Diatom Species Composition Research Articles

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

Chemical and diatom compositions of dating deep-sea sediment core of the Kuril-Kamchatka Trench, northwestern Pacific

For the first time the grain size, contents of major (Al, Ti, Fe, Mn, Ca, Mg, Na, and K) and trace elements (Mo, Ni, and Cu), total organic carbon, and stable carbon isotope were studied in the sediment cores collected at a water depth of approximately 9500 m from the Kuril-Kamchatka Trench. This study determined the factors of sedimentary environment. The quantitative content and species composition of diatoms were also studied. We have estimated the sedimentation rate based on the excess 210Pb data. According to age models, the sedimentation rate was ∼1.64 mm/year. Paleoconstructions were formed on comparing the distribution of chemical and biological parameters in deep-sea basin sediments. The studied sediments were characterized by the high content of the bioproductivity indicators and chemical elements (Fe, Ca, and Cu) corresponding to a period of increased supply of nutrients that stimulated the production of diatoms. Based on the study of chemical indicators and characteristics of nutrient utilization by phytoplankton, a period of outbreak of diatom productivity due to the introduction of volcanic ash into the sediment in the period 1860–1883 was marked. New data will complement existing information and helpful for further understanding of sedimentary geochemical characteristics in this hadal area, and allow us to relate abiotic conditions to productivity.

Разнообразие сообществ почвенных диатомовых водорослей Государственного природного заказника «Фролихинский»

The species composition of soil diatoms in Frolikhinsky State Nature Reserve was studied. Flora of diatoms algae was represented with 128 taxa of 4 classes, 12 orders, 23 families and 49 genera. The greatest diversity of species was found on the bank of the Bireya River (77 species), and the lowest – on the Barguzinsky ridge pass (3 species). In most species and intraspecific taxa of diatoms (97%) found in the reserve, the occurrence rate varied from 10 to 40%. An occurrence rate above 40% was noted only in four taxa that were identified as leading: Pinnularia borealis (80%), Adlafia bryophila (50%), Gomphonema parvulum (50%) and Planothidium lanceolatum (50%). The complex of dominant species was diverse and included representatives of 15 families. 36 species and intraspecific taxa were classified as dominants, 20 taxa were classified as subdominants. The complex of associated species included 6 taxa, 67 taxa were found singly and occasionally. Pinnularia borealis Ehrenberg had the highest occurrence at all sites. The families Fragilariaceae, Achnanthidiaceae, Naviculaceae, Ahnanthaceae, Gomphonemataceae, Cymbellaceae, Cocconeidaceae, Eunotiaceae, Pinnulariaceae, Bacillariaceae, Sellaphoraceae were characterized by high species diversity. Comparison of diatoms complexes (DC) in different plots of the reserve revealed similarities and differences of floristic diversity and taxonomic structure. The main reasons of taxonomic heterogeneity of DC in different areas are the conditions defined by their location within the natural reserve. The largest number of species was found on the shores of water bodies characterized by a high degree of moisture. The least abundant and diverse diatoms were represented in shaded and insufficiently moist areas of coniferous forests with abundant coniferous litter and acidic soils.

Pseudogomphonema lukinicum sp. nov. (Bacillariophyceae), a new endophytic diatom found inside multicellular red algae from the Northwest Pacific

Abstract In our collections from the Northwest Pacific waters, we found several specimens of the red algae Lukinia dissecta and Callophyllis perestenkoae with darker spots on their thalli, which contained an unusual pennate diatom. A detailed morphological analysis based on light and scanning electron microscopy observations made it possible to describe a new species of endophytic diatom, Pseudogomphonema lukinicum sp. nov. Stonik et Skriptsova. The new species has some morphological features typical of the genus, such as the heteropolarity of the valves, the presence of pseudosepta and small apical chambers at both poles of the valves, and nonporous girdle bands. Pseudogomphonema lukinicum has been described and distinguished from the other species in the genus on the basis of a combination of morphological traits, including relatively small cell dimensions, a slightly asymmetrical valve to the transapical axis, with obtusely rounded headpole and narrower footpole, the large asymmetrical central area, and the presence of apical chambers at both poles. Pseudogomphonema lukinicum is the second representative of Pseudogomphonema known to be living endophytically. The data on the species composition of endophytic diatoms in marine macroalgae, their habitats, and host organisms reported in the literature to date are summarized.

