Genera Achnanthes Research Articles

Three new Achnanthidium (Bacillariophyceae) species from Lake Salda (Anatolia, Turkey), a deep soda lake

Background and aims – Kützing separated the genus Achnanthidium from the genus Achnanthes based on two species: Achnanthes minutissima and Achnanthidium microcephalum. These two genera were distinguished by the presence of stalks in the Achnanthes genus and their absence in Achnanthidium. Before electron microscopy, the difference between Achnanthes and Achnanthidium was not clear, especially in Achnanthidium minustissimum sensu lato. The aim of the study is to describe three new species of Achnanthidium from Lake Salda. Material and methods – Lake Salda is located in southwestern Anatolia, in Turkey. The diatoms were collected seasonally from four stations in the lake between 2016 and 2020, from different substrata (epipelic, epiphytic, and epilithic). Key results – Three new species belonging to the genus Achnanthidium have been found in Lake Salda, Turkey. Based on the morphological observations, all new taxa are part of the Achnanthidium minutissimum complex. Achnanthidium barlasii sp. nov. and A. dumlupinarii sp. nov. show a high degree of similarity to each other, but can be separated based on valve outline and a denser areolation, especially in striae close to the apices of the raphe valve. Both species can be distinguished from A. minutissimum based on more separate apices and less elliptic valves. In the case of A. dumlupinarii sp. nov., large specimens show slight undulations of the valve, which is a unique feature. Achnanthidium anatolicum sp. nov. is the most characteristic based on its valve width, broadly rounded valve apices, and almost straight valves in girdle view. All newly described Achnanthidium species can be found in lentic environments, with alkaline water and high calcium ion content. Conclusion – The newly described taxa occurred in the unique habitat of a soda lake. The environment of the lake is highly alkaline, rich in magnesium and calcium, and derived from limestone and dolomitic limestone rocks.

Platessa arborea sp. nov. (Bacillariophyceae): A new tree moss dwelling diatom from the Eastern Himalayas, India

Platessa arborea sp. nov. new monoraphid diatom species is described from the tree moss habitat of India’s Sikkim state from the Eastern Himalayan biodiversity hotspot. This new species was described based on light and scanning electron micrographs and compared to morphologically similar taxa. Platessa arborea seems to have an affinity for the aerial habitat and has certain unique morphological features distinct from all the other Platessa species, such as its narrowly rounded apices, wide axial area, and the presence of predominantly uniseriate striae with unusually thick striae density. In India, there have been previous reports of some species from the genera Achnanthes and Cocconeis, which have been eventually transferred to the genus Platessa. However, this is the first formal documentation of the Platessa genus from India.

Achnanthes Bory Sensu Stricto (Bacillariophyta) from Terrestrial Habitats of Rio de Janeiro (Brazil), with Description of Achnanthes pseudoinflata sp. nov.

The aim of the present work was to present the ecological and morphological characteristics of species from the genus Achnanthes Bory sensu stricto, which develops in terrestrial mosses near the Rio de Janeiro Botanic Garden, Brazil. A literature comparison was made with other similar species, including the LM and SEM analysis of original material bearing Achnanthes inflata (Kützing) Grunow housed at the Grunow Collection in Vienna, and data from the available literature. Samples were collected from clumps of moss growing on tree trunks, and from a concrete wall within the botanic garden. Four taxa from the genus Achnanthes were recorded: A. coarctata, A. inflata var. gibba, A. mauiensis and Achnanthes pseudoinflata sp. nov. The main morphological differences between these taxa were cell dimensions (length and width), striae and areolae density. The most common diatom species found in these samples were Humidophila sp. (90%), Humidophila contenta (74.8%), Luticola moreirae (17.9%), and Achnanthes pseudoinflata sp. nov. (7.4%).

