Diatom Species Research Articles

Biodiversity of Diatoms as Indicators of Water Quality and Landscape Sustainable Dynamics in the Zarafshan River, Uzbekistan

For the first time, we have compiled a general list of diatoms for the Zarafshan River consisting of 428 species based on our own research and the literature data. Indicator species for nine water parameters were identified, making up more than 90% of the list. Bioindicators and statistical methods revealed that sections of the river around the city of Samarkand and further in the middle reaches reflect the complexity of the impact of the environment on diatom communities. The surveyed sections of the middle reaches of the river are divided into branches and the dynamics of water parameters and diatom communities are shown from the border with Tajikistan to the confluence of the Zarafshan with the Amu Darya. The indices of organic pollution, S, and toxic impact, WESI, were calculated. They show that there is an increase in salinity and turbidity and a decrease in organic pollution downriver. At the same time, the Navoi section is a source of water acidification. Nutrients and heavy metals, as well as phenol pollution, enter the river from various sources, mainly in the middle reaches of the river. The Zarafshan Nature Reserve in the catchment area of the upper section of the river within Uzbekistan is important for maintaining water quality. Bioindicators show an increase in self-purification, with an increase in the species richness and abundance of diatoms in the middle section of the Zarafshan River. The integrated index of river pollution, RPI, shows that most pollution comes from the northern canal of the river in the middle reaches. A general look at the Zarafshan River catchment basin and the dynamics of the identified water parameters and bioindicator species of diatoms shows that the river ecosystem successfully copes with incoming pollution, including transboundary impacts from Tajikistan. Such a conclusion could not be made based on chemical analysis of the water alone. This allowed us to recommend expanding state monitoring points to the lower section of Karakul while including biological indicators in the observations.

The Effects of Cattle Grazing on the Composition of Diatom Assemblages in the Peatland Pools of the Southeastern Alps (Italy, Adamello-Brenta Nature Park)

Mires are significant C-sinks and important habitats for biodiversity conservation. Particularly in the Alpine peatlands, grazing and trampling cause mires to degrade, causing changes in plant communities that increase bulk density, peat erosion, and nutrient excesses. We took sixteen samples of epipelic and epiphytic diatoms from mire pools subjected to varying degrees of grazing in the Adamello-Brenta Nature Park (Trento, Italy). We identified >100 diatom species (ca. 70% included in Red List threat categories). We used nMDS to identify groups of diatom species. Their statistical significance was checked with an ANOSIM and, to identify the species that contributed most to the difference between the two groups, a BEST-SIMPER procedure was carried out. The multivariate analyses allowed us to identify significant differences among the most and least grazed sites, and to select the species that contributed most to this distinction. We confirmed that some species were more frequent and abundant in the most grazed sites and behaved as opportunists in the presence of a greater nutrient input, to the detriment of rare and sensitive species, which were more numerous and abundant in the less grazed sites. We provided useful information on grazing effects, underlining the importance of managing and protecting habitats of unique environmental value.

Effects of climate warming and declining water quality on the eco-environmental evolution of Jinmucuo Lake: Evidence from sedimentary diatom assemblages

The problem of lake pollution on the Tibetan Plateau has become prominent in recent years because of the warming climate and increased human activity. However, it is difficult to obtain effective indicators to explain the long-term eco-environmental changes in plateau lakes. In this study, a sediment core from Jinmucuo Lake was taken as the research object, and the 210Pb and 137Cs isotopes, diatom assemblages, and climatic and environmental factors were analyzed. The results revealed that the lake had a sedimentation rate of 0.47 cm/a, and the age of the 30-cm sediment core was approximately 1876 AD. Diatom abundances at different ages tend to decrease. During 1876–1999, abundant diatom species, such as Cymbella lanceolata, Navicula sp., Surirella ovalis, Synedra sp., Epithemia adnata, Cymbella pusilla, Amphora ovalis and Tabularia tabulata, which included oligotrophic, mesotrophic, and eutrophic indicator species were detected, and the dominant species were Cymbella lanceolata, Navicula sp., Surirella ovalis and Synedra sp. After 2000, diatoms declined dramatically, and were undetected in most samples. Similarly, the species richness and Shannon‒Wiener index plummeted to 0 in approximately 2002. Canonical correspondence analysis revealed that total nitrogen and organic matter were the main influencing factors of diatom assemblages before 2000, whereas As and mean annual temperature were the main influencing factors after 2000. These findings indicate that diatom habitats have been rapidly destroyed by increasing temperatures and As inputs, even in the presence of abundant nutrients in the lake.