Exploring epipelic diatom species composition across wetlands conductivity gradients in southern Spain

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.

Reconnecting a stream channel to its floodplain: implications for benthic diatoms and macroinvertebrate trophic structure

Streams systems draining upland landscapes provide valuable ecosystem services, but they are vulnerable to incision and channelization caused by anthropogenic disturbance. Restoring a degraded stream to its pre‐disturbance condition by reconnecting the channel to its historical floodplain aims to recover lost hydro‐morphological processes and functions. Seeking evidence to indicate whether that aim is met in practice, we examined diatoms and the stream macroinvertebrate trophic structures in three reaches of Whychus Creek, Oregon, United States. Two reaches were reconnected to their pre‐disturbance floodplains in 2012 and 2016. The third, control reach, was not restored and was selected to represent the degraded stream condition prior to restoration. Ordinations showed that benthic diatom species composition shifted from the control reach to the restored reaches. Compared to the control reach, reconnection decreased the percentages of diatoms with nitrogen (N)‐fixing cyanobacterial endosymbionts in the 2012 restored reach and decreased diatoms tolerant to low N conditions in both the restored reaches. δ15N values in both stream macroinvertebrates and tree leaves in the riparian zone were higher in the restored reaches. These findings suggest that floodplain reconnection may modify hydro‐morphological processes and ecosystem functions in ways that enhance organic matter retention and hyporheic exchange, resulting in increased nutrient availability, improved nutrient cycling, and greater primary productivity. More generally, our results suggest that characterizing diatom species composition and trophic interactions using stable isotopes provides the basis for identifying and evaluating the beneficial effects of stream restoration on ecosystem functions and the food‐web.

Influence of hydrological changes on the composition of phytoplankton and sediment diatoms in the Rio de la Plata estuary

ABSTRACT ENSO phases produce changes in precipitation and river flow in Eastern South America. We aimed to evaluate phytoplankton and surface sediment diatoms' response to ENSO within the Río de la Plata estuary. A 180-km-long transect off the Uruguayan coast was undertaken in May 2009 (La Niña) and May 2010 (El Niño), where physical, chemical and biological variables were measured. During El Niño we registered lower temperatures/salinities throughout the transect, and the riverine zone was specifically more homogeneous in terms of temperature, salinity, turbidity and chlorophyll-a than during La Niña. We observed changes in the species composition of both planktonic and sediment diatoms. Concomitantly, a significant depletion in planktonic diatom abundance and richness in both planktonic and benthic domain during El Niño was observed. In addition, there was a higher proportion of dinoflagellates than during La Niña, which was explained by a higher water column stability. The dominance of the chain-forming and meso-eutrophic diatom Aulacoseira was registered during El Niño in both domains, mainly in the fluvial zone, related to a high river discharge. Our findings are important to anticipate changes in microalgae composition related to oceanographic variability during potential ENSO events.

Cryptochrome PtCPF1 regulates high temperature acclimation of marine diatoms through coordination of iron and phosphorus uptake.

