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The addition of Navicula sp. to shrimp nurseries can improve the growth of Penaeus vannamei reared in biofloc systems. However, the contribution of microalgae to the biofloc formation and the effective contribution to shrimp nutrition remain unknown. In this study, Navicula sp. was added to biofloc nursery systems of P. vannamei at distinct time frequencies for evaluating its nutritional contribution to shrimp growth. Nursery rearing was carried out in bioflocs for 35 days at a stocking density of 3000 post-larvae m−3. Shrimp were fed using a commercial feed plus fresh culture of Navicula sp. at different frequencies: no addition of Navicula sp. (WN – control), the addition of 10 × 104 cells mL−1 of the diatom every 5, 10 and 15 days (N5, N10 and N15, respectively). Food sources relative contribution to P. vannamei development was estimated using a Bayesian mixture model. The isotopic discrimination factor (Δ15N and Δ13C) for each food source was determined experimentally. After 35 days of culture, survival (∼93 %) was similar across all treatments but there was a significant difference in weight gain and feed conversion ratio. The N10 treatment (0.50 ± 0.05 g, 0.99 ± 0.01) exhibited better growth parameters when compared to the WN treatment (0.33 ± 0.07 g, 11.46 ± 0.30). Biofloc was the food source most assimilated by shrimp followed by Navicula sp. and commercial feed. Contribution of Navicula sp. was higher in the N5 treatment. In the treatments with diatom addition, an inverse correlation was observed between the relative contributions of biofloc and Navicula sp., indicating that Navicula sp. is not in the biofloc composition, but it is directly consumed by P. vannamei post-larvae. Biofloc and Navicula sp. exhibited larger contributions to the growth of shrimp, reinforcing the importance of natural food sources to the aquaculture of P. vannamei post-larvae. [ABSTRACT FROM AUTHOR]

The objective of this study was to explore the environmental factors having the greatest influence on the distribution and abundance of epipelic diatom species in different wetlands in southern Spain. We previously defined four groups of conductivity categories: fresh (< 0.8 mS cm−1), oligosaline (< 8 mS cm−1), mesosaline (8–30 mS cm−1) and eusaline (> 30 mS cm−1). A dbRDA analysis performed on a subset of 36 of the 53 wetlands, using a total of 25 environmental variables, showed that five environmental variables (conductivity, pH, wetland area, silicates, and total suspended solids) were the best explanatory variables for the diatom assemblage, with conductivity being the main explanatory variable. Nonmetric multidimensional scaling (nMDS) analysis performed on the set of 53 wetlands revealed significant differences in diatom composition among the four conductivity groups. The key species in the eusaline group were Tryblionella pararostrata, Halamphora sp.1 and Cocconeis euglypta, whereas in the mesosaline and oligosaline group, these were Navicula veneta, Tryblionella hungarica and Nitzschia inconspicua. Finally, in the fresh group dominated Achnanthidium minutissimum, Navicula veneta and Gomphonema exilissimum. This study on epipelic diatoms can therefore contribute to the knowledge of these organisms in a European region with a high diversity of wetland typologies. [ABSTRACT FROM AUTHOR]

Given the limited understanding of species diversity and ecological preferences of diatoms of the genus Navicula in spring ecosystems, herein we present and describe as species new to science, Navicula aquaesuavis Lange-Bert., Levkov, Cid-Rodríguez, A.A.Saber and Cantonati sp. nov. This species was collected from a mountain spring located above the tree line at 1613 m a.s.l. in the Northern Apennines. The Fontana del Vescovo (Bishop's spring), which is the locus classicus of the new species, has a low conductivity (60–70 µS cm−1), temperature of ca. 5 °C, circumneutral pH (7.3–7.5), relatively low nitrate (ca. 1 mg L−1), and also suffered from a discharge reduction from 1 to 0.1 L s−1 from 2011 to 2023. The putative new species was confirmed by a second finding in Northern Macedonia, and we thoroughly document this second population as well. We seized the opportunity to describe this new Navicula and review the global literature on the diatom genus Navicula in spring ecosystems. Using the results of this review and our own databases on springs and wells in central Europe and Egypt, we discuss the main Navicula species and their environmental preferences in spring habitats. [ABSTRACT FROM AUTHOR]

The influence of microalgae on the formation of associated prokaryotic assemblages in halophilic microbial communities is currently underestimated. The aim of this study was to characterize shifts in prokaryotic assemblages of halophilic microalgae upon their transition to laboratory cultivation. Monoalgal cultures belonging to the classes Chlorodendrophyceae, Bacillariophyceae, Trebouxiophyceae, and Chlorophyceae were isolated from habitats with intermediate salinity, about 100 g/L, nearby Elton Lake (Russia). Significant changes were revealed in the structure of algae-associated prokaryotic assemblages, indicating that microalgae supported sufficiently diverse and even communities of prokaryotes. Despite some similarities in their prokaryotic assemblages, taxon-specific complexes of dominant genera were identified for each microalga species. These complexes were most different among Alphaproteobacteria, likely due to their close association with microalgae. Other taxon-specific bacteria included members of phylum Verrucomicrobiota (Coraliomargarita in assemblages of Navicula sp.) and class Gammaproteobacteria (Salinispirillum in microbiomes of A. gracilis). After numerous washings of algal cells, only alphaproteobacteria Marivibrio remained in all assemblages of T. indica, likely due to a firm attachment to the microalgae cells. Our results may be useful for further efforts to develop technologies applied for industrial cultivation of halophilic microalgae and for developing approaches to obtain new prokaryotes with a microalgae-associated lifestyle. [ABSTRACT FROM AUTHOR]

Diatoms from two high-altitude creeks in Bosnia and Herzegovina were studied from June 2005 to May 2007. Along with diatoms, water temperature, pH, conductivity and nutrients were also monitored, indicating stable physical and chemical conditions, low organic loading and oligotrophy. A total of 130 diatom taxa (species and subspecies) were recorded. Mostly oligotrophic and oligo-mesotrophic indicators were recorded in the creeks. The most abundant genera were Eunotia (15), Pinnularia (13), Gomphonema (10) and Navicula (9). The following taxa were recorded in all samples: Cymbopleura naviculiformis (Auerswald ex Heiberg) Krammer, Decussiphycus hexagonus (Torka) Guiry & Gandhi, Eunotia arcus Ehrenberg, Frustulia vulgaris (Thwaites) De Toni, Pinnularia borealis Ehrenberg and Pinnularia viridis (Nitzsch) Ehrenberg. Five new diatom taxa for Bosnia and Herzegovina were recorded. According to the German Red List, the largest number of taxa (34 for creek 1 and 27 for creek 2) were identified as declining taxa and 12 taxa as endangered ones (three for creek 1 and nine for creek 2). The high species richness and the presence of diatom taxa included on the German Red List underline the importance of protecting and preserving this important biotope. [ABSTRACT FROM AUTHOR]

