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Community dynamics within microbial mat assemblages are complex, likely involving intricate metabolic linkages. Interactions between microbes shape these communities, particularly in extreme habitats such as those found in the Middle Island Sinkhole (MIS), Lake Huron. Herein, euxinic waters resemble early-Earth ocean conditions, and diverse microbial groups form benthic mats. The goal of this study was to examine interspecific relationships among culturable cyanobacteria (two strains of Anagnostidinema) and diatoms (Craticula cuspidata and Nitzschia palea) isolated from MIS mats in a co-culture factorial experiment. Although most crosses showed limited interactions, a significant increase in abundance of one Anagnostidinema strain was found when grown with Craticula cuspidata compared to other taxa (P < 0.0001). Nitzschia palea growth was significantly reduced when grown with either strain of cyanobacteria (P = 0.0040). Addition of both cells and filtrates from C. cuspidata cultures caused increases in Anagnostidinema percent cover. Unique metabolic capabilities of C. cuspidata may benefit some cyanobacteria, and cyanobacteria may inhibit N. palea growth via interference competition. These interactions may be masked in the mat community in situ by environmental factors or other interspecific interactions, or allow species to survive in low abundance in an otherwise unfavorable habitat. [ABSTRACT FROM AUTHOR]

The present study aimed to apply diversity indices to determine the seasonal distribution of epipelic diatom communities in the lower Zab River in Kirkuk Province. Four sites were chosen and subjected to study (Sadr River Bridge, Ashraya Village, Al-Shamit Village, Al-Shak Village), and the sampling was conducted from September 2023 to April 2024. Diatoms dominated the epipelon community; the seasonal distributions of epipelic diatoms were shown in the total numbers at the study sites. The results recorded the lowest rate for both central and pinnate diatoms at site 2 in the spring (218 × 104 /cm³) and the highest rate (512 × 104 /cm3) at site 1 in autumn. The dominancy of some epipelic diatomic species was recorded during the study period; these genera were Nitzschia, Navicula, Synedra, Cymbella, Gomphonema, Cocconies, Gyrosigma, Cyclotella, and Fragiaria. The diversity indices such as the richness index, Shannon diversity index, species evenness, and Simpson's diversity index were applied to illustrate the distribution of epipelic diatom community at the study sites. The data obtained would fill the gap in literature, providing adequate information on the topic addressed. [ABSTRACT FROM AUTHOR]

Background: Nitzschia closterium f. minutissima is a commonly available diatom that plays important roles in marine aquaculture. It was originally classified as Nitzschia (Bacillariaceae, Bacillariophyta) but is currently regarded as a heterotypic synonym of Phaeodactylum tricornutum. The aim of this study was to obtain the draft genome of the marine microalga N. closterium f. minutissima to understand its phylogenetic placement and evolutionary specialization. Given that the ornate hierarchical silicified cell walls (frustules) of diatoms have immense applications in nanotechnology for biomedical fields, biosensors and optoelectric devices, transcriptomic data were generated by using reference genome-based read mapping to identify significantly differentially expressed genes and elucidate the molecular processes involved in diatom biosilicification. Results: In this study, we generated 13.81 Gb of pass reads from the PromethION sequencer. The draft genome of N. closterium f. minutissima has a total length of 29.28 Mb, and contains 28 contigs with an N50 value of 1.23 Mb. The GC content was 48.55%, and approximately 18.36% of the genome assembly contained repeat sequences. Gene annotation revealed 9,132 protein-coding genes. The results of comparative genomic analysis showed that N. closterium f. minutissima was clustered as a sister lineage of Phaeodactylum tricornutum and the divergence time between them was estimated to be approximately 17.2 million years ago (Mya). CAFF analysis demonstrated that 220 gene families that significantly changed were unique to N. closterium f. minutissima and that 154 were specific to P. tricornutum, moreover, only 26 gene families overlapped between these two species. A total of 818 DEGs in response to silicon were identified in N. closterium f. minutissima through RNA sequencing, these genes are involved in various molecular processes such as transcription regulator activity. Several genes encoding proteins, including silicon transporters, heat shock factors, methyltransferases, ankyrin repeat domains, cGMP-mediated signaling pathways-related proteins, cytoskeleton-associated proteins, polyamines, glycoproteins and saturated fatty acids may contribute to the formation of frustules in N. closterium f. minutissima. Conclusions: Here, we described a draft genome of N. closterium f. minutissima and compared it with those of eight other diatoms, which provided new insight into its evolutionary features. Transcriptome analysis to identify DEGs in response to silicon will help to elucidate the underlying molecular mechanism of diatom biosilicification in N. closterium f. minutissima. [ABSTRACT FROM AUTHOR]

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Post-mining reservoirs are distinguished by characteristic environmental conditions where specific diatom communities can be observed. Reservoirs created as a part of the reclamation plan after human mining activities are marked by unique chemical and physical water parameters. In the course of research on the diatoms from Bogdałów reservoir, we examined the taxonomic and morphological diversity of Nitzschia taxa from the section Lanceolatae occurring in a post-mining lignite reservoir. Our study describes a new species of Nitzschia from a post-mining reservoir, Nitzschia nandorii Olszyński, Zakrzewski & Żelazna-Wieczorek, sp. nov. Morphometry and morphology analyses of new species were performed with light and scanning electron microscopy. Chloroplast morphology analysis was conducted with differential interference contrast microscopy and confocal laser scanning microscopy. Molecular data from SSU 18S, rbcL and psbC sequences were obtained from cultures of this taxon. Differential diagnosis of Nitzschia nandorii Olszyński, Zakrzewski & Żelazna-Wieczorek, sp. nov. with co-occurring taxa: N. lacuum and N. alpinobacillum was performed using morphological traits and nMDS analysis of the valves' morphometry. [ABSTRACT FROM AUTHOR]

Nitzschia soratensis and N. inconspicua are two small diatoms that are extremely similar in the light microscope though separable in subtle aspects of valve and girdle ultrastructure. They are not closely related in molecular phylogenies and differ in their ecological preferences, though they sometimes co-occur in the same communities. To test further their functional equivalence, we investigated the reproductive biology of N. soratensis, for comparison with a previously published account of N. inconspicua. Both species are automictic, lacking pairing between gametangia and gamete exchange. Nuclear staining shows the presence of two nuclei in some auxospores of N. soratensis, which are smaller than the nuclei of vegetative cells and appear to be haploid, indicating prior meiosis. These auxospores, surrounded by incunabula containing tangles of silica strips, give rise to uninucleate initial cells 18–21 µm long. Frequently, however, small N. soratensis cells produce two spherical 'pseudogametes', some of which abort while others expand and form initial valves shorter than those produced by binucleate auxospores (maximum length 14.5 µm). Similar uniparental auxosporulation, with silica strip formation, occurs in N. aff. hantzschiana, N. acidoclinata, N. fonticola and N. angustata, which are close relatives of N. soratensis according to morphological and/or molecular evidence. This group and the N. inconspicua complex may be the diatom equivalents of apomictic angiosperms, e.g. dandelions, and likely contain a multitude of microspecies. [ABSTRACT FROM AUTHOR]