Increasing ocean temperatures threaten the productivity and species composition of marine diatoms. High temperature response and regulation are important for the acclimation of marine diatoms to such environments. However, the molecular mechanisms behind their acclimation to high temperature are still largely unknown. In this study, the abundance of PtCPF1 homologs (a member of the cryptochrome-photolyase family in the model diatom Phaeodactylum tricornutum) transcripts in marine phytoplankton is shown to increase with rising temperature based on Tara Oceans datasets. Moreover, the expression of PtCPF1 in P. tricornutum at high temperature (26 °C) was much higher than that at optimum temperature (20 °C). Deletion of PtCPF1 in P. tricornutum disrupted the expression of genes encoding two phytotransferrins (ISIP2A and ISIP1) and two Na+/P co-transporters (PHATRDRAFT_47667 and PHATRDRAFT_40433) at 26 °C. This further impacted the uptake of Fe and P, and eventually caused the arrest of cell division. Gene expression, Fe and P uptake, and cell division were restored by rescue with the native PtCPF1 gene. Furthermore, PtCPF1 interacts with two putative transcription factors (BolA and TF IIA) that potentially regulate the expression of genes encoding phytotransferrins and Na+/P co-transporters. To the best of our knowledge, this is the first study to reveal PtCPF1 as an essential regulator in the acclimation of marine diatoms to high temperature through the coordination of Fe and P uptake. Therefore, these findings help elucidate how marine diatoms acclimate to high temperature.

Ecophysiological behaviour of different diatoms in response to copepod signals

ABSTRACT Phytoplanktonic communities have been moulded from a higher level in the food web by zooplankton predation. Diatoms, which are the major primary producers in present day oceans, have evolved many strategies to thrive in the presence of copepods, their predators. Chemical signals are released in the aquatic environment by microarthropods and elicit morphological, behavioural and/or physiological modifications in diatom cells which allow them to cope with predators. Other than the most studied effects of copepod signals on the release of toxins by diatoms, the role of chemical cues on growth and biology of non-toxic diatoms has been little investigated, although it may broaden our knowledge of co-evolutive physiological mechanisms. To examine the response of diatoms to copepod-derived signals, Phaeodactylum tricornutum, Chaetoceros muelleri and Cylindrotheca fusiformis (Bacillariophyceae) were grown in the presence of copepod cues. Physiological modifications occurred and differed in sign and magnitude between species: i) in P. tricornutum cell density was higher, and dry weight lower, suggesting energy allocation into cell division at the expense of lipid and protein quotas; ii) C. muelleri showed a very homeostatic behaviour; and iii) in C. fusiformis cell density was lower and lipid content higher, showing energy allocation into lipids, which likely act as deterrent to feeders. Copepod cues are here suggested to have ruled diatom species composition in the ocean by affecting species-specific growth performance and the energy allocation into macromolecules.

Paleoenvironmental reconstruction of climate by diatoms from sediments of three deep freshwater lakes of Evenkia (Siberia, Russia)

The study aimed to determine the species composition of diatoms in the bottom sediments of the freshwater lakes Zapovednoye, Cheko, and Peyungda, situated in the taiga zone of the southern region of Evenkia within the boundaries of the Tungussky State Nature Reserve. A total of 255 taxa have been identified in these lakes, with their ecological characteristics also established. The diatom community present in the bottom sediments of the aforementioned lakes showcases species that are common across all three lakes, as well as some that are exclusive to every single reservoir. An examination of the acquired data indicated the existence of overarching trends in the evolutionary trajectory of lakes Cheko, Zapovednoye, and Peyungda. Nevertheless, discernible discrepancies are observed in the species composition of diatoms within their bottom sediments, both in terms of quality and quantity, thereby delineating Lake Peyungda in a distinctive position in comparison to lakes Zapovednoye and Cheko. This disparity is likely attributed to the relatively shallow depth of Lake Peyungda, leading to an inclination towards a heightened level of eutrophication in its species composition, as opposed to the conditions observed in lakes Cheko and Zapovednoye.

