Diatom Flora Research Articles

Revision of European Brachysira species (Brachysiraceae, Bacillariophyta): II. The Brachysira styriaca and B. zellensis group

ABSTRACT This second paper on the revision of the taxonomic identity of several Brachysira species in Europe deals with Brachysira styriaca (Grunow) R.Ross and B. zellensis (Grunow) Round & D.G.Mann. Both species were described by Grunow based on material from Lake Erlauf (Lower Austria and Styria, Austria). Analysis of type material, additional historic and modern samples showed that most populations of B. styriaca from northern Europe belong to a different taxon. This was already described 70 years ago by Cleve-Euler as Anomoeoneis decipiens A.Cleve and is newly recombined here as Brachysira decipiens (A.Cleve) Van de Vijver & Kusber comb. nov. Brachysira decipiens and B. styriaca can be differentiated based on several morphological and distinct ecological preferences. Brachysira styriaca is typically found in calcium-bicarbonate, oligotrophic, alkaline lakes, whereas B. decipiens prefers acid environments. Brachysira rylandsiana Van de Vijver, D.M.Williams & Ector, sp. nov. is split from Brachysira zellensis based on the parallel valve margins, cuneately rounded apices, and several smaller, ultrastructural details. All species are illustrated with both LM and SEM observations. Their ecological preferences are derived from the accompanying diatom flora in the different investigated samples and the literature.

The diatom flora of the Tonle Sap Lake in Cambodia: Centrobacillariophycidae – inventory and description of five new taxa including Praecyclostephanos gen. nov.

We provide an update to our knowledge of the centric diatoms in the Tonle Sap Lake (Cambodia) by providing a new and highly detailed iconography of all observed taxa based on light and scanning electron microscopy. We highlight a distinctive flora, including a new genus Praecyclostephanos gen. nov. and five taxa new to science: Aulacoseira micropunctata sp. nov., A. spiralorimoportula sp. nov., Praecyclostephanos boengchhmariensis sp. nov., Stephanodiscus tonlesapensis sp. nov. and Urosolenia anlongreangensis sp. nov. The flora is mainly dominated by several species of the genus Aulacoseira. Within the Aulacoseira populations forming the background of the diatom community, taxa that reveal the change in environmental conditions appear sporadically, often as blooms. The wide range of life-forms related to their ability to float is another remarkable aspect of the centric diatom flora. This variability appears at several taxonomic scales. At the genus level, colonial and solitary life-forms are very well represented in their diversity. At the sub-genus level, mainly among the Aulacoseira species, communities present a wide range of buoyancy metrics. Accordingly, in addition to the taxonomic review, we provide additional information related to their potential as bioindicators to monitor the hydrodynamic aspects of the lake in both space and time.

New species of benthic marine diatoms (Bacillariophyta) from the Western Pacific islands of Guam and Yap

In the course of preparation of a major checklist for Yap and ongoing investigations into the benthic marine diatom flora of Micronesia, thirteen new araphid and raphid pennate diatom species have been recognized and are described here. Plagiogramma subatomus is even smaller than P. atomus and the pseudoseptum forms a box with only a small opening toward the cell interior. Licmophora romuli is similar in size and spathulate shape to L. remulus, but the majority of the striae in the lamina lack vimines. L. graphis is exceedingly delicate, pencil-shaped, with apical striae 60–70 in 10 µm. Divergita biformis and D. decipiens are straight species with striae biseriate on the margin, uniseriate on the valve face, differing in the shape and prominence of the sternum and the shape of the valve-face areolae. D. macinnisii (from Marshall Islands, but included here for comparison) is curved, again with the decussate areolar pattern on the mantle, but with single extended areolae along each side of the linear sternum. These characters slightly amend the diagnosis of the genus. Thalassionema baculum is a very short member of the genus, linear and isopolar. Climaconeis tarangensis is curved and differs from C. riddleae in stria density and areola shape; C. minaegensis is straight, without a stauros or craticular bars, of intermediate length, 228–247 µm. First SEM observations of Climaconeis lorenzii are presented and an updated key to Climaconeis is appended. Parlibellus paschalis is a tube-dwelling species differing from P. delognei is lacking cuniculi and pores in the central area. P. waabensis is a relatively large species, possibly tube-dwelling, that differs from P. delognei in shape and spacing of central striae and from P. berkeleyi in width and stria density. Pleurosigma simulacrum differs in ultrastructural details from P. intermedium. Lastly, Nitzschia tarangensis is a conopeate species, spathulate in profile with ribs along the edge of the valve depression and bordering the raphe, and with pores in the peri-raphe zone.

