Eunotia Species Research Articles

New and Interesting Diatoms from the Shiwan Wetwalls, Yunnan Province, China. III. Valve ultrastructure of four new species of Eunotia (Bacillariophyceae: Eunotiales)

Four new Eunotia (Bacillariophyceae: Eunotiales) species are described from the Shiwan Wetwalls in Yunnan Province, China, based on light and scanning electron microscopy. The four species all share the features that assign them to the genus, including asymmetry about the apical axis, raphe predominantly on the valve mantle, and presence of one or more rimoportulae, and they all possess pseudosepta. They differ from one another in several attributes, however. Three of the species possess striae contained in internal troughs, two have spines (either one stout spine at each apex or blunt spines along the dorsal margin) and one has thickened ridges between the striae. These observations of four new Eunotia species further demonstrates the diversity and uniqueness of this wetwall community in Yunnan.

Tropical African diatoms from the Eunotia asterionelloides (Bacillariophyta) species complex, with descriptions of new species

Background and aims – Diatoms from tropical Central Africa are rarely studied and documented. Waters of the Congo Basin are often acidic and thus may be dominated by diatoms from the genus Eunotia, usually found in the benthos and periphyton, but rarely in the plankton. We investigated planktonic Eunotia species from the Eunotia asterionelloides complex to determine their identity and distribution. Material and methods – Samples were collected in fishponds in the vicinity of Kisangani, D.R. Congo, from herbarium material collected from the Bonkele River, D.R. Congo, and in the Kouilou River, Republic of the Congo. These samples were prepared for diatom analysis, examined using standard methods, and documented using both light and scanning electron microscopy. Key results – Several taxa belonging to the Eunotia asterionelloides complex were observed. Taxa from this complex are recorded in literature as either E. asterionelloides or E. zasuminensis. The taxon from fishponds in the D.R. Congo was identified as E. tukanorum, previously described from Brazil. The structure of the valve outline and raphe appear similar, particularly the raphe position and length. A second species was found on aquatic macrophyte (Utricularia and Nymphaea) herbarium specimens from the D.R. Congo and a third species from the Kouilou River in the Republic of the Congo. These latter two taxa superficially resemble E. zasuminensis. Although similar in valve outline, the taxa differ morphologically. The shape of the apices in larger cells is indented to a larger degree, and the raphe differs in its structure, particularly the shape of the terminal endings. The structure and position of the rimoportula also differ. Also, one of these taxa is sometimes strongly flexed around the apical axis. Based on morphology, we consider these taxa distinct from E. zasuminensis and from each other, and thus describe Eunotia globicephala sp. nov. and Eunotia magnaparva sp. nov.

Responses of diatom composition and teratological forms to environmental pollution in a post-mining lake (SW Poland)

Various types of environmental stressors, such as heavy metals, lignite residues, or extremely low water pH, cause the formation of teratological forms of diatoms during the reproductive cycle. The damage mainly includes an abnormal diatom valve outline, changes in the striation pattern, anomalies in the raphe line/sternum, reduction in the cell size, metabolism alterations, or combined deformities. Diatom remains with such morphological deformities occur in the sediments of post-mining lake ŁK-46 (SW Poland). This lake was formed by excavation after the end of lignite exploitation in the mid-1960s. The percentage of teratological valves in the studied lake ranged from 12 to 33% of the relative abundance. The majority of abnormal diatoms have been observed in species of Eunotia. The reconstruction of the diatom-inferred pH (DI-pH), together with the concentration of heavy metals in the sediments and contemporary measurements of the water pH, indicates that the lake was contaminated to varying degrees and was acidic from the beginning of lake creation until today. The lake is located in an area of acid mine drainage (AMD), and in its vicinity, there are overburden heaps containing lignite residues, which are eroded and supplied to the lake, constantly acidifying the water. In the youngest sediments, the concentration of heavy metals increased, while the percentage of abnormal diatoms decreased. Determining which factor, i.e., extremely low water pH and the presence of lignite or heavy metals, was responsible for the formation or reduction of teratogenic forms of diatoms is very difficult.