Structural and Quantitative Features of Phytoperiphyton Communities in Watercourses of the Zeya River Basin, Amur Oblast

The results of a study of periphyton algae in the Zeya River and nine watercourses of its drainage basin (Amur Oblast) are presented. The composition of dominant species is determined, the structural features of algal communities are considered, and quantitative characteristics of some of their components are obtained. The total abundance of phytoperiphyton in the Zeya River is 583 billion cells/m2; biomass is 102–1106 g/m2. In medium-sized watercourses, the total abundance of algae ranges from 16.2 to 100 billion cells/m2; biomass is from 2.0 to 18.3 g/m2. Most of the biomass is formed by diatoms (Encyonema silesiacum, Hannaea arcus, Ulnaria ulna, Gomphoneis olivaceum, and large-celled species of the genus Gomphonema); most of the abundance is formed by cyanobacteria and diatoms from the genera Achnanthes, Fragilaria, Gomphonema, and the species Encyonema minutum.

Hydrological alterations as the major driver on environmental change in a floodplain Lake Poyang (China): Evidence from monitoring and sediment records

Abstract Due to the lack of long-term records on shallow lake environmental change, knowledge of the processes and mechanisms behind the limnological response of many shallow floodplain lakes to hydrological alterations and nutrient loading is often limited. We examined seasonal monitoring data and a dated sediment core from Lake Poyang, a large floodplain lake located on the Yangtze floodplain in the SE China. Multivariate analysis based on contemporary data (diatoms and water quality) revealed that the seasonal changes in the diatom assemblage of the lake were correlated with water temperature and Secchi depth (SD), although the weak spatial effect was not negligible. During the dry winter season, low water temperature, low SD, and high nutrient levels, were accompanied by high abundances of planktonic Aulacoseira species along with Stephanodiscus hantzschii, a species well adapted to cold and eutrophic waters. During the summer wet season, however, when water temperature and SD were high and nutrient levels low, benthic and epiphytic diatoms, such as the genus Achnanthes, dominated. Sediment records of diatoms and geochemistry were used to estimate long-term variation in the ecological condition of the lake. During the past ~60 years, the lake has shifted from a natural hydrologically connected, oligotrophic lake dominated by benthic and epiphytic diatoms to a poorly hydrologically connected, eutrophic state driven by nutrient-tolerant planktonic and eutrophic diatoms. Furthermore, our results indicate that the proposed Poyang dam may severely affect the water quality and ecosystem of the lake by altering its seasonal hydrology.

Water quality assessment of benthic diatom communities for water quality in the subalpine karstic lakes of Jiuzhaigou, a world heritage site in China

Jiuzhaigou, characterized by its magnificent waterscapes and subalpine karstic features, is both a World Heritage Site and a World Biosphere Reserve in southwestern China. In recent years, this unique ecosystem has shown signs of stress due to increasing tourism activities within the reserve. The various routine methods, whichmonitor physical and chemical properties, do not fully reflect water quality in the subalpine and alpine lakes, while the indicators using aquatic organisms to evaluate the water qualityor status of the subalpine lakes are poorly reported.Thus, in this study, benthic diatoms from multiple habitats in Jiuzhaigou were sampled and assessed for water quality monitoring.Canonical Correspondence Analysis (CCA) showed that the canonical coefficients for elevation, water temperature and total nitrogen on the first Canonical Correspondence Analysis axis were -0.84, 0.78 and -0.53, respectively, environmental variables associated with the distribution patterns of benthic diatoms. The dominance of diatom taxa indicative of nutrient enrichment indicates a clear trend toward eutrophication in the Pearl Shoal and Colorful Lake, two of the sites mostly visited by tourists. It was observed that the effect of the type of substratum on diatom community composition is not significant in subalpine lakes.The most dominant species in Jiuzhaigou lakes are the genera Achnanthes, Fragilaria, Cymbella, Cocconeis, Diatoma and Denticula. In combination with dominant and sensitive species in the benthic diatom communities,CCA and CA methods can be used to evaluate the impact of human activities on subalpine karstic lakes.The dominance of diatom taxa is indicative of nutrient enrichment and the results of CCA and CA indicate a clear trend toward eutrophication in the Pearl Shoal and Colorful Lake, two of the sites mostly visited by tourists.