Sediment diatoms from Upper Paraná River floodplain lakes

Considering changes in biodiversity over large time scales, the use of sediments to access knowledge about current and past diversity has recently been highlighted as an emerging field for biodiversity science. Therefore, this work aimed to use lake sediments to perform a taxonomic survey of abundant diatoms from two lakes sediments from the Upper Parana River floodplain and contributes to new species registrations. For diatom flora analysis were selected sediment samples from lakes. The diatoms with relative abundance ≥ 2% in at least one sediment sample were analyzed and identified under light microscopy. The study resulted in the identification of 47 taxa, including 40 at the specific level and seven possible new taxa. Among the taxa identified, 12 taxa (27%) of these had never before been documented in the Upper Parana River floodplain.

Fragilaria irregularis sp. nov. a new araphid species (Fragilariaceae, Bacillariophyta) from the River Adegoy, Krasnodar Territory, Russia

During a survey of the diatom flora of the Adegoy River (Krasnodar Territory, Russia), an unknown Fragilaria species (Bacillariophyta) was found that could not be identified using the currently available literature and here we describe it as a new species. The morphology of Fragilaria irregularis sp. nov. was studied using light and scanning electron microscopy and compared to similar species including Fragilaria deformis, F. rinoi, F. septentrionalis and Fragilariforma bicapitata. It differed from these taxa in several characters. Most observed valves showed an irregular striation pattern, a feature not observed in other species. Other important differences include valve outline (linear with parallel margins) and stria density (7–14 in 10 µm, lower compared to all other species). The new taxon has a linear valve outline with parallel to weakly convex margins, subcapitate apices and a very irregular, coarse striation pattern.

A comparative Study of Diatom Flora of the Taleghan River in Iran with Other Studies Around the World

A comparative Study of Diatom Flora of the Taleghan River in Iran with Other Studies Around the World

Floristic diversity and Ecology of EpilithicDiatoms of the ChottChergui wetland (North-West of Algeria)

This study is a phytoecological approach aimed to improve the knowledge on diatoms and their ecology in the wetland of ChottChergui in the northwesternregionof Algeria.For this work, 60 samples of solid substrates containing the epilithic diatom flora were collected in the field using a subjective method. The identification of diatom taxa was carried out according to a standard protocol while using pertinentliteraturethat specialized guides. At the level of the 5 sampling sites, water physicochemical parameters that could influence the distribution of diatoms were measured. The results obtained made it possible to recognize 36 diatom taxa belonging to 12 families, of which, the most dominant were Naviculaceae, Surirellaceae and Bacillariaceae. The calculated biodiversity indices (Shannon’s H and equitability revealed a low taxonomic richness which will probably be explained by the dominance of the typical brackish water taxa such as Mastogloiabraunii, Campylodiscusclypeus , and Navicymbulapusilla. We were also able to characterize the distribution of identified taxa according to the physicochemical parameters of each site. Furthermore, the attraction of the diatomic communities to saprobia shows the predominance of the two classes: α-mesosaprobic and β-mesosaprobe during the two seasons of fall and spring. Canonical correspondence analysis revealed that the distribution of diatom communities is positively correlated with conductivity and temperature. Some species like Navicymbulapusilla , show a significant resistance to anthropogenic eutrophication.