The Mediterranean Region holds significant ecological importance, characterised by its unique climate, biodiversity and the crucial role it plays in global ecosystems. Mediterranean streams are naturally highly-stressed environments mainly due to fluctuations in water quantity. River flow generally varies from perennial to ephemeral and temporary rivers constitute significant water resources. Streams that flow through Balearic Islands are subjected to these conditions. The majority of these streams sustain water flow for 4-5 months annually, with exceptions noted for streams associated with springs, which typically maintain water throughout most of the year. Benthic diatoms are widely recognised as reliable bioindicators of water quality, used in many aquatic ecosystems. Analysing diatom communities and their biodiversity serves as a valuable tool to ensure the ecological and sustainable utilisation of water resources as well as the accurate development of guidelines for their conservation. The field of diatom taxonomy and distribution plays a crucial role in advancing our understanding of aquatic ecosystems and their biodiversity. Species of the genus Nitzschia are extensively found throughout the Mediterranean Region, including the Balearic Islands. However, they have rarely been investigated in temporary streams. This study presents the first record of Nitzschia transtagensis Morales, Novais, Wetzel, Morais & Ector, outside the type locality and being the second record in Europe. In this study, the authors found this taxon in one temporary stream of Majorca Island, Torrent des Castellot in November 2005 (Balearic Islands). Nitzschia transtagensis occurred at 2.6% abundance in this stream with oligotrophic waters (0.052 mg·l of nitrate), slightly alkaline pH values (7.8) and water conductivity levels of 626.5 µS cm. This species was recorded in the biofilm of the stones together with other taxa such as Achnanthidium minutissimum (Kützing) Czarnecki (39.2%), Gomphonema rosenstockianum Lange-Bertalot & Reichardt (28.9%) and Halamphora oligotraphenta (Lange-Bertalot) Levkov (20.4%). The Nitzschia transtagensis frustules found in the examined material have similar dimensions and a higher fibulae count (8-11 in 10 µm vs. 6-10 in 10 µm) compared to the type material of Nitzschia transtagensis. The habitat characteristics in which this species was found are described, together with LM micrographs of this taxon. [ABSTRACT FROM AUTHOR]

Algal bioindicators, such as diatoms, often show subdued responses to eutrophication in Arctic lakes because climate‐related changes (e.g., ice cover) tend to be the overriding factors influencing assemblage composition. Here, we examined how sub‐Arctic ponds historically receiving high nutrient inputs from nesting seabirds have responded to recent climate change. We present diatom data obtained from 12 sediment cores in seaduck‐affected ponds located on islands through Hudson Strait, Canada. All study cores show consistently elevated values of sedimentary ẟ15N, an established proxy for tracking marine‐derived nutrients, indicating seabirds have been present on these islands for at least the duration of the sediment records (~100 to 400 years). We document diverse epiphytic diatom assemblages to the base of all sediment cores, which is in marked contrast to seabird‐free Arctic ponds—these oligotrophic sites typically record epilithic diatom flora prior to recent warming. Diatoms are likely responding indirectly to seabird nutrients via habitat as nutrients promote the growth of mosses supporting epiphytic diatom communities. This masks the typical diatom response to increased warming in the Arctic, which also results in habitat changes and the growth of mosses around the pond edges. Changes in sedimentary chlorophyll a were not consistently synchronous with large changes in ẟ15N values, suggesting that primary production in ponds is not responding linearly to changes in seabird‐derived nitrogen. Across all ponds, we recorded shifts in diatom epiphytic assemblages (e.g., increases in % relative abundance of many Nitzschia species) that often align with increases in chlorophyll a. The changes in diatoms and chlorophyll a, although variable, are most likely driven by climate change as they are generally consistent with longer ice‐free conditions and growing seasons. Together, our results show that to effectively use diatoms in animal population reconstructions across the sub‐Arctic and Arctic, a strong understanding of eutrophication and climate change, based on supplementary proxies, is also required. [ABSTRACT FROM AUTHOR]

Background: The increasingly severe salinization of the aquatic environment has led to serious damage to the habitats of aquatic organisms. Benthic diatoms are commonly employed as indicator species for assessing water quality and serve as a reflection of the overall health of the aquatic ecosystem. Nitzschia palea is a common diatom found in freshwater, with high oil content, rapid reproductive rate, and it is a commonly dominant species in various rivers. Results: The results showed that after 4 days (d) of saline-alkali stress, the cell density and chlorophyll a content of Nitzschia palea reached their maximum values. Therefore, we selected Nitzschia palea under 4 d stress for Tandem Mass Tag (TMT) quantitative proteomic analysis to explore the molecular adaptation mechanism of freshwater diatoms under saline-alkali stress. Totally, 854 proteins were enriched, of which 439 differentially expressed proteins were identified. Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and subcellular fractionation analysis revealed that these proteins were mainly enriched in the photosynthesis pathway, citric acid cycle (TCA cycle), fatty acid synthesis, and glutathione cycle. Conclusions: This study aims to reveal the physiological, biochemical and proteomic mechanisms of salt and alkali tolerance and molecular adaptation of Nitzschia palea under different saline-alkali concentrations. This study showed that Nitzschia palea is one candidate of the environmental friendly, renewable bioenergy microalgae. Meantime, Nitzschiapalea reveals for the proteome of the freshwater and provides the basis, it became a model algal species for freshwater diatoms. [ABSTRACT FROM AUTHOR]

Diatoms (Bacillariophyta) are abundant phytoplankton groups in marine environments, which contribute approximately 20% of global carbon fixation through photosynthesis. Moreover, diatoms exhibit the highest species diversity (approximately 18,000 diatom species) among marine photosynthetic eukaryotes, which were identified by morphological characteristics. Molecular phylogenetic analyses could shed new insights into the evolutionary relationships of diverse diatom species. Nevertheless, a comprehensive understanding of the phylogenetic relationships of diatom species still remains unclear because the available molecular data are insufficient compared with their high species diversity. Furthermore, several novel diatom species were reported from field samples with no molecular evidence. In particular, the phylogenies of diatom species constructed using organelle genomes revealed that several diatom genera are paraphyletic with high supporting values. We constructed high-resolution phylogenetic trees of diatom species using organelle genomes (plastids and mitochondria) and compared the morphologies in several paraphyletic diatom genera. Especially, the clades Nitzschia and Thalassiosira include several different diatom genera with high phylogenetic supports. Our study demonstrated that some morphological characteristics (e.g., genus characters) of several diatom genera could not represent current genus boundaries. Based on the results, we highlight the necessity for taxonomic reinvestigation. To reestablish this in diatoms, it will be essential to incorporate more genome data from a broader range of taxon samples, along with a comparison of morphological characteristics. [ABSTRACT FROM AUTHOR]

Abstract Reducing the time to settlement and metamorphosis of abalone larvae is critical for ensuring that abalone larvae settle within the seeding site for ocean ranching or to increase production in hatcheries. This study investigated the effect of biological (planktonic Nitzschia sp.) and chemical (potassium chloride) cues in inducing settlement and metamorphosis of abalone larvae Haliotis midae on diatom‐coated plastic sheets. Larvae were exposed to different concentrations of KCl (10–20 mM), with settlement being highest at 10 mM in the first 20 h. Settlement of larvae exposed to a combined KCl and Nitzschia treatment for 24 h was highest, followed by larvae exposed to KCl for 12 h, while larvae exposed to KCl for 24 h, and both controls (12 and 24 h) had the lowest settlement. However, in both experiments, larval settlement in all treatments declined after 24 h of exposure, while that of the controls (no added settlement cues) increased and surpassed the other treatments after 24 h. Finally, the settlement was very low on uncoated sheets, compared to diatom‐coated sheets, regardless of exposure to different combinations of KCl and Nitzschia. The exposure period's results should be interpreted with caution when drawing biological conclusions for field studies. This is due to the dramatic decrease in mean settlement post‐exposure to the cue. Therefore, we hypothesize that exposure of H. midae larvae to 10 mM KCl and Nitzschia sp. will not enhance settlement in the ocean, as the inducers are primarily only effective at a KCl concentration level equal to 10 mM for 12 h. However, long‐term exposure to KCl and Nitzschia over 24 h could be used in hatcheries to improve the settlement of H. midae larvae.