Diatom community structure on in-service cruise ship hulls

Diatoms are an important component of marine biofilms found on ship hulls. However, there are only a few published studies that describe the presence and abundance of diatoms on ships, and none that relate to modern ship hull coatings. This study investigated the diatom community structure on two in-service cruise ships with the same cruise cycles, one coated with an antifouling (AF) system (copper self-polishing copolymer) and the other coated with a silicone fouling-release (FR) system. Biofilm samples were collected during dry docking from representative areas of the ship and these provided information on the horizontal and vertical zonation of the hull, and intact and damaged coating and niche areas. Diatoms from the genera Achnanthes, Amphora and Navicula were the most common, regardless of horizontal ship zonation and coating type. Other genera were abundant, but their presence was more dependent on the ship zonation and coating type. Samples collected from damaged areas of the hull coating had a similar community composition to undamaged areas, but with higher diatom abundance. Diatom fouling on the niche areas differed from that of the surrounding ship hull and paralleled previous studies that investigated differences in diatom community structure on static and dynamically exposed coatings; niche areas were similar to static immersion and the hull to dynamic immersion. Additionally, diatom richness was greater on the ship with the FR coating, including the identification of several new genera to the biofouling literature, viz. Lampriscus and Thalassiophysa. These results are the first to describe diatom community composition on in-service ship hulls coated with a FR system. This class of coatings appears to have a larger diatom community compared to copper-based AF systems, with new diatom genera that have the ability to stick to ship hulls and withstand hydrodynamic forces, thus creating the potential for new problematic species in the biofilm.

Taxonomic study of the genus Achnanthes (Bacillariophyta) in Korean coastal waters

Taxonomic study of the genus Achnanthes (Bacillariophyta) in Korean coastal waters

Scalariella a new genus of monoraphid diatom (Bacillariophyta) with a bipolar distribution.

The identity of a small-celled diatom Naviculadicta pseudofallacia Witkowski, Metzeltin et Lange-Bertalot, originally described from Bear Island, southernmost island of the Norwegian archipelago Svalbard, is reconsidered. Observations of marine samples from the Kerguelen archipelago (Southern Ocean, Indian Ocean sector) revealed that this species also occurs in the Subantarctic region. The original classification within Naviculadicta was erroneous since this species is a monoraphid taxon and belongs to the Achnanthales. Its morphological features justify creating a new genus Scalariella Riaux-Gobin, which is distinguished from other achnanthoid genera by a peculiar raphe system, the stria structure of the sternum valve (each stria composed of a depressed macroareola), and the presence of a lateral solid area in the raphe valve, splitting each stria into two areolae. Based on light and electron microscopy, N. pseudofallacia is renamed Scalariella pseudofallacia (Witkowski, Metzeltin et Lange-Bertalot) Riaux-Gobin et Witkowski comb. nov. The genus also includes a second and rare species, observed in the Kerguelen material, S. oblongella Riaux-Gobin, Witkowski et Ruppel, which is described and illustrated, but which needs complementary observations. The morphology of Scalariella is compared to that of some genera split from the genus Achnanthes Bory. The biogeography of Scalariella pseudofallacia, a marine taxon probably misidentified in the past due to its small size, is reconsidered with respect to its affinity for subpolar, cold water habitats, in both hemispheres.