Diversity of Diatom Algae in the Lena Delta Nature Reserve and the Adjacent Territory in the Specific Ecological Factors of the Arctic

A total of 413 diatom taxa were known for aquatic habitats of the Lena Delta Nature Reserve. We identified 385 taxa in 14 small tundra lakes near the reserve that significantly enriched the diatom diversity of the region (666 taxa including definitions to the genus level). Thus, the species composition of diatoms in the reserve and adjacent territories was increased by 278 species. We showed that the species of the genera Pinnularia (57) and Eunotia (51) have predominance at the family and generic levels. The index of intraspecific variability Ssp./Sp. for the lakes of the reserve was 1.11, and that for the lakes of the Tiksi region 1.14, which is typical for high-latitude and high-mountain communities. The number of rare or endangered species varied in different lakes from 1 to 10, totaling 42 species for the entire study area. Bioindication has shown that potentially threatened species prefer moderate temperatures, and slightly acidic or neutral environments free from organic pollution. A comparative analysis of the species composition of diatoms in the vicinity of the Lena Delta and other northern water bodies of Yakutia and the Arctic Islands showed that the species composition of each lake in the Arctic has a discernably different species distribution. The indicator characteristics show a certain response of the species composition of diatoms to changes in salinity, pH, and organic pollution. Regularities in the spatial distribution of diatoms in the study area were revealed in connection with the environmental variables of their habitat. Statistical mapping of diatom diversity data and bioindicators revealed a pronounced response to point pollution, and also let us assume the influence of summer northeast winds on species composition of the studied lake communities. We suggest that the high diversity inherent in the diatom lakes of the Tiksi coastal zone, which can even be updated in further studies, can be considered as a property of coastal biota inherent in ecotones. Since it is in the coastal Tiksi region that a surge in the number of species is observed, this region can be considered not only an ecotone, but also a hotspot of diatom diversity. The results of the study are important for developing the basis for monitoring biodiversity under the conditions of anthropogenic and climatic changes in the Arctic.

Preboreal oscillation in the light of multiproxy analyses—Early Holocene in Lake Jelonek (North Poland)

In this work, we studied the course of climatic fluctuations at the beginning of the Preboreal period using multiproxy analyses (Chironomidae, pollen, diatoms, Cladocera, stable isotopes, macrocharcoal, microlithofacial) combined with varve chronology of sediments. The results showed a decrease in the mean July temperature and stronger continentalism followed by climate wetting at the start of the Preboreal period. This was reflected in the remodeling of the vegetation cover from birch forests to more open spaces with grass vegetation dominance, as well as that of the species composition of Cladocera and diatoms, and the high variability of isotopic composition. In addition, the results showed the impact of local conditions (fires and relict permafrost) on the amplification of environmental responses due to climate cooling. The environmental transformations presented here correspond temporally to the changes that are well documented in other parts of Europe as the Preboreal Oscillation.

Ecotonic Communities of Diatoms in the Southeastern Part of the Kamchatka Peninsula

Data about the ecotonic diatom communities of the Kamchatka Peninsula, a unique territory with strong volcanic activity, are very limited. We aimed to investigate diatom algae of the ecotones in the southeastern part of Kamchatka, including the Paratunka river valley, at the foot of the Vachkazhets volcano, and the bank of the Bystraya river. In total, 55 taxa were identified. The most diverse were the flora of the Paratunka river, with 31 taxa. Near the Bystraya river, 26 taxa were identified. Near the Vachkazhets volcano, 18 taxa were identified. Fragilariforma virescens, Planothidium lanceolatum, Pinnularia cf. subcapitata, Halamphora normanii, Nitzschia palea, and Eunotia exigua were the dominant species in the studied ecosystems, with the maximum abundance score. Pinnularia cf. subcapitata and Planothidium lanceolatum were found in all ecotones. In the studied habitats, small indifferent alkaliphilic cosmopolitan species prevailed. Our study revealed that the diatom species composition of the Kamchatka ecotones reflects their adaptability to survive in the extreme conditions of volcanic substrates. The results contribute to our knowledge of the ecology and biogeography of a number of diatom taxa.