Nitzschia is one of the largest genera of diatoms found in a range of aquatic environments, from freshwater to seawater. This genus contains evolutionarily and ecologically unique species, such as those that have lost photosynthetic capacity or those that live symbiotically in dinoflagellates. Several Nitzschia species have been used as indicators of water pollution. Recently, Nitzschia species have attracted considerable attention in the field of biotechnology. In this study, a transformation method for the marine pennate diatom Nitzschia sp. strain NIES-4635, isolated from the coastal Seto Inland Sea, was established. Plasmids containing the promoter/terminator of the fucoxanthin chlorophyll a/c binding protein gene (fcp, or Lhcf) derived from Nitzschia palea were constructed and introduced into cells by multi-pulse electroporation, resulting in 500 μg/mL nourseothricin-resistant transformants with transformation frequencies of up to 365 colonies per 108 cells. In addition, when transformation was performed using a new plasmid containing a promoter derived from a diatom-infecting virus upstream of the green fluorescent protein gene (gfp), 44% of the nourseothricin-resistant clones exhibited GFP fluorescence. The integration of the genes introduced into the genomes of the transformants was confirmed by Southern blotting. The Nitzschia transformation method established in this study will enable the transformation this species, thus allowing the functional analysis of genes from the genus Nitzschia, which are important species for environmental and biotechnological development. [ABSTRACT FROM AUTHOR]

Reducing the time to settlement and metamorphosis of abalone larvae is critical for ensuring that abalone larvae settle within the seeding site for ocean ranching or to increase production in hatcheries. This study investigated the effect of biological (planktonic Nitzschia sp.) and chemical (potassium chloride) cues in inducing settlement and metamorphosis of abalone larvae Haliotis midae on diatom‐coated plastic sheets. Larvae were exposed to different concentrations of KCl (10–20 mM), with settlement being highest at 10 mM in the first 20 h. Settlement of larvae exposed to a combined KCl and Nitzschia treatment for 24 h was highest, followed by larvae exposed to KCl for 12 h, while larvae exposed to KCl for 24 h, and both controls (12 and 24 h) had the lowest settlement. However, in both experiments, larval settlement in all treatments declined after 24 h of exposure, while that of the controls (no added settlement cues) increased and surpassed the other treatments after 24 h. Finally, the settlement was very low on uncoated sheets, compared to diatom‐coated sheets, regardless of exposure to different combinations of KCl and Nitzschia. The exposure period's results should be interpreted with caution when drawing biological conclusions for field studies. This is due to the dramatic decrease in mean settlement post‐exposure to the cue. Therefore, we hypothesize that exposure of H. midae larvae to 10 mM KCl and Nitzschia sp. will not enhance settlement in the ocean, as the inducers are primarily only effective at a KCl concentration level equal to 10 mM for 12 h. However, long‐term exposure to KCl and Nitzschia over 24 h could be used in hatcheries to improve the settlement of H. midae larvae. [ABSTRACT FROM AUTHOR]

Çanakkale is located in Western Anatolia, a region known for extensive mining in the country. In this study, three new species: Nitzschia arslaniana sp. nov., Nitzschia efeiana sp. nov., and Nitzschia szaboiana sp. nov. are described from highly acidic environments in Çanakkale. In morphology, Nitzschia arslaniana is similar to Nitzschia inconspicua but Nitzschia inconspicua is broader, with a lower fibulae density. Nitzschia efeiana is similar to Nitzschia. bremensis, Nitzschia capitellata, Nitzschia homburgiensis, Nitzschia hybrida, Nitzschia palustris, and Nitzschia pellucida. However, Nitzschia efeiana has variable fibulae widths, thickened virgae on its external valve face, and an elevated ridge on the valve margin opposite the keel. Nitzschia szaboiana is similar to Nitzschia pusilla, but the later taxon has a higher striae density. This study highlights the unique species diversity of extreme environments, including anthropogenic extreme environments, by describing three new taxa in the same genus. [ABSTRACT FROM AUTHOR]

IntroductionMarine epiphytic diatoms are natural diets for multiple marine invertebrates, including sea cucumbers, sea urchins, etc. They also act as bioindicators in marine waters to assess water quality of coastal ecosystems. Material and methodsWe isolated three strains of Navicula and two strains of Nitzschia from macroalgal epiphytes. Combined concentrations of four macroelements, five trace metals, and three vitamins in f/2 medium were optimized for these diatoms using single-factor and orthogonal tests. Results and discussionThe biomass productivities for 4-L enlarged cultures of the five isolated diatoms in their exclusively optimized f/2 media all increased by nearly 10-fold relative to f/2 medium, and that of Navicula-1 and Nitzschia-2 reached the highest, i.e., 29.52 ± 1.98 and 30.68 ± 2.84 g m-2 d-1, respectively. Moreover, the relative abundance of C20:5n3 in the exclusively optimized f/2 medium-cultured Navicula-1 notably rose by 24%, and that in Nitzschia-2 held stable at > 25%. Thus, Navicula-1 and Nitzschia-2 were screened out with outstanding growth traits and improved fatty acid compositions at high levels of combined nitrogen, phosphorus, iron, and silicon. The two diatoms have potential for becoming quality diets for marine aquaculture, and ideal candidates for effective nutrient removal.

Diatoms, a type of microalgae distributed worldwide, have been identified as potential sources of biomass, lipids, and high-value compounds. While marine diatoms have been extensively studied, the potential of freshwater diatoms still needs to be explored. In this study, a novel strain of freshwater diatom was isolated from the Jungnangcheon stream located in Seoul, Republic of Korea (37°33'08.0" N, 127°02'40.0" E). This newly isolated strain was classified through phylogenetic analysis, and its morphology was investigated using light and electron microscopy; it was named Nitzschia palea HY1. N. palea HY1 grown in freshwater media (FDM) produced higher biomass (0.68 g L-1) and fucoxanthin production (9.19 mg L-1) than in conventional diatom media. Furthermore, increasing the bicarbonate concentration from 2 to 10 mM enhanced the maximum biomass and fucoxanthin production in FDM by 2.7 fold and 1.5 fold, respectively. Remarkably, the introduction of aeration to the modified FDM (MFDM) led to a substantial increase in the maximum biomass and fucoxanthin production of N. palea HY1, exhibiting 3.8-fold and 4.1-fold enhancement, respectively, compared to FDM alone. These findings suggest that optimizing the cultivation of N. palea HY1 using MFDM could provide an alternative to marine sources for fucoxanthin production. [ABSTRACT FROM AUTHOR]