Distribution patterns of benthic diatoms during summer in the Niyang River, Tibet, China

The aim of this study was to investigate the distribution, density, community structure and biodiversity characteristics of benthic diatoms, and to analyze whether differences in species composition and abundance exist in different regions of the Niyang River, Tibet. Among the 157 taxa observed in 15 sampling sites in the main river and tributary, most were casual species (>100), the relative abundance of the genera Achnanthes and Fragilaria was 67% of the total relative abundance. Achnanthes minutissima was the most important species and dominated the whole river reaches (average relative abundance was 30%); the average diatom densities were 7.4 x 10(5) cell/cm(2) at all sites, and increased slowly from the upper section to downriver. The significant indicator taxa with higher relative abundance were Achnanthes biasolettiana (18.0%) and Fragilaria arcus (18.2%), Fragilaria capucina var. vaucheriae (31.2%), Fragilaria construens var. venter (11.3%) and Cymbella affinis (11.0%) in the upper, tributary and mid-river sections, respectively. Achnanthes minutissima was the most abundant species (56%) in the downriver section. Biodiversity indices showed a gradual decrease from the up-to down-river section, and dominant species were more abundant in the upper and mid-river sections than in the downriver section. A two-way indictor species analysis (TWINSPAN) of diatom composition clearly showed four different groups, namely the upper, mid, lower and tributary sections. Detrended correspondence analysis (DCA) supported the results of TWINSPAN, and the characteristics of site distribution and species composition in the Niyang River supported the spatial structure of diatom assemblages. This study indicates that bio-assessment programs utilizing benthic diatoms could clearly benefit lotic water with regional stratification.

Discrete free-boundary reaction-diffusion model of diatom pore occlusions

Background - Diatoms are unicellular algae, prolific in nearly all aqueous environments on earth. They are encased between two siliceous valves that each feature a variety of intricately patterned species-specific siliceous structures. How diatoms use biological and physical processes to form these tiny detailed structures is largely unknown. This work is concerned with the smallest regular structures in diatom valves, the pore occlusions, and the processes involved in their formation.Theory and method - We developed a discrete, free-boundary, reaction-diffusion computer model to assess a new physically motivated hypothesis: pore occlusion patterns in the genus Achnanthes are simply expressions of silica diffusion and deposition within a pore covered by a membrane (silicalemma), whose deformation interacts with the growth of the pore boundary to control the silica influx.Preliminary results and discussion - Simulations generate some promising pore features such as bifurcating and curved protrusions that grow towards one another, as seen in diatom pore occlusions. But they tend to be irregular and, to date, taking into account of smoothing and regularizing effects only partially symmetrized formations. Potential future work on this point is outlined.

A NEW MARINE MONORAPHID SPECIES, ACHNANTHES PSEUDOLONGIPES SP. NOV., FROM MIYAGI, JAPAN

A new monoraphid marine species, Achnanthes pseudolongipes, is described. The structure of its valves and girdle resemble those of A. longipes Agardh, as well as the shape of the plastid. However, A. longipes has biseriate striae on both valves, whereas A. pseudolongipes has uniseriate striae on the raphid valve and biseriate (or triseriate) on the araphid valve. In the genus Achnanthes sensu stricto, only A. pseudolongipes possesses both uniseriate and biseriate striae. The number of striae between costae is one of the most effective features of the valve for the identification of taxa in the genus Achnanthes sensu stricto.

FRESHWATER SPECIES OF ACHNANTHES BORY FROM HAWAII

We surveyed subaerial habitats on the four main islands of Hawaii, USA for freshwater algae to examine patterns of distribution and to search for endemic species. Habitats sampled included cliff faces that ranged in moisture content from very dry to periodically moist from groundwater fog and rain. In this report we focus on the species richness, distribution and morphology of the diatom genus Achnanthes sensu stricto. We document the distribution and morphology of Achnanthes inflata and describe five new species in this genus.

THE COMPLEX EXTRACELLULAR POLYSACCHARIDES OF MAINLY CHAIN-FORMING FRESHWATER DIATOM SPECIES FROM EPILITHIC BIOFILMS(1).

