similar species: Delicatophycus minutus M.J.Wynne]. Two of the three species we described are separated from the closest species by dimensions. Their description improved knowledge on two taxa (Eunotia minor s.l. and Planothidium lanceolatum s.l.) likely to be only partially resolved species complexes. We could also refine knowledge on the ecological profiles of the three newly-described species. Eunotia crassiminor sp. nov., as compared to Eunotia minor, appears to occur in colder inland waters with a circumneutral pH and a strict oligotrophy as well with respect to nitrogen. The typical habitat of Planothidium angustilanceolatum sp. nov. appears to be oligotrophic mountain flowing springs with low conductivity. Delicatophycus crassiminutus sp. nov. was observed only in limestone-precipitating springs, and is therefore likely to be restricted to hard water springs and comparable habitats where CO₂ degassing leads to carbonate precipitation. Springs are a unique but severely threatened wetland type. Therefore, the in-depth knowledge of the taxonomy and ecology of characteristic diatom species is important, because diatoms are excellent indicators of the quality and integrity of these peculiar ecosystems in the face of direct and indirect human impacts. Full article

Volcanic activity has a great impact on terrestrial ecosystems, including soil algae in general and diatoms in particular. To understand the influence of volcanoes on the biodiversity of diatoms, it is necessary to explore the flora of these microorganisms in regions with high volcanic activity, which includes the Kamchatka peninsula. During the study on diatoms in the soils of Mutnovsky and Gorely volcanoes of Kamchatka, 38 taxa were found. The Mutnovsky volcano diatom flora was more diverse and accounted for 35 taxa. Eunotia curtagrunowii, Humidophila contenta, and Pinnularia borealis were the dominant species. In the Gorely volcano, only 9 species were identified, with Caloneis bacillum and Pinnularia borealis prevailing in the samples. Overall, the genera Pinnularia and Eunotia were the most diverse in the studied area. The diatom flora of the studied volcanoes comprises mostly cosmopolitan small-sized taxa with a wide range of ecological plasticity. Our data confirm the high adaptive potential of diatom algae and add new knowledge about the ecology and biogeography of this group of microorganisms. Full article

This study examines the spatiotemporal variations in diatom assemblages and selected metal concentrations (Pb, Cr, Cd, Al, and Zn) in bed sediments of lakes Telaga Pengilon and Telaga Warna in Dieng, Indonesia to document natural and/or anthropogenic changes in the local aquatic and terrestrial environment. The analyses focused on sediments collected from a 150-cm core taken from a sill between the two lakes, which exhibit significant differences in water chemistry. The core was subdivided into 14 stratigraphic intervals allowing for an analysis of the vertical (and temporal) variations in diatom composition and selected metal concentrations. A total of 103 taxa from 25 genera were identified in the core. Diatom assemblages were dominated by Eunotia (56%), Pinnularia (17.2%), and Frustulia (4.6%). The most abundant species was Eunotia, a diatom that can tolerate a wide range of pH conditions. Given that pH within waters of the two lakes differs significantly, the abundance of Eunotia suggests that pH in the area between Telaga Pengilon and Telaga Warna varied through time, potentially ranging from about 2.5 to 8. Changes in pH were likely related to alterations in hydrological conditions. Metal concentrations varied with depth/time of deposition within the core. Peak metal concentrations appear to be related to the influx of debris from a volcanic eruption. Based on the principle component analysis (PCA), the input of volcanic materials also influenced diatom assemblages and resulted in a distinct layer of broken diatom frustules. Relatively low metal concentrations in surface sediments suggest that the erosion of hillslope soils in response to agricultural activity did not significantly impact the lakes. Full article