Search Results (21)

The review is focused on dictyopterenes A, B, C, and D found in marine algae, covering their (a) distribution; (b) methods of isolation and identification; (c) absolute configuration; and (d) biosynthesis considerations. Dictyopterenes A and B are usually present in high amounts in Dictyopteris spp. Dictyopterene A was found to be abundant in D. prolifera, D. undulata, D. latiscula, D. polypodioides, and D. membranacea. Dictyopterene B (hormosirene) was found as the major compound in D. plagiogramma, D. australis, Hormosira banksii, D. potatorum, D. willana, D. antarctica, Xiphophora chondrophylla, X. gladiata, Scytosiphon lomentaria, Colpomenia peregrina, and Haplospora globosa. Dictyopterene C (dictyotene) was a major compound in D. undulata, D. prolifera, D. membranacea, Gomphonema parvulum, Amphora veneta, Phaeodactylum tricornutum, and D. vermicularis. Dictyopterene D (ectocarpene) was present in Ectocarpus siliculosus, Analipus japonicus, D. prolifera, D. undulata, and Sargassum linifolium. The following enantiomers were found: (1S,2R)-dictyopterene A, (1R,2R)-dictyopterene B, (1S,2S)-dictyopterene B, (1S,2R)-dictyopterene B, (R)-dictyopterene C, and (S)-dictyopterene D. In marine algae, C₁₁-hydrocarbons are derived from C₂₀ polyunsaturated fatty acids by the oxidative cleavage via, e.g., 9-hydroperoxyicosa-(5Z,7E,11Z,14Z,17Z)-pentaenoic acid. An alternative biosynthetic pathway for dictyopterene A and B via the proposed intermediates (S)-dictyoprolenols was considered by oxidative cleavage of hydroperoxyicosatetraenoic acid. Full article

Benthic diatoms are being used as indicators to assess the biological quality of surface waters in Kosovo. The Klina River is the left tributary of the White Drin River Basin, with a length of 69 km. The study assessed the level of surface water quality in the Klina River using 12 diatomic indices calculated with the Omnidia program. For this purpose, three stations monitored the river Klina in the autumn of 2021 to conform to international standards. A total of 88 diatom taxa were identified, with the dominant species being Rhoicosphenia abbreviata (C. Agardh) Lange-Bertalot, Gyrosigma acuminatum (Kützing) Rabenhorst, Cocconeis placenula Ehrenberg, Gomphonema minutum (Ag.) Agardh f. minutum, Gomphonema clavatum Ehr, Meridion circulare (Greville) C.A. Agardh, Cocconeis pediculus Ehrenberg, Diatoma vulgaris Bory, and Nitzschia dissipata (Kützing) Grunow ssp. dissipata etc. This study assessed the surface water quality in the Klina River using diatom indices, indicating that the river is in good to moderate ecological condition. Environmental variables such as hydrogen ion concentration (pH) and dissolved oxygen (DO) had significant positive correlations (<0.01) with the biological diatom index (IBD), Descy’s pollution metric (Descy), Sladeček’s pollution metric (SLA), the European index (CEE), and Watanabe’s Index (WAT), while the total suspended solids (TSS) also showed a strong negative significant correlation (<0.01) with the generic diatom index (IDG), Indice Diatomique Artois Picardie (IDAP), the eutrophication pollution index (EPI-D), the trophic diatom index (TDI), the Pampean diatom index (IDP), and Steinberg and Schiefele’s index (SHE). Total phosphorus (TP), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) presented a significant negative correlation (<0.05) with the IBD, Descy, SLA, CEE, and WAT indices. Our findings provide insights for organizations dealing with the state of the environment and water protection in Kosovo, and these results can be used as a starting point for assessing the ecological quality of water and monitoring environmental pollution in the Kosovo region. Full article

