Benthic Diatom Flora Research Articles

Environmental Factors Structuring Diatom Diversity of the Protected High Mountain Lakes in the Kaçkar Mountains National Park (Rize, Turkey)

The altitude of the habitat is one of the important regulators of species survival. Kaçkar Mountains National Park is located in the Eastern Black Sea region of Turkey. This is the first study on the benthic diatom flora of the high mountain lakes in Kaçkar Mountains National Park, which is situated between 2782 and 3075 m a.s.l. A total of 84 diatom species were identified from benthic communities of 15 habitats in summer (19 July, 28 August) and autumn (10 September) months of 2020. The genus Pinnularia (thirteen species) formed the basis of the taxonomic list, followed by Eunotia (five species), Navicula (five species), and Frustulia (four species) genera, respectively. The waters in all the studied lakes were fresh, low-saline, with low-alkaline or circumneutral pH and organically uncontaminated, as evidenced by prevailed bioindicator groups. Statistical methods and comparative floristic results confirm the role of the lake altitude for the diatom species distribution. The species richness of the studied lakes was higher in lakes with lower altitudes. The statistical approach also revealed the potential for an increase in the number of species in high mountain lakes if the study of the diatom flora of the Kachkar Mountains National Park is continued and the species composition of the lakes is replenished. Further studies will be needed to continue exploring this pattern. To protect studied high mountain lakes, their ecological conditions must be constantly monitored in the Kaçkar Mountains National Park.

Biodiversity of the benthic diatom flora in the coastal zone of the Gulf of Gdańsk: a case study of the Gdynia–Sopot transect

The objective of this study is to determine microhabitat preferences of benthic species occurring in epilithic (living on stones), epipsammic (growing on sand), epipelic (growing on mud) and epiphytic (living on seagrass) assemblages of the shallows of the Gulf of Gdańsk (southern Baltic Sea). The study material was collected from 19 sites along the Gdynia–Sopot coastal zone, including the Port of Gdynia. Most of the identified diatom taxa were observed in two or three microhabitats. However, diatom species living in only one type of microhabitat and those occurring in all analyzed microhabitats were also recorded. Autecological preferences of the identified diatoms indicate organic pollution of the coastal zone of Gdynia and Sopot. However, a higher frequency of α-mesosaprobionts and polysaprobionts indicates an increase in organic pollution in the Port of Gdynia and Marina Sopot, which is associated with intense port activity and large tourist traffic.

Two new Halamphora (Bacillariophyta) species from the marine coasts off Livingston Island, Antarctica.

During a survey of the marine benthic diatom flora on the coasts off Livingston Island (South Shetland Islands, Maritime Antarctic Region), two Halamphora species that could not be identified based on the currently available literature, were observed. Detailed light and scanning electron microscopy observations and thorough comparison with similar taxa in the literature revealed that both taxa should be described as new species. The first taxon, Halamphorakenderoviana sp. nov., was most likely misidentified in past Antarctic studies, and included within the range of another taxon, Halamphoracoffeaeformis. Analysis of literature data showed that the second new taxon, Halamphoramoncheviana sp. nov., has been previously reported from the Antarctic Continent (but as an unidentified species). The new taxa are compared with similar Halamphora taxa worldwide. Data on their ecology and distribution are also provided.

Flow Intermittence Drives the Benthic Algal Composition, Biodiversity and Diatom-Based Quality of Small Hilly Streams in the Pannonian Ecoregion, Hungary