Despite more than 100 years of research, a number of questions concerning the evolution of the post-glacial connection between Lake Ladoga, the largest European lake, and the Baltic Sea remain unanswered. In particular, the location and chronological frames of the paleo-outlet from Lake Ladoga in the Holocene remain debatable. Paleolimnological studies were performed in small lakes in the northern part of the Karelian Isthmus (NW Russia), where the outlet from Lake Ladoga, the Heinjoki Strait, is thought to have existed until the lake drained to the south due to the tilting of its basin. The presence of the indicative "Ladoga species" (e.g., Aulacoseira islandica, Achnanthes joursacense, Cymbella sinuata, Ellerbeckia arenaria, Navicula aboensis, N. jaernefeltii, N. jentzschii, etc.) in the diatom assemblages is used as evidence for the influence of Lake Ladoga during the accumulation of coarse-grained sediments at the bottom of the ancient channel. It also confirms the functioning of the hypothetical northern local branch of the strait. Decreased abundances of the "Ladoga species" and the onset of the accumulation of fine-grained sediments suggest that the water discharge via this paleo-outlet rapidly reduced starting from ca. 4100 cal BP. The termination of the functioning of the Heinjoki Strait is recorded as an abrupt disappearance of the indicative taxa from the diatom record. This was dated to ca. 3500–3200 cal BP, which corresponds to the estimated ages of the birth of the River Neva, the present outlet from Lake Ladoga. [ABSTRACT FROM AUTHOR]

Biofouling on marine surfaces causes immense material and financial harm for maritime vessels and related marine industries. Previous reports have shown the effectiveness of amphiphilic coating systems based on poly(dimethylsiloxane) (PDMS) against such marine foulers. Recent studies on biofouling mechanisms have also demonstrated acidic microenvironments in biofilms and stronger adhesion at low-pH conditions. This report presents the design and utilization of amphiphilic polymer coatings with buffer functionalities as an active disruptor against four different marine foulers. Specifically, this study explores both neutral and zwitterionic buffer systems for marine coatings, offering insights into coating design. Overall, these buffer systems were found to improve foulant removal, and unexpectedly were the most effective against the diatom Navicula incerta. [ABSTRACT FROM AUTHOR]

Periphytic algal colonization is common in aquatic systems, but its interspecific competition remains poorly understood. In order to fill the gap, the process of periphytic algal colonization in the Middle Route of the South to North Water Diversion Project was studied. The results showed that the process was divided into three stages: the initial colonization stage (T1, 3–6 days), community formation stage (T2, 12–18 days) and primary succession stage (T3, 24–27 days). In T1, the dominant species were Diatoma vulgaris (Bory), Navicula phyllepta (Kützing) and Fragilaria amphicephaloides (Lange-Bertalot) belonging to Heterokontophyta; these species boasted wide niche widths (NWs), low niche overlap (NO) and low ecological response rates (ERRs). In T2, the dominant species were Diatoma vulgaris, Cymbella affinis (Kützing), Navicula phyllepta, Fragilaria amphicephaloides, Gogorevia exilis (Kützing), Melosira varians (C.Agardh), Phormidium willei (N.L.Gardner) and Cladophora rivularis (Kuntze). These species displayed wider NWs, lower NO, and lower ERRs than those in T1. In T3, the dominant species were Diatoma vulgaris, Cymbella affinis, Navicula phyllepta, Fragilaria amphicephaloides, Achnanthes exigu (Grunow), etc. Among them, Heterokontophyta such as Diatoma vulgaris and Cymbella affinis had a competitive advantage based on NWs and ERRs. Cyanobacteria like Phormidium willei lost their dominant status due to the narrower NW and the increased NO. It could be concluded the interspecific competition became fiercer and shaped the colonization process; this study will be helpful in understanding the colonization of periphytic algal communities. [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]

This study aimed to assess the ecological health of a RAMSAR site lake by leveraging diatoms as ecological indicators. Utilizing six trophic and four saprobic indices, we evaluate the lake's ecological status. Monthly samples were collected from five sites between June 2014 and May 2015. Our findings revealed that the lake exhibited hypereutrophic characteristics according to TN and TP concentrations, as well as trophic state indices, except TIDL. Notably, the TIVD index showed a significant correlation with TN and TP, while SISla correlated significantly with TN. Despite the substantial organic matter load, our analysis positioned the lake at a beta mesosaprobic level with moderate ecological status across three saprobic indices. Interestingly, the annual average dissolved oxygen (DO) concentration classified the lake water as Class I in terms of water quality. The moderate saprobic index values suggest efficient organic matter oxidation, potentially influenced by high DO concentrations in the lake littoral. Our study underscores the importance of integrating trophic and saprobic indices to comprehensively evaluate ecosystem health and ecological status in shallow eutrophic lakes, offering insights into nutrient enrichment and organic pollution load, respectively. [ABSTRACT FROM AUTHOR]

The sea cucumber Holothuria inornata is a species whose populations are at risk. This study aims to investigate its reproduction, embryonic and larval development, and the settlement of H. inornata under an algae-based diet. Twenty breeders were utilized, which underwent a 1.5-h desiccation followed by a thermal shock (27 to 32 °C). Embryonic development stage was recorded, and from the auricularia larval stage, three treatments were evaluated: A: Chaetoceros muelleri and Isochrysis galbana (1:1 ratio); B: C. muelleri, I. galbana, Tetraselmis suecica, and Pavlova lutheri (1:1:1:1 ratio); and C: Chaetoceros muelleri, I. galbana, T. suecica, P. lutheri, Navicula sp. (LPU-6) (1:1:1:1:1 ratio), with a larval density of 100 larvae L−1 in triplicate. The embryonic development in H. inornata lasts for 3 days, five larval stages were recorded: (1) Auricularia (days 3–8, 300 to 520 μm), (2) late auricularia (days 8–11, 520 to 670 μm), (3) doliolaria (days 11–13, 460 to 550 μm), (4) late doliolaria (days 13–16, 400 to 440 μm), and (5) pentacula (days 15–19, 650 to 900 μm). The post-settlement survival rate was 0% under treatment A, 2.38 ± 0.16% under treatment B, and 3.79 ± 0.41% under treatment C. Based on these findings, we concluded that H. inornata specie spawn through a combined desiccation-thermal shock process with a larval period of up to 19 days, and subsequently produce juvenile individuals in captivity with a varied microalgae diet. [ABSTRACT FROM AUTHOR]

Diatoms are key primary producers across marine, freshwater, and terrestrial ecosystems. They are responsible for photosynthesis and secondary production that, in part, support complex food webs. Diatoms can produce phytochemicals that have transtrophic ecological effects which increase their competitive fitness. Polyunsaturated aldehydes (PUAs) are one class of diatom-derived phytochemicals that are known to have allelopathic and anti-herbivory properties. The anti-herbivory capability of PUAs results from their negative effect on grazer fecundity. Since their discovery, research has focused on their production by pelagic marine diatoms, and their effects on copepod egg production, hatching success, and juvenile survival and development. Few investigations have explored PUA production by the prolific suite of benthic marine diatoms, despite their importance to coastal trophic systems. In this study, we tested eight species of benthic diatoms for the production of the bioactive PUAs 2,4-heptadienal, 2,4-octadienal, and 2,4-decadienal. Benthic diatom species were isolated from the Salish Sea, an inland sea within the North Pacific ecosystem. All species were found to be producers of at least two PUAs in detectable concentrations, with five species producing all three PUAs in quantifiable concentrations. Our results indicate that production of PUAs from Salish Sea benthic diatoms may be widespread, and thus these compounds may contribute to benthic coastal food web dynamics through heretofore unrecognized pathways. Future studies should expand the geographic scope of investigations into benthic diatom PUA production and explore the effects of benthic diatoms on benthic consumer fecundity. [ABSTRACT FROM AUTHOR]

