Diatom Composition Research Articles

Composition of diatoms Sphagnum bogs in the zone of influence of oil fields (Nizhnevartovsk)

Composition of diatoms from 6 plots of riding sphagnum swamps contaminated by oil and oil products has been studied. Twenty three species from 9 genera, 8 families, 2 classes were revealed. The influence of oil-field objects on the species composition and dynamics of algae abundance depending on the degree of pollution and reclamation works is studied. Three species of Bacillariophyta were dominated.

Subtle variability in water quality structures tropical diatom assemblages in streams of Cape York Peninsula, Australia

Contemporary benthic diatom assemblages were examined from 52 riverine and palustrine wetlands on Cape York Peninsula, Australia, to determine their environmental sensitivities and develop inference models. Multivariate analyses identified strong relationships between nine environmental variables and the diatom assemblage composition, with the aim to select variables for developing models. Total alkalinity, bicarbonate concentration, pH, electrical conductivity (EC) and latitude were most consistently and strongly correlated with diatom composition. The river basins sampled generally have an east–west orientation, so latitude potentially represents biogeographic differences between basins. Comparison of diatom assemblages between river basins showed significant differences, but substantial overlap in species. Diatom-based transfer functions were developed for each environmental variable and tested using the relationships between measured values and values predicted by the transfer functions. These were significant, and had low root mean square errors. An independent validation dataset for EC was analysed and applied to the EC transfer function. Results showed good predictions, giving confidence in its relevance beyond the training dataset. These understandings and models of the environmental effects on diatom assemblages allow for their application to future monitoring programs and reconstruction of past water quality conditions using fossilised diatoms in layered aquatic sediments of Cape York.

Temporal changes in biological traits of diatom communities in response to an oil spill in a subtropical river.

Diatom growth strategies, which are used as a proxy to analyze disturbances and environmental impacts, can also provide reliable information about environmental gradients. In this study, we used diatom communities and biological traits to assess the structure of epilithic diatoms after an oil spill in a large tributary of the Iguaçu River (Paraná, Brazil). Epilithon and water samples were taken on July 12th, 2004, and after an unexpected oil spill, on the following days: 09/19, 10/03, and 10/13/2004. We observed that the spill caused a distinct shift in both diatom composition and guild group. Diversity decreased and pollution-tolerant diatoms of the motile group became dominant in response to the elevated nutrient levels and reduced light. Tube-forming diatoms, which are strong competitors for light, dominated the epilithon 24 days after the oil spill. Both diatom guilds and growth forms were successfully used to predict the environmental conditions. While diatom guilds responded to disturbances along a temporal gradient, changes inside the guilds were the main factor for understanding the environmental gradient.

Benthic diatoms of the Tabolki Lake (reserve “Yelnya”, Republic of Belarus)

The first data on the species composition of the benthic diatoms of the Tabolki Lake are given. A brief analysis of the taxonomic and ecological-geographical structure of the diatom complex has been carried out.

Peculiarities of composition and vertical distribution of centric diatoms in the Klyuchik Lake (Nizhny Novgorod Region)

The composition and development of phytoplankton of highly mineralized Lake Klyuchik (Nizhny Novgorod Region) were considered. The lake is unique of having a distinct ecotone on hydrochemical parameters. The prevalence of diatom algae, which are dominant in the number of species (46% of the total species composition) and abundance indices, was revealed. The vertical distribution of algae development was the most heterogeneous in the ecotone zone. In the bottom layers of the ecotone there was a mass development of the centric diatom Cyclotella distinguenda Hustedt with uniquely high abundance (several ten million cells/l) and biomass (more than 130 g/m3).

Biological assessment of the river Nalchik (Hara) (Central Caucasus) on indicator species (Bacillariophyta)

For the first time a biological assessment of the Nalchik River (Hara) (Central Caucasus) was made on the basis of species composition and abundance of diatoms. The formation of a database for monitoring water ecosystems in the region has been started.