The ecological significance of benthic diatom taxocoenoses in marine ecosystems renders them a suitable reference when making decisions on conservation, as well as ecological and biogeographical issues. This study focuses on floristics of epiphytic diatoms of macroalgae from the central region of the Gulf of California and their biogeographical affinities. Based on current floristics for benthic diatoms of the Mexican NW, it was hypothesized that species richness would be higher for the central gulf (transitional) than for the tropical Revillagigedo Archipelago. Additionally, it was hypothesized that it would be composed mainly of common taxa of the region, with tropical and temperate components. Likewise, it was hypothesized that Mastogloia (tropical) would include less taxa and Lyrella would include more taxa in the transitional central gulf. The diatom flora yielded 333 taxa and 101 genera, and out of which the best represented were Navicula with 29 taxa, Amphora (27), Cocconeis (25), Nitzschia (24), Diploneis (19), Achnanthes (13), Halamphora (14), Fallacia (10), Lyrella (9), and Mastogloia (8), adding up to 53% of the total. The inspected diatom taxocoenosis included mostly taxa commonly distributed in the Mexican NW, albeit with 16 new records. This, plus the high species richness, as well as the proportions of selected taxa depicting this diatom taxocoenosis as being of transitional biogeographical affinity, back the posed hypotheses. [ABSTRACT FROM AUTHOR]

ARTICLE HIGLIGHTS - Differences in river hydraulic characteristics affect ecological river health - The influence of flooding on the dynamics of physical and chemical characteristics of river water - Life strategy, adaptation of periphyton to environmental changes - Development of green infrastructure for river conservation ABSTRACT Belik River is one of the urban rivers in the Special Region of Yogyakarta which has hydrological problems both in quantity and quality. This triggered the construction of various types of channel modifications. This study aimed to identify water quality and the ecological effects of channel modifications based on the presence of periphyton communities as bioindicators. Sampling was carried out in January 2021 and March 2021. Samples were taken at 4 sampling sites with different channel characteristics with 3 repetitions at each location. The physico-chemical parameters measured included pH, detergent, nitrate, sulfate, total phosphate, TSS, TDS, DO, CO2, water temperature, depth, transparency, discharge, and current velocity. The results showed that the abundance of periphyton in January 2021 was higher than in March 2021. In January 2021 there were found 91 periphyton species dominated by Nitzschia improvisa, Nitzschia terricola, and Nitzschia philippinarum. Meanwhile, in March 2021 there were found 61 species of periphyton dominated by Nitzschia improvisa. Based on the results of Canonical Correlation Analysis (CCA), it was shown that in general the distribution and abundance of periphyton in the Belik River were influenced by CO2, total phosphate, discharge, DO, nitrate, TSS, and depth. The Shannon Wiener Diversity Index showed that water quality in January 2021 has decreased in March 2021. From the cluster analysis, it is known that there are differences in water quality and abundance of periphyton in the four types of river channels. It can be concluded that differences in hydraulic characteristics affected water quality and the ecological health of Belik River.

This study aims to examine the ecological status of the Aksaz wetland based on diatom indices and diatom community. Sampling was done between March 2020 and December 2020. 50 taxa belonging to benthic diatom flora were identified. Navicula Bory and Nitzschia Hassall genera were observed in all samples and constituted 47% of the identified taxa. The index and ecological quality values in the Aksaz wetland indicate that the water body is moderately polluted. [ABSTRACT FROM AUTHOR]

Durinskia capensis is a kleptoplastic dinoflagellate species from high intertidal marine rock pools, which can use a variety of diatoms for photosynthesis. However, very few of the diatoms permit indefinite survival of the dinoflagellate and rbcL sequences show that D. capensis isolated from nature contains one of two closely related Nitzschia species as its kleptoplastids. In culture, without a supply of these 'essential' Nitzschia cells to replenish the intracellular store of diatom plastids and other organelles, D. capensis eventually loses all its kleptoplastids and dies. Inside Durinskia, diatoms do not possess frustules and so cannot be compared morphologically with free-living forms. Recently, one of the essential Nitzschia species was isolated from the type locality of D. capensis and grown in culture, allowing comparison with similar Nitzschia species, particularly N. agnita and N. kuetzingioides, examined from type material. We conclude that the 'essential diatom' of D. capensis differs morphologically from these and other Nitzschia species and it is therefore described as N. captiva sp. nov. Nitzschia agnita and N. kuetzingioides, on the other hand, are conspecific and N. agnita has priority. Nitzschia captiva and N. agnita are extremely similar in valve shape, dimensions, pattern and ultrastructure, but can be separated by their girdle structure. Nitzschia agnita appears to be a freshwater species, though somewhat salt-tolerant. In contrast, N. captiva, which is known principally from records of the kleptoplastids of D. capensis rather than from frustules, is so far marine. [ABSTRACT FROM AUTHOR]

Algal blooms can lead to low dissolved oxygen and fluctuating pH, and the toxins produced by some species can be toxic to aquatic animals. In this study, we assessed the potential of ozone nanobubble technology for reducing a diatom species, Nitzschia sp., commonly found in freshwater ponds in Hong Kong. This study suggests that ozone at a low dose of 0.025 ± 0.003 ppm was sufficient to reduce algae by 66.4% within 5 minutes of treatment. An even higher killing effect (68.2%) was observed when ozone was delivered using nanobubbles for 9 minutes. A 24-hour delayed effect was also detected, with a further reduction of approximately 10% of the algae for both ozone treatments (macro and nanobubble delivery methods). In addition to controlling algae, applying ozone at a level that is not detrimental to fish may also benefit the dissolved oxygen levels in pond systems. [ABSTRACT FROM AUTHOR]

Nitzschia martiana, recently restored to Homoeocladia (C. Agardh) emend Lobban et Ashworth, has needle-like cells and forms macroscopic colonies that are so distinctive that they have been reported on the basis of light microscopy alone. It is the type species for Homoeocladia, which have long flaps (conopea) arising from the sternum and covering a valve depression. This group has extreme diversity at the ultrastructural level and it would not be surprising to find another similar to H. martiana. However, Nitzschia venerata, sp. nov., is a surprising look-alike found in a coral reef seaweed sample from Saipan, Northern Mariana Islands (Western Pacific Ocean). It was studied with light- and scanning electron microscopy. Attempts to find colonies in live and preserved samples were unsuccessful. It is very long and narrow, with a valve depression like that in conopeate species. However, ultrastructurally it is not conopeate because the long flaps arise from the valve face and grow toward the keel and can therefore be classified as scuta. Although tube formation remains unknown, the extreme length and narrowness of the cells suggest it might occur, so that scientists identifying potential H. martiana should be alert to the possibility that they have N. venerata or some other needle-like Homoeocladia. [ABSTRACT FROM AUTHOR]

Nitzschia dubiiformis Hust 1939 is a globally distributed species belonging to the family Bacillariaceae. This study reported the complete chloroplast genome sequences of N. dubiiformis. The genome of N. dubiiformis was 179,935 bp in length, consisting of 48,722 bp of large single copy, 103,427 bp of small single copy, and 13,893 bp of a pair of inverted repeat regions. It encoded 188 genes, including 151 protein-coding genes, 6 rRNA and 31 tRNA genes. The GC content of complete chloroplast genome was 30.4%. The phylogenomic analysis suggests that there is a close relationship between N. dubiiformis and N. traheaformis. [ABSTRACT FROM AUTHOR]