Comparison between p-distance and single-locus species delimitation models for delineating reproductively tested strains of pennate diatoms (Bacillariophyceae) using cox1, rbcL and ITS.

Several automated molecular methods have emerged for distinguishing eukaryote species based on DNA sequence data. However, there are knowledge gaps around which of these single-locus methods is more accurate for the identification of microalgal species, such as the highly diverse and ecologically relevant diatoms. We applied genetic divergence, Automatic Barcode Gap Discovery for primary species delimitation (ABGD), Assemble Species by Automatic Partitioning (ASAP), Statistical Parsimony Network Analysis (SPNA), Generalized Mixed Yule Coalescent (GMYC) and Poisson Tree Processes (PTP) using partial cox1, rbcL, 5.8S + ITS2, ITS1 + 5.8S + ITS2 markers to delineate species and compare to published polyphasic identification data (morphological features, phylogeny and sexual reproductive isolation) to test the resolution of these methods. ASAP, ABGD, SPNA and PTP models resolved species of Eunotia, Seminavis, Nitzschia, Sellaphora and Pseudo-nitzschia corresponding to previous polyphasic identification, including reproductive isolation studies. In most cases, these models identified diatom species in similar ways, regardless of sequence fragment length. GMYC model presented smallest number of results that agreed with previous published identification. Following the recommendations for proper use of each model presented in the present study, these models can be useful tools to identify cryptic or closely related species of diatoms, even when the datasets have relatively few sequences.

Descriptions of three new diatom species in the genus Eunotia (Eunotiaceae, Bacillariophyta) from the Eocene Arctic

Eunotia is the largest and most diverse genus within the family Eunotiaceae, a primarily freshwater group of diatoms often found in dilute, acidic and humic-stained environments. Species in this genus are characterized by being asymmetric along their apical axis, symmetric about the transapical axis, and with a simple and reduced raphe system situated largely on the mantle and restricted to the apical ends of the valve. In addition, Eunotia taxa have one or more rimoportula per valve, usually close to the apex. Because of their reduced raphe system, coupled with the presence of rimoportulae, Eunotia and its relatives are often viewed as the oldest lineage of raphe-bearing diatoms. To date, the oldest remains of Eunotia species have been reported from the early to middle Eocene, including from the Giraffe Pipe locality, an ancient Eocene fossil site located in northern Canada near the Arctic Circle. Rocks from this site contain a large and diverse assemblage of Eunotia taxa. The purpose of this study is to begin to characterize this assemblage with descriptions of three new species, Eunotia giraffensis sp. nov., E. petasum sp. nov. and E. pseudonaegelii sp. nov. The new species, representing the longest specimens found at the Giraffe Pipe locality, each possess characteristics common to Eunotia making them easily assigned to this genus. Because the Eunotia lineage was well established by the early part of the Eocene, it is likely to be significantly older.

The identity of Eunotia paludosa Grunow 1862 (Eunotiaceae, Bacillariophyta), a revision, and the description of three new species of Eunotia Ehrenberg

Eunotia paludosa is an abundant and frequent diatom species in ombrotrophic, Sphagnum-dominated bog ponds in Europe. Analysis of the type material from Mandling, Austria, revealed that our currently accepted concept of E. paludosa, based on morphology, was incorrect. The valves in the type population of E. paludosa possess distinct, relatively large, acute spines on the dorsal margin, which are not present in what is currently understood under E. paludosa. Based on the comparison with the E. paludosa type material, three new Eunotia species are described. Eunotia sphagnicola encompasses all European populations formerly and thus incorrectly identified as E. paludosa. The former E. paludosa populations in the sub-Antarctic region are described as E. insularum, a widespread species on almost all sub-Antarctic islands. Finally, E. zackenbergensis was described from Greenland. The three new species differ from each other in valve dimensions, valve outline and shape of the apices.

