scholarly journals Diatom (Bacillariophyceae) flora of early Holocene freshwater sediments from Skalafjord, Faeroe Islands

2003 ◽  
Vol 22 (2) ◽  
pp. 183-208 ◽  
Author(s):  
Ewa Witon ◽  
Andrzej Witkowski
Keyword(s):  
Species Composition ◽  
Northern Europe ◽  
Diatom Species ◽  
Marine Waters ◽  
Core Section ◽  
Lower Water Level ◽  
Storegga Slide ◽  
Marine Flora ◽  
Rising Sea Level ◽  
Freshwater Diatom

Abstract. Relative abundance data of diatom (Bacillariophyceae) species were generated for sediment core SKPC-01B from the Skalafjord, Faeroe Islands. The record shows distinct temporal changes in species composition. In the lowermost 65 cm of the 230 cm long core a species-rich freshwater diatom assemblage was found. Most of the taxa observed in this section are typical of oligotrophic to dystrophic lakes in northern Europe (Scandinavia, Iceland and Spitsbergen). Above this interval the diatom flora is dominated by marine taxa. The change from a freshwater to a marine flora is inferred to be caused by rising sea-level that took place about 7700–6400 years BP. Drastic changes in the diatom species composition within the transitional core section show that environmental change in the Skalafjord took place in several pulses. The first stage included strong inflow (possibly catastrophic) of marine waters. As a possible trigger of this phenomenon the tsunami released by the Storegga Slide is proposed. Before the final flooding by marine waters, freshwater conditions were re-established within the Skalafjord. These results have important implications for the interpretation of the palaeogeographical development of the Eysturoy area. Hence, it is suggested that the Storegga Slide led to inflow of marine waters at a distinctly lower water level in the area of the Skalafjord than proposed in recent publications and that the inundation of the threshold in the fjord happened after the tsunami.

Thalassiosira duostra (Bacillariophyta), a new for the flora of Russia freshwater diatom species

2019 ◽  
Vol 53 (1) ◽  
pp. 7-14
Author(s):  
S. I. Genkal
Keyword(s):  
Species Composition ◽  
Original Description ◽  
Published Data ◽  
Diatom Species ◽  
Centric Diatoms ◽  
Internal Part ◽  
Quantitative Characteristics ◽  
Internal Arrangement ◽  
Freshwater Diatom

The study of archive materials has made it possible to specify species composition of the genus Thalassiosira and discover a new for the flora of Russia representative of centric diatoms, T. duostra, in Cheboksary and Tsimlyansk reservoirs and the Oka River. The valve diameter and number of central futoportulae in the examined material differ insignificantly from the original description and published data. By the general valve outline, structure and arrangement of central and marginal fultoportulae and quantitative characteristics, T. duostra is very similar to Сonticribra weissflogii and Thalassiosira faurii, which may result in inaccurate identification of these species. In the Сonticribra weissflogii the rimoportula is located not in a ring of marginal fultoportulae but closer to the valve center and its internal part is significantly larger than in Thalassiosira duostra. The external arrangement of marginal fultoportulae (tubes of the processes are outwardly directed at different angles) and their internal arrangement (the processes are arranged in two rings, they are more dense in the ring which is closer to the valve face) is a good specific feature that differentiates T. duostra and T. faurii.

Distribution of moss-inhabiting diatoms along an altitudinal gradient at sub-Antarctic Îles Kerguelen

2007 ◽  
Vol 19 (1) ◽  
pp. 17-24 ◽  
Author(s):  
Niek J.M. Gremmen ◽  
Bart van de Vijver ◽  
Yves Frenot ◽  
Marc Lebouvier
Keyword(s):  
Species Richness ◽  
Species Composition ◽  
Altitudinal Gradient ◽  
Cross Validation ◽  
Strong Relationship ◽  
Distribution Patterns ◽  
Common Species ◽  
Important Variable ◽  
Diatom Species ◽  
Expected Species Richness

Altitudinal gradients provide excellent opportunities to study relationships between species distribution and climatic variables. We studied the species composition of 39 samples of moss-inhabiting diatoms, collected at 50 m intervals from 100–650 m above sea level. The samples contained a total of 130 diatom species, of which 51 occurred in 10 or more samples. Altitude appeared to be the most important variable explaining variation in species composition. Of the 51 common species, 33 showed a significant relationship with altitude. Although the majority of the latter declined with increasing altitude, for nine species the probability of occurrence first increased with increasing elevation, but decreased again at higher altitudes, and four species increased systematically with elevation. As a result, expected species richness per sample decreased from an estimated 43 at 100 m to 25 species per sample at 650 m. Diatom distribution patterns proved to be suitable predictors of the altitudinal position of sample sites. Cross-validation yielded a strong relationship between predicted and observed altitudes.

scholarly journals Distrionella coxiana, a new fragilarioid diatom species (Bacillariophyceae) from Tierra del Fuego, Patagonia, Argentina

2019 ◽  
Vol 152 (2) ◽  
pp. 385-391
Author(s):  
Valeria Casa ◽  
Gabriela Mataloni ◽  
Bart Van de Vijver
Keyword(s):  
Typical Feature ◽  
Morphological Features ◽  
Tierra Del Fuego ◽  
New Taxon ◽  
Diatom Species ◽  
Unique Combination ◽  
Diatom Flora ◽  
Electron Microscopical ◽  
Scanning Electron ◽  
Freshwater Diatom

