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We investigated diatom assemblages for the last 19 ka in a piston core KY07-04 PC01 collected from the northern Okinawa Trough, East China Sea. Most of the diatom taxa in the Core KY07-04 PC01 were subtropical to temperate marine species throughout the core. Pronounced turnover of major diatom groups from periphytic to planktonic taxa occurred during deglaciation between 17 and 14 ka ago. During the Last Glacial Maximum (LGM) to early deglaciation, the representative taxa were Paralia spp., a periphytic diatom abundant in continental shelves of the modern East China Sea covering the Chinese Coastal Water. Relative abundances of Paralia spp. rapidly decreased during 15–14 ka ago, corresponding to sea-level rise, displaced by planktonic taxa such as Thalassionema. Thalassionema nitzschioides varieties living in subtropical water increased since 12 ka and have reached the present level at 8 ka ago, suggesting strengthening the influences of Kuroshio water in the northern East China Sea during the early to middle Holocene. Warm planktonic diatom taxa such as Nitzschia bicapitata also gradually increased from 12 to 8 ka ago. Near the core top, a sudden increase in N. bicapitata might relate to the intensifying Kuroshio during the latest Holocene.

Light and scanning electron microscope observations are made on some members of the section Obtusae in the genus Nitzschia (Bacillariales, Bacillariophyceae). We use type and other material derived from both the National Water Quality Assessment (NAWQA) program in the USA and from Egypt to assess five different taxa, two of which are described as new to science (Nitzschia lowei, sp. nov., Nitzschia potapovae, sp. nov.) and another is made as a new nomenclatural combination (Nitzschia kurzeana var. multistriata (Hohn) comb. nov.). Other names used in the literature for some of these taxa are considered and discussed. Based on the features of sigmoid valves, eccentric raphe not in an elevated keel, lack of a conopeum, strongly bent, elongated external proximal raphe ends extending onto the valve face, and presence of a differentiated central 'nodule', members of this group are clearly differentiated from the generitype of Nitzschia and most other recognized sections of the genus.

Extensive research has been conducted at Lake Tanganyika to understand its vulnerability to a warming climate and fishing pressure. However, much of this work has been restricted to the more accessible northern basin. Studies from a limited geographic region of the lake are insufficient to explain whole-lake dynamics of the world’s longest lake (~ 670 km N-S). While strong evidence suggests that lake warming has played a critical role in decreasing fish abundance, limnological changes associated with warming have not been investigated lake wide. This study used paleolimnological data from two deep-water sediment cores from southern Lake Tanganyika to determine whether changes observed in the northern and central basins are, in fact, representative of lake-wide phenomena. We infer a decrease in diatom concentration after ~ 3000 cal yrs BP to reflect a decrease in net primary productivity associated with decreasing convective mixing. In contrast, the episodic presence of benthic invertebrates (ostracodes and molluscs) at these deep sites between ~ 1800–500 cal yrs BP, along with high Mn, indicates episodic pulses of much deeper ventilation of the southern basin than has been recognized previously. The presence of periphytic diatom species and benthic invertebrates during periods of strong stratification suggests that the lake bottom was periodically ventilated by descending denser (cooler or more sediment-rich) influent waters along the steep slopes of the coastline. Fish fossil abundance also is correlated with the dominance of heavily silicified diatom taxa, which itself requires stronger wave activity and upwelling of deep, nutrient-rich water. Fossil diatom assemblages show P and Si gradients between the two sites. LT17-TANG17-6A shows a shift in dominance towards lightly silicified taxa (Nitzschia spp.) after ~ 200 cal yrs BP. LT17-TANG17-2A shows a reduction in concentration of mostly the lightly silicified taxa, with few periods having heavily silicified taxa. These results are indicative of a relative reduction in convective lake mixing but are not always coincident with temperature trends, suggesting local windiness may also be important for stratification history. Thus, changes in lake productivity in the southern basin appear to be climate mediated, but in ways not previously documented in the northern and central parts of the lake.

Although most of the tens of thousands of diatom species are obligate photoautotrophs, many mixotrophic species can also use extracellular organic carbon for growth, and a small number of obligate heterotrophs have lost photosynthesis entirely. We sequenced the genome of a nonphotosynthetic diatom, Nitzschia sp. strain Nitz4, to determine how carbon metabolism was altered in the wake of this rare and radical trophic shift in diatoms. Like other groups that have lost photosynthesis, the genomic consequences were most evident in the plastid genome, which is exceptionally AT-rich and missing photosynthesis-related genes. The relatively small (27 Mb) nuclear genome did not differ dramatically from photosynthetic diatoms in gene or intron density. Genome-based models suggest that central carbon metabolism, including a central role for the plastid, remains relatively intact in the absence of photosynthesis. All diatom plastids lack an oxidative pentose phosphate pathway (PPP), leaving photosynthesis as the main source of plastid NADPH. Consequently, nonphotosynthetic diatoms lack the primary source of NADPH required for essential biosynthetic pathways that remain in the plastid. Genomic models highlighted similarities between nonphotosynthetic diatoms and apicomplexan parasites for provisioning NADPH in their plastids. The ancestral absence of a plastid PPP might constrain loss of photosynthesis in diatoms compared to Archaeplastida, whose plastid PPP continues to produce reducing cofactors following loss of photosynthesis. Finally, Nitzschia possesses a complete β-ketoadipate pathway. Previously known only from fungi and bacteria, this pathway may allow mixotrophic and heterotrophic diatoms to obtain energy through the degradation of abundant plant-derived aromatic compounds.

Planktonic diatoms of the family Bacillariaceae, including Nitzschia spp, Pseudo-nitzschia spp and Cylindrotheca closterium, are common and often highly abundant in the Adriatic Sea. During the 30 ...

The study of the sinking phenomenon of diatom cells, which have a slightly larger specific gravity (~1.3) compared to that of water, is an important research topic for understanding photosynthetic efficiency. In this study, we successfully demonstrated the observation of the sinking behaviors of four different species of diatom using a homemade “tumbled” optical microscope. A homemade 1 mm3 microchamber was employed to decrease the effects of convection currents. In the microchamber, diatom cells were basically settled in a linear manner without floating, although some of the cells were rotated during their sinking. Sinking speeds of the four species of diatom cells, Nitzschia sp., Pheodactylum tricornutum, Navicula sp., and Odontella aurita, were 0.81 ± 5.56, 3.03 ± 10.17, 3.29 ± 7.39, and 11.22 ± 21.42 μm/s, respectively, based on the automatic tracking analysis of the centroids of each cell. Manual analysis of a vector between two longitudinal ends of the cells (two-point analysis) was effective for quantitatively characterizing the rotation phenomenon; therefore, angles and angular velocities of rotating cells were well determined as a function of time. The effects of the cell shapes on sinking velocity could be explained by simulation analysis using the modified Stokes’ law proposed by Miklasz et al.

The study of diatoms (Bacillariophyta) collected in 2000–2001 with a plankton net from the hypersaline Kara-Bogaz-Gol Bay revealed 13 species and varieties of the genera Campylodiscus, Cocconeis, Diploneis, Epithemia, Navicula, Nitzschia, Planothidium, Surirella, and Tryblionella. These diatoms occurred at water salinities from 44 to 250‰. Consequently, salt-tolerance limits were extended for most taxa: 11 species and varieties previously considered in the literature as less salt-tolerant appeared to be halophilous. Planothidium cf. lanceolatum, Epithemia sorex and Nitzschia dissipata differed from their diagnoses by a smaller number of striae on their valves (9–11, 10–12 and 25–35 striae in 10 μm, respectively). P. cf. lanceolatum, Surirella brebissonii var. kuetzingii, and Tryblionella compressa are the first records for the Caspian Sea.