<strong><em>Eunotia</em> Ehrenberg (Eunotiaceae, Bacillariophyta) in a subtropical floodplain: a new species and taxonomic contributions</strong>

The Upper Paraná River floodplain is one of the few remaining non-dammed stretches in Brazil. It has a typical fluvial dynamics represented by the flood pulse and a highly complex habitat, which allows the existence and maintenance of a great biodiversity, including diatom species. As it happens in tropical lowland environments, also in this floodplain, the genus Eunotia is one of the most diverse and abundant diatom groups. Therefore, this study addresses morphologic and morphometric details of a new species and the most abundant Eunotia species in sediment cores from two wetland lakes. The morphological characteristics from each species were obtained through microscopy documentation of cell walls, and compared with other related species.

Eunotia (Bacillariophyceae) from a subtropical stream adjacent to Iguaçu National Park, Brazil, with the proposition of a new species

Abstract: Eunotia species from a stream located in the surrounding area of the Iguaçu National Park conservation unit were analyzed. Samples were monthly collected from September 2012 to August 2013. The periphytic material, manually obtained by squeezing aquatic macrophytes, was oxidized and analyzed under light and scanning electron microscopy. Twenty-one infrageneric taxa of Eunotia were identified, measured, and illustrated. Eunotia caniculoides sp. nov. is proposed as a new species, and eight taxa are new records for Paraná state.

Temporal Evolution of Diatoms in a Temporary Pond Situated in the Massif du Sancy Mountains (Massif Central, France) and Description of a New Pinnularia Species

A floristic survey was performed on a temporary pond, “Laqui du Seignavoux”, situated in the Mont-Dore massif of the French Massif Central, between 2017 and 2019. Except in 2017, each year, we performed four sampling campaigns from April/May to December. Water samples and diatoms were collected. The temporary pond evolved from a poorly mineralized ecosystem due to snow, inducing oligotrophic and oligosaprobic water, well oxygenated in spring, to a more mineralized, less oxygenated, eutrophic–hypereutrophic, and polysaprobic environment in summer. This change in abiotic conditions was found to be linked to the presence of cattle, beginning in May, that trample and excrete in the pond, leading to higher ammonium and nitrate concentrations. During this period, the dominant species were Pinnularia sp., Nitzschia palea, and Nitzschia palea var. tenuirostris. In spring and winter, different species of Eunotia dominated the community such as Eunotia pseudogroenlandica. Finally, light microscopy (LM) and scanning electron microscopy (SEM) observations on a new species of the genus Pinnularia from the temporary pond are presented and the ecological preferences are discussed.

Diatom-based water-table reconstruction in Sphagnum peatlands of northeastern China

Peatlands are important ecosystems for biodiversity conservation, global carbon cycling and water storage. Hydrological changes due to climate variability have accelerated the degradation of global and regional ecosystem services of peatlands. Diatoms are important producers and bioindicators in wetlands, but comprehensive diatom-based inference models for palaeoenvironmental reconstruction in peatlands are scarce. To explore the use of diatoms for investigating peatland hydrological change, this study established a training set consisting of diatom composition and twelve environmental factors from 105 surface samples collected from five Sphagnum peatlands in northeastern China. Diatom communities were dominated by Eunotia species. Ordination analyses showed that depth to the water table (DWT) was the most important factor influencing diatom distribution, independently accounting for 4.99% of total variance in diatom data. Accordingly, a diatom-based DWT transfer function was developed and thoroughly tested. The results revealed that the best-performing model was based on weighted averaging with inverse deshrinking (R2 = 0.66, RMSEP = 8.8 cm with leave-one-out cross validation). Quantitative reconstruction of DWT on a short peat core collected from the Aershan Peatland (Inner Mongolia) recorded climate-mediated hydrological changes over the last two centuries. This study presents the first diatom-water table transfer function in Sphagnum peatlands, and highlights the potential of diatoms as a powerful tool to assess the magnitude of past hydrological changes in peatlands of northeastern China, as well as similar peaty environments worldwide.

The genus Eunotia Ehrenb. (Bacillariophyta) in the Cheremsky Nature Reserve, Ukrainian Polissya, and refined terminology relevant to the raphe system morphology.