Description of Witkowskia famintsinii sp. nov. (Cymbellales, Bacillariophyceae) with morphological investigation of Witkowskia strigosa comb. et stat. nov.

In this study, the morphology of two species of diatoms from the Mường Hoa River, Vietnam, was investigated using LM and SEM. The first species was identified as Navicula similis var. strigosa. The second species has been unknown to science until today. As a result, we concluded that in both species areolae in striae are occluded by tectula, a type of pore occlusions, unique for Witkowskia, a recently erected genus of cymbelloid diatoms. Based on this feature, we propose Witkowskia strigosa comb. et stat. nov. in this paper and describe Witkowskia famintsinii sp. nov. below. The species are morphologically compared with other similar representatives of Witkowskia genus. In addition, we suggest that Witkowskia strigosa comb. et stat. nov. and Naviculadicta nanogomphonema, described from Ecuador, should be treated as synonyms. Thus, the taxonomic problem of the genus Naviculadicta is discussed.

Chromosome-level genome assembly of the cosmopolitan diatom Skeletonema costatum provides insights into ecological adaptation

The cosmopolitan diatom species Skeletonema costatum is an ecologically important dominant phytoplankton frequently found in the coastal estuarine and marine waters, and often causes harmful algae blooms. Despite of its critical ecological importance, chromosome-level genome assemble is still unavailable, hindering in-depth understanding of their evolution and environmental adaption. Here, we report a chromosome-level genome assembly for the marine diatom species S. costatum. The assembled genome size was 136.49 Mb, with a contig N50 of 302 Kb and 95.30 % of the reads anchored into 23 pseudo-chromosomes with a scaffold N50 of 6.19 Mb. A total of 28,321 protein-coding genes were predicted, with 86.03 % being functional annotated. The BUSCO assessment of genome assembly and genome annotation were both above 90 %. Phylogenetic analysis showed the expected topology, with S. costatum and its closely related species S. marinoi diverged from their common ancestor around 22.6 million years ago. The genome size of S. costatum is comparatively larger than those of its closely related diatoms, due mostly to its higher transposable element contents and larger number of proteincoding genes. Collinearity analysis revealed strong collinearity between S. costatum and other Skeletonema with most chromosomes showing clear one-to-one correspondences. A larger family of nine copies of the cryptochrome genes that function as blue light photoreceptors were identified in S. costatum, which could contribute its ecological success. The availability of the high-quality chromosome-level genome assembly for S. costatum represents a valuable resource that may facilitate comparative genomics for revealing important ecological clues and gene families, and future genetics and environmental studies among Skeletonema species.

Buryatia strelnikovae (Bacillariophyta), a New Species of Diatoms for Science

The study of algological material from tundra lakes of the adjacent territories of the Ust-Lena Reserve (Yakutia) using scanning electron microscopy revealed a new species of diatoms for science Buryatia strelnikovae sp. nov. The new species has morphological similarities with other species of the genus B. oviformis and B. crassa. It differs from the former by large values of the number of striae and areolae of 10 µm, from the latter by smaller length and width of the sash and large values of the number of strokes and areoles of 10 µm, but differs from them in smaller leaf length and width, large values of the number of striae and areolae of 10 µm.