Climate change is putting increasing pressure on flowing waters. Drastic water level fluctuations in rivers or drying up of small and medium-sized streams all contribute to the biodiversity crisis threatening freshwater ecosystems. Benthic diatoms are important elements of biofilm in small streams. However, knowledge on the relationship between benthic diatoms and flow intermittence is incomplete, especially in regions recently impacted by recurrent drying. Thus, we investigated benthic diatom flora of small intermittent, hilly streams in the warm temperate region of Europe (the Pannonian Ecoregion). Our hypotheses were addressed to compositional changes, biodiversity loss and diatom-based ecological assessment. The results revealed clear flow intermittence-induced differences in taxa and trait composition of diatoms. Altogether six species for the dry phase and three species in the aquatic phase were identified as indicative ones by using indicator value analyses. In contrast to water regime induced changes in assemblages, there was a seasonal overlap in taxa and trait composition. During the study period, the drying up of streams did not result in significant biodiversity loss either at taxa or trait levels. Functional dispersion, however, reduced significantly by summer. Overall, neither the hydrological regime nor seasonal changes had a significant effect on diatom-based quality indices, except for the Rott trophic index (TID index). The TID index values were significantly lower in dry phases than in aquatic ones. These results suggested that the drying up of streams has a very complex influence on benthic diatoms. It seems that taxonomical and functional redundancy can reduce the negative impact of short-time flow intermittence on assemblages. As a practical benefit, the results are the first to support the use of diatom-based quality indices in the assessment of flow intermittence in the temperate region.

Benthic diatoms of the Black Sea: rare, invasive, extinct species and assessment of taxonomic exclusivity

Assessment of benthic diatom taxonomic diversity under increasing anthropogenic pressure on the Black Sea shelf is necessary to preserve the genetic fund of Bacillariophyta, especially for rare and relict endangered species, as well as for controlling of invasive ones. Currently, the Black Sea benthic diatom flora includes 1100 species and intraspecific taxa, among which almost 50% are singleton species. Assumed the Black Sea flora consists from relict of the Ponto-Caspian and Karangat flora, native species, freshwater species, introducers from the Mediterranean basin, and a group of aliens acclimating to another environmental condition. 8 new genera and over 280 newly found for the Black Sea diatom flora species were noted. Also species not recorded in the World Ocean during the XX century were discovered. Groups of 33 and 11 significant for preservation species were highlighted which the ranks of high and highest taxonomic exclusivity were assigned, respectively. Species formed a mono-species branch on a hierarchical tree, i.e. belonging to the same genus, family or order, has the highest preservation priority compared to a species included in a poly-species branch and phylogenetically close to many others. Disappearance of species with high taxonomic exclusivity leads to significant changes in the structure of diatom hierarchical tree. Maintenance of intact habitat conditions for species with a high taxonomic exclusivity should be primary measure to preserve the high diversity of the Black Sea’ flora Bacillariophyta.

New species of benthic marine diatoms (Bacillariophyta) from the Western Pacific islands of Guam and Yap

In the course of preparation of a major checklist for Yap and ongoing investigations into the benthic marine diatom flora of Micronesia, thirteen new araphid and raphid pennate diatom species have been recognized and are described here. Plagiogramma subatomus is even smaller than P. atomus and the pseudoseptum forms a box with only a small opening toward the cell interior. Licmophora romuli is similar in size and spathulate shape to L. remulus, but the majority of the striae in the lamina lack vimines. L. graphis is exceedingly delicate, pencil-shaped, with apical striae 60–70 in 10 µm. Divergita biformis and D. decipiens are straight species with striae biseriate on the margin, uniseriate on the valve face, differing in the shape and prominence of the sternum and the shape of the valve-face areolae. D. macinnisii (from Marshall Islands, but included here for comparison) is curved, again with the decussate areolar pattern on the mantle, but with single extended areolae along each side of the linear sternum. These characters slightly amend the diagnosis of the genus. Thalassionema baculum is a very short member of the genus, linear and isopolar. Climaconeis tarangensis is curved and differs from C. riddleae in stria density and areola shape; C. minaegensis is straight, without a stauros or craticular bars, of intermediate length, 228–247 µm. First SEM observations of Climaconeis lorenzii are presented and an updated key to Climaconeis is appended. Parlibellus paschalis is a tube-dwelling species differing from P. delognei is lacking cuniculi and pores in the central area. P. waabensis is a relatively large species, possibly tube-dwelling, that differs from P. delognei in shape and spacing of central striae and from P. berkeleyi in width and stria density. Pleurosigma simulacrum differs in ultrastructural details from P. intermedium. Lastly, Nitzschia tarangensis is a conopeate species, spathulate in profile with ribs along the edge of the valve depression and bordering the raphe, and with pores in the peri-raphe zone.