In order to promote the development of biodiversity, the present study conducted three sampling surveys at 26 representative sampling sites selected from the Chishui River, a freshwater river in China, in July (rainy season), November (flat water period), and April 2024 (dry season), respectively, focusing on the relationship between benthic algae and the response of water environmental factors. The results revealed that a total of 140 species from 48 genera and 7 phyla of benthic algae were identified, with the highest number of species belonging to the diatom phylum (85 species). The average density of benthic algae was highest during the flat water period, followed by the dry season and the flood season. Microcystis sp. was the dominant species during the flood season, while Gomphonema sp., Achnanthes tumescens, and Oscillatoria sp. were common dominant species during the dry and flat water periods. Achnanthes tumescens was the absolute dominant species in the upstream during the dry and flat water periods; Leptolyngbya sp. was the absolute dominant species in the midstream during the flat water period, and Oscillatoria sp. was the absolute dominant species in the middle reaches during the dry season. The Shannon-Wiener index, Margalef index, and species richness of benthic algae during the dry and flat water periods decreased from upstream to downstream. Non-metric multidimensional scaling analysis revealed significant differences in the community structures of benthic algae in the upper, middle, and downstream areas of the Chishui River during different periods, while cluster analysis indicated high similarity among benthic algae communities in locally adjacent areas. The differences in the benthic algae community structure increased with environmental and geographical distance, with environmental distance playing a greater role than geographical distance. RDA (Redundancy Analysis) identified TN (Total Nitrogen), TP (Total Phosphorus), DO (Dissolved Oxygen), EC (Electrical Conductivity), and NH₃-N (Ammonia Nitrogen) as key water environmental factors influencing the structure of benthic algal communities in the Chishui River. Full article

Rivers are crucial hydrological cycle components, supporting ecosystems and human activities. Managing and protecting river water quality is essential. Diatoms, microscopic algae, are widespread and sensitive to changes in water quality, making them effective bioindicators. This study focused on the Kuils River in the Western Cape, South Africa, where diatom sampling was conducted at four sites. Their communities are affected by different physicochemical parameters, such as changes in pH, salinisation, eutrophication, and organic enrichment. A total of 98 diatom species were identified. The Omnidia software was used to calculate the Generic Diatom Index, Specific Pollution Index, and Trophic Diatom Index. Historical physicochemical data such as pH, chemical oxygen demand, and phosphorus were obtained from the Department of Water and Sanitation between 2019 and 2021 and were used to provide a reference for comparing diatoms. The results showed clear signs of pollution, as shifts in diatom species composition were observed. Pollution-tolerant species such as the Nitzschia palea (Kützing) W Smith 1856, Navicula viridula (Kützing) Ehrenberg 1838, Eunotia bilunaris (Ehrenberg) Schaarschmidt 1880, and Ulnaria ulna (Nitzsch) Compère 2001 dominated, while less pollution-tolerant species like Gomphonema parvulum f.saprophilum Lange-Bertalot and E. Reichardt 1993 and Stephanocylus meneghinianus (Kutzing) Kulikovskiy, Genkal, and Kociolek 2022 were less abundant. Both diatom indices and physicochemical data indicated poor water quality in the Kuils River. The study concludes that diatoms are a valuable tool for biomonitoring river water quality and recommends their use alongside traditional physicochemical methods for future assessments of river systems. Full article

A study of diatoms in eight watercourses (four spawning rivers and four streams) in the area of the Ozernovsky Mining and Metallurgical Complex (MMC) on the Kamchatka Peninsula was carried out for the first time. A total of 174 taxa were identified, and a comparative analysis of periphyton species diversity at the sampling stations was carried out. A new species for science was proposed: Gomphonema anissimovae Glushchenko, Kezlya & Kulikovskiy sp. nov. The composition and quantitative characteristics of plankton were analysed only in samples collected from rivers. It was shown that all rivers are oligotrophic in terms of phytoplankton biomass. The work includes lists of taxa with indication of their abundance, as well as illustrative material of found diatom taxa, which will provide an opportunity to monitor changes in planktonic and periphyton microalgae communities in the studied watercourses in the context of potentially high anthropogenic load from industry. Full article