This study examines the polar lipid profiles of two freshwater algae, Scenedesmus costatus and Nitzschia palea. HILIC-ESI-MS/MS analysis was used to determine and quantify the major phospholipids and glycolipids, as well as their relative molecular species, extracted from the two microalgal cultures. Glycolipids were eluted first, followed by phospholipids partially co-eluting with a sulfoglycolipid. The fragmentation pattern in the negative ionization mode for galactolipids was studied, revealing the stereospecific distribution of fatty acids on the glycerol backbone. Green algae frequently include 18:3 fatty acid in both phospholipids and galactolipids, while monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) were more saturated and contained shorter acyls. The diatom phospholipids contained mainly molecular species with saturated or monounsaturated fatty acids, while MGDG and DGDG exhibited a higher proportion of polyunsaturated fatty acids, such as the unique and abundant MGDG (20:5/20:2). [ABSTRACT FROM AUTHOR]

Diatoms are photoautotrophic microalgae classified under class Bacillariophyceae, engulfed by hard silicate frustules, which give mechanical support and protection from bacterial infections. They exude polysaccharides extracellularly that help them with their gliding motion (locomotion). However, the bioactivity of such compounds was least explored from freshwater diatoms. In the present study, a single species of pennate diatom identified as Nitzschia palea was isolated and molecularly characterized by 18S rRNA smaller subunit gene (partial) sequencing and submitted to GenBank NCBI and accession number retrieved as ON360983. Based on logarithmic growth curve analysis, the exponential phase was obtained from 3rd to 4th day of diatom culture. The exopolysaccharide was extracted by the hot-water extraction method, and characterized by FT-IR. The total yield of exopolysaccharide from Nitzschia palea was estimated as 1.56 mg in 100 mL of culture after 7 days of incubation. The estimated carbohydrate content was 51.35 µg/100 µL. The monosaccharide constituents were determined by acid hydrolysis of exopolysaccharide, silylation (derivatization), followed by GC–MS analysis and tabulated. The extracted exopolysaccharide was evaluated for its anti-cancer potential against the Human Adenocarcinoma lung cancer cell line (A549) and the estimated IC50 value was 62.64 µg/mL. Acridine orange staining assay and DNA fragmentation assay also confirmed the apoptotic activity of exopolysaccharide derived from the diatom Nitzschia palea. [ABSTRACT FROM AUTHOR]

The algal succession in Microcystis blooms of varying biomass under continuous aeration was studied in a greenhouse. There were four treatments (control, Low, Medium, and High) with initial chlorophyll a (Chl-a) of 32.5, 346.8, 1413.7, and 14,250.0 μg L−1, respectively. During the experiment, Cyanophyta biomass was the lowest in the Medium treatment (P < 0.05), while its Chlorophyta biomass was the highest (P < 0.05). Both Chlorophyta and Bacillariophyta biomass were the lowest in the High treatment (P < 0.05). Bacillariophyta biomass, particularly the diatom Nitzschia palea was the highest in the Low treatment (P < 0.05), and Nitzschia palea cells were attached to the Microcystis colonies. Thus, the algal shift in Microcystis blooms under aeration disturbance depends on its initial biomass, and it shift to green algae or/and diatom dominance in the control, Low, Medium treatments. Diatom cells, particularly N. palea, grew in an attached form on Microcystis colonies in treatment Low, in which the colonies provided media for the adherence. The mechanism of the algal shift with different biomass must be related to the nutrient level, low light and aerobic conditions under aeration disturbance as well as the aeration itself, which destroyed the Microcystis colonies' advantage of floating on the water. [ABSTRACT FROM AUTHOR]

The diatom Nitzschia acidoclinata is a widespread eurybiontic alga. There is little information on its life cycle properties and cardinal points. To fill this gap, we analyzed six N. acidoclinata clones from a range of habitats in Asiatic Russia regarding their genetic diversity, morphology, morphometry, geography, and ecology. A comparison of 15 N. acidoclinata rbcL sequences sampled across its relatively wide distribution area and contrasting habitats revealed no distinct genotypes in the species. We demonstrated that the valve morphology, their length, and the sexual activity of the investigated clones varied depending on the phase of their life cycle. In this species, abrupt size reduction was observed. It was revealed that N. acidoclinata reproduced by pedogamy, and its auxosporulation was season-dependent and observed in spring and autumn only. The mating activity in our clones was detected only when the cell size was reduced to 9–22 µm in length. The available data on sexual reproduction in the genus Nitzschia suggest that neither clades nor subclades comprise pedogamous or anisogamous taxa at the same time. However, isogamy could occur in the same clade with either pedogamy or anisogamy. These data provide a fundamental basis for the development of N. acidoclinata mass cultivation and long-term maintenance in culture technologies. [ABSTRACT FROM AUTHOR]

In contrast to surveys based on a few genes that often provide limited taxonomic resolution, transcriptomes provide a wealth of genomic loci that can resolve relationships among taxonomically challenging lineages. Diatoms are a diverse group of aquatic microalgae that includes important bioindicator species and many such lineages. One example is Nitzschia palea, a widespread species complex with several morphologically defined taxonomic varieties, some of which are critical pollution indicators. Morphological differences among the varieties are subtle and phylogenetic studies based on a few genes fail to resolve their evolutionary relationships. We conducted morphometric and transcriptome analyses of 10 Nitzschia palea strains to resolve the relationships among strains and taxonomic varieties. Nitzschia palea was resolved into three clades, one of which corresponds to a group of strains with narrow linear‐lanceolate valves. The other morphological group recovered in the shape outline analysis was not monophyletic and consisted of two clades. Gene‐tree concordance analyses and phylogenetic network estimations revealed patterns of incomplete lineage sorting and gene flow between intraspecific lineages. We detected reticulated evolutionary patterns among lineages with different morphologies, resulting in a putative recent hybrid. Our study shows that phylogenomic analyses of unlinked nuclear loci, complemented with morphometrics, can resolve complex evolutionary histories of recently diverged species complexes. [ABSTRACT FROM AUTHOR]

In January 2019, epilithic diatoms were collected from two streams on Mount Gumdan and Mount Yongma near Lake Paldang in central South Korea. A total of 16 diatoms were isolated and classified by molecular and morphological analysis. Morphology was studied by LM and SEM, while the molecular study focused on small subunit (SSU) rRNA and ribulose bisphosphate carboxylase (rbcL) genes. Molecular analysis showed that the three species had clear differences in phylogenetic distance. Based on these findings, we studied the ultrastructure of three species. Among the morphological characteristics, Hannaea librata is longer but narrower and always has conical spines, while the similar species H. pamirensis has bifurcated spines in the central region and conical spines near the pole. Gomphonema seminulum is wider in the axial–central area than G. pumilium. Nitzschia inclinata has a bended valve apex, while N. oligotraphenta has a straight apex. [ABSTRACT FROM AUTHOR]

Despite the biodiversity and ecosystem services provided by lotic ecosystems, they are strongly affected by anthropogenic activities. Therefore, biological monitoring and assessment strategies are crucial in helping maintain these ecosystems and developing mitigation policies. We provide a global overview of the use of benthic diatoms as bioindicators in lotic environments, by analyzing 764 articles published in the past 20 years. We analyzed the influence of substrate type on samplings, which species have been highlighted as indicators and for which type of impacts, which anthropogenic impacts have been most commonly evaluated, and which metrics have been commonly used in studies using diatoms to assess and monitor the quality of lotic environments. We found that the most studied anthropogenic impact is artificial eutrophication and that some species, especially Nitzschia palea, have been thoroughly mentioned as indicators of this impact. Indicator species related to other types of impact are less common, demonstrating the need for studies on this issue. Moreover, we verified that traditional taxonomic metrics, such as diversity and diatom indices, have been widely used. Some alternative metrics have been used recently, such as those based on teratological valves, lipid bodies, valve size, and DNA metabarcoding. The number of biomonitoring and assessment studies based on diatoms has increased considerably in the past 20 years. Nonetheless, the demand for natural resources and consequently the degradation of lotic ecosystems have accelerated significantly. Thus, the development of low-cost and time-efficient biological assessment and monitoring strategies is essential for evaluating the health of lotic environments. [ABSTRACT FROM AUTHOR]