Benthic diatoms have been studied in different areas of the Mediterranean Sea, but no data have been available for Israeli coastal waters until the present time. In this work, the composition, ecology, and phytogeography of diatoms of the macrophytes epiphyton are presented for the first time. Altogether, 85 diatom taxa were found among the epiphyton of 25 species of green, brown, and red macroalgae from the Israeli coast between March and May of 2021. These diatoms represent three classes, 17 orders, 26 families, and 41 genera. The taxonomic composition, ecology, and phytogeography of species are discussed. The distribution of diatoms are compared to that of other macrophytes and anthropogenic loads across the shoreline. The dominant species are given. Ecological characteristics and abundance in communities of revealed species are represented and statistically analyzed. The index of saprobity S varies between 1.69–2.71. Sites that stressed aquatic communities are indicated. The influence of the anthropogenic loads on the coastal territories is defined as a major factor that stimulated diatom species richness. Sites with anthropogenic stress for aquatic communities are indicated. Based on the composition of bioindicators, it is concluded that the section of the Israeli coast studied is oligo-mesotrophic compared to the eutrophic Gulf of Tartus. [ABSTRACT FROM AUTHOR]

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

Gigatonne-scale atmospheric carbon dioxide removal (CDR) will almost certainly be needed to supplement the emission reductions required to keep global warming between 1.5–2 °C. Ocean alkalinity enhancement (OAE) is an emerging marine CDR method with the addition of pulverised minerals to the surface ocean being one widely considered approach. A concern of this approach is the potential for dissolution products released from minerals to impact phytoplankton communities. We conducted an experiment with 10 pelagic mesocosms (M1–M10) in Raunefjorden, Bergen, Norway, to assess the implications of simulated silicate- and calcium-based mineral OAE on a coastal plankton community. Five mesocosms (M1, M3, M5, M7, and M9) were enriched with silicate (∼ 75 µ mol L -1 Na2SiO3), alkalinity along a gradient from 0 to ∼ 600 µ mol kg -1 , and magnesium in proportion to alkalinity additions. The other five mesocosms (M2, M4, M6, M8, M10) were enriched with alkalinity along the same gradient and calcium in proportion to alkalinity additions. The experiment explored many components of the plankton community, from microbes to fish larvae, and here we report on the influence of simulated mineral based OAE on diatom silicification. Macronutrients (nitrate and phosphate) limited silicification at the onset of the experiment until nutrient additions on day 26. Silicification was significantly greater in the silicate-based mineral treatment, with all genera except Cylindrotheca displaying an increase in silicification as a result of the increased concentration of dissolved silicate. In contrast to the effect of differences in dissolved silicate concentrations between the two mineral treatments, increases in alkalinity only influenced the silicification of two genera, Pseudo-nitzschia and Nitzschia. The four other genera (Arcocellulus, Cylindrotheca, Skeletonema, and Thalassiosira) investigated here displayed no significant changes in silicification as a result of alkalinity increases between 0 and 600 µ mol kg -1 above natural levels. In summary, our findings illustrate that the enhancement of alkalinity via simulated silicate- and calcium-based methods has limited genus-specific impacts on the silicification of diatoms. This research underscores the importance of understanding the full breadth of different OAE approaches, their risks, co-benefits, and potential for interactive effects. [ABSTRACT FROM AUTHOR]

Many diatoms form long chains and the distribution of chain lengths within a species depends on several environmental factors, among them grazing risk. Larger grazers, such as copepods, efficiently handle and ingest even very long chains but are less efficient with individual cells, whereas most smaller grazers are unable to feed on chains exceeding a few cells in length. Copepod cues make several species shorten their chain length, and theory predicts that cues from small grazers should induce increased, but this remains to be tested, despite the importance of diatoms in marine food webs. Here, we expose three species of chain‐forming diatoms, Skeletonema marinoi, Chaetoceros affinis, and Thalassiosira rotula to cues from various actively feeding micrograzers and record their response. The effect of grazer presence on chain length varies depending on both the type of grazer and the diatom species. For example, S. marinoi increased its chain length when exposed to grazing cues from the heterotrophic dinoflagellate Gyrodinium dominans and the ciliate Euplotes sp. but not to a copepod nauplii (Temora longicornis). C. affinis also responded to cues from grazing G. dominans by increasing chain length, and the response increased with exposure time. Finally, T. rotula did not respond to grazing cues from G. dominans, but rather inhibited the dinoflagellates' ability to feed, presumably through the release of chemical compounds. Our results suggest that some chainforming diatoms can sense and appropriately respond to fast‐growing micrograzers, thus contributing to the success of diatoms in marine environments. [ABSTRACT FROM AUTHOR]

In this article, the history and taxonomy of Placoneis gastrum, the type species of the genus Placoneis, was discussed. We investigated the structure of pore occlusions in Placoneis and related genera. As a result, we propose a new classification for tectulum-like types of pore occlusions. The new classification is congruent with previously-published and newly-constructed phylogenies based on molecular data. Based on the different structures of the pore occlusions, species of Placoneis are transferred to Witkowskia gen. nov. Hence, 168 new combinations are introduced. A new diatom species, with a similar morphology to Placoneis flabellata, was discovered in Bắc Kạn Province, Vietnam. It is described in this article as Chudaevia densistriata sp. nov. Placoneis flabellata is transferred to Chudaevia gen. nov. We also illustrate Placoneis flabellata herein and compare it to Chudaevia densistriata sp. nov. An unknown diatom, similar to Placoneis coloradensis, was discovered in Chukotka, Russia. It is introduced as Placoneis elinae sp. nov. below. Additionally, we discuss the distribution of some species of Witkowskia gen. nov. and Chudaevia gen. nov. [ABSTRACT FROM AUTHOR]

Diatoms are important primary producers in marine and freshwater environments, but little is known about the signalling mechanisms they use to detect changes in their environment. All eukaryotic organisms use Ca2+ signalling to perceive and respond to environmental stimuli, employing a range of Ca2+-permeable ion channels to facilitate the movement of Ca2+ across cellular membranes. We investigated the distribution of different families of Ca2+ channels in diatom genomes, with comparison to other members of the stramenopile lineage. The four-domain voltage-gated Ca2+ channels (Cav) are present in some centric diatoms but almost completely absent in pennate diatoms, whereas single-domain voltage-gated EukCatA channels were found in all diatoms. Glutamate receptors (GLRs) and pentameric ligand-gated ion channels (pLGICs) also appear to have been lost in several pennate species. Transient receptor potential (TRP) channels are present in all diatoms, but have not undergone the significant expansion seen in brown algae. All diatom species analysed lacked the mitochondrial uniporter (MCU), a highly conserved channel type found in many eukaryotes, including several stramenopile lineages. These results highlight the unique Ca2+-signalling toolkit of diatoms and indicate that evolutionary gains or losses of different Ca2+ channels may contribute to differences in cellular-signalling mechanisms between species. [ABSTRACT FROM AUTHOR]