Biodiversity of benthic diatom flora in the coastal zone of Puck Bay (southern Baltic Sea): a case study of the Hel Peninsula

Abstract The paper presents the results of the analysis of diatoms from surface sediments (stones, sands) and macroflora (seagrass, macroalgae) collected at 16 sampling sites located along the inner coastal zone of Puck Bay (southern Baltic Sea) along the Hel Peninsula. The main diatom species of epilithon, epipsammon and epiphyton were characterized with respect to their autecological preferences (habitat, salinity, trophic status, saprobity). Three groups of diatoms were distinguished with respect to the type of substrate based on the results of benthic flora analysis: diatoms (i) of one type of substrate, (ii) of two types and (iii) those occurring on all types of substrates. Moreover, the distribution of benthic diatom communities indicates ecological differences in the study area. Marine and brackish-water species were observed in large numbers in the coastal zone of the Outer Puck Bay, whereas freshwater flora occurred with a higher frequency in the coastal zone of the Puck Lagoon. The content of polysaprobionts and of α-mesosaprobionts indicates that the region of the Hel Tip is highly eutrophicated and very polluted. The coast in the vicinity of Kuznica is less polluted, whereas the best environmental conditions are found in the Jurata–Jastarnia region, as evidenced by the frequency of diatoms that are β-mesosaprobionts.

Water level fluctuations in Lake Baringo, Kenya, during the 19th and 20th centuries: Evidence from lake sediments

This article presents a fossil diatom-based, semi-quantitative reconstruction of water level fluctuations for Lake Baringo over the past 200 years as a consequence of climatic variations. A 285 cm long sediment core sample was collected using a Rod-Operated Single-drive Stationary Piston corer. Lake level was inferred using indices based on the proportion of planktonic to benthic diatom taxa (P/B ratio). The sediment archive presented distinct zones dominated by planktonic and benthic diatom flora. An initial transgression in the early 19th century was characterised as a shallow water environment dominated by planktonic Aulacoseira spp. This was a response to extreme drought during the late 18th to early 19th century. Mid-19th century was defined by a high lake stand. The late 19th to early 20th centuries experienced low water level following the widely documented aridity at the time. The mid-20th century was marked by a spectacular rise in water level that coincided with remarkably wet years during the early 1960s and late 1970s. The first decade of the 21st century witnessed widespread changes in water level. The proxy records show that lake ramping and drawdown over the years follow approximately 50-year climatic cycles.

Spatial Variations in the Benthic Diatom Flora and Its Diversity in the Highland-Plateau Rivers (Central India)

Spatial Variations in the Benthic Diatom Flora and Its Diversity in the Highland-Plateau Rivers (Central India)

Thermal autecology describes the occurrence patterns of four benthic diatoms in McMurdo Dry Valley streams

Benthic microbial mats in the glacial-fed meltwater streams are hotspots of productivity in the McMurdo Dry Valleys (MDV), Antarctica. Benthic diatoms are common in these mats and the >45 primarily endemic taxa represent the most diverse group of eukaryotes in the MDV. In this harsh polar desert, streams are thermally dynamic with daily water temperatures varying 6–9 °C and daily maximum temperatures as high as 15 °C. Stream temperature may play a role in determining growth rates and survival strategies. To understand taxon-specific adaptations to their environment, we measured the growth rates of unialgal cultures of four diatom taxa (Psammothidium papilio, Hantzschia abundans, Hantzschia amphioxys, and Hantzschia amphioxys f. muelleri) under three temperature conditions (7.6, 10, and 15 °C) that were representative of maximum daily stream temperatures. We found that P. papilio exhibited a constant growth rate across the full temperature range; this species is most common in streams that begin to flow early in the summer and with less variable thermal regimes. Growth rates for H. abundans were greatest at 15 °C, but showed a non-linear relationship with temperature. H. amphioxys f. muelleri grew faster than the other taxa studied and thrived at 10 °C. Hantzschia amphioxys grew only at the two lower temperatures. These results aligned with the observed relationships between each taxon’s relative abundance and stream temperatures in the long-term record maintained by the MDV Long-Term Ecological Research program. Overall, our observations suggest that differences in thermal optima may be one factor contributing to and maintaining the diversity of benthic diatom flora in the MDV.