This electron microscopy study of materials from streams on the western slope of the Kharaulakh Range has revealed 59 taxa of diatom algae from 32 genera that makes it possible to broaden the composition of Bacillariophyta at the species level (from 5 to 64), as well as at the genus level (from 5 to 37). A total of 35 species and varieties of diatoms that are new for the Lena River mouth have been detected. Five forms from the genera Diploneis, Gomphonema, Naviculadicta, and Nitzschia have been identified only to the genus level. Among the algae found in this study, Diatoma problematica has been recorded for the first time for the flora of Russia and 17 species and varieties from the genera Achnanthidium, Cymbella, Diatoma, Diatomella, Encyonema, Eucocconeis, Gomphonema, Nitzschia, Pinnularia, Psammothidium, and Rexlowea have been recorded for the first time for the flora of Yakutia. Most species new for the Republic of Sakha (Yakutia) are rare freshwater algae that prefer oligotrophic waters.

Con la finalidad de identificar las diatomeas y su comportamiento en un perfil de sedimento y su relación a eventos naturales y antropogénicos, se realizó un muestreo en el lago Cocibolca. Un total de 46 taxa fueron identificadas con la mayor diversidad en el sitio PLN I (41 taxa) y menor en el sitio PLN II (24 taxa). Los géneros más representativos en el PLN I fueron: Aulacoseira (12,20%), Fragilaria (7%), Navicula (12,20%), Nitzschia (7,32%), Pseudostaurosira (12,20%), y Surirella (9,76%). En el sitio PLN II fueron: Aulacoseira (20,83%), Nitzschia (12,50%), Pseudostaurosira (12,50%), Surirella (8,33%), Cyclotella (8,33%) y Synedra (8,33%). Dentro del género Aulacoseira la especie A. muzzanensis mostró ser la más dominante (44%; PLN I) y (64,58% PLN II). De las especies encontradas, cuatro de ellas (Aulacoseira ambigua, A. subartica, Discotella stelligera y Stephanodiscus) presentan oscilaciones significativas como es el reemplazo de una especie por otra que depende de los cambios ambientales en el medio acuático. El sitio PLN I muestra más evidencia de los cambios que tuvo el cuerpo de agua en algún tiempo, que se ve reflejado en la dominancia que presenta una especie que al desaparecer es reemplazada por otra. Es de suponer que por un tiempo las condiciones del lago fueron variandas, observándose mejor en este sitio. La aplicación de los indices de Shannon y Simpson muestran que el sitio PLN I es donde se observan los valores más altos calculados, 1,081 y 2,412 bit respectivamente

A total of 131 taxa of species and intraspecies rank of diatom algae from 41 genera have been identified during a scanning electron microscopy study of material from several rock pools on islands and the shore of the Kandalaksha Gulf in the White Sea. Among them, one species (Cymbopleura cf. angustata var. fontinalis Krammer) is new for the flora of Russia; 16 forms from 12 genera are identified only to the rank of genus. The highest taxonomic diversity has been recorded in Lake Nadezhda (38) on Lodeiny Island. The species Brachysira brebissonii, Frustulia crassinervia, Nitzschia alpina, and Tabellaria flocculosa are the most widespread in these water bodies.

The qualitative and quantitative composition of planktonic societies in the southern part of the Kerch Strait in the coastal zone of the Taman Peninsula in September 2018 was studied. The phytoplankton consisted of 84 species, the average values of its abundance and biomass were 106 ± 22 million cells/m3 and 227 ± 32 mg/m3 respectively. The leading role in its composition was played by Nitzschia tenuirostris (by number) and Proboscia alata (by biomass). Zooplankton was represented by 24 species and taxa, its quantitative indicators were 32.5 ± 3.3 thousand individuals/m3 and 0.24 ± 0.02 g/m3 respectively. The copepod Oithona davisae dominated in terms of numbers, Oithona davisae, Parasagitta setosa, Decapoda and Cirripedia larvae dominated in biomass. An analysis of the composition and structure of planktonic communities showed their low structural diversity and evenness, as well as a stress state due to natural and anthropogenic factors. A close trophic relationship was revealed between the quantitative indicators of copepods and phytoplankton, excluding the dominant microalgae, the shape and size of which prevent them from being grazed.

This research examined temporal and spatial patterns of microphytobenthos (MPB) and relationships with environmental variables in a Pacific Northwest, USA estuary with complex environmental gradients. Sediment composition, salinity, and nutrients varied between sites closer to the estuary mouth (MAR), and those further upstream (RIV) and seasonal patterns in these variables also differed between MAR and RIV sites. Average MPB biomass was 57.8 ± 22.9 μg chlorophyll cm−3 at MAR sites and 29.9 ± 13.3 μg chlorophyll cm−3 at RIV sites. Relationships between MPB biomass and environmental conditions depended on season. The MPB diatom assemblage was influenced primarily by location within the estuary and secondarily by season. Epipsammic taxa, including Catenula adhaerens, Planothidium delicatulum, and Opephora spp. 1, were most abundant at MAR sites, while highly motile taxa in the genera Navicula senso lato and Nitzschia were abundant at RIV sites. Seasonal shifts in diatom community structure were evident at RIV sites and were driven primarily by changes in dominant epipelic taxa. Relationships between the MPB diatom assemblage and environmental conditions varied between MAR and RIV sites. Physical variables, including distance from the estuary mouth, sediment composition, land use in the 100 m buffer, and to a lesser extent, salinity, were correlated to the MAR assemblage. In contrast for RIV sites, salinity and nutrients were correlated to the diatom assemblage. Despite the complexity inherent in elucidating diatom–environmental relationships, our results suggest that tidal flat diatoms can be used to assess the environmental conditions of estuaries.

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.

Microphytobenthos (MPB) or benthic microalgae are recognized as the dominant flora in shallow neritic ecosystems such as mangroves. The diversity, biomass and community composition of microphytobenthos in selected mangrove ecosystems along the southwest coast of India were assessed. A total of 110 species of microphytobenthos classified under 49 genera were identified during the study. Nine subclasses of MPB were identified—subclass Bacillariophycidae, Fragilariophycidae, Urneidophycidae, Coscinodiscophycidae, Melosirophycidae, Thalassiosirophycidae, Biddulphiophycidae, Oscillatoriophycidae and Nostocophycidae. Division Heterokontophyta (diatoms) was the best-represented division followed by division Cyanophyta. Diatoms comprised 81% of the microphytobenthic community in the selected mangrove ecosystems, and among these, the pennate diatoms (93%) dominated the total diatom population. The major diatom genera observed during the study were Amphora, Navicula, Pleurosigma, Gyrosigma, Mastoglia, Diploneis, Cocconeis, Lyrella, Entomoneis, Caloneis, Bacillaria and Nitzschia. Episammic and epipelic diatoms were observed (Cocconeis sp., Pleurosigma sp.) along Kollam and Kannur, whereas at Kochi, epipelic diatoms were dominant (Nitzschia sp., Navicula sp.). The study also provides a spatial comparison between the microphytobenthic communities within the study area and can act as a baseline data for the trophodynamic studies of the highly diverse ecologically and economically significant mangrove ecosystems.