Background and aims – Small-celled araphid diatoms form an important part of the diatom flora in our rivers and lakes. Although several of these species are frequently reported, their correct taxonomic identity is often obscured due to a lack of good knowledge of the original (type) material. Material and methods – Several historical (nineteenth century) original samples were retrieved from different European and North American diatom collections. The samples have been analysed using light (LM) and scanning electron microscopy (SEM). Key results – Staurosirella crux comb. nov., based on Ehrenberg’s Navicula crux, proved to be the oldest valid name for Staurosirella harrisonii, the latter now being considered a younger synonym. A new European species, S. neorhomboides sp. nov., is described to replace the name S. rhomboides, now considered a younger synonym of S. leptostauron. The North American populations of S. rhomboides and S. martyi differ sufficiently from the type populations and are described as new species: S. moralesii sp. nov. and S. manoyloviana sp. nov. The new combination Staurosirella informis comb. nov. is proposed for a taxon described in 1856 from the French Pyrenees as Odontidium informe. Staurosirella leptostauron turns out to be insufficiently described and is now documented for further use. Conclusion – The analysis of the original (type) material corrected several taxonomic errors and better characterised the morphology of several commonly observed Staurosirella species. [ABSTRACT FROM AUTHOR]

A novel monoraphid diatom species, Cocconeis crisscrossis You, Yu, Kociolek & Wang, sp. nov. is examined and described from the Qingyi River and Maolan Nature Reserve of southern China. The morphological description is based on light microscopy and scanning electron microscopy observations and the new species is compared with similar taxa in this genus. The characteristics unique to Cocconeis crisscrossis sp. nov. include its central area extending irregularly to both sides, it having closed valvocopulae with heavily silicified fimbriate margins and poles of the valvocopulae have 'sword-shaped' siliceous extensions. These features differentiate this new species from others in the genus. This new species was found in alkaline waterbodies, including streams, waterfall and ponds. It was usually found as an epiphyte on the stones; however, it was present on other substrates such as mosses. [ABSTRACT FROM AUTHOR]

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The current article describes Navicula vanseea sp. nov., a new species of diatom from Lake Van, a highly alkaline lake in Eastern Anatolia (Türkiye). The description is based on light and scanning electron microscopy performed on two monoclonal cultures. The complete nuclear rRNA clusters and plastid genomes have been sequenced for these two strains and the complete mitogenome for one of them. The plastome of both strains shows the probable loss of a functional ycf35 gene. They also exhibit two IB4 group I introns in their rrl, each encoding for a putative LAGLIDADG homing endonuclease, with the first L1917 IB4 intron reported amongst diatoms. The Maximum Likelihood phylogeny inferred from a concatenated alignment of 18S, rbcL and psbC distinguishes N. vanseea sp. nov. from the morphologically similar species Navicula cincta and Navicula microdigitoradiata. [ABSTRACT FROM AUTHOR]

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]

River toxic metal (TM) pollution is a serious challenge of present-day Iran, given that the majority of national developments are situated close to rivers. In this research, we measured and compared physicochemical quality properties, algae chlorophyll, carotenoid, and allophycocyanin contents, bioaccumulation factor (BAF), sediment quality indices, and the concentrations of Cd, As, and Pb in both sediment and algae samples across four seasons and at six reference stations along the Zayandeh-Rood River in Central Iran. The most abundant species were Spirogyra abbreviata, Spirogyra adnata, Characium acuminatum, and Navicula sp. The mean concentrations of TMs (mg/kg) were as follows: Pb(21.07) > As(5.46) > Cd(0.98) in sediment and Pb(25.99) > As(6.18) > Cd(0.85) in algae, revealing a similar pattern. The correlation coefficients between algae and sediment TMs were mostly positive with BAF > 1 which indicate the ecological implications of algae as bioaccumulators of these TMs. The lack of significant correlations between algae characteristics and the accumulation of TMs can be attributed to their threshold tolerance and the use of a multi-species analysis. Based on sediment quality indices, the river was identified as being highly polluted with Cd. This pollution can be traced back to the uneven distribution of various anthropogenic activities along the river's course, especially agricultural practices and steel manufacturing plants. As a result, there is a consistent but progressively increasing distribution and accumulation of TMs downstream. These findings emphasize the critical need for continuous monitoring of TMs in both sediment and algae to safeguard the health of the ecosystem. [ABSTRACT FROM AUTHOR]

With the continuous development of space station construction, space ecosystem research has attracted increasing attention. However, the complicated responses of different candidate plants and algae to radiation stress remain unclear. The present study, using integrated physiologic and proteomic analyses, was carried out to reveal the molecular mechanism of Navicula sp. in response to ultraviolet (UV) irradiation stress. Under 12~24 h of high-dose UV irradiation conditions, the contents of chlorophyll and soluble proteins in Navicula sp. cells were significantly higher than those in the control and 4~8 h of low-dose UV irradiation groups. The activity of catalase (CAT) increased with the extension of irradiation time, and the activity of superoxide dismutase (SOD) decreased first and then increased. Furthermore, differential volcano plot analysis of the proteomic data of Navicula sp. samples found only one protein with a significant difference. Differential protein GO analysis unveiled that UV irradiation can activate the antioxidant system of Navicula sp. and further impact photosynthesis by affecting the photoreaction and chlorophyll synthesis of Navicula sp. The most significant differences in KEGG pathway analysis were also associated with photosynthesis. The above results indicate that Navicula sp. has good UV radiation resistance ability by regulating its photosynthetic pigment content, photosynthetic activity, and antioxidant system, making it a potential candidate for the future development of space ecosystems. [ABSTRACT FROM AUTHOR]

The loose‐equilibrium concept (LEC) predicts that ecological assemblages change transiently but return towards an earlier or average structure. The LEC framework can help determine whether assemblages vary within expected ranges or are permanently altered following environmental change.Long‐lived, slow‐growing animals typically respond slowly to environmental change, and their assemblage dynamics may respond over decades, which transcends most ecological studies. Unionid mussels are valuable for studying dynamics of long‐lived animals because they can live >50 years and occur in dense, species‐rich assemblages (mussel beds). Mussel beds can persist for decades, but disturbance can affect species differently, resulting in variable trajectories according to differences in species composition within and among rivers.We used long‐term data sets (10–40 years) from seven rivers in the eastern United States to evaluate the magnitude, pace and directionality of mussel assemblage change within the context of the LEC.Site trajectories varied within and among streams and showed patterns consistent with either the LEC or directional change. In streams that conformed to the LEC, rank abundance of dominant species remained stable over time, but directional change in other streams was driven by changes in the rank abundance and composition of dominant species.Characteristics of mussel assemblage change varied widely, ranging from those conforming to the LEC to those showing strong directional change. Conservation approaches that attempt to maintain or create a desired assemblage condition should acknowledge this wide range of possible assemblage trajectories and that the environmental factors that influence those changes remain poorly understood. [ABSTRACT FROM AUTHOR]