Diatoms are dominant organisms in phototrophic biofilms in aquatic habitats. They produce copious amounts of extracellular polymeric substances (EPS), which mainly consist of carbohydrates and traces of proteins and glycoproteins. This study focuses on the characterization of EPS from a total of 14 diatoms belonging to the six genera Achnanthes, Cymbella, Fragilaria, Punctastriata, Staurosira, and Pseudostaurosira, all of which were isolated from epilithic biofilms of the littoral zone of Lake Constance. EPS from all isolates were extracted by a sequential extraction procedure resulting in five different fractions. The monosaccharide composition of each fraction was analyzed by HPLC equipped with a pulse amperiometric detector, yielding results similar to those obtained by probing the EPS structures with monomer-specific fluorophore-linked lectins. Significant differences in carbohydrate composition occurred in the different fractions of single isolates. Most of the diatom isolates in our study form chain-like colonies in which the cells are attached to each other by intercellular pads. Here we demonstrate that these pads can be dissolved in hot bicarbonate and that they show a heterogeneous composition of monosaccharides in contrast to other fractions, which mostly were dominated by one or two monosaccharides. Principal component analysis indicates a correlation between carbohydrate composition of EPS fractions and the phylogenetic relationship of the respective species, indicating that EPS analyses under defined culture conditions may support taxonomic analyses.

Revision of the genus Achnanthes Bory s. lato (Bacillariophyta). 2. New monosutural genera and the key for their identification

Revision of the genus Achnanthes Bory s. lato (Bacillariophyta). 2. New monosutural genera and the key for their identification

Diatom Biodiversity and Distribution on Wetwalls in Great Smoky Mountains National Park

Diatoms and other algae were collected and identified from subaerial habitats (wetwalls) in Great Smoky Mountains National Park as part of a larger biodiversity survey of the Park. Algal collections were made across a range of moisture gradients and bedrock mineralogies with pH ranging from 3.8 to 7.7. None of the communities collected were entirely submerged in water, but were often associated with moist bryophytes, cyanobacterial mats, and dripping groundwater seeps. Some of the collections were from cliff faces wetted only periodically. To date, 41 diatom genera and over 223 species have been identified from these habitats. Several of these genera are widely distributed across aquatic habitats; however, several of the genera are “subaerial specialists” and possess morphological features such as reduced size, reduced external openings in the cell wall, or additional external siliceous membranes that allow them to survive in relatively dry habitats. Widely distributed species with high fidelity to subaerial habitats occur in the genera Achnanthes, Cymbopleura, Decussata, Diadesmis, Luticola, Melosira, Microcostatus, Nupela, Psammothidium, and Orthoseira. Many of the species constitute new Park records, national records, or are new to science.

Revision of the genus Achnanthes Bory s. lato (Bacillariophyta). 1. Genera Achnanthes Bory s. str. and Achnanthidium Kützing s. str.

This review deals with taxonomic studies of the genus Achnanthes Bory. The diagnoses of the newly described genera separating from the genus Achnanthes Bory s. lato on the basis of SEM studies are given, as well as a list of taxonomic combinations within these genera. The first part of the review includes a discussion of new types of areolae: macroareolae and postmacroareolae, and a new feature − level of frustule heterovalvy, suggested for use in the description of diatom taxa. Improved descriptions of genera Achnanthes s. str. and Achnanthidium Kützing s. str. are presented.

THE TYPIFICATION OF ACHNANTHES BORY BASED ON ECHINELLA STIPITATA LYNGBYE, WITH AN ACCOUNT OF THE MORPHOLOGY AND FINE STRUCTURE OF LYNGBYE'S SPECIES