Floristic diversity and Ecology of EpilithicDiatoms of the ChottChergui wetland (North-West of Algeria)


 This study is a phytoecological approach aimed to improve the knowledge on diatoms and their ecology in the wetland of ChottChergui in the northwesternregionof Algeria.For this work, 60 samples of solid substrates containing the epilithic diatom flora were collected in the field using a subjective method. The identification of diatom taxa was carried out according to a standard protocol while using pertinentliteraturethat specialized guides. At the level of the 5 sampling sites, water physicochemical parameters that could influence the distribution of diatoms were measured. The results obtained made it possible to recognize 36 diatom taxa belonging to 12 families, of which, the most dominant were Naviculaceae, Surirellaceae and Bacillariaceae. The calculated biodiversity indices (Shannon’s H and equitability revealed a low taxonomic richness which will probably be explained by the dominance of the typical brackish water taxa such as Mastogloiabraunii, Campylodiscusclypeus ,and Navicymbulapusilla. We were also able to characterize the distribution of identified taxa according to the physicochemical parameters of each site. Furthermore, the attraction of the diatomic communities to saprobia shows the predominance of the two classes: α-mesosaprobic and β-mesosaprobe during the two seasons of fall and spring. Canonical correspondence analysis revealed that the distribution of diatom communities is positively correlated with conductivity and temperature. Some species like Navicymbulapusilla, show a significant resistance to anthropogenic eutrophication.

PONTO-CASPIAN AND MEDITERRANEAN FAUNAL AND FLORAL RECORDS OF UPPER PLEISTOCENE-HOLOCENE SEDIMENTS FROM THE İZMİT GULF (MARMARA SEA, TURKEY)

İzmit Gulf is located between Kocaeli and Armutlu peninsulas at east of Marmara Sea and the interaction area of North Anatolian Fault Zone (NAFZ) and Marmara Graben systems. In this study, the faunal and floral contents (ostracod, foraminifer, mollusc and diatom) of the samples belonging to seven drilling cores were studied and obtained the radiocarbon and optically stimulated luminescence (OSL) age data in order to establish on the Black Sea – Marmara Sea - Mediterranean water connections and palaeoenvironmental changes. The sediments in this study are Late Pleistocene-Holocene aged and only cover the Marine Isotope Stages MIS-5 (interglacial), MIS-3 (an interstadial period between MIS-4 and MIS-2 glacial epochs) and MIS-1. The determination of ostracod and mollusc fauna of the Mediterranean and Ponto-Caspian origin provide important clues to water exchange between the Mediterranean and the Black Sea. Although some Mediterranean originated ostracods occur sporadically with low abundance, absence of foraminiferal fauna and existence of Ponto-Caspian ostracods together with fresh water and cosmopolitan diatom flora indicate that the area strongly interacted with the Black Sea waters during MIS-5. The faunal and floral characteristics of the sediments deposited during MIS-3, clearly denote that the Izmit Gulf was connected with the Black Sea and the Mediterranean Sea at the beginning of MIS-3 (ca. 52.0 - 40.0 ky BP) and the shallow shelf areas were frequently affected by both the Black Sea discharge and Mediterranean input. A thick Holocene sedimentary sequence recovered from the southern Hersek Burnu drilling cores reflects the environmental changes after the latest Black-Mediterranean seas connection. The studied ostracod and mollusc assemblages are mainly characterized by the Mediterranean originated species with a few relict Ponto-Caspian fauna. Also, the benthic foraminiferal assemblages are dominated by normal marine and euryhaline species, reflecting the salinity fluctuations in the Holocene interval.

Moss-inhabiting diatom communities from Ile Amsterdam (TAAF, southern Indian Ocean)

Background and aims – Despite the ongoing taxonomical revision of the entire (sub)-Antarctic diatom flora, our knowledge on the ecology and community associations of moss-inhabiting diatoms is still rather limited. In the present study, our research aim was to survey the diversity together with the environmental factors structuring the epiphytic moss diatom communities on Ile Amsterdam (TAAF), a small volcanic island in the southern Indian Ocean.Material and methods – A morphology-based dataset and (physico)chemical measurements were used for the ecological and biogeographical analysis of moss-inhabiting diatom flora from Ile Amsterdam. In total, 148 moss samples were examined using light microscopy.Key results – The analysis revealed the presence of 125 diatom taxa belonging to 38 genera. The uniqueness of the Ile Amsterdam diatom flora is mainly reflected by the species composition of the dominant genera Pinnularia, Nitzschia, Humidophila, and Luticola, with a large number of unknown and often new species. This highly specific diatom flora, together with differences in the habitats sampled and the isolated position of the island, resulted in very low similarity values between Ile Amsterdam and the other islands of the Southern Ocean. From a biogeographical point of view, 40% of the taxa have a typical cosmopolitan distribution, whereas 22% of all observed species can be considered endemic to Ile Amsterdam, with another 17% species showing a restricted sub-Antarctic distribution. The NMDS analysis, based on a cluster dendrogram, divides the samples into six main groups. For each group, indicator species were determined. Both environmental data and diatom distributions indicate that apart from elevation, specific conductance, pH, and moisture are the major factors determining the structure of moss-inhabiting diatom communities on Ile Amsterdam.Conclusion – The isolated geographic position and unique climatological and geological features of the island shaped the presence of a unique diatom flora, characterised by many endemic species. The results of the study are of prime importance for further (palaeo-)ecological and biogeographical research.