This version of the article has been accepted for publication, after peer review and is subject to Springer Nature’s AM terms of use, but is not the Version of Record and does not reflect post-acceptance improvements, or any corrections. The Version of Record is available online at https://doi.org/10.1007/s00300-021-02818-3. Oil production in Arctic ice-covered areas poses a risk for pollution of the ecosystem including that within the brine channel network of sea ice. Sea-ice autotrophs contribute substantially to Arctic primary production, but are inherently difficult to test for oil exposure responses in situ. This study had two objectives, first, we developed a suitable lab-based mesocosm system, second, we tested oil effects on sea-ice algae. Specifically, we investigated if Alaska North Slope crude oil exposure reduces ice algal abundance, biomass and concentration of extracellular polymeric substances (EPS) using indoor ice tanks over a 10-day exposure period. Six tanks in one cold room were used in pairs for the following treatments: (1) control, (2) oil release as a layer under ice and (3) release of dispersed oil. All tanks were inoculated with sea-ice microbial communities collected from Utqiaġvik, Alaska. After 10 days of exposure, the abundance of algae, dominated by the pennate diatom genus Nitzschia, and the concentrations of EPS and chlorophyll a were significantly lower in the oiled treatments compared to the control. We suggest light attenuation by the oil, reduced algal mobility, and oil toxicity as causes for this reduction. Observed changes in cell fluorescence characteristics based on DNA staining could be linked to the oil exposure and could provide a new tool for assessment of toxicity in microalgae.

Microphytobenthos (MPB) plays an integral role in contributing to the productivity and sustenance of shallow marine ecosystem. MPB forms an integral component in the trophic structure of mangrove forest and its biogeochemistry. Microphytobenthos from three selected mangrove ecosystems (S1, Kannur; S2, Kochi and S3, Kollam) along the southwest coast of India was studied in detail for 1 year (2018–2019). Spatial and temporal (seasonal) variations in the community structure were addressed along with major environmental factors influencing the pattern of distribution. A total of 148 species of microphytobenthos under 58 genera were identified during the study. Diatoms (Bacillariophyceae) were the most abundant and diverse class of MPB present followed by Cyanophyceae, Dinophyceae and Euglenophyceae. The analysis of physicochemical parameters showed that salinity, temperature, sediment texture and nutrient characteristics were the major factors governing the community structure of MPB. Seasonally, maximum abundance was observed during monsoon and pre-monsoon with lesser diversity and extensive mats of cyanobacteria dominated by Oscillatoria spp. However, post-monsoon season with high nutrient concentration, increased salinity and more of sandy sediment texture supported diverse assemblage of diatoms. Dominant diatoms observed were Amphora spp., Diploneis sp., Navicula spp., Nitzschia spp., Pleurosigma sp. and Gyrosigma sp. Regionally, S3 Kollam was observed to be more diverse with the dominance of diatoms, whereas S2 Kochi observed lesser diversity with cyanobacterial dominance. Increased sediment grain size (sand ~ 68%) favoured diverse diatom assemblage at S3 resulting in an overall high MPB diversity of the area than S1 and S2.

Phytoplankton community was investigated during two contrasting periods using offshore plankton samples in the volcanic area of Methana peninsula (Saronikos Gulf): the first at early autumn (warm period, September 2016) and the second one at early spring (cold period, March 2017). In order to investigate the phytoplankton community structure in the complex geo-biochemical conditions of the area, samples were collected from stations near the CO2 hydrothermal vents, at the hydrothermal sulfur and radioactive springs and at a fishery nearby Methana town. Three major phytoplankton groups, Bacillariophyceae, Dinophyceae, and Prymnesiophyceae, were studied, using inverted microscopy. In early autumn, Dinophyceae were dominant in the majority of the stations with cell concentrations of Prorocentrum spp. up to ~ 35.5 × 103 cells l−1. In early spring, the dominant class was Bacillariophyceae with dominant genus Nitzschia/Pseudo-nitzschia presenting cell concentrations up to ~ 33.9 × 103 cells l−1. Furthermore, Prymnesiophyceae appeared in both spring and autumn samples with small fluctuations. Total phytoplankton cell concentrations followed a seasonal trend, presenting slightly lower values in the hydrothermal-effected area in comparison with the broader Saronikos Gulf, confirming the prevalence of oligotrophic conditions. Seasonal variation was very strong, revealing an association with water temperature and nutrient content. Those environmental variables proved to have a strong effect that was reflected in the phytoplankton community structure.

New diatom strains of Nitzschia were isolated from phytoplankton and benthos of saltwater lakes inMongolia. The strains were identified based on morphological characteristics and phylogenetic analysis using the 18SrDNA gene. The new strains have been included into the Bacillariales clade with a high statistical support. Analysis ofthe fatty acid composition of the studied strains showed that 16:0 palmitic, 18:0 stearic, and 16:1 palmitoleic acids weredominant – they accounted for up to 97.5 % of the total fatty acids. New strains of Nitzschia from Mongolian lakes showedthe minimum content of polyunsaturated fatty acids, including omega-3 and omega-6. Taking into account the peculiaritiesof the profiles of fatty acids, and primarily the amount of saturated and monounsaturated acids, new strains of Nitzschiacan be considered for biotechnological use as a potential raw material for the production of biofuel.

The paraphyletic diatom genus Nitzschia comprises over 1000 morphologically distinct pennate taxa, known from the benthos and plankton of freshwater, brackish and marine environments. The principal diagnostic characters for delimitation of Nitzschia species include valve shape, the position and structure of the raphe, presence/absence and shape of the proximal raphe endings the shape of the terminal raphe fissures, areola structure, and specific morphometric features such as cell size, and stria and fibula density. In this study, we isolated 12 diatom strains into culture from samples collected at the surface or greater depths of the southeastern Adriatic Sea. Morphological analyses included LM, SEM and TEM observations, which, along with specific morphometric features, allowed us to distinguish three new Nitzschia species. These findings were congruent with the results of phylogenetic analyses performed on nuclear-encoded SSU (18S) rDNA and chloroplast-encoded rbcL and psbC genes. One of the new species (Nitzschia dalmatica sp. nov.) formed a lineage within a clade of Bacillariaceae containing members of the Nitzschia sect. Dubiae, which was sister to Psammodictyon. A second lineage was part of a novel clade that is significantly distinct from other Nitzschia species sequenced so far and includes Nitzschia adhaerens sp. nov. and N. cf. adhaerens. A further new species was found, Nitzschia inordinata sp. nov., which appeared as the sister group to the N. adhaerens clade and the conopeoid Nitzschia species in our phylogenetic trees. Our findings contribute to the overall diversity of genus Nitzschia, especially in identifying some deep branches within the Bacillariaceae, and highlight under-scoring of this genus in marine plankton.

Tilapia fish (Oreochromis mossambicus) is a type of freshwater consumption fish, flat body shape with grey, brown or black colour. The purpose of this study was to describe the types of food found in the stomach of tilapia fish (Oreochromis mossambicus) in Talaga Lake, Donggala Regency. This research was conducted in April 2019. The method used in this study was a volumetric occurrence frequency method by a surgical sampling of fish to extract the stomach and analyze it. Based on the results of the analysis of the stomach contents of the Mujair fish (Oreochromis mossambicus), two groups of feed were obtained, namely Vegetable food (Fitoplaknton) in the form of Navicula placentula, Schroederia segitera, Schoroederia anchora, Zignemopsis circumcaniratum, Anabaena sp, Oscillatoria princeps, Spirogyra protifica, Bacillaria sp, Nitzschia aetinastroides, Oedogonium sp, Coelastrum chodati, and animal feed (Zooplankton) in the form of Tubipex sp, Brachionus havanaensis, Cyclops sp, Carcinus sp, Arcella sp, Acetes sp.