Background and aims – A few years ago, a new survey started of the freshwater diatom flora from peatbogs of Tierra del Fuego (southern Argentina). During this survey, an unknown fragilarioid diatom belonging to the genus Distrionella that could not be identified using the currently available literature was discovered. Methods – Using both Light Microscopical and Scanning Electron Microscopical techniques, the morphology of the unknown Distrionella species has been analysed. The new taxon is properly described, illustrated and compared with all other possible similar Distrionella taxa, known worldwide. Key results – Distrionella coxiana possesses a unique combination of morphological features that excludes conspecificity with all other members of the genus; it is characterized in having narrow, linear valves with small, capitate apices. Transapical ribs, a typical feature of the genus Distrionella, are only weakly developed. One rimoportula is observed close to the apices. Both apices have well-developed apical porefields. The girdle bands bear one complete row of poroids often accompanied by a second, incomplete row of small poroids. Notes on the occurrence and ecology of the new taxon are added.

scholarly journals Two sub-Antarctic and Northern Europe distributed diatom species found in a middle-mountain lake in France

2019 ◽  
Vol 166 (2) ◽  
pp. 212-220 ◽  
Author(s):  
David Heudre ◽  
Carlos E. Wetzel ◽  
Bart Van de Vijver ◽  
Laura Moreau ◽  
Luc Ector
Keyword(s):  
Mountain Lake ◽  
Northern Europe ◽  
Diatom Species

Diatom species composition along a thermal gradient in the Portneuf River, Idaho, USA

Hydrobiologia ◽  
1989 ◽  
Vol 185 (1) ◽  
pp. 41-54 ◽  
Author(s):  
Deanna K. Vinson ◽  
Samuel R. Rushforth
Keyword(s):  
Species Composition ◽  
Thermal Gradient ◽  
Diatom Species ◽  
Portneuf River

Encyonema aquasedis sp. nov. and Kurtkrammeria salesopolensis sp. nov.: two new freshwater diatom species (Cymbellales, Bacillariophyceae) from an oligotrophic reservoir in southeastern Brazil

Phytotaxa ◽  
2016 ◽  
Vol 247 (1) ◽  
pp. 62 ◽  
Author(s):  
Gisele Carolina Marquardt ◽  
Angélica Cristina Righetii Da Rocha ◽  
Carlos Eduardo Wetzel ◽  
Luc Ector ◽  
Carlos Eduardo de Mattos Bicudo
Keyword(s):  
New Species ◽  
Surface Sediments ◽  
Low Ph ◽  
Southeastern Brazil ◽  
Diatom Species ◽  
Southeast Brazil ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes ◽  
Scanning Electron ◽  
Freshwater Diatom

Recent research of the plankton and the surface sediments from Ribeirão do Campo reservoir (São Paulo, southeast Brazil) led to identification of two new cymbelloid diatom species: Encyonema acquasedis sp. nov. and Kurtkrammeria salesopolensis sp. nov. Their morphology was studied under both light and scanning electron microscopes aiming at describing the two species in detail. The morphology of each species is compared and discussed with morphologically similar taxa. The new species are different from all others in the Cymbellales due to a combination of characteristics including valve outline, striae, areolae structure, and raphe system. Both species were collected from an oligotrophic environment with both low pH and conductivity.

scholarly journals Fragilaria rinoi sp. nov. (Fragilariales, Fragilariophyceae) from periphytic river samples in Central Portugal

2016 ◽  
Author(s):  
Cristina Delgado ◽  
M. Helena Novais ◽  
Saúl Blanco ◽  
Salomé F.P. Almeida
Keyword(s):  
Central Area ◽  
River Basins ◽  
Scanning Electron Micrographs ◽  
Diatom Species ◽  
Alkaline Ph ◽  
Mean Values ◽  
Central Portugal ◽  
Lis River ◽  
Scanning Electron ◽  
Freshwater Diatom

A new benthic freshwater diatom, Fragilaria rinoi Almeida & C.Delgado sp. nov., is described from river periphyton samples in Portugal. Fragilaria rinoi sp. nov. is illustrated and discussed based on populations collected from the Vouga, Mondego and Lis river basins in central Portugal and compared with the type material of Fragilaria vaucheriae (Kütz.) J.B.Petersen. The morphological features of the new diatom species are documented through light and scanning electron micrographs, including a comparative analysis with related species of the genus (F. candidagilae Almeida, C.Delgado, Novais & S.Blanco, F. intermedia Grunow in Van Heurck, F. neointermedia Tuji & D.M.Williams, F. recapitellata Lange-Bert. & Metzeltin, F. perminuta (Grunow) Lange-Bert., F. vaucheriae and F. microvaucheriae C.E.Wetzel & Ector). Fragilaria rinoi sp. nov. is characterized by solitary cells without spines, lanceolate valves with slightly rostrate apices, a narrow, linear axial area, and a large, unilateral central area. Fragilaria rinoi sp. nov. may be confused with F. microvaucheriae in terms of length, striae density and outline, although a morphometric analysis revealed that F. rinoi sp. nov. is significantly wider. Fragilaria rinoi sp. nov. is present in rivers with high dissolved oxygen concentrations, medium to high conductivity, neutral to slightly alkaline pH and high mean values of nitrates and ammonium.

scholarly journals Ecological assessment using diatom community in Avarga Toson Lake (Mongolia)

2021 ◽  
Vol 20 (1) ◽  
pp. 526-530
Author(s):  
Ts. Bukhchuluun
Keyword(s):  
Species Composition ◽  
Human Activities ◽  
Dominant Species ◽  
Sediment Accumulation ◽  
Ecological Assessment ◽  
Livestock Grazing ◽  
Diatom Species ◽  
Diatom Community ◽  
Diatom Communities ◽  
High Sediment

A total of 32 diatom species were recorded in Avarga Toson Lake. Motile diatom species are dominatingin diatom communities. The species composition of two coexisted lakes is markedly different. Diatom richness, speciescomposition, and dominant species indicate that Burd lake is polluted by livestock grazing or domestic pollution, andToson Lake is polluted by human activities with high sediment accumulation at the bottom.

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