Can a benthic diatom community complement chemical analyses and discriminate between disturbed and undisturbed saline wetland habitats? A study of seven soda pans in Serbia

Soda pans are protected in the European Union as Natura 2000 areas in the category of “Pannonic saline steppes and marshes”. There are at least six soda pans of reference status in Serbia and only a half have strict legal protection. The number of similar, but disturbed (modified) habitats that could be reconstructed is still unknown. We conducted sampling in five natural and two disturbed soda pans aiming to compare a difference in physical and chemical water properties and benthic diatom communities. In addition, we tried to apply recently developed Diatom Index for Soda Pans (DISP) and Trait-based index (TBI) to test the applicability of taxonomic and trait-based approaches in ecological status assessment of soda pans in the southern part of the Carpathian Basin. In contrast to natural soda pans, lower pH and nutrients levels were recorded in disturbed pans. A total of 86 taxa of benthic diatoms, including 11 new for diatom flora of Serbia, were identified. A lower species richness and Shannon index was recorded in natural soda pans. Nitzschia austriaca, N. supralitorea, Navicula veneta and N. wiesneri were dominant diatoms in soda pans of the reference status. Both diatom indices were in average lower in disturbed pans, and this difference was statistically significant for DISP index. We concluded that two indices, supplemented with indicator values for some local diatom species, can be a promising tool for soda pan conservation in this part of the Carpathian Basin.

New and interesting freshwater diatoms (Bacillariophyceae) from a biodiversity hotspot area in China

Biodiversity "hotspot" areas have been shown to possess unique diatom floras. During our diatom studies of some of these types of areas in China, samples were collected from Hainan and Guangdong Provinces, and four species from 4 different genera are proposed as new to science based on LM and SEM observations. These new taxa are Eunotia dinghunsis Liu & Kociolek, sp. nov., Brachysira subirawanae Kociolek & Liu, sp. nov., Microcostatus muscus Liu & Kociolek, sp. nov. and Iconella sanyatangum Liu & Kociolek, sp. nov. In addition, a species known previously only from Java and Sumatra, Pinnularia rivularis Hustedt, was observed, and herein we provide LM and the first SEM observations of this species.

<strong><em>Pinnularia qinghainensis</em>: a new diatom species (Bacillariophyta) found in the brackish Lake Qinghai, China</strong>

During the investigations of the diatom flora of Lake Qinghai, China (see Liu et al. 2020 for details), specimens of an undescribed species of Pinnularia Ehrenberg (1843: 45) were encountered, which are hereby illustrated and described.

<p><strong><em>Encyonema oblonga</em> (Bacillariophyta, Cymbellaceae), a new species from Shanxi Province, China</strong></p>

A new species, Encyonema oblonga Liu & Xie, is collected during a survey of the freshwater diatom flora of Manghe River, Shanxi, China. The valves of this new species are oblong with rounded apices and have the features typical of Encyonema, including complex areolae. We compare the new species with the most similar taxa, E. leei, E. leei var. sinensis and E. appalachianum and consider that E. leei var. sinensis is the valid name. The morphology of E. oblonga is documented with light and scanning electron microscopy.