Contribution to the Lake Algal Flora and Microcrustacean Fauna of the Great Lakes Depression, Mongolia

In this paper the taxonomic composition of phytoplankton, diatoms and microcrustaceans (cladocerans and copepods) in lakes of the Great Lakes Depression (Mongolia) is examined. The inventories were based on samples collected in seven lakes and in one small reservoir between 2005 and 2009. Four lakes and the reservoir are of fresh water, (110 - 300 µS/cm of water conductivity) and the three remaining lakes are endorheic and with more mineralized water (5,270 – 9,550 µS/cm of water conductivity). In the phytoplankton 136 taxa were identified, where 29 species and 10 genera are the new records for Mongolia. In case of Diatoms 122 species were identified and 48 of them are the new records for Mongolia. Thirty-nine species of cladocerans and 9 species of copepods were identified, 13 species of cladocerans and one copepod are new for Mongolian fauna. In general, the taxa belonging to the different analyzed groups (pytoplankton, diatoms and microcrustaceans) are known throughout the Palaearctic region. Most taxa of all the analyzed taxonomic groups take place in the lakes with low mineralization, while lakes with more mineralized waters had significantly lower species richness.

The diatoms as a component of bottom algocenoses in the mouth of the Oka River

The preliminary estimation of composition and structure of diatoms in the benthos of the Oka River allowed to determine the clear spatiotemporal confinedness of structure in such communities of them which has the most diverse composition in the low water period while water temperature decreasing.

Diatoms in the phytoplankton of the Vetluga River

Data on the taxonomic composition and significance of diatoms in the phytoplankton of one of the major tributaries of the Cheboksary reservoir (Vetluga River) are given. The leading role of diatoms in phytoplankton biomass is shown. The emergence and vegetation of alien species are revealed.

Centric diatoms from paleolakes of the Baikal rift zone, Russia

Using light and scanning electron microscopy centric diatoms were investigated from paleolakes of the Barguzin, Tunkinskaya valleys and Vitim Plateau. Representatives of Aulacoseira, Actinocyclus, Alveolophora, Pseudoaulacoseira and Concentrodiscus were common and widespread. The greatest similarity in species composition of diatoms was found between the paleo-lakes of the Barguzin Valley and the Vitim Plateau.

New data of diatoms in the Lake Mogilnoye (Kildin Island, Barents Sea)

The diatom flora of the relict meromictic Lake Mogilnoye over the past 100 years has been analyzed. An inventory and taxonomic revision of diatom composition were carried out.

Diatom diversity in headwaters influenced by permafrost thawing: First evidence from the Central Italian Alps

Glacier melting and permafrost thawing are the most evident effects of the current climate change that is strongly affecting high mountain areas, including the European Alps. As the thawing rate of subsurface ice is lower than for glacier ice, it is expected that, while glaciers retreat, an increasing number of Alpine headwaters will become more influenced by permafrost degradation during the 21st century. Despite the expected change in the relative importance of glacier and permafrost in determining Alpine hydrology, studies addressing effects of permafrost thawing on chemical and, especially, biological features of adjacent surface waters are still scarce. The present study contributes to characterise the epilithic and epiphytic diatom diversity in a set of permafrost-fed headwaters in three sub-catchments differing in bedrock lithology of the Italian Central Alps (Trentino Alto-Adige) in relation to water chemistry and habitat features. In addition, it explores chemical and biological differences between permafrost-fed streams and headwaters with no direct contact to permafrost, namely glacier-fed (kryal) and precipitation-/groundwater-fed (rhithral) streams. Permafrost-fed waters showed higher electrical conductivity and enhanced ion concentrations than glacier- and precipitation-fed waters, while concentration of trace elements (e.g. Sr, Ni, Zn, As) were more irregularly distributed among waters of different origin, though they showed a tendency to reach higher levels in permafrost-fed waters. Diatom species richness and diversity were lower in permafrost-fed headwaters, and were principally related to water pH and trace metal concentrations. Epiphytic diatom assemblages were more diverse than epilithic ones, independently from the water origin, while differences in species composition were not sufficient to unequivocally identify a typical diatom composition for the different water types considered in this study.