Raygoza-Alcantar, L.N.; Vázquez, G., and Rodríguez-Zaragoza, F.A., 2024. Spatiotemporal relationship between diatom diversity and environmental gradients at La Mancha coastal lagoon (Veracruz, Mexico). Journal of Coastal Research, 40(2), 366–381. Charlotte (North Carolina), ISSN 0749-0208. This study analyzed the composition and distribution of diatoms in the La Mancha tropical coastal lagoon, Veracruz, Mexico, under different environmental conditions. Water samples were collected from the surface and bottom of the lagoon at five sites during the "nortes" (cold winter fronts), dry, and rainy seasons. The physical and chemical variables of the lagoon water were also analyzed. Diatom taxa were identified and quantified. Sixty-five taxa were determined and classified according to functional groups. Sites 1 and 2 were considered potential sources of nutrients and folin phenol active substances (FPAS). In addition, two horizontal gradients were observed. The first concerned nutrient concentration, which increased in the area of the mouth of the Caño Grande River and decreased towards the bar. The second was a salinity gradient characterized by high values in the area of the bar and decreasing values towards the river mouth. Diatom richness and diversity were higher in the areas influenced by the opening of the bar and the Caño Grande River discharges in the "nortes" season. Diatom composition varied across seasons, sites, and depth levels; functional groups only varied between sites (p ≤ 0.05). A redundancy analysis recorded the species that responded to the salinity and temperature gradients, including Paralia sulcata, Odontella spp., and Grammatophora oceanica. The species that responded to high nutrient concentrations, total phosphorus, and transparency were Aulacoseira granulata, Stephanocyclus meneghinianus, Ulnaria ulna, Gyrosigma acuminatum, Navicula subrhynchocephala, and Amphipleura pellucida in different seasons in the area close to the river mouth and mangrove swamp. The correlation between diatom density and FPAS indicates that Psammodictyon constrictum and Amphiprora pseudoduplex have optimal growth when the FPAS concentration increases. [ABSTRACT FROM AUTHOR]

Two members of the marine diatom genus Falcula, which has been little known for a long time, were found from the surface of some Japanese seaweeds; one was assigned to F. cf. media and the other was described as a new species, F. rectangularis sp. nov. Aside from the arcuate valves and slit-like apical fields, typical of the genus, detailed morphological observations using light and scanning electron microscopy revealed resemblance between F. cf. media and F. rectangularis in areolae, stria density and lack of costae. However, the two species can be distinguished based on several morphological features, including the valve length, plastid arrangement, and frustules in girdle view. A three-gene molecular phylogeny recovered these two species as monophyletic with a high interspecific rbcL difference, which in turn were sister to the clade containing taxa that belong to the orders Cyclophorales and Protoraphidales with low support. The members in this poorly supported assemblage share apical fields composed of slits. The two species of Falcula were phylogenetically distinct from Pseudofalcula hyalina, a member previously assigned to Falcula. [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]

This study investigated recent seasonal changes in the phytoplankton community in the southern coast of Korea, analyzing monthly samples collected at four stations (St.1-4) in Jinhae Bay from 2017 to 2022. Environmental factors except nutrients were similar each station. Water temperature ranged from 6.0 to 29.0°C and DO ranged from 2.7 to 11.6 mg L-1 with salinity ranging from 25.9 to 33.8 psu. There was no significant differences in environmental factors between stations except for nutrients. Phytoplankton cell concentrations ranged from 5.0×10³ cells L-1 to 7×105 cells L-1, with patterns similar to chlorophyll-a at each site. Phytoplankton taxa identified here were 42 genera and 77 species, including 49 diatoms, 27 dinoflagellates, and one Dictyochophyceae species. Diatoms dominated throughout all monitoring stations and seasons; however, dinoflagellates exhibited sporadic patterns during spring seasons. Nine harmful phytoplankton were identified, including one diatome Psuedo-nitzschia and eight dinoflagellate Alexandrium spp., Akashiwo sanguinea, Margalefidinium polykrikoides, Dinophysis spp., Gymnodinium spp., Pheopolykrikos hartmannii, Polykrikos kofoidii and Prorocentrum spp. The appearance pattern of the harmful phytoplankton showed a high correlation with seasonal factors. This study provides fundamental data on the composition of phytoplankton and their relationship with environmental factors in Jinhae Bay. In addition, they may be useful for understanding long-term changes in harmful phytoplankton in the southern coasts of Korea. [ABSTRACT FROM AUTHOR]

Introduction: Non-perennial rivers and streams are increasingly present, in part because of climate change, even in the temperate climate. However, how the loss of connectivity and complete drying affect microphytobenthos in general and diatom communities in particular has gone mostly unstudied. Methods: With this paper, we aim to close this gap, identifying diatom biodiversity through manual digital microscopy and rbcL amplicon sequencing, to observe a) which method is better suited to it and b) how the ecotone flowpool-dry affects diatom diversity under duress. Three karstic, non-perennial rivers and streams with a gradient from natural to anthropogenically disturbed were sampled under flooding conditions and after a long and intense drought in 2022. Results: Our results show that digital microscopy shows a higher diversity and species richness than amplicon sequencing. We posit that this might be due to a reduced pool of subaerophile taxa having been sequenced and being part of the reference database. Furthermore, the effect of drying only resulted in a reduction in diversity after this drought, although the biofilm was still alive under these conditions. Discussion: To use amplicon sequencing for non-perennial river diatom diversity monitoring, the reference databases will have to be adapted to such systems, as most rivers may be subjected to drying regularly in the future. [ABSTRACT FROM AUTHOR]

The Argentine Sea is worldwide recognized as a highly productive area, characterized by extensive phytoplankton blooms during spring and summer. Despite the well-known importance of frontal areas for biomass accumulation, phytoplankton diversity remains poorly studied. In an unprecedented approach for the Argentine Sea, we combined microscopy and 18Sv4 metabarcoding analyses for a refined assessment of summer phytoplankton composition in three understudied frontal areas of the Argentine Sea (?43°-55°S), with contrasting oceanographic conditions. Metabarcoding and microscopy analyses agreed on the detection of the dominant phytoplanktonic groups in the different frontal areas studied; chlorophytes in Valde's Peninsula, dinoflagellates in waters off Blanco Cape, and diatoms in de los Estados Island. The analysis of the phytoplankton community was significantly enriched by combining both techniques, microscopy provided cel l abundances and biomass data and metabarcoding provided greater detail on species composition, revealing an important specific richness of dinoflagellates, diatoms and other delicate groups, such as chlorophytes. However, we also considered differences between the methods for certain taxa at a lower taxonomic level (species/genus) of the dominant taxa, such as the underestimation of the diatoms Asterionellopsis glacialis and Pseudo-nitzschia spp. and the overestimation of Chaetoceros contortus by metabarcoding in comparison to microscopic counts. The detection of several taxa belonging to small and delicate groups, previously overlooked due to the lack of distinct morphological features, establishes a baseline for future studies on phytoplankton diversity in the Argentine Sea. [ABSTRACT FROM AUTHOR]