Diatoms define a novel freshwater biogeography of the Antarctic

Terrestrial biota in the Antarctic are more globally distinct and highly structured biogeographically than previously believed, but information on biogeographic patterns and endemism in freshwater communities is largely lacking. We studied biogeographic patterns of Antarctic freshwater diatoms based on the analysis of species occurrences in a dataset of 439 lakes spread across the Antarctic realm. Highly distinct diatom floras, both in terms of composition and richness, characterize Continental Antarctica, Maritime Antarctica and the sub‐Antarctic islands, with marked biogeographic provincialism in each region. A total of 44% of all species is estimated to be endemic to the Antarctic, and most of them are confined to a single biogeographic region. The level of endemism significantly increases with increasing latitude and geographic isolation. Our results have implications for conservation planning, and suggest that successful dispersal of freshwater diatoms to and within the Antarctic is limited, fostering the evolution of highly endemic diatom floras.

Diatom Assemblages From Surface Sediments of Two Coastal Lagoons, the Central Part of the Red Sea, Saudi Arabia and Their Associated Environmental Variables

The composition and distribution pattern of diatom assemblages in the surface sediments of Sharm Al-Kharrar and Al-Shuaiba lagoons, situated on the central part of the Red Sea coastline of Saudi Arabia, were analyzed. A total of 191 diatom species from 53 genera were identified. A highly diverse diatom flora dominated by the genera Mastogolia, Amphora sensu lato, Lyrella, and Navicula sensu lato species was observed. Diatom species composition showed the dominance of the benthic forms over the epiphytic and planktonic ones, which can be attributed to the shallowness of the environments. The relationship between the recognized diatom taxa and measured environmental variables was explored using multivariate statistical techniques. Hierarchical ascending clustering and detrended correspondence analyses differentiated six representative diatom assemblages in each Lagoon. Canonical correspondence analysis revealed that grain size, organic matter content, and water depth appeared to be significant environmental factors affecting the distribution and structure of the documented diatom assemblages, while pH, salinity, and temperature were less influential. The majority of species recorded were polyhalobous benthic diatoms, accompanied by a limited abundance of mesohalobous and substantial amounts of oligohalobous forms, which are probably of allochthonous origin and resulting from freshwater input of near seasonal wadi streams and human activities. A comparison between the recognized diatom assemblages and the previously recorded taxa in surrounding areas was made.

Nagumoea hydrophicola sp. nov. (Bacillariophyta), the first diatom species described from sea snakes

Although diatoms colonize a vast diversity of immersed hard-surfaced objects and organisms, many diatom species, and sometimes entire genera, show a clear preference towards a particular type of substratum. Studies of animal-associated diatoms indicate that some epizoic forms may require this specific habitat to thrive, and new diatom taxa are expected to be found on as yet unexplored animal hosts. The current study is the first to investigate the diatom flora of sea snakes. Three museum specimens of yellow-bellied sea snakes (Hydrophis platurus) collected over a period of 23 years from the south-eastern coast of South Africa were examined for their diatom flora. Diatoms were abundant on the sea snakes, but communities were composed of only a few species. A previously undescribed species of Nagumoea contributed over 99% of the total diatom assemblage on both the sea snake skin and sea-snake-associated barnacles (Octolasmis sp.). This diatom dominant is described here as Nagumoea hydrophicola sp. nov., based on detailed observations of its frustule ultrastructure using light and scanning electron microscopy. The species is most similar to N. serrata, sharing a similar valvocopula morphology with two rows of pores. However, it can be distinguished from all currently known congeners by its lanceolate central area, short distal raphe endings not reaching the valve mantle, and doubly perforated abvalvar girdle bands. Environmental preferences of the new species are discussed in the context of its host’s biology.

Развитие Солонцовских озер как показатель динамики увлажнения в Центральном Сихотэ-Алине в позднем голоцене