Introduction. Microscopic algae form organic matter, oxygen and geological rocks (diatomitis, stromatolitis, chalk) in reservoirs, clean them from contaminants, take part in the circulation of various chemical elements (C, N, P, O, Si), are food for hydrobions (infusoria, worms, molluscs, crustaceans, fish).The aim of the work was to study the currents state of phytoplankton of the Lower Danube Lakes.Results. As a result of the researches of Lower Danube Lakes (Kagul, Katlabug, Kytai, Kugurlui, Yalpug) it was determined that 125 species of microscopic algae, belonging to 78 genera, 37 families, 23 orders, 10 classes and 7 divisions, were identified in the phytoplankton of the studied reservoirs. The representatives of green (46 species), diatoms (35) and blue-green (23) ones prevailed among the algae. 11 species from the identified algae turned out to be new for the Lower Danube Lakes. Genera of Closterium (5 species), Nitzschia (5), Lepocinclis (4), Monoraphidium (4), Oscillatoria (4), Tetrastrum (4), Cymbella (3), Crucigenia (3) and Tetraedron (3) formed the basis of specific variety of the Lower Danube Lakes. 92 species of algae were found in lake Yalpug 87, Katlabug – 81, Kytai – 72, Kugurlui – 70 and Kagul – 67 species of algae. Algal flora of the Lower Danube Lakes is freshwater, alkaliphilic, β-mesosaprobic and cosmopolitan. The quantity of algae varied within the range (70-3331)·106 cells·m-3, biomass – 0.66-5.60 g·m-3.Conclusion. The obtained data can serve for monitoring and calculation of feed base for hydrobionts of the Lower Danube Lakes.Key words: microalgae, phytoplankton, species composition, quantity, biomass, the Lower Danube Lakes.

Here, we present the data obtained from the samples collected in a field campaign during the spring of 2015 which aims for a better understanding of the diversity and distribution patterns of freshwater diatoms in Madeira Island. Following European and Portuguese standards and recommendations for routine diatom sampling and analysis, we collected samples in 40 sites, distributed in 27 permanent streams and identified the diatom species present, using general diatom floras and studies in Portuguese freshwater diatoms. Little is known about the diversity and distribution of freshwater diatom assemblages from Madeira Archipelago. This study reports a survey in 40 sites in Madeira Island distributed in 27 permanent streams. A total of 965 diatom (Bacillariophyta) occurrences were recorded, belonging to 130 different taxa from 44 genera and 27 families. The families with the highest number of occurrences were Bacillariaceae (176), Achnanthidiaceae (135) and Naviculaceae (133). The two diatom endemisms, described previously in Madeira Island (Lange-Bertalot 1993), Nitzschia macaronesica Lange-Bertalot and Navicula madeirensis Lange-Bertalot, were only observed in a small number of sites, located mostly at Laurissilva forest. Sixty species are new records, not only to Madeira Island, but also to the Madeira Archipelago.

We have investigated two canal-raphe bearing taxa from two freshwater long-term ecological monitoring sites in the NEON program from Puerto Rico. The identity of these two taxa have been misunderstood, and they have been mistaken for one another, due to being similar in size, shape and having interrupted striae across the valve face. Denticula occidentalis Østrup was described from the U.S. Virgin Islands, and like its congeners has fibulae that extend across the valve face as thickened ribs. The species also has valvocopulae that are typical for the genus, with arched sections that clasp onto the knob-like fibulae. Denticula occidentalis has a discontinuous raphe system, and external proximal raphe ends are hooked towards the valve center and elongated. Grunowia portoricensis, sp. nov. has fibulae restricted to the raphe side of the valve, though unlike most members of the genus the fibulae are knob-like. The raphe is continuous across the central area. Though described here as new to science, the species has been illustrated previously from Venezuela. Distinctions between Nitzschia, Denticula and Grunowia are discussed.

Carrier culture is the combination of suspension culture and adherent culture. Carriers could be used to improve the culture efficiency of large-scale culture of adherent benthic diatom. In order to identify a suitable carrier for mass suspension culture of the benthic diatoms Nitzschia sp. powders of seven macroalgae were used as carriers for diatom attachment including Ulva pertusa, degummed Laminaria japonica, Sargassum muticum, Chaetomorpha valida, Zostera marina, Sargassum fusiforme and Sargassum thunbergii. Diatoms could grow on the surface of the suspended carriers and could effectively utilize the nutrients released by the decomposition of these carriers. Among the seven carriers, Ulva pertusa powder was the most effective for Nitzschia culture when comprehensively considering the nutrition of the harvested diatoms and nutrient utilization of the algae carrier by diatoms. The seaweed powder was dried at 80 °C before used as carrier, this process should meet the sterilization requirements for microalgal culture and is easy to implement in the large-scale cultivation of diatoms. Diatoms cultured with carriers were used to feed juveniles Stichopus japonicus with a wet weight of 5.0 ± 2.0 g, as well as diatoms cultured using conventional methods without carriers, and no significant differences were observed between the two kinds of feed. Compared to sea cucumbers fed with commercial feed, the growth rate of S. japonicus fed with carrier-cultured diatoms was approximately 1.5 times greater, and the activities of non-specific immune enzymes were improved in the coelomic fluid including acidic phosphatase, alkaline phosphatase and superoxide dismutase. Feeding sea cucumber with fresh diatoms could effectively reduce the total nitrogen and total phosphorus in the culture water, improve the water quality, and promote the breeding of sea cucumbers, regardless of whether the carrier culture was adopted.

The Fram Strait is an area with a relatively low and irregular distribution of diatom microfossils in surface sediments, and thus microfossil records are scarce, rarely exceed the Holocene, and contain sparse information about past richness and taxonomic composition. These attributes make the Fram Strait an ideal study site to test the utility of sedimentary ancient DNA (sedaDNA) metabarcoding. Amplifying a short, partial rbcL marker from samples of sediment core MSM05/5-712-2 resulted in 95.7 % of our sequences being assigned to diatoms across 18 different families, with 38.6 % of them being resolved to species and 25.8 % to genus level. Independent replicates show a high similarity of PCR products, especially in the oldest samples. Diatom sedaDNA richness is highest in the Late Weichselian and lowest in Mid- and Late Holocene samples. Taxonomic composition is dominated by cold-water and sea-ice-associated diatoms and suggests several reorganisations – after the Last Glacial Maximum, after the Younger Dryas, and after the Early and after the Mid-Holocene. Different sequences assigned to, amongst others, Chaetoceros socialis indicate the detectability of intra-specific diversity using sedaDNA. We detect no clear pattern between our diatom sedaDNA record and the previously published IP25 record of this core, although proportions of pennate diatoms increase with higher IP25 concentrations and proportions of Nitzschia cf. frigida exceeding 2 % of the assemblage point towards past sea-ice presence.

Microalgae were isolated, identified, and cultivated for enhanced biomass production and lipid accumulation. A marine microalgae was isolated from coastal rock pools of Tuticorin, Tamil Nadu, and identified as Nitzschia sp. RRSE2 upon microscopic examination and molecular sequence analysis. The experimental results showed that the maximum growth, biomass, and lipid content were obtained at pH 8 using the F/2 medium. These parameters revealed a notable difference when NaCl was added at 3% concentration. Meanwhile, the nutrients NaNO3 (18.75 mgL-1) and NaH2PO4 (3.48 mgL-1) were shown to be suitable nitrogen and phosphorus sources, respectively, for the production of lipids. On day 14, the maximum lipid concentration of 77.5 mgL-1 was produced using optimized culture conditions. Additionally, the maximum number of 17×105 cells mL-1 and the biomass concentration of 0.69 gL-1 were achieved on this same day. Finally, the fatty acid composition of the algal lipid was analyzed by gas chromatography/mass spectrometry (GC/MS) analysis.