Composición, abundancia y distribución de Diatomeas en dos localidades de la provincia del Guayas entre octubre 2013 y febrero 2014.

El presente trabajo se desarrolló en dos localidades de la Provincia del Guayas entre octubre y febrero 2014. El objetivo de esta investigación fue comparar la composición, abundancia y distribución de diatomeas centrales en las aguas estuarinas de la parroquia Posorja y en el Cantón General Villamil Playas de influencia oceánica. Los arrastres superficiales se realizaron quincenalmente a bordo de una embarcación un motor de 75 HP a una velocidad de 2 nudos, en un tiempo de 5 minutos de recorrido por cada estación a 1 milla de la orilla del mar. En total se identificaron 71 especies en las que predominan las Diatomeas Centrales con 60 especies y se registraron 11 especie de Diatomeas Pennales, la especie con mayor densidad. Chaetoceros coarctatus, mayor densidad poblacional con 15576 cel. 100m3, correspondiendo al 12,80% en las dos áreas muestreadas de un total de 36 muestras colectadas. Mediante el índice de Shannon – Wiener se muestra una similitud entre estaciones. En Posorja hubo irregularidad en todas las estaciones, coincidente con el índice de Simpson que registró que no hay similitud entre estaciones. La abundancia y distribución corresponde al 51% de las Diatomeas del orden Centrales en Posorja en tanto el 49% concierne a General Villamil.

Komposisi Diatom (Bacillariophyceae) Perifitik pada Substrat Kaca di Sungai Kapuas Kecil Kota Pontianak Kalimantan Barat

Periphytic diatom (Bacillariophyceae) is diatom that lives attach on a substrate and it was dependent on the environmental conditions in an aquatic ecosystem. This study was aimed to determine the composition of periphytic diatom (Bacillariphyceae) on glass substrate and the condition of physical chemical water in Kapuas Kecil River. This study was conducted from September to December 2017. The sampling stations were chosen by purposive random sampling method and divided into four stations. At each station in the river were installed 5 baskets each with 5 glass slides. Samples were collected from three baskets with sampling intervals on day 2, 5, 10, 15, and 20. The result shows that the composition of periphytic diatoms (Bacillariophyceae) in Kapuas Kecil River consists of 29 genera from 2 orders (Pennales and Centrales) and 12 families. The most commonly genera found of periphytic diatom were Eunotia, Gomphonema, Frustulia and Nitzschia.

Influence of environmental variables on the diatom communities of oligotrophic reservoirs for public water supply (Guarulhos, Southeast Brazil)

Abstract Aim: Our study aimed at analyzing the diatom community structure of the plankton, periphyton, and surface sediments, and their relationship with the environmental variables of two reservoirs, Tanque Grande and Cabuçu, located in the city of Guarulhos, Metropolitan Region of São Paulo. Methods Three sampling stations were stablished in each reservoir. Samples of water and periphyton were collected during the dry (August 2013) and the rainy periods (January 2014), while the sediment was sampled only during the dry period. Water abiotic limnological variables were determined and quantitative and qualitative analyses were performed after the oxidation of diatom samples. Results Both reservoirs presented low values of electrical conductivity, pH and nutrients. The diatom community was represented by 30 taxa distributed in 20 genera. The diatom diversity was higher in the plankton, with three exclusive species. All taxa collected from the surface sediments also occurred in the plankton. The periphyton was represented by six taxa that were exclusive to this habitat. Conclusion Our results indicated that the environmental variables were responsible for the limnological changes in the two reservoirs. In the studied reservoirs, the species composition of diatoms differed slightly between the plankton and the surface sediments, while we found a different community in the periphyton, with the presence of exclusive species. The two climatic periods showed differences in the abundance of species, but no considerable differences in the species composition between the two reservoirs were observed.

Host-derived population genomics data provides insights into bacterial and diatom composition of the killer whale skin.