The stages of development of small Solontsovskie (Shanduyskie) Lakes located in the middle mountains of the Central Sikhote-Alin within large landslides, formed on the slopes of the paleovolcano, are identified on the basis of complex study of the sediment section of the Nizhnee Lake. The ecological-taxonomic composition of the diatom flora, the botanical composition of peat have been analyzed, and the tendencies of lacustrine sedimentation depending on the different scale of hydroclimatic changes in the Late Holocene have been established. The age model is based on 6 radiocarbon dates. The temporary resolution for the reconstructions is 30–60 years. A comparison of the development of Nizhnee and Izyubrinye Solontsi Lakes was carried out, the stages of watering and shallowing of lakes were identified on the basis of their dynamics, which made it possible to restore the change in moisture in the middle mountains. Organogenic deposits in lacustrine basins accumulated at high rates (up to 1.7–1.9 mm/ year). The most detailed data were obtained for the last 2.6 thousand cal. yr BP based on the study of the sediment section of the Nizhnee Lake, which responded more sensitively to changing climatic conditions. Frequent changes in diatom assemblages and peat-forming plants indicate unstable hydroclimatic conditions with varying degrees of watering and drainage up to complete overgrowth of water bodies. According to the data of diatom analysis, a successive change in the trophicity of the lake was traced. A frequent change of sphagnum mosses of different sections with different trophic preferences was established. The main reason for the change in the hydrological regime of the lakes was variations in precipitation during the short-term climatic changes. The correlation of the identified paleoclimatic events with global data has been carried out. Cooling periods, as a rule, were accompanied by a decrease in moisture, but the Little Ice Age was wet due to an increase in precipitation.

Freshwater centric diatoms from Middle Miocene deposits of the Khanka Depression, Primorye Territory (Far East of Russia)

The centric diatom flora from the Middle Miocene deposits of the Khanka Depression of Primorye (Far East of Russia) was in detail studied. The centric diatoms were presented by 10 species and intraspecies taxa belonging to four genera (Aulacoseira Thwaites, Alveolophora Moiseeva et Nevretdinova, Ellerbeckia Crawford, Melosira Agard) and three orders (Aulacoseirales, Paraliales and Melosirales). A detailed study with the use of LM and SEM allowed us to establish the high morphologic variability of the predominant representatives of the genus Aulacoseira. The diagnoses for the Alveolophora tscheremissinovae, Ellerbeckia kochii, Melosira undulata species were supplemented. The comparison of the taxonomic compositions of the centric diatoms from the Khanka complex with the even-aged complexes from other regions has shown the wide spreading of the genus Aulacoseira taxa in the freshwater bodies during this time period.

Tras los pasos de Frenguelli en los Esteros del Iberá: el rol de las nuevas tecnologías en la revalorización de las colecciones biológicas históricas

Joaquín Frenguelli formó parte en 1923 de una expedición a la Región del Iberá, organizada en el marco de un proyecto nacional, conocido como Proyecto Mollard. Los pormenores del viaje fueron documentados en publicaciones, aportando descripciones técnicas y paisajísticas precisas de las localidades, especialmente de aquellas donde se recolectaron muestras. Una colaboración entre el Museo de La Plata y la Universidad de Colorado (EE.UU.), vinculada a estudiar la flora de diatomeas de agua dulce de Argentina, permitió que en mayo de 2019 se organizara una campaña a esta región, casi 100 años después de la expedición de Frenguelli, posibilitando así la experiencia única de repetir su itinerario. El objetivo principal de este trabajo fue ubicar las localidades originales visitadas por Frenguelli mediante el empleo de tecnologías modernas, tales como imágenes satelitales y sistemas de información geográfica, a fin de colectar en ellas nuevos materiales que servirán para evaluar los cambios ocurridos en los 97 años que median entre ambas expediciones. Para ello, se digitalizó una carta esquemática publicada en 1924 sobre la base de las descripciones en la bibliografía, se georreferenciaron de manera aproximada las localidades visitadas por Frenguelli, ajustando su ubicación a campo mediante la interpretación de las descripciones de los parajes dadas por el autor y, además, se tomaron muestras en los mismos sitios, con registro de sus coordenadas geográficas con GPS. Finalmente, se obtuvieron y procesaron imágenes satelitales cercanas a la fecha de la campaña, a fin de analizar la cobertura vegetal y uso de la tierra actual en toda el área de estudio. El análisis comparativo de todos estos materiales permitió establecer que, si bien grandes áreas se conservan en estado natural, en otras áreas de la región hubo grandes cambios vinculados con la expansión de las áreas urbanas, la disponibilidad de caminos y rutas y, principalmente, cambios significativos en el uso del suelo relacionados mayormente con la forestación. Los resultados obtenidos constituyen, en su conjunto, información de base, muy escasa hasta el presente, para llevar a cabo futuros estudios ambientales en la región.