Effects of salinity and temperature on growth performance, biochemical composition, and biosilification process of Cyclotella cryptica

Microalgae are valuable resources for producing high-value compounds, but large-scale cultivation in open raceway ponds (ORPs) faces challenges due to salinity and temperature fluctuations, which affect biomass yield and quality. Developing strains with high productivity and stable quality across varying salinity and temperature levels offers a promising approach to overcoming these challenges. Cyclotella cryptica, a marine diatom species, is known for its robustness under diverse salinity conditions, but its biochemical composition and frustule morphology in respond to salinity remains largely unknown. Moreover, the responses of C. cryptica to temperature fluctuations are largely unexplored, posing a barrier to its industrial application in ORPs. In this study, C. cryptica was cultivated under six salinity levels (19–34 ‰ at 3 ‰ intervals) and five temperature regimes (17–33 °C at 4 °C intervals) to investigate the effects of these environmental factors on growth performance, macronutrient composition, fatty acid (FA) profile, and carotenoid content. Additionally, we examined the biosilica content, frustule morphology, and the transcriptional levels of five frustule biogenesis related genes (CcSin1, CcSin2, and CcSAP1–3) to assess the impact of salinity and temperature on the biosilification process. Our findings revealed that salinity exerts minimal effects on growth, macronutrient composition, FA profile, and carotenoid content, whereas it induces significant variations in frustule morphology and biosilica deposition. In contrast, temperature markedly influences all evaluated parameters. These insights into the adaptive mechanisms of C. cryptica to salinity and temperature variations are crucial for optimizing the scale-up cultivation strategy of this species in ORPs.

Impact of extreme drought on diatom traits and species composition in temperate lowland streams

Impact of extreme drought on diatom traits and species composition in temperate lowland streams

Diatom pyrenoids are encased in a protein shell that enables efficient CO2 fixation

Pyrenoids are subcompartments of algal chloroplasts that increase the efficiency of Rubisco-driven CO2 fixation. Diatoms fix up to 20% of global CO2, but their pyrenoids remain poorly characterized. Here, we used invivo photo-crosslinking to identify pyrenoid shell (PyShell) proteins, which we localized to the pyrenoid periphery of model pennate and centric diatoms, Phaeodactylum tricornutum and Thalassiosira pseudonana. In situ cryo-electron tomography revealed that pyrenoids of both diatom species are encased in a lattice-like protein sheath. Single-particle cryo-EM yielded a 2.4-Å-resolution structure of an invitro TpPyShell1 lattice, which showed how protein subunits interlock. T.pseudonana TpPyShell1/2 knockout mutants had no PyShell sheath, altered pyrenoid morphology, and a high-CO2 requiring phenotype, with reduced photosynthetic efficiency and impaired growth under standard atmospheric conditions. The structure and function of the diatom PyShell provide a molecular view of how CO2 is assimilated in the ocean, a critical ecosystem undergoing rapid change.

Ulnaria asymmetrica sp. nov. (Bacillariophyta), a new fossil species from the Trout Creek Miocene locality, Oregon, USA

A new species of Ulnaria (Kützing) Compère is described from the Miocene Trout Creek fossil locality, situated in Harney County, Oregon, USA. The rock material from which the new species is described consisted of a subsample taken from the matrix harboring a plant fossil collected in 1932 or 1933 and archived at the Field Museum of Natural History, Chicago, Illinois, USA. The new species differs from all other taxa in the genus by possessing club-shaped valves that are asymmetric about the transverse axis, and frustules that are cuneate-shaped in girdle view. In addition to its unique shape, valves of the new species have a well-developed ocellulimbus (pore field) at each apex, a single rimoportula at one or both poles and closed girdle bands. The virgae are thick relative to the vimines, areolae possess exterior closing plates, and on larger specimens, the uniseriate striae can become biseriate near the valve margins. Material at the Trout Creek locality was deposited approximately 15.6–14 Ma during the Middle Miocene Climatic Optimum (MMCO). Given the diatom species co-occurring with the new Ulnaria species, it likely inhabited the plankton.