Recent exploration into the interactions and relationship between hosts and their microbiota has revealed a connection between many aspects of the host's biology, health and associated micro‐organisms. Whereas amplicon sequencing has traditionally been used to characterize the microbiome, the increasing number of published population genomics data sets offers an underexploited opportunity to study microbial profiles from the host shotgun sequencing data. Here, we use sequence data originally generated from killer whale Orcinus orca skin biopsies for population genomics, to characterize the skin microbiome and investigate how host social and geographical factors influence the microbial community composition. Having identified 845 microbial taxa from 2.4 million reads that did not map to the killer whale reference genome, we found that both ecotypic and geographical factors influence community composition of killer whale skin microbiomes. Furthermore, we uncovered key taxa that drive the microbiome community composition and showed that they are embedded in unique networks, one of which is tentatively linked to diatom presence and poor skin condition. Community composition differed between Antarctic killer whales with and without diatom coverage, suggesting that the previously reported episodic migrations of Antarctic killer whales to warmer waters associated with skin turnover may control the effects of potentially pathogenic bacteria such as Tenacibaculum dicentrarchi. Our work demonstrates the feasibility of microbiome studies from host shotgun sequencing data and highlights the importance of metagenomics in understanding the relationship between host and microbial ecology.

Impoundment intensity determines temporal patterns of hydrological fluctuation, carbon cycling and algal succession in a dammed lake of Southwest China

Hydrological control of lakes has been increasingly practiced in many parts of the world, however, the long-term ecological impact of hydrological regulation and their dependence on lake impoundment intensity has been rarely examined. We combined a spatial survey of surface sediments with sediment core analyses to quantify the limnological changes over the last two centuries for an oligo-mesotrophic lake, which was dammed in 1957 and reinforced during 1987–1990, respectively. A water depth inference model constructed from surface sediment clay components was applied to a well-dated sediment core for water level reconstruction. The inferred water depth increased from 6.2 ± 0.9 m to 8.7 ± 1.7 m after dam construction and further to 13.6 ± 2.6 m after dam enforcement, resulting in an increase in the magnitude of water level fluctuation (WLF). Accordingly, bulk sediment C/N ratio and median grain size spiked in ∼1957 and ∼1990, respectively, reflecting a large input of terrestrial sources due to impoundment. With a consistent loss of littoral zone and benthic diatoms over time, a significant decrease in C/N ratio and an abrupt depletion of carbon isotopic signal suggested a shift of carbon transfer towards a pelagic pathway after ∼1990. While there was a significant increase in algal production since ∼1990, the accumulation rate of carbon and nitrogen burial displayed an accelerating drop since ∼1957, reflecting a diluting effect derived from expanding water storage. Furthermore, there was a significant increase in both the ratio between inorganic and organic carbon fluxes and sediment burial of inorganic carbon, reflecting enhanced degradation and low storage of aquatic organic carbon in stratified deep waters since ∼1990. Hydro-morphological variables were found to exert strong impact on diatom communities, with an increasing interplay with nutrient and climate variables over time. While there existed a significant shift of diatom composition in ∼1960, species richness and community dissimilarity showed a significant decrease when water depth was raised to above ∼10 m or the magnitude of WFL was above ∼2 m. Thus, our sediment surveys provide evidence on the significant impact of lake regulation on hydro-morphology, carbon burial and ecological shift over time, as well as its stronger interaction with other forcing with increased impoundment intensity.

On the Relationship between Holocene Environmental Variability and the Diatom Composition in the Peña Lagoon, Se Uruguay