Lake Edward is one of the African Rift Valley lakes draining into the Nile River basin. We conducted three sampling series in Lake Edward in October-November 2016, March-April 2017 and January 2018, in distinct seasonal conditions and in several sites varying by depth and proximity to river outlets, including the Kazinga Channel, which connects the hypertrophic Lake George to Lake Edward. The phytoplankton was examined using microscopy and marker pigment analysis by high performance liquid chromatography (HPLC) and subsequent CHEMTAX processing for estimating abundance of phytoplankton groups. Chlorophyll a concentration in the pelagic and littoral open lake sites barely exceeded 10 µg L−1 whereas, in contrast, in the semi-enclosed Bay of Katwe influenced by the Kazinga Channel chlorophyll a was up to 100 µg L−1. Despite substantial seasonal variations of limnological conditions such as photic and mixed layer depths, cyanoprokaryotes/cyanobacteria represented on average 60% of the phytoplankton biomass, followed by diatoms, which contributed ~25% of chlorophyll a, and by green algae, chrysophytes and cryptophytes. 248 taxa were identified with clear prevalence of cyanobacteria (104 taxa), from the morphological groups of coccal and filamentous species (non-heterocytous and heterocytous). The high proportion of heterocytous cyanobacteria, along with a relatively high particulate organic carbon to nitrogen (C:N) ratio, suggest N limitation as well as light limitation, most pronounced in the pelagic sites. During the rainy season, the most abundant diatoms in the plankton were needle-like Nitzschia. Comparison with previous studies found differences in water transparency, total phosphorus, and phytoplankton composition.

Diatoms are fascinating group of microorganisms; abundant in all aquatic habitats. They are used as reliable environmental indicators. In the present study diatoms flora of Kalath and Khirganga thermal springs of Kullu district, Himachal Pradesh were examined for the first time. Water temperature for these springs range between 39-48°C with neutral to slightly acidic pH. Total eighteen taxa of diatoms (Bacillariophyceae) reported during study belonging to seven genera. Diatom species of Nitrogen heterotrophic- Nitzschia and Gomphonema dominated in these thermal springs. It indicates water of these springs is rich in nitrogen due to pollution. Present study adds twelve new taxa to the algal flora of Himachal Pradesh.

The oomycete genus Ectrogella currently comprises a rather heterogeneous group of obligate endoparasitoids, mostly of diatoms and algae. Despite their widespread occurrence, little is known regarding the phylogenetic affinities of these bizarre organisms. Traditionally, the genus was included within the Saprolegniales, based on zoospore diplanetism and a saprolegnia/achlya-like zoospore discharge. The genus has undergone multiple re-definitions in the past, and has often been used largely indiscriminately for oomycetes forming sausage-like thalli in diatoms. While the phylogenetic affinity of the polyphyletic genus Olpidiopsis has recently been partially resolved, taxonomic placement of the genus Ectrogella remained unresolved, as no sequence data were available for species of this genus. In this study, we report the phylogenetic placement of Ectrogella bacillariacearum infecting the freshwater diatom Nitzschia sigmoidea. The phylogenetic reconstruction shows that Ectrogella bacillariacearum is grouped among the early diverging lineages of the Saprolegniomycetes with high support, and is unrelated to the monophyletic diatom-infecting olpidiopsis-like species. As these species are neither related to Ectrogella, nor to the early diverging lineages of Olpidiopsis s. str. and Miracula, they are placed in a new genus, Diatomophthora, in the present study.

Epilithic diatoms were isolated and cultured during ecological investigations of the Hangang River, South Korea. Three species belonging to the genera Fragilaria, Nitzschia, and Encyonema were investigated using morphological and molecular data. Their morphological characteristics were analyzed using light microscopy (LM) and scanning electron microscopy (SEM). The nuclear small subunit (SSU) rRNA and ribulose-1, 5-bisphosphate carboxylase/oxygenase (rbcL) genes were used to study the molecular characteristics of these taxa. We herein describe three new species: 1) Fragilaria thornata, which has spatulate spines tapering towards their tips; 2) Nitzschia hantanense, which has a small-sized frustule with convex margins and parallel striae in the central part of the valve that become strongly radial towards the poles; 3) Encyonema equalis, which has a space between projections, located on the upper siliceous struts, that is consistent whether near the margin or near the raphe. According to the molecular analysis of three species, there also give a strong evidence to separate these three species as new species based on the phylogenetic tree and genetic distance of SSU rRNA and rbcL gene. The result of all analyses support that Fragilaria thornata, Nitzschia hantanense and Encyonema equalis are new to science.

Phosphorus (P) is an essential biogenic element in aquatic ecosystem, and its speciation in sediment may influence the water quality. The composition of P in suspended particular matters (SPM) and sediments were analyzed. Metal ions bonding PO43- and chelating organic P (OP) were explored by Visual MINTEQ simulation and infrared spectroscopy. Inorganic P (IP) mainly comprises orthophosphate and pyrophosphate in SPM. OP mainly includes α-glycerol phosphate, β-Gly, monophosphate, and mononucleotides from aquatic plants in SPM. Cyclotella, Nitzschia, Amphiprore, and terrestrial C3 plants are the main source of aquatic plants in JH, while they are from Oscillatoria and Merismopedia in JL. These aquatic plants directly determine whether OP or IP is taken to surface sediments during the setting of SPM. The bonding between PO43− and Ca is more preferential than Al and Fe, so the excess PO43− makes Ca compounds bonding IP (Ca-IP) and Al/Fe/Mn (hydr) oxides associated IP (Al/Fe/Mn-IP) dominant, but limited PO43− preferentially contributes more Ca-IP. Metal ions in saline water can firmly cheat with OP via P-OH and/or P=O groups to promote the burial of OP.

Global warming is rapidly altering physicochemical attributes of Arctic waters. These changes are predicted to alter microbial networks, potentially perturbing wider community functions including parasite infections and saprotrophic recycling of biogeochemical compounds. Specifically, the interaction between autotrophic phytoplankton and heterotrophic fungi e.g. chytrids (fungi with swimming tails) requires further analysis. Here, we investigate the diversity and distribution patterns of fungi in relation to abiotic variables during one record sea ice minimum in 2012 and explore co-occurrence of chytrids with diatoms, key primary producers in these changing environments. We show that chytrid fungi are primarily encountered at sites influenced by sea ice melt. Furthermore, chytrid representation positively correlates with sea ice-associated diatoms such as Fragilariopsis or Nitzschia. Our findings identify a potential future scenario where chytrid representation within these communities increases as a consequence of ice retreat, further altering community structure through perturbation of parasitic or saprotrophic interaction networks., Estelle. S. Kilias et al. show that chytrid fungi exhibiting swimming tales are primarily encountered at sites influenced by sea ice melt and that its representation positively correlates with sea ice-associated diatoms. This study predicts that chytrid representation within its Arctic communities may increase as ice retreats further.