Spatial and temporal patterns of benthic diatom flora in Lake Stechlin, Germany

Phytoplankton and planktonic centric diatoms of Lake Stechlin have been extensively studied, while attached diatoms have received much less scientific interest. In the present study, the composition of benthic diatoms and their diversity metrics were determined and compared along the shoreline of the lake in spring 2013 and autumn 2014. Overall, 118 taxa classified in 52 genera were found, of which 15 species belonged to threat categories of the Red List for Central Europe. Species richness (33 ± 4), Shannon diversity (2.47 ± 0.23), and species composition did not show any differences between different basins. Besides the spatial homogeneity, considerable temporal differences were observed. In spring 2013, species number was significantly lower, while the proportion of Mediophyceae species was higher due to the high abundance of Stephanodiscus rugosus and S. neoastraea. Nonmetric multidimensional scaling (NMDS) showed significant differences between samples from the two years for the total and the Bacillariophyceae species composition. TP concentration of water samples suggested a mesotrophic status and most of the diatom taxa were considered eutraphentic and meso-eutraphentic.

Структурные основы региональных отличий таксономического разнообразия донных диатомовых (Bacillariophyta) Чёрного моря

Важной задачей сохранения микроводорослей Чёрного моря является оценка разнообразия диатомовой флоры и выявление закономерностей его формирования. Работа сфокусирована на анализе разнообразия бентосных диатомовых в регионах северного шельфа Чёрного моря и причин их различий на разных уровнях таксономической иерархии. На основе литературных и собственных данных проведена ревизия региональных флор Bacillariophyta и осуществлена оценка разнообразия с помощью индексов таксономической отличительности TaxDI. Современное таксономическое богатство диатомовых бентоса Чёрного моря насчитывает 1094 вида и ввт (953 вида, 149 родов, 61 семейство, 32 порядка и 3 класса). У берегов Крыма отмечено 884 вида и ввт (81 % общего числа видов диатомовых Чёрного моря), в СЗЧМ ― 556 (51 %), у побережья Болгарии ― 271 (25 %), Румынии ― 358 (33 %), Кавказа ― 310 (28 %). Прослежено отклонение показателей индексов TaxDI от среднеожидаемого уровня для Чёрного моря в целом, которое зависит от строения филогенетических ветвей в каждом из трех классов. Наибольшее влияние на формирование древа Bacillariophyta оказывают олиго- и моновидовые ветви. Характер отклонения структуры региональных флор диатомовых от среднеожидаемого уровня обусловлен видами, формирующими моно- или олиговидовую ветвь вплоть до уровня порядка. Выделены подобные 33 вида с рангом высокой таксономической исключительности, которые отмечены в нескольких регионах. При их исчезновении из состава региональной флоры элиминируется целая ветвь из иерархического древа диатомовых. Особо выделена группа из 12 регион-специфичных видов с рангом наивысшей исключительности, обнаруженных однократно лишь в одном из регионов. Элиминация такого вида из флоры данного региона приводит к редукции моновидовой ветви (включая род, семейство и порядок) из флоры всего Чёрного моря. Это вызовет снижение таксономического разнообразия и изменения структуры иерархического древа Bacillariophyta как конкретного региона, так и архитектоники древа Bacillariophyta Чёрного моря в целом. Структура регионального древа диатомовых Крымского региона близка к среднеожидаемой структуре флоры Чёрного моря. Минимальное значение индекса TaxDI для Крыма (81,38) указывает на большую долю поливидовых ветвей в структуре древа, его максимальную видовую насыщенность (вид/род = 7) и пониженную вертикальную выровненность. У Румынии значение TaxDI максимально (85,9), что обусловлено значительной долей моно- и олиговидовых ветвей и минимальной насыщенностью видами в структуре древа (вид/род = 4).