A new marine epipsammic diatom species Cymbellonitzschia biseriata (Bacillariophyceae) from Fujian, China

A new marine epipsammic diatom species, Cymbellonitzschia biseriata C.H. Li, H.H. Liu, Y.H. Gao & C.P. Chen sp. nov. from Fujian Province, China, is described, and is the first record of this genus in China. The morphological observations and species description are based on scanning electron microscopy and light microscopy. The main characteristics of C. biseriata are as follows: valves are semi-lanceolate; striae are biseriate or change from uniseriate to biseriate; canal raphe is located and discontinuous on the ventral side; distal raphe ends are curved and extended to the dorsal side of the valve, forming raised helictoglossae; areolae are occluded by domed hymenes; girdle consists of 4–7 perforated bands. The new species is only known at present from its type locality, Weitou Bay, Quanzhou City, Fujian Province, China.

Pollution load and dynamics of phytoplankton communities in relation to environment variables in Lake Babogay, Ethiopia

ABSTRACT The objective of this study was to investigate the water quality of Lake Babogaya in Ethiopia. Water samples were collected from six different sites, and analyzed for total coliform (TC), fecal coliforms (FC), and Escherichia coli (E.coli) content. Additionally, potential of hydrogen (pH), dissolved oxygen (DO), total dissolved solids (TDS), electrical conductivity (EC), and Secchi depth were measured. Nutrients and heavy metals were determined using standard methods. The abundance of phytoplankton was estimated by calculating the biovolume of the species. The results indicated that pH, TDS, DO, and turbidity ranged from 8.78 + 0.31 to 9.52 + 0.04, 129 + 4 to 419 + 3 ppm, 5.50 to 7.25 mg/l, and 0.96 to 17.29 NTU, respectively. TC bacteria exceeded the World Health Organization (WHO) standards at all sites, while FC levels exceeded in most samples. Cadmium and chromium were low in both seasons, whereas lead in the dry season exceeded the WHO limits. The levels of iron were high across all sites in the dry season and low in most sites in the wet season. Five major taxonomic phytoplankton groups were identified, comprising a total of 31 species with highest richness of green algae, blue-green algae, and diatoms species.

Phytoplankton community composition as a driver of annual autochthonous organic carbon dynamics in the northern coastal Baltic Sea

Phytoplankton are the major primary producers in the pelagic system. They greatly influence biogeochemical cycles but little is known about the importance of shifting phytoplankton community composition for carbon dynamics. This study investigates the impact of seasonal changes in coastal phytoplankton communities on pelagic carbon fluxes. A field sampling campaign, covering an annual cycle in primary production, was conducted to assess the seasonal changes of phytoplankton communities and relevant organic carbon parameters in the coastal Baltic Sea. The monitoring frequency ranged from 1 to 3 wk, adapted to match the seasonal phytoplankton blooms. In addition, sediment traps were deployed to determine the particulate carbon and nutrient export to the seafloor in every season. We found that the phytoplankton biomass during the spring bloom was as high as 550 µg C l-1 and was dominated by diatom species (88% of total phytoplankton biomass). In comparison, the more species-rich summer bloom reached a combined maximum biomass of 236 µg C l-1. However, the highest export flux of particulate organic carbon was found in the middle of August (561 mmol C m-2 d-1) and, not as expected, around the spring bloom in May (226 mmol C m-2 d-1), suggesting a high potential for carbon recycling within the pelagic food web rather than being exported to the seafloor or advected laterally. Our study emphasizes the importance of keystone species and diversity for carbon transport processes in marine coastal ecosystems and highlights complex relationships between phytoplankton biomass production, community composition and carbon dynamics.