The environmental contingency caused by the recent massive arrivals of pelagic sargasso (Sargassum natans and S. fluitans) on Mexico's Caribbean coasts have given rise to several areas of scientific research. Our work proposed identifying the diatom flora adhered to the thalli of these two sargasso species collected on the coasts of Cancun, Isla Mujeres, and Puerto Morelos. We recorded 184 diatom taxa (all illustrated) from 65 genera. Taxa from the genera Mastogloia (37), Cocconeis (11), Nitzschia (10), Diploneis (8), and Amphora (9) represented 41% of the total, while 38 of these genera were represented by a single species. In the total floristic count, 41 taxa occurred exclusively on S. fluitans, 52 exclusively on S. natans (22 and 28%, respectively) and 91 (49%) were found on both. Species of Navicula were scarce, and Navicula barbara var. densestriata was here transferred to the genus Lyrella (Lyrella barbara var. densestriata (Foged) López-Fuerte & Siqueiros Beltrones comb. nov.). Overall, 17 (9%) of the identified taxa were new recordings for Mexico's coasts. Supporting the hypothesis proposed, the 37 Mastogloia taxa suggested a tropical affinity, while the high species richness denoted that the surfaces of both sargasso species constituted favorable substrata for the growth of diatom assemblages. [ABSTRACT FROM AUTHOR]

The taxonomic composition of the diatom flora of the Taleghan River and reservoir in Iran is described. The Taleghan River is one of the main tributaries of the Sepid Roud River, which is the second-longest river in Iran (∼ 670 km). Its headwaters are located in the Alborz Mountains in northwestern Iran and discharge into the Caspian Sea (North Iran). The current study was conducted from November 2017 to October 2018. A total of 167 taxa belonging to 49 genera and 27 families were identified. Nitzschia (28 spp.) Navicula (20 spp.), Cymbella (12 spp.), and Gomphonema (10 spp.) were the most abundant genera. The identified taxa can be classified as oligosaprobic to eutrophic and Canonical Correspondence Analysis (CCA) showed that temperature, NO32−, salinity, turbidity, EC, Si, and DO were the most significant environmental variables influencing diatom assemblages across seasons and sites in the river. [ABSTRACT FROM AUTHOR]

To determine the species distribution of an amnesic shellfish poisoning (ASP) toxins-producing diatom Nitzschia navis-varingica outside its current restricted geographical distribution range in Asian coastal waters, samples were collected from two sites of Bootless Bay, located on southwest coast of Papua New Guinea near Port Moresby. A total of twenty-one strains of N. navis-varingica were isolated and the clonal cultures established. The species identity was confirmed by molecular characterization based on the ribosomal DNA markers. The LSU rDNA phylogenetic inference revealed a monophyletic clade of all strains, clustered with N. navis-varingica with high bootstrap supports. ASP toxin production in the strains was investigated by HPLC with fluorescence detection and subsequently confirmed for the representative isolates by LC-MS/MS with multiple reaction monitoring (MRM) mode. All eleven strains from site A showed presence of domoic acid (DA) and isodomoic acid (IB); the toxin quota ranged from 0.70 to 4.63 pg cell−1 (average 2.75 ± 1.26 pg cell−1, n = 11), with the composition of DA and IB of 21 DA: 79 IB. While for strains from site B, four out of ten strains showed presence of DA and IB, with the toxin quota ranged from 1.40 to 3.84 (average 2.57 ± 1.17 pg cell−1, n = 4); the composition was 52 DA: 48 IB. The strains examined in this study were divided into toxic and probably non-toxic groups in ITS2 phylogeny. This represents the first record of domoic acid-producing Nitzschia navis-varingica from Papua New Guinea. [Display omitted] • First recorded finding of the toxic diatom Nitzschia navis-varingica in Papua New Guinea. • Verification of domoic acid and isodomoic acid B in the strains by HPLC and LC-MS/MS. • Confirmation of the two toxin composition types, i.e. domoic acid-isodomoic acid B and only isodomoic acid B. • Taxa of N. navis-varingica were divided into toxic and probably non-toxic groups in ITS2 phylogeny. [ABSTRACT FROM AUTHOR]

Marine diatoms are one of the marine phytoplankton functional groups, with high species diversity, playing important roles in the marine food web and carbon sequestration. In order to evaluate the species-specific responses of coastal diatoms to the combined effects of future ocean acidification (OA) and warming on the coastal diatoms, we conducted a semi-continuous incubation on the large centric diatom Thalassiosira sp. (~30 μm) and small pennate diatom Nitzschia closterium f.minutissima (~15 μm). A full factorial combination of two temperature levels (15 and 20°C) and pCO2 (400 and 1,000 ppm) was examined. The results suggest that changes in temperature played a more important role in regulating the physiology of Thalassiosira sp. and N. closterium f.minutissima than CO2. For Thalassiosira sp., elevated temperature significantly reduced the cellular particulate organic carbon (POC), particulate organic nitrogen (PON), particulate organic phosphate (POP), biogenic silica (BSi), chlorophyll a (Chl a), and protein contents, and the C:N ratio. CO2 only had significant effects on the growth rate and the protein content. However, for the smaller pennate diatom N. closterium f.minutissima , the growth rate, POC production rate, and the C:P ratio significantly increased with an elevated temperature, whereas the cellular POP and BSi contents significantly decreased. CO2 had significant effects on the POC production rate, cellular BSi, POC, and PON contents, the C:P, Si:C, N:P, and Si:P ratios, and sinking rate. The interaction between OA and warming showed mostly antagonistic effects on the physiology of both species. Overall, by comparison between the two species, CO2 played a more significant role in regulating the growth rate and sinking rate of the large centric diatom Thalassiosira sp., whereas had more significant effects on the elemental compositions of the smaller pennate diatom N. closterium f.minutissima. These results suggest differential sensitivities of different diatom species with different sizes and morphology to the changes in CO2/temperature regimes and their interactions. [ABSTRACT FROM AUTHOR]

We report the first occurrence of a diatom species, Nitzschia navis-varingica in the Sea of Marmara. Previously, this species was observed in the Mediterranean Sea in 2016. Samples were collected from the coast of Darıca, Istanbul, Turkey, on 22 June 2021 during a large-scale mucilage event. The species was isolated, cultured under laboratory conditions, and investigated with scanning electron microscopy and light microscopy. [ABSTRACT FROM AUTHOR]