Uruguayan Southern lagoons exhibit high Holocene resolution paleoenvironmental-paleoclimatic records for inferring long-term regional changes. The multiproxy analysis of three sediment cores enabled the recognition of Holocene climatic variability from the paleolimnological record of the Pena lagoon over the last 2,458 cal. years BP. Four main stages were identified throughout the record. The first stage (2,458–1,500 cal. years BP) was characterized as a shallow meso-eutrophic system with high abundances of aerophilic benthic species, epiphytic taxa and planktonic taxa. The second stage (1,415–390 cal. years BP) showed a noticeable change in the diatom assemblage dominated by the fresh-brackish benthic species Staurosira construens, but also presented fluctuations in the abundance of Aulacoseira ambigua and Aulacoseira granulata, which indicate the occurrence of temperate to cold and semiarid climatic conditions including intervals of high rainfall. The core chronology allowed us to ascribe this stage to the Little Ice Age (LIA). The third stage, post 390 cal. years BP, showed the highest proportion of freshwater planktonic species throughout the entire core, thus indicating the development of an eutrophic system under relatively warm and wet conditions, which were assigned to the Current Warm Period. After ca. 1,962 AD, a sharp increase in the abundance of epiphytic species highlights the onset of the fourth stage, which was characterized by littoral expansion and, consequently, the proliferation of associated macrophytes due to anthropogenic impacts.

Functional and Compositional Responses of Periphyton Mats to Simulated Saltwater Intrusion in the Southern Everglades

Periphyton plays key ecological roles in karstic, freshwater wetlands and is extremely sensitive to environmental change making it a powerful tool to detect saltwater intrusion into these vulnerable and valuable ecosystems. We conducted field mesocosm experiments in the Florida Everglades, USA to test the effects of saltwater intrusion on periphyton metabolism, nutrient content, and diatom species composition, and how these responses differ between mats from a freshwater versus a brackish marsh. Pulsed saltwater intrusion was simulated by dosing treatment chambers monthly with a brine solution for 15 months; control chambers were simultaneously dosed with site water. Periphyton from the freshwater marsh responded to a 1-ppt increase in surface water salinity with reduced productivity and decreased concentrations of total carbon, nitrogen, and phosphorus. These functional responses were accompanied by significant shifts in periphytic diatom assemblages. Periphyton mats at the brackish marsh were more functionally resilient to the saltwater treatment (~ 2 ppt above ambient), but nonetheless experienced significant shifts in diatom composition. These findings suggest that freshwater periphyton is negatively affected by small, short-term increases in salinity and that periphytic diatom assemblages, particularly at the brackish marsh, are a better metric of salinity increases compared with periphyton functional metrics due to functional redundancy. This research provides new and valuable information regarding periphyton dynamics in response to changing water sources in the southern Everglades that will allow us to extend the use of periphyton, and their diatom assemblages, as tools for environmental assessments related to saltwater intrusion.

Biogeochemical Responses to Holocene Catchment‐Lake Dynamics in the Tasmanian World Heritage Area, Australia

AbstractEnvironmental changes such as climate, land use, and fire activity affect terrestrial and aquatic ecosystems at multiple scales of space and time. Due to the nature of the interactions between terrestrial and aquatic dynamics, an integrated study using multiple proxies is critical for a better understanding of climate‐ and fire‐driven impacts on environmental change. Here we present a synthesis of biological and geochemical data (pollen, spores, diatoms, micro X‐ray fluorescence scanning, CN content, and stable isotopes) from Dove Lake, Tasmania, allowing us to disentangle long‐term terrestrial‐aquatic dynamics through the last 12 kyear. We found that aquatic dynamics at Dove Lake are tightly linked to vegetation shifts dictated by regional hydroclimatic variability in western Tasmania. A major shift in the diatom composition was detected at ca. 6 ka, and it was likely mediated by changes in regional terrestrial vegetation, charcoal, and iron accumulation. High rainforest abundance prior ca. 6 ka is linked to increased terrestrially derived organic matter delivery into the lake, higher dystrophy, anoxic bottom conditions, and lower light penetration depths. The shift to a landscape with a higher proportion of sclerophyll species following the intensification of El Niño‐Southern Oscillation since ca. 6 ka corresponds to a decline in terrestrial organic matter input into Dove Lake, lower dystrophy levels, higher oxygen availability, and higher light availability for algae and littoral macrophytes. This record provides new insights on terrestrial‐aquatic dynamics that could contribute to the conservation management plans in the Tasmanian World Heritage Area and in temperate high‐altitude dystrophic systems elsewhere.