Entomoneis parikhani sp.nov., Aras Nehri (İran)’nden yeni bir diatom (Entomoneidaceae, Bacillariophyta)

The diatom Entomoneis has a series of unique features such as connecting lines with different shapes, sigmoid raphe on the bilobate keel, different curtains, and multiple girdle bands. Most species belonging to this genus are found in marine and saline habitats. In fact, the genus Entomoneis is an epipelic diatom that is found in streams with high salinity and high electrolyte concentration. To date, no specific type of freshwater has been identified for this species. In this study, a new species of freshwater diatom, Entomoneis parikhani, is described based on detailed morphological observations using a scanning electron microscope. The samples were collected the Aras River near Oltan village of Parsabad city in the northwest Iran. A special feature of Entomoneis parikhani is its triple valve. The genus Entomoneis comprises of diatoms with sigmoidal raphe canals and girdle bands. This taxon is similar to Entomoneis annagodhei and Entomoneis tenera, as shown by LM and SEM observations, and there are sufficient morphological differences to separate Entomoneis parikhani. This new species had very small cells, delicate frustules without valve lines, and wide lanceolate valves. In this study, the wide distribution of this taxon in the Aras River has been evaluated.

First record of the species Encyonema bonapartei Heudre, C.E.Wetzel & Ector (Cymbellales, Bacillariophyceae) in Serbia

Encyonema bonapartei Heudre, C.E.Wetzel & Ector is a diatom species originally documented in 2016, following its discovery in three canals in the eastern region of France. In 2021, an extensive hydrobiological survey in a mountainous part of southwestern Serbia led to the first finding of this taxon outside of France, i.e. in the Uvac Special Nature Reserve – in Lake Zlatar (Zlatarsko jezero) and in the Marić River (Marića reka). Detailed light microscopy and scanning electron microscopy observations of a large population recorded in Lake Zlatar confirmed the unique morphological characteristics of E. bonapartei, which is also the first record for the diatom flora of Serbia. The present work provides new information on the distribution and ecological preferences of E. bonapartei, taking into account physical and chemical characteristics of its habitats in Serbia.

Diatoms of soils and pyroclastic deposits from South Kamchatka volcanoes

Twenty-four species of diatoms belonging to 14 genera, 12 families and 5 orders were identified from soils and pyroclastic deposits of the Gorely, Mutnovsky, Avachinsky, Koryaksky and Vilyuchinsky volcanoes (Kamchatka Peninsula, Russia). Two species of these (Nupela tenuicephala, Pinnularia bullacostae) are new to the flora of the Kamchatka Peninsula, three ones (Eunotia palatina, Neidium bergii, Stauroneis borrichii) to the Russian Far East, and another three (Psammothidium lacustre, Humidophila sceppacuerciae, Gomphonema reichardtii) to the flora of Russia. Three revealed taxa (Navicula sp., Chamaepinnularia sp., and Pinnularia sp.) are probably new to science, as their morphological and morphometric characteristics differ from those of previously described species.

Environmental and Climatic Drivers of Phytoplankton Communities in Central Asia.

Artificial water bodies in Central Asia offer unique environments in which to study plankton diversity influenced by topographic barriers. However, the complexity of these ecosystems and limited comprehensive studies in the region challenge our understanding. In this study, we systematically investigated the water environment parameters and phytoplankton community structure by surveying 14 artificial waters on the southern side of the Altai Mountains and the northern and southern sides of the Tianshan Mountains in the Xinjiang region. The survey covered physical and nutrient indicators, and the results showed noticeable spatial differences between waters in different regions. The temperature, dissolved oxygen, total nitrogen, and total phosphorus of artificial water in the southern Altai Mountains vary greatly. In contrast, the waters in the northern Tianshan Mountains have more consistent physical indicators. The results of phytoplankton identification showed that the phytoplankton communities in different regions are somewhat different, with diatom species being the dominant taxon. The cluster analysis and the non-metric multidimensional scaling (NMDS) results also confirmed the variability of the phytoplankton communities in the areas. The variance partitioning analysis (VPA) results showed that climatic and environmental factors can explain some of the variability of the observed data. Nevertheless, the residual values indicated the presence of other unmeasured factors or the influence of stochasticity. This study provides a scientific basis for regional water resource management and environmental protection.