New data on a hotspot of diatom diversity in the vicinity of the Lena Delta Nature Reserve in the Arctic

In 14 small tundra reservoirs in еру vicinity of Lena Delta Wildlife Reserve, we identified385 taxa, which in the compilatory list made up a significant diversity (666 taxa including definitions to the genus level) of diatoms. Thus, the species composition of diatoms in the reserve and adjacent territories was replenished by 278 species. The number of rare or endangered species is 42 for the entire study area. Statistical mapping of indicators of community and habitat diversity revealed a strong reaction to point one-time pollution and made it possible to assume the influence of summer northeast winds on the species composition. We suggest that the high diversity inherent in the diatom lakes of coastal zone, can be considered as a property of coastal biota inherent in ecotones. Comparative floristics of diatoms from Svalbard to Chukotka established a high individuality of the species composition in the lakes of the Arctic. Since it is in the coastal region that a surge in the number of species is observed, this region can be considered not only an ecotone, but also a hotspot of diatom diversity. The results of the study are important for developing the basis for monitoring biodiversity under the conditions of anthropogenic and climatic changes in the Arctic.

Diatoms of the lake Yanychkovo (Sverdlovsk region)

In this paper, we analyze the results of studies of the lake Yanychkovo (Sverdlovsk region) for 2016– 2022. Stock and own data on species composition, dominant complexes, abundance and biomass of diatoms for this period are summarized.

Results of diatom analysis of bottom sediment columns from the southern part of the Sea of Azov and the Kerch strait

The features of the species composition of diatoms from the Ancient and New Azov deposits of the Sea of Azov were studied. For New Azov deposits, the dominance of several taxa was revealed: species and varieties of Actinocyclus octonarius, Actinoptychus senarius, resting spores of the genus Chaetoceros spp., Thalassiosira decipience. Actinocyclus octonarius var. tonsure and A. pseudopodolicus should be considered indicator taxa, which mark the Novoazovsk layers. The Ancient Azov layers are characterized by a significant decrease in the abundance of A. octonarius, the absence of such taxa as A. octonarius var. tonsure, A. pseudopodolicus, Actinoptychus senarius. Paralia sulcata can be considered as marking species the Ancient Azov deposits (the period of the New Black Sea transgression).

Ecological distribution of modern diatom in peatlands in the northern Greater Khingan Mountains and its environmental implications.

Relationships between diatom assemblages and environmental variables in peatlands of the northern Greater Khingan Mountains are helpful for understanding the indicative significance of diatoms to environment changes, and potentially provide a reference for environmental monitoring and paleoenvironment reconstruction in the edge of monsoon region. In this study, we analyzed modern diatom assemblages and their relationships with environment factors in 30 surface samples from shrubby-herbaceous and herbaceous peatlands based on ordination analysis. Benthic and epiphytic Pennatae diatoms are mainly ecological types, whereas planktonic Centricae diatoms are relatively fewer. The most diverse genera are Pinnularia and Eunotia. Eunotia paludosa and Achnanthidium minutissimum dominated in shrubby-herbaceous peatlands, while Navicula minima and Fragilaria capucina dominated in herbaceous peatlands. The diatom community structures are different in different vegetation types and the diatom species diversity in herbaceous peatlands is higher than that in shrubby-herbaceous peatlands. CODMn and pH are the most important environmental factors affecting diatom species composition and diversity. Eunotia bilunaris, Eunotia mucophila, and Eunotia paludosa can be used as indicators of acidic water environments. Caloneis silicula, Fragilaria capucina, Hantzschia amphioxys, and Navicula radiosa can be applied to indicate the weak alkaline conditions. Eunotia bilunaris and Eunotia paludosa can indicate low conductivity, while Sellaphora pupula indicates the medium-high conductivity. Fragilaria capucina and Navicula radiosa can indicate oligotrophic habitats.