The Ergene River is the most significant fluvial ecosystem located in the Thrace Region of Turkey. But it is being exposed to an intensive organic - inorganic pollution by means of agricultural - industrial applications conducted around its basin. In this research, the epipelic (EPP) diatoms of the Ergene River were investigated and the water quality was evaluated using the determined physical, chemical and biological data. EPP diatom samples were collected from upstream, middlestream and downstream of the Ergene River and certain physicochemical parameters (dissolved oxygen, oxygen saturation, pH, electrical conductivity, total dissolved solids, salinity, turbidity, nitrate, nitrite, ammonium, phosphate, sulphate, fluoride, chemical oxygen demand, biological oxygen demand and oxidation-reduction potential) were measured during the field - laboratory studies. Also, the Biological Diatom Index (BDI) was used to determine the trophic status of the Ergene River in terms of EPP diatoms. According to the results of the physicochemical analysis, upstream of the Ergene River has Class I - II water quality and middle - downstream of the Ergene River have Class III - IV water quality in general. According to the results of the biological analysis, 24 diatom species were recorded in the upstream samples, 4 diatom species were recorded in the middlestream samples. and 7 diatom species were recorded in the downstream samples. Cymbopleura amphicephala (Nageli) Krammer, Nitzschia umbonata (Ehrenberg) Lange-Bertalot and Nitzschia capitellata Hustedt were determined as the most dominant species in the up - middle - downstream of Ergene River respectively. According to the result of the BDI, the upstream of Ergene River was found to be in an oligotrophic state - has high water quality and the middle - downstream of Ergene River were found to be in a eutrophic state - have poor water quality.

Nitzschia taikiensis sp. nov. is a brackish diatom species found in the Toberi River marsh, eastern Hokkaido, Japan. This species has characteristics similar to Nitzschia subamphioxoides Hustedt, which was originally described by Hustedt in 1959. In the present study, we conducted a comparative morphological analysis of N. taikiensis and N. subamphioxoides. The obtained results showed that they are different species. Sampling sites of N. taikiensis were located in salt marsh environments with very low salinity (1-5‰), acidic pH (5.2-5.9) and high mud content (95.0-97.5%). Identification of this species was relatively easy based on LM and SEM image analysis of its frustule features, such as the external form and stria density. This species has not been previously reported in Japan, which could be attributed to the reduction or loss of Japanese freshwater and salt marsh environments in the coastal areas, resulting from urban and industrial development.

Diatoms constitute an essential component for biomonitoring studies to determine the ecological quality of waterbodies. In this study, benthic diatoms of Burdur River Basin were investigated as a consequence of a project on river basin management plan. This is the first detailed taxonomical study of diatoms taken from 13 streams, 4 lakes and 6 reservoirs of Burdur River Basin and a total of 223 taxa have been observed. Among genera, Navicula Bory (27) and Nitzschia Hassal (27) were represented with the highest numbers of taxa and followed by Gomphonema Agardh with a total of 22 species. Navicula antonii Lange-Bertalot and Nitzschia palea var. debilis (Kutzing) Grunow had the highest relative abundance with 17.1% and 15.5% respectively. As a closed basin, salinity varied greatly from fresh to saline water between the sampling stations and diatom composition contained species with a different tolerance level. Navicula antonii and Nitzschia frustulum (Kutzing) Grunow observed in all habitats indicating their euryhaline characters; however Navicula digitoconvergens was only detected in saline Acigol lake with a high relative abundance (38%) in autumn. Other two dominant species were Halamphora coffeiformis (Kutzing) Levkov and Navicula cincta (Ehrenberg) Ralfs in Acigol lake showing their tolerance to high salt content as a brackish species. According to first results, 11 species were new records for Turkish diatom flora. The high biodiversity of diatoms revealed the presence of different habitat characteristics within the basin. These results are an important contribution of Turkish diatom flora and could be useful for monitoring specific areas like Burdur River Basin.

The article represents the research on influence of a number of hydrochemical parameters on the phytoplankton formation in the Tiligulsky Liman in 2015 and the forecast of possible changes in terms of increasing salinity. In the northern, central, southern and coastal part of the Liman, 65 species of microalgae were found, which were mainly diatoms (44) and dinoflagellates (12 species). The coastal waters were characterized by the highest number of phytoplankton (4.3 million cells·l-1) due to the massive development of green algae. The biomass was almost the same at all regions (1618.2 – 1955.8 mg·m-3), except the southern (358.7 mg·m-3). The salinity varied in the following range: 13‰ – in the coastal part, 24‰ – in the south and north, 25‰ – in the central. In the lower part it was revealed the dominance of dinoflagellates of the genera Prorocentrum, Protoperidinium, Gymnodinium (contribution to biomass up to 82%), on the sea coast – green algae Monoraphidium contortum (Thur.) Komark.-Legn., M. minutum (Nageli) Komark.-Legn. (up to 11% by biomass and 67% by abundance). Flagellates reached a fairly high abundance at different sites (up to 10% by biomass and 15% by abundance). Among the diatoms Skeletonema costatum (Grev.) Cl. developed massively in the southern part of the Liman; Ceratoneis closterium (Ehr.) Reimann et JCLewin and Tabularia fasciculata (Ag.C) DMWilliams et Round – in the coastal part; Chaetoceros socialis – in the central, Navicula sp. – in the northern. Correlation and ordination analysis revealed that salinity is the main factor determining the development of plankton microphytes at the studied sites. Oxygen content, depth and temperature are also important factors in the bottom horizon. The content of nutrients is more significant on the surface horizon. Regarding the salinity, 35 species-indicators of salinity were identified, of which 11% were indifferent (freshwater-brackish-water), 37 – mesogalobes (brackish-water) and 51 polyhalobes (marine). In comparison with the studies of the 1980s and 2000s, it was found that the share of freshwater-brackish-water species has decreased significantly, and freshwater algae were absent. Further increase in salinity will lead to raising of the proportion of eurygaline species, such as diatoms Achnanthes brevipes, Halamphora coffeaeformis, Navicula salinarum, N. pontica, N. cancellata, Nitzschia hybrida, Tabularia fasciculata, Ceratoneis closterium, Cocconeis scutellum. These species can withstand fairly large salinity ranges and are the first who massively develop in salinized water bodies.

Our study evaluates differences in the distribution and ecology of genetic variants within several ecologically important diatom species that are also key for Water Framework Directive monitoring of European rivers: Fistulifera saprophila (FSAP), Achnanthidium minutissimum (ADMI), Nitzschia inconspicua (NINC) and Nitzschia soratensis (NSTS). We used DADA2 to infer amplicon sequence variants (ASVs) of a short rbcL barcode in 531 environmental samples from biomonitoring campaigns in Catalonia and France. ASVs within each species showed different distribution patterns. Threshold Indicator Taxa ANalysis revealed three ecological groupings of ASVs in both ADMI and FSAP. Two of these in each species were separated by opposite responses to calcium and conductivity. Boosted regression trees additionally showed that both variables greatly influenced the occurrence of these groupings. A third grouping in FSAP was characterized by a negative response to total organic carbon and hence was better represented in waters with higher ecological status than the other FSAP ASVs, contrasting with what is generally assumed for the species. In the two Nitzschia species, our analyses confirmed earlier studies: NINC preferred higher levels of calcium and conductivity. Our findings suggest that the broad ecological tolerance of some diatom species results from overlapping preferences among genetic variants, which individually show much more restricted preferences and distributions. This work shows the importance of studying the ecological preferences of genetic variants within species complexes, now possible with DNA metabarcoding. The results will help reveal and understand biogeographical distributions and facilitate the development of more accurate biological indexes for biomonitoring programmes. info:eu-repo/semantics/acceptedVersion