Achnanthes was described by Bory to include three species, A. adnata, A. dubia and A. baccillarioides, formerly included under Echinella stipitata Lyngbye. Boyer typified the genus Achnanthes using A. adnata and this typification has been accepted by subsequent authors. However no extant material of A. adnata is known. Since this species was based on E. stipitata, Lyngbye material was sought and examined. This material contains specimens of Achnanthes sensu stricto and can be used as the generitype of that genus. Light and electron microscopical observations of this material are presented. C. A. Agardh created the name Achnanthes brevipes as an avowed substitution for A. adnata and this is the name that has generally been used. There is little doubt that E. stipitata, A. adnata and A. brevipes refer to the same species. Since A. brevipes has been used most extensively in the literature there is a case for conserving this name. Based on our observations we propose that Lyngbye's material be accepted as the type for Achnanthes but that the name A. brevipes be considered for conservation against E. stipitata and A. adnata.

Fine-structure of the vegetative frustule, perizonium and initial valve of Achnanthes yaquinensis (Bacillariophyta)

This study clarifies the fine structure of the vegetative and initial valves of Achnanthes yaquinensis and briefly compares them to other Achnanthes species. It also elucidates the structure of the perizonium, based on auxospore development in short-term cultures. The araphid valve has marginal ridges and terminal spines that allow connecting valves to form a chain. The terminal spines develop from the rapheless sternum. The complete cingulum consists of 3–5 split bands with two rows of areolae. These features can be used to discriminate species within the genus. Sexual reproduction is isogamous with two mother cells producing two auxospores, which are enclosed in mucilage. The perizonium develops on one side of an auxospore only, comprising one large central longitudinal band and four closed bands. There are no transverse perizonial bands. The raphid valve of the initial cell forms first, underneath the longitudinal perizonium, followed by the araphid valve, which is not covered by any perizonial bands. The araphid valve of the initial cells lacks a marginal spine, and the rapheless sternum lies more centrally than in the vegetative cell. The relationship of the genus Achnanthes to other monoraphid diatoms is discussed briefly.

The paleolimnological analysis of sediments from high mountain lake Nižné Terianske pleso in the High Tatras (Slovakia)

Sedimentological climate proxies and a 200-year long climate record, reconstructed using a data-set of European-wide meteorological data, have been compared at the high mountain lake Nižne Terianske pleso in the High Tatras, Slovakia. Diatoms, chrysophyte stomatocysts, chironomids, plant pigments and spheroidal carbonaceous particles (SCPs) were analysed as well as sediment lithostratigraphic parameters. Using a radiometric approach the sediment core was dated and a depth of 4.6 cm was found to correspond to 1852 AD. The sediment accumulation rate (0.0034 g·cm−2·yr−1) was one of the lowest identified in the European mountain lake project, MOLAR. Despite this slow accumulation rate a remarkably coherent lithological and stratigraphic record has been recovered. The sediments of this remote mountain site, largely free from the effects of direct human impact, have been found to display a wealth of variability over the last 200 years. The record of spheroidal carbonaceous particles, indicators of anthropogenic pollution deposition, begins around 4.5–5.0 cm in depth (1833–1857). Temporal patterns are typical of European lake sites with the concentration peaking in the late 1970's. The SCP/210Pb inventory ratio for the site is also in good agreement with the European latitudinal pattern. A strong influence of sample age on the chrysophyte assemblage composition in the upper-most 4–6 cm indicates that the main changes in the cysts have been related to long term environmental changes, probably pH. Analysis of chironomid remains revealed a stable profundal community. Chironomids as a whole showed no correlations to temperature fluctuations in the last 200 years. Relatively abundant remains of Diamesa sp. head capsules and other taxa closely associated with stream conditions in the older layers contrast with the absence of Diamesa sp. in the recent sediments. This change is considered to be evidence for the existence of a stronger, more stable inlet supplied from permanent granular snow fields in the lake basin. The most important changes in diatom assemblages were observed at 3cm. Many species of the genus Achnanthes spp. together with Navicula schmassmannii and Orthoseira roeseana made up the greatest part of the diatom community above 3 cm, being absent or rare lower in the record. A positive correlation between diatoms and mean summer temperature was found.