Many marine organisms, especially molluscs, produce mucus, which can be used in several physiological processes, such as locomotion and defence. In addition to utilization for themselves, mollusc mucus may influence intertidal community dynamics. Therefore, the biochemical composition of Onchidium typhae Buchannan, 1800 mucus was investigated. The effects of mucus on the microphytobenthos growth rate, representing the ecological functions of the mucus, were also tested. The results showed that the mucus was mainly composed of water (82.5%), and a large proportion of the organic content in mucus consisted of proteins (40%), followed by carbohydrates (13.33%) and lipids (0.19%). The effects of mucus on microphytobenthos growth were conditional and genus‐specific. Growth of Navicular sp. and Nitzschia sp. significantly responded to different concentrations and incubation times of the slug mucus. Fresh and concentrated mucus inhibited the growth of both species; low mucus concentration and longer incubation time showed a significant increase in the growth rates of both species. However, no effect of mucus on the Thalassiosira sp. growth rate was observed. These effects of mucus on diatom growth are discussed. Moreover, our findings suggested that the intertidal slug O. typhae may act as an intertidal ecosystem engineer, which can facilitate and influence benthic phytoplankton community dynamics. [ABSTRACT FROM AUTHOR]

Lake eutrophication is associated with cyanobacterial blooms. The pennate diatom Nitzschia palea (N. palea) inhibits the growth of the cyanobacterium Microcystis aeruginosa (M. aeruginosa); therefore, increasing the relative abundance of N. palea may contribute to the inhibition of Microcystis blooms. Several studies have demonstrated that blue light irradiation promotes diatom growth and inhibits cyanobacterial growth. In this study, we evaluated the effects of blue light irradiation on N. palea and M. aeruginosa abundance. Monocultures and co‐cultures of N. palea and M. aeruginosa were exposed to blue light and fluorescent light at 32 μmol photons m−2 s−1. The relative abundance of N. palea under fluorescent light decreased gradually, whereas the abundance under blue light was relatively higher (approximately 74% and 98% under fluorescent light and blue light, respectively, at the end of the experiment). The inhibition efficiency of blue light on the growth rate of M. aeruginosa was related to the light intensity. The optimal light intensity was considered 20 μmol photons m−2 s−1 based on the inhibition efficiency of 100%. Blue light irradiation can be used to increase the abundance of N. palea to control Microcystis blooms. Practitioner Points: The effects of blue light irradiation on N. palea abundance was discussed.Monocultures and co‐cultures of N. palea and M. aeruginosa were exposed to blue light and to fluorescent light.The relative abundance of N. palea increased upon irradiation with blue light in co‐culture with M. aeruginosa. [ABSTRACT FROM AUTHOR]

During a biological survey carried out in a high-altitude saline lake of the Bolivian Altiplano and in Türkmenbaba plateau in Sakarya river catchment in Kütahya and Korudere and Havuzdere streams in Marmarean river catchment in Yalova, Turkey, two unknown Nitzschia species were found in various population densities. Detailed light and scanning electron microscopy observations allowed their description as taxa new to Science. Differential diagnostic criteria with respect to similar taxa, together with ecological and biogeographical implications of these findings, are briefly discussed. The most noteworthy feature in N. tortuosa sp. nov. is the pervalvar twist seen at poles, well discernible in scanning electron microscopy (SEM), whereas N. seblae sp. nov. resembles N. tropica but presents broader valves and lower striae and fibulae densities. [ABSTRACT FROM AUTHOR]

The electrochemical behavior of titanium (Ti) was investigated before and after anodic polarization at different potentials in simulated seawater solutions. The results showed that the Ti anodically polarized at 3.2 VSCE was much more stable than those at 0.5 VSCE and the open-circuit potential (OCP), and the passive film formed at the low potentials could be transformed to a more protective film after polarization at the high potential. The polarization at the high anodic potential could effectively enhance the long-term durability of Ti under natural immersion conditions. Nitzschia closterium f. minutissima could only slightly influence the electrochemical behavior of Ti. The film formed at the 3.2 VSCE on Ti appeared to have very limitedly better antifouling performance than those formed at the 0.5 VSCE and OCP. [ABSTRACT FROM AUTHOR]

Harmful effect of nanomaterials on aquatic organisms has accelerated in recent decades due to the growth emission of nanomaterials into water. In the present study, we analysed the toxic effects of TiO2, ZnO and MWCTN on diatoms Nitzschia palea in both individual and a combined way. After a short-term (96 h) exposure, the changes of cell density, chlorophyll a, MDA, SOD, CAT, total protein content and morphological structure were determined. Our results showed that: (1) The growth of N. palea was inhibited with the increase of concentration of nanomaterials; (2) The chlorophyll a content of N. palea was sensitive to these three individual nanomaterials; (3) Low concentration of nanomaterials promoted the MDA content in N. palea, but high concentration inhibited it; (4) The protein content of N. palea increased first and then decreased, indicating that nanomaterial stress inhibited diatom protein synthesis and showed dose-effect relationship; (5) After nanomaterial exposure, the SOD enzyme activity of N. palea was significantly inhibited, the CAT enzyme activity showed significantly decreased after exposure, comparing with control. The results of this study provide data for the study of algae nano-toxicology and provide a theoretical basis for the study of the toxicity of nanomaterials to freshwater microalgae. [ABSTRACT FROM AUTHOR]

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 years of phytoplankton monitoring at the coastal site of the LTER Senigallia-Susak transect, a nitzschioid diatom with morphology matching that of Nitzschia section Nitzschiella (dilated central portion and two long rostra) was frequently observed. In this study, we describe this new species as Nitzschia gobbii sp. nov., combining morphological (transmission electron microscopy and scanning electron microscopy) and molecular (LSU and ITS rDNA) data. The morphology of Nitzschia gobbii makes it easy to confuse with other common species in the Adriatic Sea (Cylindrotheca closterium and Pseudo-nitzschia galaxiae). The partial LSU rDNA sequences of strains of Nitzschia gobbii sp. nov. were resolved in a well-supported clade. In this area, this species has been mainly recorded in spring-summer with a maximum abundance of 3.2 × 106 cells l–1. None of the tested Nitzschia gobbii strains produced domoic acid in detectable amounts. [ABSTRACT FROM AUTHOR]

Phototrophic biofilms are exposed to multiple stressors that can affect them both directly and indirectly. By modifying either the composition of the community or the physiology of the microorganisms, press stressors may indirectly impact the ability of the biofilms to cope with disturbances. Extracellular polymeric substances (EPS) produced by the biofilm are known to play an important role in its resilience to various stresses. The aim of this study was to decipher to what extent slight modifications of environmental conditions could alter the resilience of phototrophic biofilm EPS to a realistic sequential disturbance (4-day copper exposure followed by a 14-day dry period). By using very simplified biofilms with a single algal strain, we focused solely on physiological effects. The biofilms, composed by the non-axenic strains of a green alga (Uronema confervicolum) or a diatom (Nitzschia palea) were grown in artificial channels in six different conditions of light intensity, temperature and phosphorous concentration. EPS quantity (total organic carbon) and quality (ratio protein/polysaccharide, PN/PS) were measured before and at the end of the disturbance, and after a 14-day rewetting period. The diatom biofilm accumulated more biomass at the highest temperature, with lower EPS content and lower PN/PS ratio while green alga biofilm accumulated more biomass at the highest light condition with lower EPS content and lower PN/PS ratio. Temperature, light intensity, and P concentration significantly modified the resistance and/or recovery of EPS quality and quantity, differently for the two biofilms. An increase in light intensity, which had effect neither on the diatom biofilm growth nor on EPS production before disturbance, increased the resistance of EPS quantity and the resilience of EPS quality. These results emphasize the importance of considering the modulation of community resilience ability by environmental conditions, which remains scarce in the literature. [ABSTRACT FROM AUTHOR]