Numerous species of Eunotia Ehrenb., widely distributed in the world flora, prefer acidic, dystrophic or oligotrophic freshwater habitats with low conductivity and usually occur in epiphytic or epilithic hydrotopes. In Ukraine, only 32 species and eight varieties of Eunotia were known until this study. For the first time, 9 more species have been recorded mainly from the Cheremsky Nature Reserve, located in Ukrainian Polissya. New findings include 2 species widely distributed in the world flora on most continents and 7 rare species known from several locations, among them E.genuflexa, E.jarensis and E.ruzickae, which are probably European endemics as they have not been reported from other continents. For the present time in the Cheremsky Nature Reserve, the 20 species recorded here, the highest species richness of Eunotia in Ukraine, bring the total number of Eunotia in Ukraine to 41 species, which comprises only 7% of Eunotia species in the world flora. This is indirect evidence of insufficient investigation of the wetlands in Ukraine where Eunotia usually is represented with high species richness. Several definitions are suggested to describe morphological features that are peculiar to the diatom frustule particular to the Eunotia species. The genus Eunotia possesses a mirror-symmetric, mantle-offset, brevisslit raphe system, which may or may not have terminal raphe fissures. Morphological analysis provided in this study revealed the absence of terminal raphe fissures for many species of Eunotia. Instead, the distal ends of the raphe slits finish on the outer valve surface by funnel holes, sometimes pore-like ones, connected with the helictoglossae. However, in the literature those distal ends of the raphe slits were described erroneously as terminal raphe fissures. For the first time different types of raphe system are grounded. Two species Eunotiaimplicata Nörpel-Schempp et al. in Alles et al. and Eunotiaincisa W. Smith ex Gregory were lectotypified.

Observation of Eunotia enigmatica (Bacillariophyta), a rare South-American diatom species, in the Congo Basin, tropical Africa

ABSTRACTIn material collected in the Losambila river, a small tributary of the Congo River at Yangambi (Tshopo Province, Democratic Republic of the Congo), an unusual Eunotia species was observed. The same taxon was also detected in material taken at the beginning of 2018 in a small tributary of the Luapula river in the Haut-Katanga Province in the South of DR Congo. We could identify it as Eunotia enigmatica, recently described from reservoirs in south-eastern Brazil. The valve morphology of the Congolese material is compared with the Brazilian. E. enigmatica was not observed frequently but was not rare either. In two samples of the Losambila river this taxon reached up to 5.6 and 5.4 % of the total diatom assemblage. It is not the only species with a distribution known from Africa and South-America observed in the Losambila River. Encyonopsis frequentis, also described from South America, was more common than E. enigmatica in samples collected in the Tshopo Province, and reached up to 16.8% of the total diatom composition in the Losambila river. However, Encyonopsis frequentis was not observed in the samples where E. enigmatica was present. The same applies to the material from the tributary of the Luapula river where Encyonopsis frequentis was not found in the sample where E. enigmatica was present.

Eunotia (Bacillariophyta) biodiversity from high altitude, freshwater habitats in the Mugecuo Scenic Area, Sichuan Province, China

Mugecuo Scenic Area is located in the northern Hengduan Mountains between the Sichuan Basin and the Qinghai-Tibet Plateau and has a subtropical humid monsoon climate. The area is at an altitude of 2600–3800 m above sea level (asl), with water originating mostly from melting mountain snow. In the region, a total of 20 Eunotia species have been identified, including two new species: E. mugecuo sp. nov., consisting of valves arched, clavate, ends broadly rounded, and terminal raphe fissures at the junction between valve face and mantle. The other newly-identified species is classified named as E. filiformis sp. nov., consisting of valves gently bent, ends not noticeably or only slightly inflated, broadly rounded, with external terminal raphe fissures curving in an angle of 180° back from apical nodules. Five newly recorded species have been identified in China, including E. odebrechtiana, E. michaelis, E. pomeranica, E. pseudogroenlandica and E. superpaludosa. Here, we discuss the new species and new taxon records through light and scanning microscopic documentation of valve morphology, along with key internal and external valve characteristics, and analyze the distribution of Eunotia in the Mugecuo Scenic Area.