Benthic diatoms of the southern coast of the Gulf of Finland (Lebyazhiy nature reserve)

The benthic diatom flora of the southern coast of the Gulf of Finland (Lebyazhiy nature reserve) was studied. Species and varieties of diatoms were identified based on their morphological features using light and electron microscopy. A total of 154 diatom taxa were identified, including several varieties. They are centric diatoms, araphid diatoms, monoraphid diatoms, symmetrical biraphid diatoms, asymmetrical biraphid diatoms. Most of them belong to symmetrical biraphid diatoms but the most abundant are araphid diatoms. An assemblage composed of epipelic, epiphytic, epilitic, epipsammic and planktonic species have been found. Salinity was the important factor that determined the composition of diatoms. The diatom community contains freshwater, freshwater-brackish, brackish and marine taxa. The diatom assemblage included taxa (58 %) widely distributed in the Baltic Sea. Nine species are recorded for the first time in the Gulf of Finland, twelve species — in the Baltic Sea. This first comprehensive checklist of the diatoms in the study area compiled with an account of earlier published works and with an account of modern nomenclature changes is presented. Refs 32. Figs 2.

Diatom species composition in the Raska river (Southwestern Serbia)

The paper presents data on the composition of epilithic diatoms in the Raska River. Samples were collected by scraping stone surfaces with a brush from 5 localities along the Raska River in April, June, August and November 2011 and March and May 2012. Diatom frustules were cleaned using cold acid method, and mounted on permanent slides. An investigation of the Raska River resulted in description of 106 diatom taxa. The most species rich genera are Navicula (10), Gomphonema (10) and Nitzschia (9), while other genera are presented with one or more species. Detailed floristic analysis of the benthic diatom flora in this river has not been conducted before. Therefore, this paper provides a groundwork for future researches.

Two new Mastogloia species (Bacillariophyceae), M. parlibellioides and M. lyra, from coral reefs in Guam, Western Pacific1

Abstract This paper describes the morphology of two new species of Mastogloia identified during a survey of the marine benthic diatom flora of Guam. Mastogloia parlibellioides sp. nov., classified in the section Decussatae, is distinctive in the combination of its valve shape and stria pattern reminiscent of Parlibellus, as well as the presence of rudimentary division walls extending from the free margin to the middle of each partectum. Mastogloia lyra sp. nov., classified in the section Sulcatae, subgroup 2, has internal lyre-shaped lateral sterna and partecta that are displaced toward the midline of the valve by a siliceous flange, which shows oblique partectal ducts. The descriptions of these two new species increase the knowledge base of biodiversity in a Pacific Ocean Mastogloia hotspot.

A revision of the diatom genus <i>Lyrella</i> Karayeva (Bacillariophyta: Lyrellaceae) from the Black Sea, with descriptions of five new species

The focus of this study is the benthic diatom flora of the coastal zone of the Black Sea, in particular that of the Ukrainian part of the Crimean Peninsula. Critically revised taxa belonging to the genus Lyrella Karayeva (Bacillariophyta: Lyrellaceae) are presented. We compared information on Navicula section Lyratae, published over the last few decades, with our observations using both light (LM) and scanning electron microscopy (SEM). Lyrella taxa considered here are characterized in terms of their morphology and ultrastructure. Light and electron micrographs of holotype (where possible) and published line-drawings are provided. The nomenclature is revised and valid taxonomic names with their synonyms are proposed. Information on the taxonomy, autecology, biogeography (distribution in the Black Sea and elsewhere) and on the diversity of Lyrella taxa is presented. Comprehensive bibliography, and list of Black Sea taxa in Lyrella combined 25 species and infraspecific taxa are included. Five of these species are new: Lyrella abruptapontica sp. nov., Lyrella karayevae sp. nov., Lyrella pontieuxini sp. nov., Lyrella pseudolyra sp. nov. and Lyrella ruppelii sp. nov. In addition, six new combinations are proposed: Lyrella dilatata, Lyrella aestimata, Lyrella rudiformis, Lyrella granulata, Lyrella rattrayi and Lyrella bacillifera. Four Lyrella taxa are reported from Black Sea diatom assemblages for the first time: Lyrella barbara, Lyrella dilatata, Lyrella fogedii and Lyrella majuscula.