Climate change and human activities may alter the structure and function of boreal peatlands by warming waters and changing their hydrology. Diatoms can be used to assess or track these changes. However, effective biomonitoring requires consistent, reliable identification. To address this need, this study developed a diatom voucher flora of species found across a boreal fen gradient (e.g., vegetation) in interior Alaskan peatlands. Composite diatom samples were collected bi-weekly from three peatland complexes over the 2017 summer. The morphological range of each taxon was imaged. The fens contained 184 taxa across 38 genera. Eunotia (45), Gomphonema (23), and Pinnularia (20) commonly occurred in each peatland. Tabellaria was common in the rich and moderate fen but sparse in the poor fen. Eunotia showed the opposite trend. Approximately 11% of species are potentially novel and 25% percent matched those at risk or declining in status on the diatom Red List (developed in Germany), highlighting the conservation value of boreal wetlands. This voucher flora expands knowledge of regional diatom biodiversity and provides updated, verifiable taxonomic information for inland Alaskan diatoms, building on Foged’s 1981 treatment. This flora strengthens the potential to effectively track changes in boreal waterways sensitive to climate change and anthropogenic stressors. Full article

Incorporating diatoms species and their autecology from reference stream conditions is essential for improving the accuracy of North American diatom bioassessments. This study documents a voucher flora and physicochemical conditions of Upper Three Runs Creek (UTRC), a tributary to the Savannah River that has been protected from heavy human activity for the last 50 years. The algae of UTRC and its watershed have been monitored continuously during this time by the Academy of Natural Sciences in Philadelphia to detect potential impacts from the Savannah River Site and Plant Vogtle. Standard protocols were used to sample and denote substrate types and preferences and to estimate relative abundances of diatom species. Data from artificial substrates (diatometers) were compared to composite samples. Phenotypic plasticity of taxa from Gomphonema parvulum, Eunotia incisa, and Tabellaria flocculosa sensu lato species complexes were considered in biodiversity metrics. We provide documentation of these separations. A total of 297 species/operational taxonomic units (OTUs) were recorded. For 2018 samples, Eunotia rhomboidea accounted for 8.3% for separated taxa methods and G. parvulum sensu lato (16.2%) dominated for combined taxa methods. Luticola goeppertiana (5.4%) was the most abundant taxon in the 1956 samples. The 1956 composite samples species richness means were greater and significantly greater than those for other sample types (ANOVA, df = 3, p = 0.004). The recounted 1956 composite samples had the highest species richness (153) followed by the left diatometer (129). At the same location, the right and left diatometers were not similar. Both methods (diatometers and composite sampling) are useful when assessing species richness. Diatom community composition indicated an acidic and highly oxygenated environment. Full article

During this investigation, sixteen species from the genus Gomphonema were found in a shallow bay (near Oimur, Kabansky District) located on the eastern shore of Lake Baikal. Eleven of these taxa have been described previously. Five species are described as new to science. We provide ecological information about these Gomphonema species, including their distribution within and outside Lake Baikal, and compare and contrast the new taxa with morphologically similar congeners. The diversity of morphologies present in Lake Baikal among the Gomphonema species suggests there has been both in-lake speciation as well as the introduction of various groups of species. The idea that Lake Baikal may support a high number of endemics by their partitioning niches based on depth is supported by the different groups of gomphonemoid diatoms present. Full article

Siliceous diatom frustules present a huge variety of shapes and nanometric pore patterns. A better understanding of the light modulation by these frustules is required to determine whether or not they might have photobiological roles besides their possible utilization as building blocks in photonic applications. In this study, we propose a novel approach for analyzing the near-field light modulation by small pennate diatom frustules, utilizing the frustule of Gomphonema parvulum as a model. Numerical analysis was carried out for the wave propagation across selected 2D cross-sections in a statistically representative 3D model for the valve based on the finite element frequency domain method. The influences of light wavelength (vacuum wavelengths from 300 to 800 nm) and refractive index changes, as well as structural parameters, on the light modulation were investigated and compared to theoretical predictions when possible. The results showed complex interference patterns resulting from the overlay of different optical phenomena, which can be explained by the presence of a few integrated optical components in the valve. Moreover, studies on the complete frustule in an aqueous medium allow the discussion of its possible photobiological relevance. Furthermore, our results may enable the simple screening of unstudied pennate frustules for photonic applications. Full article