Neoglacial lake-ecosystem changes above and below the subarctic Fennoscandian treeline inferred from changes in diatom functional groups

Algal communities act as sensitive indicators of past and present climate effects on northern lakes, but their responses can vary considerably between ecosystems. Functional trait-based approaches may help us better understand the nature of the diverse biotic responses and their underlying ecosystem changes. We explored patterns in diatom (Bacillariophyceae) growth forms and species composition during the Neoglacial in two shallow lakes typical of subarctic regions, including a dark-colored woodland lake and a clear tundra lake. Sediment carbon and nitrogen elemental and isotope biogeochemistry and spectral indices were used to track broadscale changes in lake productivity, the inflow of organic carbon from land, and benthic substratum over the past three millennia. The biogeochemical indices tracked declines in land-lake connectivity as well as lake-water and sediment organic enrichment above and below the subarctic treeline driven by Neoglacial cooling. This broadscale environmental transition was intercepted by periods of elevated primary production associated with transient Neoglacial warm anomalies and, in particular, the twentieth century warming. Although the Neoglacial development of the lakes showed conspicuous similarities, diatom functional and taxonomic responses were not uniform between the lakes pointing to intrinsic differences in the development of benthic habitats and underwater-light regimes. Many of the observed biotic shifts aligned with expectations based on earlier research linking diatom functional traits to changing light and organic levels but the results also point to further research needs, particularly to better differentiate the individual and interactive effects of substratum and light. Despite distinct anthropogenic imprints in the biogeochemical record, the scale of human impact on the lakes’ biota has not, as yet, been profound, but the changes are nonetheless clear when compared to the previous three millennia of natural lake development.

Identifying pre‐Hispanic water storages in agricultural areas of south‐central Andes through diatom evidence

AbstractIn the Andes, there are several pre‐Hispanic irrigation networks with structures destined for water storage. However, it has not been widely discussed in archaeological research. This is probably due to their being difficult to identify. The aim of this study is to explore the use of diatom assemblage analysis as a methodological tool suitable to help in the identification and characterization of these ancient hydraulic structures. We analyzed two archaeological structures interpreted as water reservoirs from north‐western Argentina (EH1 in Antofagasta de la Sierra and U‐88R1 in Yocavil) and compared them to current reservoirs. The diatom species composition and the changes in the dominant ecological groups in the studied structures highlight different periods of hydraulic behavior. EH1 contained and stored water, but there were periods of time in which there was a lack of use or abandonment of the structure. However, the U88‐R1 structure does not have diatom evidence of containing standing water for a prolonged time but presence of wet soils. Thus, the structure could have been used for other water management strategies. The results show that diatom analysis is a methodological tool with a high potential to study ancestral hydrotechnologies.

Ice algae in current water-ice environmental condition of the Arctic Ocean

In the Arctic Ocean (AO) of today, there are noticeable changes in the composition and structure of biological communities inhabiting the water-ice environment. Over the past two decades, a decrease in the number of species of the sea ice flora and fauna has been noted in the central regions of the AO due to the changing physical environment of their habitat. In view of the current climatic instability in the AO, it is important to monitor and evaluate their composition, structure and dynamics of development. It is also important to preserve the methods of processing the materials collected in order to compare the state of the water-ice biota on similar spatial and temporal scales of the basin. In the present study, centric and pennate diatoms dominating in ice floristic communities were selected as indicators of changes. The aim of the work is to analyze the physical state of the water-ice environment and the species composition of ice diatoms based on the materials of the expeditions within the NABOS program at the Research Vessel (R/V) “Akademik Treshnikov” in the Arctic Basin in 2018 and 2021. The field work included observations of the state of the sea-ice cover in the area of the expeditions, the selection of ice cores to assess the salt composition and species composition of the algae, as well as CTD-sounding of the under ice — water layer. The analysis of the materials collected showed significant differences in the species composition and abundance of algae between the seasons, which indicates the formation of independent floristic communities in the current conditions of unstable physical environment in the central regions of the AO, which confirms the previously obtained results in the period 2007–2015. The materials under discussion were obtained in a short period of time and in limited spaces in the zones of production of annual ice in the waters of the shelf seas and zones of removal to the central regions of the AO. At the same time, short-term observations provide “instant” information about the qualitative and quantitative state of sea-ice biological communities. In order to obtain reliable estimates, long-term observations are needed, which may be organized in the near future based on new logistical approaches to the study of the marine Arctic.