The genus Amphorotia (Bacillariophyta) in subtropical Asian coastal areas: Species diversity in fossil material from the Pearl River system, China

ABSTRACTAmphorotia is a diatom genus of considerable morphological and biogeographical significance. It was established by transferring several Eunotia species and describing several new species. The most species were found dispersed towards Southeast Asia. In coastal areas of China, a number of species of Amphorotia were found and the assemblages contained several new taxa. This article provides additional information on five previously described species and describes one new species, Amphorotia zhujiangensis sp. nov., and one uncertain but special species, A. sp. These are based on fossil material from a deltaic borehole, subaquatic sediment cores and surface sediments collected in the Pearl River estuary region. Morphological data were derived from light and scanning electron microscopy. A detailed morphological comparison of seven Amphorotia species is included, indicating the existence of a diverse group in brackish waters. Relationships within the family Eunotiaceae are briefly discussed. The biogeographical range of regional habitats occupied by Amphorotia species in tropical Southeast Asia is also expanded.

The genus Eunotia (Bacillariophyta) in the Falkland Islands and species-area relationships in sub-Antarctic islands

We document the morphology of 15 species of Eunotia from freshwater habitats in the Falkland Islands using light and electron microscopy, and describe four new species, Eunotia australovalida, Eunotia inconspicua, Eunotia floweriana and Eunotia latecapitata. Diatom assemblages were studied from a range of habitats on East Falkland, West Falkland, Saunders Island and Pebble Island, which differed in water chemistry and hydrological conditions including streams, ponds, lakes, springs and damp terrestrial habitats. Significant site and species groups obtained by cluster analysis are related to environmental conditions. Island species-area relationships for Eunotia from the sub-Antarctic region, and the wider geographic distributions of seven Eunotia species from the Falkland Islands are shown.

Diatom responses to environmental changes in the Upper Paraná River floodplain (Brazil) during the last ~ 1000 years

The floodplain of the Upper Parana River, Brazil, is strongly influenced by hydrology, which in turn affects geomorphological and environmental conditions, and controls the form of islands in the river. Such islands develop by deposition of river-borne sediment that creates small lateral sediment bars. Geomorphological processes can produce a variety of aquatic environments on such islands, e.g. channels, backwaters, lakes, transitional areas, and swamps. Our objective was to test whether subfossil diatoms preserved in the sediment on an island in the Upper Parana River floodplain responded to changes in limnological conditions brought about by such geomorphological modifications. We hypothesized that the composition of diatom assemblages in the sediment shifted in response to past geomorphic, and hence limnological conditions. We analyzed diatom subfossils in a 2-m-long sediment core with a calibrated date near the base of 1047–1224 cal yr AD. Absence of diatoms at the bottom of the sequence was associated with the channel phase, followed by appearance of diatoms 1229–1381 cal yr AD that were adapted to flow, in the backwater phase. After another 100–200 years, presence of Eunotia species in the lake phase suggests a decrease in pH, phosphorus and nitrogen. Replacement of Eunotia spp. by Diadesmis species, following a transition phase, suggests different environmental conditions, with reduced water depth. Diatoms in surface deposits are distinct from assemblages in the other phases in the core and contain taxa that suggest a disturbed environment, with variations in water depth and flow. The data illustrate the importance of physical and hydrological factors in shaping diatom communities and show the utility of diatoms as bioindicators in this floodplain environment.

Eunotia amazonica sp. nov. (Bacillariophyta), a common stalk-forming species from the Rio Negro basin (Brazilian Amazon)