The benthic diatom assemblages of the glacier Avusor Great Lake and Koçdüzü Great Lake were investigated in August 2019. A total of 71 diatom species belonging to 34 genera were determined in the samples, 49 species from Avusor Great Lake and 37 from Koçdüzü Great Lake. Only 15 diatom species were common to both lakes. Total floristic similarity between the neighbouring lakes was only 21.12%. Genera with the highest number of species were Eunotia (8), Gomphonema (6), Pinnularia (6), Navicula (5) and Aulacoseira (4). The diatom flora of both lakes was formed by cosmopolitan species with a large influence from species in alpine and subalpine area. A comparison of the diatom assemblages of the investigated lakes showed differences in both relative abundance and species present in the individual lakes. Bioindicative analysis showed that the water of Koçdüzü Great Lake is more alkaline and less saturated with organic substances than Avusor Great Lake. In both lakes, the communities are composed of species adapted to living in the benthos of fresh waters of moderate temperature well enriched with oxygen. In both lakes, the water quality was Class 2 with a saprobity index of S = 1.08 in Avusor Great Lake and 0.97 in Koçdüzü Great Lake, but their communities were composed of species with both oligotrophic and mesotrophic status. Statistical comparison of the species composition of studied lakes with other high mountain lakes and the lakes in northern Turkey revealed the role of altitude as the main factor in the formation of diatom floras. Full article

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. Full article

Myristica swamps are one of the rarest wetland ecosystems within the sub-tropical evergreen forests of the Western Ghats, India. As their name indicates, they harbor trees belonging to the ancient family Myristicaceae. Due to the waterlogged conditions and high humic decomposition, these swamps are acidic, harbor rare and endemic biotas, and provide ecosystem services to humans. Monitoring this rare ecosystem is crucial because the swamps that once formed a large hydrological network across the Western Ghats are now confined to isolated patches due to human disturbance such as agricultural interventions, roads, and dam construction. Due to the change in land use, there is also a drastic change in water chemistry and associated biodiversity. Biomonitoring is more precise than physical and chemical monitoring. So, the current study aimed to undertake a comprehensive analysis of the physical, chemical, and biological assessment of these swamps. The diatom assemblages are strongly affected by water chemistry and serve as a powerful indicator of environmental changes in the freshwater aquatic systems. However, there is no information on diatom assemblages in these swamps, and the present study aimed to determine the diatom assemblage structure in the Myristica swamps and their response to changing water quality. Diatom samples were taken at 17 different swamps across the central Western Ghats, and a set of environmental parameters was evaluated. Analysis revealed a total of 91 species of diatoms belonging to 27 genera across the 17 sites, from which 44 diatom species showed restricted distribution to this unique environment. Overall, the dominant diatom genera inside the swamps included, Navicula (19.8%), Gomphonema (16%), Eunotia (13.3%), Ulnaria (9.4%), Achnanthidium (8%), Frustulia (6.2%), Planothidium (5.2%), and Brachysira (2.8%). High diatom species richness was observed in the swamps having less anthropogenic disturbance, and diatom assemblage composition was primarily determined by dissolved oxygen, pH, and conductivity. The significant number of geographically restricted taxa in this study points towards our limited understanding of this tropical biome and calls for a dire need for more studies from here, not only to improve our knowledge concerning the diversity, ecology, and biogeography of these diatoms but to further encourage their use in applied (paleo) environmental sciences. Our results indicate that diatoms can prove useful environmental indicators even in harsh environments like swamps and can be a potential tool for assessing ecological and climatic change. Full article