Benthic diatoms form an important component of the microphytobenthos and have long been utilised as suitable bioindicators in aquatic systems. However, knowledge on benthic diatom community succession on hard substrata (biofilm) remains understudied in austral marine coastal systems. In this study, we investigated benthic diatom colonisation on artificial substrates (Plexiglass) over a period of 5 weeks at two locations with different physical environments along the warm temperate coast of South Africa. Results revealed relatively similar physico-chemical conditions but highly contrasting diatom community development were observed between the two sites. While there were some shared taxa, site-specific dynamics resulted in significantly different diatom species diversity and richness, facilitated by common (e.g., Nitzschia ventricosa and Cocconeis scutellum) and a large percentage of rarely observed species such as Cocconeis testudo and Lyrella lyra. A total of 134 species belonging to 44 genera were observed during the study. The overall diatom composition differed spatio-temporally during the experimental period, with the fluctuating species occurrences and abundances highlighting the rapid microalgal species turnover within days, under natural conditions. Environmental variables were shown to have varying influences as drivers of the diatom community descriptors. Multivariate modelling confirmed that study site and the interaction between site and sampling occasion were important predictors of diatom abundances, and the overall observed community composition. The current results suggest that benthic diatoms on artificial substrata could be incorporated as suitable indicators of change along the coastline subject to further investigations, taking into account site-specific differences driven by habitat complexity and environmental variability. The experimental method proved to be efficient and can be implemented to study the response of benthic diatoms to localised nutrient enrichment around the coastline.

Diatom biomass could be an alternative feedstock for producing bio-oil through hydrothermal liquefaction (HTL) technique. Additionally, diatom biomass could have high-value metabolites, such as pigments and polyunsaturated fatty acids. Hence, this study investigated the feasibility of using indigenous marine diatom biomass as a potential feedstock for biocrude oil and high-value products. At first, different growth parameters (i.e., nutrient type and concentration, and salinity) were studied for locally isolated Amphora sp. and Nitzschia sp. diatoms in indoor experiments. For all the parameters, Nitzschia sp. showed better growth rate and biomass yield compared to Amphora sp. Therefore, Nitzschia sp. was selected as the candidate strain, and it was grown outside in a 1000-L raceway tank. The final biomass yield was 0.57 g/L, and the biomass was first concentrated using a tangential flow filtration membrane followed by a centrifuge. The harvested biomass’s lipid, protein, carbohydrate, and ash contents were 22.2, 15.5, 34.4, and 27.8%, respectively. The docosahexaenoic acid and eicosatetraenoic acid contents were 13.0 and 10.9% of lipid, respectively. The carotenoid content in the biomass was 12 mg/g biomass. Next, hydrothermal liquefaction (HTL) treatment was applied to Nitzschia biomass at a temperature range of 300–400 °C. Biocrude yield and their higher heating values (HHV) ranged from 36.5 to 57.2% and from 24.7 to 35.1 MJ/kg, respectively; while the maximum biocrude yield was obtained at 375 °C, the highest HHV was obtained at 300 °C. The aromatics and the heterofunctional compounds were the major compounds for all the biocrude samples. The energy recovery (i.e., 64.3%) and energy return on investment (i.e., 1.68) for the biocrude samples were higher at 375 °C, mainly due to the higher biocrude yield at this temperature. Overall, Nitzschia sp. is a potential candidate strain for bio-oil production in a biorefinery route. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature. The work was supported by Qatar National Research Fund (QRLP-10-G-1712005). Scopus

The influence of selected factors on the diversity and composition of tychoplanktonic diatom community in limnocrene spring Zelenci was investigated. The spring that was studied is located in a glacial valley in the south-eastern calcareous Alps. Samples of tychoplankton were collected with a plankton net between October 2012 and August 2015 and for each sample, selected abiotic factors were measured. Over 100 different diatom species were identified, the most abundant being Achnanthidium minutissimum and Denticula tenuis. The most species-rich genera were Navicula, Fragilaria, Nitzschia, Cymbella and Gomphonema. The most significant impact on species composition of tychoplanktonic diatom community was from the conductivity of the water and the consecutive number of the month. Diversity was correlated negatively with concentration of orthophosphate and positively with pH and water level. Benthic species from the low profile ecological group dominated the tychoplankton community, with a share of 30–72%. High profile and motile species characteristic for benthos reached higher shares on average than euplanktonic species. This indicates the essential role of underwater springs in the maintenance of a species-rich tychoplanktonic community.

The aim of this study was to understand the ecohydrological interactions of periphyton assemblages in a canal (Bishalakhi) located in the Indian Sundarban. Sixteen environmental variables and periphyton (scrapped from a known area of submerged natural substrates) were collected seasonally (pre-monsoon, monsoon, and post-monsoon) from three sampling stations between July 2017 and September 2018. Data was analyzed to determine periphyton diversity, abundance, spatiotemporal dynamics, and their relationship with environmental variables using R-software. Eleven environmental variables (water temperature, water depth, water velocity, specific conductivity, total alkalinity, salinity, Mg2+, PO4−P, TP, SiO4−Si, and transparency) showed significant difference (p CCA2 (0.93) > CCA3 (0.93). The majority of the diatom (36 species) had a strong affinity with dissolved oxygen and total nitrogen. The water velocity and specific conductivity were found to influence the distribution of species (Phormidium sp., Ankistrodesmus falcatus, Diploneis sp., Synedra sp., Eunotia sp., and Nitzschia recta) in the canal environment. The results of this study advance the current understanding of the relationship between periphyton and its environment and may aid for better planning of periphyton-based aquaculture in the semilotic canals of Indian Sundarbans.

In diatoms the use of molecular tools to corroborate traditional (morphological) identification offers a new perspective in the field of biogeography. This manuscript reports the first record of the raphid pennate diatom Nitzschia volvendirostrata along the coast of Mexico, which in turn represents an expansion of the geographic range along the American continent. The cells were isolated from benthic samples taken from Balandra lagoon, La Paz, Baja California Sur, Mexico and cultured as a monoclonal culture. Morphology and morphometry of the diatom obtained from light and electron microscopy reveal that they correspond to the original description of N. volvendirostrata and also its chloroplast sequences, rbcL and psbC, showed 98.7 to 100 % similarity and a close phylogenetic relationship with N. volvendirostrata. The reported places for this taxon show that it has a tropical-temperate biogeographical affinity.

Heramza K, Barour C, Djabourabi A, Khati W, Bouallag C. 2021. Environmental parameters and diversity of diatoms in the Aïn Dalia dam, Northeast of Algeria. Biodiversitas 22: 3633-3644. Diatoms have long been used as biological indicators of the quality of aquatic environments due to their important capacity to respond to environmental change. As this flora has been very little studied in Algeria, the present study aimed to monitor the Spatio-temporal dynamics of diatoms at the Aïn Dalia dam (north-eastern of Algeria) and determine the main abiotic factors contributing to these variations from June 2017 to May 2018 in four selected stations. Our results showed that the waters of Aïn Dalia dam waters vary from moderately (St1 and St3) to significantly polluted (St2 and St4). They host the community of planktonic diatom flora composed of 72 species. The interspecific biodiversity was marked in summer and autumn (57 and 56 species respectively) and in the St4 station (52 species). In terms of abundance, more than 40% of the overall density was found in the St4 station and the fall period. Among the dominant genera, Cyclotella, Thalassiosira, Synedra and Navicula are found in moderately polluted waters, while Nitzschia, Melosira and Surirella in significantly polluted waters. Some environmental parameters, including nutrients (PO43-and NO2-), SM, temperature, dissolved oxygen, and pH played a key role in the functioning and evolution of this lake. Hence, these parameters demonstrated important fluctuations during our study and influenced directly the diatom distribution. These results showed that diatom assemblages are influenced by anthropogenic disturbances, and can be used as indicators of environmental quality.