Two new diatom species belonging to the genus Gomphonemopsis are described, Gomphonemopsis nana sp. nov. and Gomphonemopsis gaoi sp. nov. These two species were compared in detail with congeners. Gomphonemopsis nana is distinguished by its high stria density and small size. This species was found so far to be epiphytic only on the eelgrass collected from Qingdao Bay (Yellow Sea). Gomphonemopsis gaoi is characterized by its isopolar valves, simple proximal raphe endings and acutely rounded apices. This taxon was separated from the exoskeleton of marine copepods sampled from the Futian Mangrove Nature Reserve (South China Sea). In addition, two new combinations, Gomphonemopsis oahuensis (Hustedt) Lang Li, Yuhang Li & Changping Chen, comb. nov. and Gomphonemopsis platypus (Østrup) Lang Li, Yuhang Li & Junxiang Lai, comb. nov. are proposed. This study increases the records and knowledge of Gomphonemopsis along the coast of China. [ABSTRACT FROM AUTHOR]

Diverse macrovegetation can provide heterogeneous habitats for benthic diatoms. The removal of macrophytes as direct plant control, however, can be considered as a threat, which can even lead to remarkable microhabitat alterations. Lake Tisza (Hungary) has a high nature conservation value, but it is also an important recreation centre, which is why very delicate water management is necessary including vegetation thinning. Here, we studied the importance of microhabitat heterogeneity (emergent, submerged and floating macrophytes) in maintaining diverse periphytic diatom assemblages. We hypothesized that the substrate type has greater influencing role on the composition and diversity of diatoms than the lake heterogeneity related to basins. We also assumed that floating vegetation hosts the most different and least diverse diatom assemblages. Our results mostly proved these hypotheses. Heterogeneous assemblages were formed on the different substrates (support hypothesis), however, the basin level differences were also detected (reject hypothesis). Our results also highlighted, that macrophyte species with lesser morphological complexity hosted the least diverse periphytic assemblages (support hypothesis). However, many unique and red list taxa were found on floating plants (reject hypothesis). These findings emphasize the key role of microhabitat complexity in maintaining diverse and healthy functioning of microbial assemblages in a multi-purpose reservoir. [ABSTRACT FROM AUTHOR]

Since its separation from Stauroneis in 1999, several new species of Craspedostauros were discovered in a variety of habitats and geographic locations, adding morphological and phylogenetic data to the investigations of the genus. In a survey of littoral diatoms of Sweden, both on the west and east coasts, two epiphytic stauros-bearing species were encountered and assigned to Craspedostauros following the characteristic features of this genus, including the possession of a stauros narrower than the central area and cribrate areolae. One species is described as new to science; Craspedostauros lateralis sp. nov., and the other is of uncertain identity but bears morphological similarity to C. laevissimus. Caspedostauros lateralis is a marine epiphytic species found in the west coast of Sweden, off Gothenburg city. Based on light and electron microscopy, a detailed description of the morphological and ultrastructural features of these species is given and a comparison of the distinguishing characters with allied species is discussed. Some ecological data and the occurrence of associated species on the host macrophyte are provided. [ABSTRACT FROM AUTHOR]

Summary: Diatoms are globally abundant microalgae that form extensive blooms in aquatic ecosystems. Certain bacteria behave antagonistically towards diatoms, killing or inhibiting their growth. Despite their crucial implications to diatom blooms and population health, knowledge of diatom antagonists in the environment is fundamentally lacking.We report systematic characterisation of the diversity and seasonal dynamics of bacterial antagonists of diatoms via plaque assay sampling in the Western English Channel (WEC), where diatoms frequently bloom. Unexpectedly, peaks in detection did not occur during characteristic spring diatom blooms, but coincided with a winter bloom of Coscinodiscus, suggesting that these bacteria likely influence distinct diatom host populations.We isolated multiple bacterial antagonists, spanning 4 classes and 10 bacterial orders. Notably, a diatom attaching Roseobacter Ponticoccus alexandrii was isolated multiple times, indicative of a persistent environmental presence. Moreover, many isolates had no prior reports of antagonistic activity towards diatoms. We verified diatom growth inhibitory effects of eight isolates. In all cases tested, these effects were activated by pre‐exposure to diatom organic matter. Discovery of widespread 'cryptic' antagonistic activity indicates that bacterial pathogenicity towards diatoms is more prevalent than previously recognised.Finally, examination of the global biogeography of WEC antagonists revealed co‐occurrence patterns with diatom host populations in marine waters globally. [ABSTRACT FROM AUTHOR]

The importance of diatoms in bioindication and palaeolimnology is significant. For these applications, and species identification in general, a sound understanding of morphological variability is essential. Some species of the centric diatom genera Cyclostephanos and Stephanodiscus can form long, chain-like colonies. In these genera colony formation is associated with the morphology of the spines, which hold the cells together. One objective of this study was to investigate other possible differences in the valve morphology of solitary and colonial cultures. In addition, all strains were sequenced to account for the possibility that solitary and colonial forms may be different species, using three different loci (LSU, rbcL, cox1). The results show that colony formation not only affects the spine morphology but also other morphological features of the valve. The current interpretation that C. invisitatus and C. delicatus are facultative colony formers is supported by the results of this study. The evidence furthermore suggests that C. incognitus is a morphotype of C. invisitatus. A similar morphological pattern leads to the hypothesis that S. hantzschii and S. binderanus could possibly be solitary and colonial forms of the same species, which is also in agreement with the molecular analysis. These findings have implications for the taxonomy of the group and its application and open up a way for future investigations of morphological changes due to colony formation in other groups and taxa. Molecular data support facultative colony formation. Colony formation affects the valve morphology. Stephanodiscus hantzschii and S. binderanus may be conspecific. [ABSTRACT FROM AUTHOR]

The phytoplankton population of Qionghai Lake was surveyed in December 2015, March 2016, June 2016, September 2016, and March 2017. A total of 196 species (including varieties) belonging to 77 genera of 7 phyla were identified. The phytoplankton communities were dominated by Chlorophyta and diatoms, and there were significant differences across the five sampling sites. The phytoplankton abundance, which ranged between 13.85 × 104 and 335.54 × 104 cells·L−1, was significantly higher in spring and summer than in autumn and winter. Chlorella sp. and Cyclotella sp. were the dominant populations, and their dominance degree reached as high as 0.54 and 0.33, respectively. The diversity of the phytoplankton populations was significantly higher in spring and summer than in autumn and winter, and the Shannon–Wiener index and Margalef index ranged from 2.49–3.65 and 2.47–3.10, respectively. The water quality of Qionghai Lake was generally good. The trophic level index was between 30 and 60, showing that the water body was overall in a mesotrophic to slightly eutrophic state. The Spearman correlation analyses revealed that ammonium nitrogen (NH4+-N), water temperature (WT), permanganate index (CODMn), and transparency (SD) were the most important environmental factors that influenced the phytoplankton communities. For example, NH4+-N was significantly correlated with Chroococcus sp. (r = 0.41, p < 0.05) and Cryptomonas ovata Ehrenberg (r = 0.45, p < 0.05), and WT was significantly correlated with Cryptomonas marssonii Skuja (r = 0.43, p < 0.05) and Cryptomonas ovata (r = 0.53, p < 0.01). [ABSTRACT FROM AUTHOR]