Antifouling activity and ecotoxicological profile of the cyanobacterial oxadiazine nocuolin A

Pursuing effective and biocompatible natural compounds to supplant current biocidal antifouling (AF) technologies remains crucial and challenging. Among natural products hosts, cyanobacteria are recognized as producers of bioactive secondary metabolites that are underexplored in terms of anti-biofilm and AF potential. Nocuolin A, a natural oxadiazine previously isolated and known to be produced by different cyanobacterial strains, has demonstrated bioactive potential, particularly against tumor cell lines. Considering this potential and its exquisite chemical structure, here nocuolin A was investigated as a potential natural AF agent through an integrative approach including AF bioactivity testing across distinct levels of biological organization, mode of action assessment, ecotoxicity evaluation, and ecological risk predictions. Nocuolin A was found to inhibit the settlement of mussel (Mytilus galloprovincialis) plantigrades (EC50 = 3.905 μM) while showing no toxicity to this biofouling species (LC50 > 100 μM). Additionally, while exhibiting no inhibitory activity against the growth of five marine biofilm-forming bacterial strains, it significantly suppressed the growth of the marine biofilm-forming diatom Navicula sp. (EC50 = 1.561 μM), and had a lethal effect on this diatom species (>3.1 μM). The AF targets of nocuolin A on mussel plantigrades revealed no correlation with acetylcholinesterase and tyrosinase metabolic processes; however, proteins involved in oxidative stress, muscle regulation, and energy production were highlighted. The results also provide insights into the ecological risk of nocuolin A, including its ecotoxicity against Artemia salina nauplii (LC50 = 2.480 μM), Amphibalanus amphitrite nauplii (LC50 = 0.0162 μM), and Danio rerio embryos (LC50 = 0.0584 μM). When matching these results with simulated environmental values, nocuolin A was deemed a considerable threat to the ecosystems. While this research highlights the AF activity of nocuolin A, it also emphasizes the potential adverse environmental impact when applied in preventive coatings.

Annual cycle of phytoplankton in the Pacific ocean near Guatemala in relation to physicochemical parameters

Due to the lack of basic information on the behavior of the phytoplankton community of the Guatemalan Pacific, particularly of the factors that cause harmful algal blooms, monthly monitoring was performed during a year (January–December 2021), which included three hydrometeorological seasons at three sampling sites in Puerto Quetzal (Texaco Buoy, Recalada Buoy and Entre Morros Buoy) at two depths (1.5 m and 5.0 m). These sites are influenced by shipping and nearby human populations. The structure of the phytoplankton community (species composition, abundance, richness and diversity), with an emphasis on potentially toxic and non-toxic harmful species, were evaluated. A total of 53 diatom species from 26 genera and 13 orders and 42 dinoflagellate species from 14 genera and six orders were identified. No significant differences between the sampling depths and different quarters of the year were found. The comparison of the total cell abundance between the three sites showed no significant differences. The results obtained present novel information on the phytoplankton community of the Guatemalan Pacific, filling a gap in a region where algal blooms occur annually with consequent ecological impacts and human poisonings.

Blending census and paleolimnological data allows for tracking the establishment and growth of a major gannet colony over several centuries

Seabird colonies with long-term monitoring records, i.e., > 50 years, are rare. The population data for northern gannets (Morus bassanus) in Cape St. Mary’s (CSM) Ecological Reserve (Newfoundland and Labrador, Canada) is robust, extending back to 1883 when the colony was presumed established. We inferred the colony’s historical population shifts by measuring ornithogenic proxies in a dated sediment record collected from a nearby pond. Our record extended to the early eighteenth century, but the proxy data only began to show significant signs of seabird presence between ca. 1832 and 1910, aligning with the period gannets were first observed at CSM. Through the twentieth century, we observed significant increases in δ15N, P, Zn, Cd, and chlorophyll a, coeval with a shift in the dominant diatom species, indicating rapid colony growth. The proxies were overall highest in ca. 2005, corresponding to the reported historical maximum of the gannet colony in 2009. Our results validate that paleo-reconstructions using ornithogenic proxies can accurately reflect population trends and provide a stronger understanding of the colony’s establishment and growth. This study highlights the value of applying paleolimnological methods in seabird population studies to frame the history of a colony’s dynamics and inform conservation efforts.