The study of the importance of physicochemical parameters of water for algal growth and development in Jagdishpur Reservoir was carried out in the present research. Occurrence of algal species and values of water quality parameters also indicate the ecological nature and the present status of the reservoir. Water samples were collected from Jagdishpur Reservoir in Kapilvastu District (Nepal), in two seasons (wet and dry). The following physicochemical parameters of water were analyzed: temperature, pH, dissolved oxygen, alkalinity, concentration of nitrates and phosphates, free CO₂, hardness, conductivity, total dissolved solids. The values of free CO₂, hardness, phosphate, temperature, and dissolved oxygen were high in wet season while alkalinity, nitrate, conductivity and total dissolved solid were high in dry season. Altogether 81 algal species belonging to 53 genera and 6 classes were recorded. Higher number of algal species was recorded in the dry season rather than in the wet season. The highest number of species was noted among Chlorophyceae, followed by Cyanobacteria > Bacillariophyceae > Euglenophyceae > Crysophyceae and Dinophyceae. Cosmarium had the highest number of species (13) among all genera. During the wet season, Cosmarium, Calothrix and Phormidium were the genera with the highest number of species while Bulbochaete, Trachelomonas and Gomphonema were genera with the lowest number of species. During the dry season, Cymbella, Cosmarium and Rhopalodia were genera with highest number of species while Euglena, Gloeotrichia and Trachelomonas were genera with lowest number of species. Algal diversity was positively correlated with the increase of alkalinity, conductivity and TDS, while negatively correlated with free CO₂, hardness, concerntration of phosphates and nitrates, DO, pH and temperature. Shannon–Weiner diversity index value was higher during the dry season than in the wet season. Full article

The aim of this research was to investigate the structure of the benthic diatom community and its relations to selected environmental parameters. We collected samples in 16 karst ponds in the alpine region of Slovenia, where the Alpine karst is found. Since the predominating substrate in these ponds was clay, the epipelic community was analyzed. Hydromorphological characteristics, and physical and chemical conditions were also measured at each site. We found 105 species of diatoms, which belonged to 32 genera. The most frequent taxa were Gomphonema parvulum (Kützing) Kützing, Navicula cryptocephala Kützing, Sellaphora pupula (Kützing) Mereschkowsky (species group) and Achnanthidium pyrenaicum (Hustedt) Kobayasi. The pond with the lowest diversity was found at the highest altitude, while, on the other hand, the most species-rich pond was found at the lowest altitude. Regarding the ecological types, the most common were motile species. We confirmed a positive correlation between the number of diatom species and the saturation of water with oxygen, while correlation between species richness and NH₄-N was negative. The content of NO₃-N and NH₄-N explained almost 20% of the total variability of diatom community. Unlike our expectations, we calculated a negative correlation between the diversity of macroinvertebrates and diatoms, which is probably a consequence of different responses to environmental conditions. Full article

Temporary high-elevation lakes represent vulnerable and unstable environments strongly threatened by tourism, hydrogeological transformations and climate changes. In-depth scientific knowledge on these peculiar habitats is needed, on which to base integrated and sustainable management plans. Freshwater diatoms, thanks to their high diversity and their particular sensitivity to the water chemistry, can be considered powerful ecological indicators, as they are able to reflect environmental changes over time. The aim of the present study was to analyze the diatomic diversity of the Pilato and Palazzo Borghese lakes, two small temporary high-mountain basins, falling in a protected area within the Apennine mountains chain (central Italy). Diatoms data were collected, at the same time as 12 physicochemical parameters, through six microhabitat samplings, from 17 June to 30 August 2019. In both lakes, a total of 111 diatomic species and varieties were identified. The most species-rich genera were Gomphonema, Navicula, and Nitzschia. The Pilato Lake showed a diatomic community dominated by few species, favored by more stable and predictable environmental conditions than the Palazzo Borghese Lake, which hosted a more diversified community, guaranteed by greater spatial and temporal heterogeneity. Both lakes were characterized by the presence of diatomic species typical of good quality waters. The occurrence of numerous aerial species reflected adaptation strategies adopted to colonize environments subjected to extended drought periods. Endangered diatomic species of particular conservational interest were recorded, confirming the need to preserve their habitats. Full article