Introduction: The aquaculture industry is constantly growing, registering a global production of almost 88 million tonnes by 2020. This industry brings environmental problems if its effluents are not properly treated. In 2020, the first technology-based company of CONICET was established in Argentine Patagonia whose purpose is the aquaculture production of the green sea urchin, Arbacia dufresnii to develop a range of nutraceutical products. Its cultivation system entails a commitment to sustainability since its creation, and yet it generates effluents with high levels of nitrates and phosphates. Objective: Given this scenario, and valuing bioremediation as a water treatment tool, the use of marine microalgae as phytoremediating agents of aquaculture effluent is proposed in this work. Methods: The microalgae Chaetoceros gracilis, Navicula sp., Tetraselmis suecica, Rhodomona salina, Nanochloropsis galvana and Cylindrotheca closterium were use; which are used as food for sea urchins larvae in the production process. An experiment was designed that compares the microalgal growth and the removal capacity of nutrients in the effluent in contrast to the artificial culture medium currently used in the production cycle. Results: It is possible to remedy the aquaculture industry's effluent by employing the selected microalgae, with a percentage of removal efficiency of 100 % of the nitrate and an average removal efficiency percentage of 50 % for all the microalgae tested. Likewise, significantly higher microalgal biomass values were obtained when the culture was carried out in the effluent the culture in the artificial environment. Conclusions: The advances in research provided in this work show that it is possible to take advantage of a discard to cultivate microalgae, even improving microalgal productivity for use as food, reducing the costs involved in the microalgal production sector by changing the use of the type of current culture medium (F/2) for that from a current discard. These advances, if scaled and validated, can improve industry sustainability standards within the framework of a circular economy. [ABSTRACT FROM AUTHOR]

The region of Bruges (Flanders, Belgium) was an economic and cultural centre during the Late Middle Ages because it was connected to the North Sea via a large tidal inlet called the Zwin, along which smaller towns developed. One of these towns was Aardenburg (Zeeland, The Netherlands), which developed from a Roman castellum to become one of the important medieval towns in the hinterland of Bruges. Unfortunately, archaeological, historical and (palaeo)environmental data about the Roman to medieval evolution of the Zwin area are scarce. However, the continuous occupation of Aardenburg during the first millennium AD and its location on a Pleistocene sand ridge bordering the coastal plain provide a unique opportunity to investigate the natural dynamics of the coastal evolution and the interplay with the human impact that shaped the Zwin region before its heyday. The variable character of the depositional environments on the dynamic coastal plain makes local environmental studies essential for understanding larger patterns, which were previously reduced to a simplistic outdated model over the entire region. Palynological and diatom assemblages of two sequences in Aardenburg allow the reconstruction of the terrestrial and aquatic palaeoenvironments from the Middle Holocene to the high Middle Ages. The results reveal landscape evolution in relation to woodlands, peat bogs, coastal environments and human presence, consistent with previous regional landscape evolution. A distinct increase in marine influence during the Roman and early medieval periods, when human activities played a significant role, was followed by an increase in inland indicators from the high medieval period onwards. This evolution is in accordance with the expansion of the town and the reclamation of the coastal landscape as it evolved to become a cultural centre in the Late Middle Ages. [ABSTRACT FROM AUTHOR]

During the investigation of the freshwater diatoms from Tibet, a monoraphid species was observed from a hot spring near Anduo County, located on a plateau in the central portion of Tibet. This species shares the diagnostic features of Crenotia, such as the valve bent along the transapical axis, striae uniseriate to biseriate from centre to the apices and areolae with special structures located at the end of each stria. We compared the morphological characters of this new species with the others in this genus and show it to be new; it is named Crenotia tibetia sp. nov. This species has small valves with slightly protracted ends with nearly capitate apices, lanceolate axial area, central area unilaterally expanded to the margin, striae uniseriate to biseriate, but, in some valves, the striae are only uniseriate. Areolae are round small to irregular in shape and, at the end of each stria, there is a horseshoe-shaped areola present. Observations of developing valves show all the striae begin biseriate, then they become covered by silica to form uniseriate striae. Comparisons are made amongst the species in this genus and with genera assigned to the Achnanthidiaceae. [ABSTRACT FROM AUTHOR]

During a survey of the Indonesian diatoms, five Luticola D.G.Mann taxa that could not be identified, based on the available literature were discovered. Based on light microscopy, scanning electron microscope observations and comparisons with similar taxa, all of them are described as new species. All taxa were found on mosses growing on tree trunks and concrete on the islands of Banda Besar and Seram and from spring on Java Island. Luticola insularis sp. nov. is most similar to L. aequatorialis and L. simplex, but it can easily be distinguished from both taxa, based on the lower striae density, the narrower valves and the well-developed silica ridges on the valve face/mantle junction. Luticola bandanensis sp. nov. resembles L. frequentissima, but they can be easily distinguished, based on their valve widths and the direction of the grooves located on the distal and proximal raphe endings. Luticola elliptica sp. nov. is most similar to L. sparsipunctata, L. tenuis and L. bryophila. Amongst all the species compared, L. elliptica sp. nov. is the only one with a highly asymmetrical central area, with the isolated pore located on the wider side. Luticola malukuana sp. nov. shares similarities with L. dismutica and L. areolata, but it has a notably higher stria density. From L. areolata, it can also be separated by the morphology of striae and the lack of ghost areolae in the central area. Luticola poliporea sp. nov. is unique in the whole genus due to the presence of multiple isolated pores. [ABSTRACT FROM AUTHOR]

The genus Cocconeiopsis was separated from Navicula, but its systematic position is in debate. We sequenced the complete chloroplast and mitochondrial genome of Cocconeidaceae for the first time with Cocconeiopsis kantsiensis and investigated its phylogeny and evolutionary history. Results showed that the plastid genome was 140,415 bp long with 167 genes. The mitochondrial genome was 43,732 bp long with 66 genes. Comparative analysis showed that the plastid genome structure of C. kantsiensis was most similar to those of three Navicula species and Halamphora americana, and its size was significantly smaller than that of a monoraphid species. Its mitochondrial genome was similar to that of related species except for Phaeodactylum tricornutum. The multigene phylogeny reconstruction showed that Cocconeiopsis was sister to Didymosphenia but distant from Naviculaceae. The two-gene phylogenetic analysis containing 255 species showed Cocconeiopsis was sister to Cocconeis, and distant from Naviculaceae as well. Divergence time estimation indicates the common ancestor of cocconeid species occurred about 62.8 Ma and Cocconeiopsis diverged with monoraphid Cocconeis about 58.9 Ma. Our results support the assignment of Cocconeiopsis to Cocconeidaceae and that monoraphid cocconeids were likely evolved from the lineage of Cocconeiopsis. [ABSTRACT FROM AUTHOR]