Diatom distribution in the surficial sediments of Lake Fuxian, Yunnan Plateau, China

Examination of surficial sediments at 14 sites shows minor, but consistent differences in the numbers and kinds of diatom assemblages in different regions of Lake Fuxian. Diatom assemblages in the surficial sediments at all sites were dominated by Cyclotella ocellata , Cyclotella rhomboideo-elliptica , Stephanodiscus hantzschii , Fragilaria crotonensis Cyclostephanos dubius and Stephanodiscus minutulus Aulacoseira granulata Achnanthes minutissima . A detrended correspondence analysis (DCA) defined two groups of sites generally corresponding to the two main parts of the Lake Fuxian basin. They reflected the two geomorphological regions of the lake basin, which basin in the northern were wider and deeper than that in the southern basin and the corresponding differences in hydrochemistry. It was characterized by lower diatom abundance in the southern part of the lake where there was main inflow water with high nutrient concentrations flows from the eutrophic Lake Xingyun. The total diatom abundance was 4.8 × 10 7 valves g -1 and 3.6 × 10 7 valves g -1 in northern and southern part of the lake, respectively. It was characterized by higher abundance of S. minutulus in the northern part of the lake (18.2%); there were some phosphorus post-mines which led to higher total phosphorus concentration than that in southern part. The most outstanding characteristic of diatom assemblages from Lake Fuxian lost the extreme degree of endemism with increasing trophic levels. Endemic diatoms species are not the most abundant component of assemblages at all sites. Small abundances of benthic diatoms were found in all samples. Although low abundances were present in sediments, the benthic diatom flora was very diverse. Species diversity was increased in Lake Fuxian, which may be related to natural influences of nutrient loads and local anthropogenic effects.

Benthic diatom flora in relation to chemical and physical factors in high mountain lakes in the Rila Mountains (southwestern Bulgaria)

Benthic diatom flora in relation to chemical and physical factors in high mountain lakes in the Rila Mountains (southwestern Bulgaria)

Palaeolimnological assessment of environmental change over the last two centuries in oligotrophic Lake Nohipalu Valgjärv, southern Estonia

The main objectives of this study were to reconstruct the environmental conditions for a small oligotrophic lake during the last two centuries, to determine if the environment of the lake was anthropogenically mediated, and to assess the pre-impact reference conditions with palaeolimnological techniques. A short sediment core from Lake Nohipalu Valgjarv was analysed in detail for diatom assemblages as well as for loss-on-ignition measurements. Accurate chronology of the sediment core was established and evaluated by different independent approaches – Pb, Cs, and Am dating, and the distribution of spheroidal fly-ash particles in sediments. Quantitative inference models based on sedimentary diatoms were applied to reconstruct changes in past lake water pH. Before the mid-19th century, Nohipalu Valgjarv was an oligotrophic lake with clear water continuously transparent down to the bottom and with rich benthic diatom flora. Since the early second half of the 19th century, presumably as a result of forest logging around the lake, water transparency decreased and benthic diatom productivity diminished, and the lake did not recover any more to natural baseline conditions. Due to peat mining activities in the Meenikunno bog, the quality of lake water has changed during the last two decades. The lowered lake level, deteriorated light climate, and decreased pH are the most important environmental variables that have influenced the lake ecosystem.

Use of Kohonen Self Organizing Maps (SOM) for the characterization of benthic diatom associations of the River Danube and its tributaries

Benthic diatom flora of the River Danube was investigated along the river from the source streams to the end of the Hungarian stretch during a four-year period. Characteristic diatom community assemblages were established using KOHONEN Self-Organizing Map (SOM) algorithm. We found five sample clusters, arranged according to the location. The first three groups are located in the German-Austrian stretch, while the fourth and fifth groups are located in the Slovakian-Hungarian stretch. Characteristic species of the clusters 1 and 2 are Achnanthidium minutisimum (KUTZ.) CZARNECKI, Denticula tenuis KUTZ., Nitzschia fonticola GRUN., Psammothidium bioretii (GERMAIN) BUKHT. & ROUND, Melosira varians AG., Planothidium subatomoides (HUST.) BUKHT. & ROUND, character species of cluster 3 is Amphora pediculus (KUTZ.) GRUN., while character species of the clusters 4 and 5 are Nitzschia dissipata (KUTZ.) GRUN., Navicula cryptotenella LANGE-BERT., Cocconeis placentula var. euglypta (EHR.) GRUN., Rhoicosphenia abbreviata (AG.) LANGE-BERT., Nitzschia inconspicua GRUN. This arrangement is also well in agreement with the poorer water quality of the lower, and the better water quality of the upper stretch.