In this article we describe Nitzschia anatoliensis Górecka, Gastineau & Solak sp. nov., an example of a diatom species inhabiting extreme habitats. The new species has been isolated and successfully grown from the highly alkaline Van Lake in East Turkey. The description is based on morphology (light and scanning electron microscopy), the sequencing of its organellar genomes and several molecular phylogenies. This species could easily be overlooked because of its extreme similarity to Nitzschia aurariae but molecular phylogenies indicate that they are only distantly related. Furthermore, molecular data suggest that N. anatoliensis may occur in several alkaline lakes of Asia Minor and Siberia, but was previously misidentified as Nitzschia communis. It also revealed the very close genetic proximity between N. anatoliensis and the endosymbiont of the dinotom Kryptoperidinium foliaceum, providing additional clues on what might have been the original species of diatoms to enter symbiosis. [ABSTRACT FROM AUTHOR]

RESUMO Criptógamos do Parque Estadual das Fontes do Ipiranga, São Paulo, SP. Algae 46: Bacillariophyceae (Bacillariaceae). O levantamento florístico da família Bacillariaceae (Bacillariophyceae) foi realizado para a área do Parque Estadual das Fontes do Ipiranga, São Paulo, Brasil, com base em 28 unidades amostrais. O exame do material do ponto de vista morfológico foi realizado ao microscópio óptico após oxidação e confecção de lâminas permanentes. Quatro gêneros, 27 espécies e três variedades que não são as típicas de suas respectivas espécies foram identificados. Nove desses táxons foram registrados pioneiramente para o Estado de São Paulo [Nitzschia acicularis Hustedt, N. acidoclinata Lange-Bertalot, N. clausii Hantzsch, N. dissipata (Kützing) Rabenhorst, N. intermedia Hantzsch, N. palea (Kützing) W. Smith var. tenuirostris Grunow, N. subacicularis Hustedt, Tryblionella debilis Arnott ex O’Meara e T. victoriae Grunow] e dois para o Brasil [Grunowia solgensis (Cleve-Euler) Aboal e N. dissipata (Kützing) Rabenhorst var. borneensis Kützing]. Todo material foi identificado com base em amostras populacionais, descrito através de suas características morfológicas e medidas e ilustrado por fotomicrografias.

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. [ABSTRACT FROM AUTHOR]

A near-complete diploid nuclear genome and accompanying circular mitochondrial and chloroplast genomes have been assembled from the elite commercial diatom species Nitzschia inconspicua. The 50 Mbp haploid size of the nuclear genome is nearly double that of model diatom Phaeodactylum tricornutum, but 30% smaller than closer relative Fragilariopsis cylindrus. Diploid assembly, which was facilitated by low levels of allelic heterozygosity (2.7%), included 14 candidate chromosome pairs composed of long, syntenic contigs, covering 93% of the total assembly. Telomeric ends were capped with an unusual 12-mer, G-rich, degenerate repeat sequence. Predicted proteins were highly enriched in strain-specific marker domains associated with cell-surface adhesion, biofilm formation, and raphe system gliding motility. Expanded species-specific families of carbonic anhydrases suggest potential enhancement of carbon concentration efficiency, and duplicated glycolysis and fatty acid synthesis pathways across cytosolic and organellar compartments may enhance peak metabolic output, contributing to competitive success over other organisms in mixed cultures. The N. inconspicua genome delivers a robust new reference for future functional and transcriptomic studies to illuminate the physiology of benthic pennate diatoms and harness their unique adaptations to support commercial algae biomass and bioproduct production. [ABSTRACT FROM AUTHOR]

Tidal flat is often the dominant habitat type in US Pacific Northwest (PNW) estuaries. This research examined environmental factors that explain the spatial patterns of microphytobenthos (MPB) biomass and community structure in a PNW estuary with complex nutrient dynamics. MPB biomass, individual species abundances, diatom community metrics, and diatom community structure were strongly correlated with distance from the estuary mouth, salinity, substrate composition, and pore water-soluble reactive phosphorus (SRP). The microphytobenthos was dominated by diatoms and diatom diversity and species richness were negatively associated with salinity, substrate sand content, and pore water SRP. Diatom community structure varied with estuary position, with the epipsammic taxa Catenula adhaerens, Opephora spp. 1, and Planothidium delicatulum dominating the assemblage at sites near the estuary mouth and epipelic taxa, such as Nitzschia frustulum and Nitzschia palea, being more abundant at sites in the middle and upper estuary. Distance from the estuary mouth and salinity were the most important predictors of diatom assemblage structure, based on CCA analysis. MPB biomass was highest at sites in the lower estuary, characterized by higher salinities, SRP, and substrate sand composition. Pore water nitrogen and surrounding land use were not important predictors of MPB biomass or community structure. We attribute our findings to the nutrient dynamics of Yaquina estuary, which is high in nutrients due to both coastal upwelling and watershed-derived nitrate and exhibits an increasing gradient of phosphorus towards the estuary mouth. [ABSTRACT FROM AUTHOR]

Graphene based nanomaterials (GBMs) have been drawing the attention of the scientific communities these past years. As their market is increasing every year, their potential environmental and health risk are to be assessed. As microbial communities represent the basis of every ecosystem, it is essential to evaluate the risks of GBMs on these communities. The effects of GBMs on bacteria has been widely studied, while the effects on phototrophic species are less represented. In this study, the diatom Nitzschia palea was exposed to graphene oxide (GO) and reduced graphene oxide (rGO), at 0.1, 1 and 10 mg L−1. rGO had no effect on the diatom while GO induced an increase in growth, indicating the importance of the oxidation rate in the observed effect. Further results showed that shading effect of GO was countered by increased chlorophyll contents and by the accumulation of GO into the biofilm. This "sticking" mechanism increased the proximity between the biofilm and the GO, which might favour interactions between GO and the biofilm. These interactions led to the increase of defects and the reduction of GO. In addition, increased heterotrophic activity was suggested. To our knowledge, no diatom before Nitzschia palea has been shown to enhance its growth in presence of a GBM, but also capable to modify it. These results demonstrate the potential of GBMs, and in particular those with higher oxidation rates, to disrupt the contribution of the diatom Nitzschia palea to carbon cycling, which could have broader consequences at ecosystem scale. [Display omitted] [ABSTRACT FROM AUTHOR]

The use of traditional antifouling techniques in coatings leads to an increase in "ineffective" antifouling agents. Polyurethane (PU) can be easily customized by adding functional segments or anchoring antifouling agents to enhance its antifouling properties and reduce the "ineffective" content. In this study, inspired by the ancient Macedonian phalanx's efficient combat strategy of combining spears and bucklers, a series of environmental benzothiazole-silicon-contained polyurethane (PBTS) antifouling coatings with in-situ migration property in water was prepared. The content and length of the benzothiazole-modified siloxane functional chain segment were modified to improve its antifouling properties. The PBTS coatings can realize adhesion inhibition ratios up to 88.2 % and 96.3 % for Nitzschia closterium and Halamphora sp., a comprehensive antibacterial ratio of 70 % and good mussel adhesion inhibition capabilities. Importantly, the PBTS10-1 coating showed an outstanding performance in the field test. With this strategy, efficient antifouling "combat" was achieved and a promising environmental PDMS-modified PU with good adhesion strength was suggested. [Display omitted] • This work was inspired by the efficient Macedonian phalanx. • BTS were synthesized to improve antifouling properties with in-situ migration. • PBTS coatings exhibited excellent antifouling properties in the field test. [ABSTRACT FROM AUTHOR]