The composition of diatom assemblages of epilithon, epiphython and epipelon in the Shchugor River was presented. Biofoulings of rocky substrates, macrophytes, filamentous algae and samples from the surface of bottom sediments were studied. The diatom assemblages had a diverse composition and included 218 species with varieties and forms from 60 genera, 27 families and 12 orders. The order Naviculales (56 taxa) and the family Fragilariaceae (39 taxa) played a major role. The genera Gomphonema (17 taxa), Nitzschia (16), Navicula (14), Eunotia (14) were dominant by the species abundance. The identified diatoms were mostly epiphytes, indifferent to salinity and alkaliphilous species, clean water indicators. The most common community in the river was epilithon, whereas epiphyton distinguished by the most diverse composition. The epipelon was poorly developed, having the lowest number of diatom taxa.Dominant, subdominant, accompanying species of the diatoms were very similar in different phytobenthos groups, the Sørensen-Czekanowski coefficients varied from 0.70 to 0.81. The dominant species were Achnanthidium minutissimum, Encyonema minutum, Fragilaria gracilis, Gomphonema exilissimum, G. ventricosum, Hannaea arcus, Meridion circulare. The sub-dominant species were Cocconeis placentula, Nitzschia fonticola, Ulnaria ulna and Staurosirella pinnata. Based on the Berger-Parker and Simpson variety indices, the occurrence of taxa in the genera and families in the epiphyton was more uniform. The assessment of benthic diatoms demonstrated that the Shchugor River is a typical mid-mountain river. Diatom communities of epilithon, epiphython and epipelon can be used for the monitoring of ecological status of the river.

An overview of the diatom research in the DR Congo is given based on literature data starting in 1938 with the work of Zanon and excluding the East African Lakes as these were already discussed in previous papers. For each literature record the diatom genera mentioned are presented as well as all diatom taxa described from the Congo as new. In total, 106 new taxa were documented, of which Nitzschia with 40 taxa is far the most important genus followed by Navicula s.l. and Pinnularia and with 15 and 13 taxa respectively. Particular attention was paid to the local research of students found in unpublished theses at bachelor, licentiate, master and PhD level. Diatom records in these works are almost all restricted to genus level, although in the last decade an attempt to delimit species can be observed. This accompanies the renewed taxonomic interest in the Congo basin during the last decade. Renewed taxonomic interest can also be seen in the genera: the first period being situated during the lumping period, while more recent works follow the current taxonomic classification, for example Navicula s.l. versus Navicula, Cavinula, Craticula, Diadesmis, Geissleria, Humidophila, Luticola, etc.

Currently there are few studies on modern diatom ecology in large lakes on the Tibetan Plateau. To illustrate spatial patterns of diatom communities and study the correlation with environmental variables, 143 surface sediments were sampled from the largest lake (Selin Co) on the central Tibetan Plateau. A total of 143 diatom species belonging to 30 genera were identified, most of which were halophilic and basophilic species. Our results show that diatom communities exhibit a distinct spatial pattern in different environments including fluvial rivers, the inlet of Selin Co, the small lake region and the large lake region of Selin Co. Based on a depth-constrained cluster analysis, the diatom taxa were divided into three different communities: the shallow sedimentary zone (0–12 m), middle sedimentary zone (12–22 m) and deep sedimentary zone (22–48 m). The dominant species were Cocconeis placentula, Nitzschia hungarica and Anomoeoneis costata respectively. Through Canonical correspondence analysis, it was indicated that the spatial distribution of the diatom assemblages was mainly influenced by water depth, grain size and temperature, with water depth being the dominant factor. WA-PLS and WA regression models were used to establish a diatom-depth transfer function (r2boot = 0.73, RMSEP = 0.19; r2boot = 0.76, RMSEP = 0.19), further demonstrating the correlation between the diatom community and water depth. Our results defined the spatial distributions and controlling factors of diatom assemblages from the different environments.

A new species of Nitzschia Hassall is described from a small spring in southern Portugal. Nitzschia transtagensis sp. nov. has a unique morphology in the Lineares section, resembling Nitzschia hier...

Springs are highly important habitats for biodiversity trend. Hence three springs in Golestan Province were selected for floristic study of diatom assemblages. Samples were collected seasonally from stony and sediment substrates. In total, 75 taxa belong to 38 genera were identified. Gomphonema and Nitzschia each with 7 species, Navicula with 6 species, Surirella with 5 species and Cymbella with 4 species were the most species-rich genera. Results revealed that Gol-e-Ramian Spring with 61 taxa had the highest species richness. Achnanthidium nanum,Cocconeis placentula, Fragilaria crotonensis, Gomphonema micropus, Meridion circulare, Nitzschia vermicularis, and Planothidium frequentissimum were the most abundant taxa. Most of the species identified in the present research have been observed within running water environments in Golestan province and other parts of Iran. Our study improved knowledge about the diatom communities ofsprings in Golestan province.

Identification of algae of Shakh-Kenar, Gavkhouni Wetland, was studied from September 2017 to November 2018 at three stations with three replication. Totaly, 69 species and 43 genera belonging to six divisions were identified. Species were belonging to the Bacillariophyta, Chlorophyta, Cyanophyta, Euglenophyta, Dinophyta and Chrysophyta. The density variations of the algae were between 98 and 1597 cells/cm3. The highest density was found at station 1 in autumn. According to the Shannon-Weaver Index, the highest and the lowest diversity were observed in autumn and winter, respectively. Bacillariophyta, especially pennate forms; such as Navicula, Nitzschia, Cymbella, and Ulnaria were semi dominant in the most stations. From Chlorophyta; Pediastrum, Cladophora and Scenedesmus were showed conspicuous increase in summer and early autumn. Chroococcus disperses (Keissl.) Lemn, Merismopedia punctata Meyen, Oscillatoria sp. were demonstrated more abundance in autumn. Phacus sp., Euglena caudata Hubner, Trachelomonas playfair Defl., Glenodinium quadridense (Stein.) Schiller, Ceratium hirundinella (OF. Muell.) Duj and Peridinium cinctum Muell., were observed in later summer and autumn. Regarding to taxa list, kind of pollution index algae and water quality index were recognized from Chlorophyta, Cyanophyta, Dinophyta and Euglenophyta, that they play important role modify water odor/taste, corrosion of tubes, methods, and production of toxins.

An unidentified diatom species belonging in the genus Nitzschia isolated from samples in the Omani coastal region of the Arabian Sea is the focus of the present study. This species has been successfully cultivated in the laboratory and DNA was harvested and sequenced. Light microscopy (LM) and scanning electron microscopy (SEM) examination of the strain revealed some distinct features, of which the ultrastructure of canal raphe and the absence of central nodule are the most remarkable ones. In terms of morphology, the strain being studied resembles taxa belonging in Nitzschia sect. Lanceolatae. However, our phylogenetic tree based on a three-gene dataset, comprising concatenated nuclear-encoded small-subunit ribosomal DNAs (SSU) and chloroplast encoded (rbcL and psbC) shows that our strain is sister to N. filiformis, which belongs in Nitzschia sect. Obtusae. This species that we have named Nitzschia omanensis, is thus far only known from the harsh coastal waters of Oman, which are characterized by very high daily temperatures and extremely low precipitation.