Caves represent unique and extreme ecosystems inhabited by specifically adapted and metabolically diverse organisms (phototrophs, heterotrophs, and mixotrophs). Hydrogeologically active river caves, such as Stopić Cave (Serbia), have additional characteristics. Knowledge is lacking on the cyanobacteria and algae living in these specific ecosystems and, in particular, in the water bodies within caves. The main objectives of this study were to investigate the diversity, composition, and seasonality of cyanobacterial and algal communities of the Trnavski stream flowing through Stopić Cave and to assess water quality. Initial analysis of planktonic and benthic samples collected during the winter, spring, and summer of 2020 from six sites along the Trnavski stream flowing through Stopić Cave identified 132 cyanobacterial and algal taxa. Subsequent detailed analysis of benthic diatoms increased the total number of identified taxa to 242, with representatives of Bacillariophyta, Cyanobacteria, and Chlorophyta being the most common. Representatives of Xanthophyceae, Chrysophyceae, Euglenophyceae, Dinophyceae, and Cryptophyceae were also recorded. The highest total number of taxa was found in the spring (n = 156), and the lowest number in the summer (n = 60). Many taxa were specific to only one season, with the majority of these belonging to Cyanobacteria and Chlorophyta. The values recorded for pH, conductivity, and light intensity showed that there was relatively little seasonal variation; in contrast, water temperature varied greatly among seasons. According to most diatom indices, the water quality of Trnavski stream was good at most sampling sites during the study period. [ABSTRACT FROM AUTHOR]

The present investigation embarks on understanding the spatial distribution of the microalgae population in the Hoggar and Tassili regions of the Central Sahara of Algeria. Thirty-eight sites were sampled between April 2016 and April 2017. Environmental parameters were measured at each station. A total of 77 taxa belonging to 7 classes were identified: Bacillariophyceae (27), Cyanophyceae (15), Chlorophyceae (14), Zygnematophyceae (13), Euglenophyceae (5), Dinophyceae (2), and Xanthophyceae (1). The highest values of the Shannon-Weaver and Equitability indexes were recorded at station H5S1 (H’ = 4.62, E = 0.95), respectively, in the region of Hoggar. In the Tassili region, the highest values were recorded at station T1S2 (H’ = 4.50, E = 0.88), respectively. Canonical correspondence analysis (CCA) was established between the environmental parameters and species in both regions. According to the results, pH, altitude, and depth were the most important environmental factors influencing the microalgae diversity. [ABSTRACT FROM AUTHOR]

The use of ultraviolet-C (UV-C) irradiation in marine biofouling control is a relatively new and potentially disruptive technology. This study examined effects of UV-C exposure on the biofilm-forming diatom, Navicula incerta. UV-C-induced mutations were identified via Illumina HiSeq. A de novo genome was assembled from control sequences and reads from UV-C-exposed treatments were mapped to this genome, with a quantitative estimate of mutagenesis then derived from the frequency of single nucleotide polymorphisms. UV-C exposure increased cyclobutane pyrimidine dimer (CPD) abundance with a direct correlation between lesion formation and fluency. Cellular repair mechanisms gradually reduced CPDs over time, with the highest UV-C fluence treatments having the fastest repair rates. Mutation abundances were, however, negatively correlated with CPD abundance suggesting that UV-C exposure may influence lesion repair. The threshold fluence for CPD formation exceeding CPD repair was >1.27 J cm−2. Fluences >2.54 J cm−2 were predicted to inhibit repair mechanisms. While UV-C holds considerable promise for marine antifouling, diatoms are just one, albeit an important, component of marine biofouling communities. Determining fluence thresholds for other representative taxa, highlighting the most resistant, would allow UV-C treatments to be specifically tuned to target biofouling organisms, whilst limiting environmental effects and the power requirement. [ABSTRACT FROM AUTHOR]

Identification of phytoplankton trapped in the gills suggests initial selectivity and food preference in marine bivalve molluscs. In this study, pre-ingested phytoplankton in the gills of Mytella strigata were determined and compared to the existing phytoplankton in the waters of three sites in the Philippines (Pangasinan, Cavite, and Bataan). Pre-ingested phytoplankton of M. strigata varied with size (p<0.05) and site (p<0.05). Coscinodiscus spp. and Skeletonema spp. were most abundant across sizes (<20mm, 20-40mm, and >40mm) and sites. Particle selection observed in the gills suggests food preference for centric diatoms such as Coscinodiscus spp., Skeletonema spp., and Navicula spp. The pre-ingestion of these diatoms ranged from 26% to 46% of the total phytoplankton composition in the waters of different sites. The results highlight particle selection during filtration and indicate a potential food preference of M. strigata. [ABSTRACT FROM AUTHOR]

Background: The "Diatom Test" is based on the recovery of diatoms in high concentration in the organs of drowned persons because diatoms pass through the alveoli into the great circulation. Acid digested extracts of various internal organs and water collected from waterbodies demonstrate the presence of diatoms. If quantitatively and qualitatively these diatoms match to each other, that is the confirmatory diagnosis of death due to drowning in that drowning medium. This study was conducted to analyze the effectiveness of alternate method of diatom extraction using diluted Sulphuric acid solution and to compare its effectiveness with the traditional method of extraction of diatoms using concentrated nitric acid. Methods: It was a prospective study. Samples were collected from ten different water bodies which included lakes, rivers, canals and reservoirs, for a period of one year in all the seasons. The pH and temperature of water were recorded during sampling. From each of water samples, diatoms were extracted using both classical and alternate method. And then compared by observing the diatoms at 100X magnification under compound microscope. Total 22 genera of diatoms were identified. Most of them were pennales and few were centrales. The time demanded for complete digestion of samples with strong acids like concentrated nitric acid was much lesser time than with diluted acids as it hasstronger digestive capability in comparison to diluted sulphuric acid. The structures of different diatoms specifically Cyclotella, Cybella, Navicula were better found in almost intact state with clear background after digestion by diluted sulphuric acid. Conclusion: Depending on different criterion, digestion by diluted sulphuric acid has procured better result than concentrated nitric acid digestion method. Therefore, for qualitative and quantitative diatom analysis alternate diatom extraction method is a better choice than traditional method. [ABSTRACT FROM AUTHOR]

The study is focused on the ecological and physiological properties, production, and biochemical characteristics of the diatom Nitzschia amabilis. The optimum salinity (35‒36‰), illumination (2.95 klx), and photoperiod (14 h) at which the highest specific cell growth rate is achieved was determined. The coefficient of light saturation (Ik) was calculated and turned out to be lower than one, which indicates the high energy efficiency of photosynthesis. The results of experiments on salinity showed the ability of the alga to grow in the range of 4–68‰, indicating its relatively broad euryhalinity. The biochemical composition of N. amabilis during acumulative cultivation was studied. In general, polyunsaturated fatty acids predominated in the studied strain; eicosapentaenoic, arachidonic, and docosahexaenoic acids were dominant. The main share of saturated fatty acids consisted of palmitic acid. The productivity indicators of N. amabilis in relation to lipids, fucoxanthin, and PUFAs, which were 2.5–3 times higher in the flow cultivation mode than in the cumulative mode, have been established. [ABSTRACT FROM AUTHOR]