ABSTRACTA new stalk-forming diatom was observed at high relative abundances on periphytic samples collected in the Rio Negro hydrographic basin (Brazilian Amazon) and is here described using light and scanning electron microscopy. We also present ecological preferences of the new species. Eunotia amazonica sp. nov. co-dominated periphytic samples collected during the rainy seasons of 2013 and 2014 near the city of Manaus (Amazonas, Brazil). The main diagnostic feature of the new species is the stalk-forming growth form (‘Cymbella-like’) illustrated here for the first time in the genus Eunotia Ehrenberg. Previous reports on growth forms in common European databases for this genus included colonial (‘ribbon-like’) but also ‘mobile’, ‘fixed by pads’ or ‘without structures of fixation’. We demonstrated that the three dominant Eunotia species in periphytic samples from the Rio Negro all exhibited distinct ‘growth forms’ or habits: Eunotia amazonica sp. nov. (stalked), Eunotia intricans Metzeltin & Lange-Bertalot (ribbon-like) and Eunotia rabenhorstiana (Grunow) Hustedt (branched-arborescent). The high diversity of species, many of which are unknown to science, as well as the poorly known life-forms and habits of the Eunotiaceae in the region, partially prevent the use of metrics based on life-form to assess ecological changes. Generic assumptions based on robust statistical methods may obscure reality and lead to biased conclusions of diatom community changes in poorly explored regions such as Neotropical freshwater rivers, where the Eunotiaceae are largely dominant, particularly in the Amazon basin.

Freshwater diatoms diversity of national parks in Nigeria I: Okomu national park, South-South, Nigeria

This study represents the first taxonomic and ecological description of the diatom flora of water and sediments in two freshwater lakes within Okomu National Park Edo State, Nigeria, using light and scanning electron microscopy (SEM). Twenty-nine species of diatoms belonging to fifteen genera, Achnanthes, Achnanthidium, Chamaepinnularia, Cymbella, Discotella, Eolimna, Eunotia, Frustulia, Gomphonema, Luticola, Nitzschia, Pinnularia, Placoneis Sellaphora and Stauroneis were identified. The taxa were dominated by Eunotia spp. Water pH of 5.9-6.3 and surface temperature of 28 oC probably implies that the diatoms especially Eunotia spp are exploring an ecological niche that is probably favourable for its growth. Okomu National Park appears to be a hotspot for Eunotia species diversity, and further study of the oligotrophic waters of this site is recommended.Keywords: Diatom, Diversity. Freshwater, National Park, Okomu, Season, Tropical.

Taxonomy and distribution of the genus Eunotia Ehrenberg in aquatic ecosystems of Vietnam

Taxonomy and geographical distribution of diatom taxa from the genus Eunotia are discussed. Fourteen Eunotia species are found in aquatic ecosystems of Central and South-Eastern Vietnam: E. indosinica, E. karveerensis, E. sulcata, E. cf. vumbae, E. novaecaledonica, E. naegelii, E. paramuscicola, E. rabenhorstii, E. tropica, E. sioliopsis, E. australominor, E. mucophila. Two species which are new for science are described Eunotia skvortzovii Glushchenko & Kulikovskiy sp. nov. and Eunotia fogedii Glushchenko & Kulikovskiy sp. nov. Eunotia sulcata Hustedt ex Glushchenko & Kulikovskiy is validated. The species are illustrated by original LM and SEM microphotographs. The main qualitative and quantitative taxonomic data are given. The distribution is found species is discussed.

New and interesting Eunotia (Bacillariophya) taxa from the Democratic Republic of the Congo, tropical central Africa

Background and aims - Large-celled Eunotia species from tropical central Africa are documented in order to define morphological variation within species and to describe new or poorly documented taxa. Methods - Samples were collected from the Congo River between Kisangani and Bumba in the Democratic Republic of the Congo. These samples were prepared for diatom analysis and examined according to standard methods and documented using both light and scanning electron microscopy. Key results - A single population of Eunotia zygodon is used to demonstrate the high degree of change in gross cell morphology during its life cycle, changes previously observed in cultures of this genus. Cells of this taxon from each extremity of the reproductive cycle could be, and probably often were, placed in discrete taxa during sample analysis, especially as this taxon occurs rather infrequently. We also describe Eunotia leonardii as new to science. It has an undulate valve margin and is closely related to Eunotia serra and Eunotia georgii but differs in respect to overall cell size and the structure of the terminal raphe endings. The bi-undulate Eunotia papilio var. africana is raised to the rank of species and named Eunotia fuseyi as it is clearly a discrete taxon from E. papilio s. str.