Benthic Diatoms Research Papers - Academia.edu (original) (raw)

Foreword to the English Edition After the time known informally by diatomists as the “Era of the Green Books” (i.e. the Süßwasserflora) which lasted about until the mid 1990s and during which all the information one needed to have to... more

Foreword to the English Edition
After the time known informally by diatomists as the “Era of the Green Books” (i.e. the Süßwasserflora) which lasted about until the mid 1990s and during which all the information one needed to have to address the central European diatom microflora was included in four books, there was an explosion of new publications as fundamental concepts underpinning the taxonomy of diatoms were revised, a large number of new species were described, and many familiar taxa bounced between genera. These are exciting times for those interested in the phylogeny,
biogeography and diversity of diatoms, but also hugely frustrating times for those concerned with the routine identification of diatoms for practical purposes. Application of the EU WFD needs a consistent approach to the naming of the organisms upon which assessments depend. HOFMANN et al. (2011) represented a welcome exception to the trend of an ever-more diffuse literature on diatoms, since it gave analysts, once again, a single identification text for the species most likely to be found during routine assessments in central Europe.
In order to facilitate use outside the German-speaking area, we decided to translate this work into English. At the same time, the lead Editor used this opportunity to update the work to include the latest information on the taxonomy and ecology. Decisions on revisions were made following a very empirical criterion: all taxonomy and ecology papers of which we are aware published until autumn 2016 were considered, and all genera and species (if quantitatively relevant)
were included if they appeared to be recognized in the main online resources (in particular, ‘Diatoms of the Unites States’, ‘AlgaeBase’ etc.), and by the community of diatomists. This is a very practical criterion, which might sometimes lead to inclusion of taxa whose merits are
still being debated, as long as it appears that they still might have some useful application in everyday practice and some recognition in applied ecology.
Following this process, 26 genera were included in the updated English edition of the book whilst in just three cases genera that were included in the first (German) edition have been removed (although they are still mentioned and briefly explained in the book). 10 species have been added to the book, 27 more have been newly mentioned under ‘Similar taxa’, taxonomic concepts were clarified / updated for 36, and 39 were transferred from one genus to another. The clarification and updating made it necessary to produce new identification keys for two
genera (Diploneis and Sellaphora). Information on plastids (only occasionally available in the German edition) has been added whenever possible to the descriptions of the genera. Terminology of both taxonomic features and also ecological concepts was updated in the Glossary. We have also improved the information on ecology and distribution for 22 species. These improvements to the text are accompanied by several additional references. Formal taxonomic
changes were carried out only when strictly necessary in order to simplify difficult situations or improve the rationale of genus affiliation: one new species description (of a morphologically distinct Sellaphora of waters of high saprobic level), seven formal transfers (comb. nov.), one
formal name changes (nom. nov.). The full text of the species descriptions of the German edition has been replaced by more schematic profiles, in which the different points are provided
in a “bullet point” style. This replaces the rich German prose, capable of conveying even nuances of the morphology, with something far more accessible to international audiences.
This English edition, like the earlier German ones, is intended primarily as a tool to facilitate consistent and accurate identification of diatoms in central Europe. We are, however, confident that it might be of general interest for all those looking for an up-to-date overview of most freshwater benthic diatom genera and of the characteristics of their most commonly encountered species.
Marco Cantonati & Martyn Kelly

Science popularization paper briefly introducing the diatom identification volume: Freshwater Benthic Diatoms of Central Europe (FBDCE): Over 800 Common Species Used in Ecological Assessment. M. Cantonati, M.G. Kelly & H. Lange-Bertalot... more

Science popularization paper briefly introducing the diatom identification volume: Freshwater Benthic Diatoms of Central Europe (FBDCE): Over 800 Common Species Used in Ecological Assessment. M. Cantonati, M.G. Kelly & H. Lange-Bertalot (Eds.): 942 pp. Koeltz Botanical Books (ISBN 978-3-946583-06-6). English edition with updated taxonomy and added species of: Hofmann G., Werum M. & Lange-Bertalot H. 2013. Diatomeen im Süßwasser-Benthos von Mitteleuropa. Bestimmungsflora Kieselalgen für die ökologische Praxis. Über 700 der häufigsten Arten und ihre Ökologie. Lange-Bertalot, H. (Ed.): 908 pp. 2. korrigierte Aufl. Koeltz Botanical Books.
The principal goal of this volume is to provide an effective tool for diatom identification in applied ecology (diatom-based assessments and monitoring, environmental sciences etc.).

In total, 82 taxa of Bacillariophyta are found in periphyton on experimental glass and plexiglas plates exposed in coastal areas of the Black Sea (Karantinnaya Bay) and Japan Sea (Rynda Bay) in the summer and autumn of 2007 and 2000,... more

In total, 82 taxa of Bacillariophyta are found in periphyton on experimental glass and plexiglas plates exposed in coastal areas of the Black Sea (Karantinnaya Bay) and Japan Sea (Rynda Bay) in the summer and autumn of 2007 and 2000, respectively. Among them, 47 species were registered in the Black Sea only, 57 species — in the Japan Sea only, and 22 species were common ones. Benthic forms of the periphyton diatoms prevailed (72 %), planktonic and bentoplanktonic forms were less presented (15 % and 13 %, respectively). Majority of the species belonged to marine (60 %) or brackish-marine (30 %) ones. Cosmopolitan species represented 33 % of the total number of species. The number of diatom species in periphyton communities was 5–17 in the Black Sea and 6–22 in the Japan Sea; their cells density was 65·103–389·103 cells·cm–2 in the Black Sea and 0.04·103–4·103 cells·cm–2 in the Japan Sea; and their biomass was 0.02–0.18 mg·cm–2 in the Black Sea and 0.0001–0.02 mg·cm-2 in the Japan Sea. The maximum of periphyton diatoms abundance was observed in June for the Rynda Bay (SST 12 оC) and in July for the Karantinnaya Bay (SST 25 оC). Similarities and differences between periphyton communities in two seas are discussed.

From field-collected samples, two Icelandic diatom species were studied under light and electron microscopy, resulting in a newly described species and an emended description with a nomenclatural status change. A discussion on the... more

From field-collected samples, two Icelandic diatom species were studied under light and electron microscopy, resulting in a newly described species and an emended description with a nomenclatural status change. A discussion on the morphological features of these taxa and their taxonomic affinities with related species is presented. Nitzschia imae is described from Blue Lagoon, south-west Iceland. The main diagnostic criteria include the presence of two differences morphotypes, one with obtusely rounded apices and the other with slightly asymmetrical valve outline and broadly rounded apices. Additionally, we propose an emended description for Hannaea arcus var. linearis since there is no concordance between morphometric features in the protologue and the type illustration.

Aquatic ecosystem biomonitoring tools are largely lacking for many developing countries, resulting in adoption of tools developed from other countries/regions. In many instances, however, the applicability of adopted tools to the new... more

Aquatic ecosystem biomonitoring tools are largely lacking for many developing countries, resulting in adoption of tools developed from other countries/regions. In many instances, however, the applicability of adopted tools to the new system has not been explicitly evaluated. The objective of this study was to test the applicability of foreign diatom-based water quality assessment indices to urban streams in Zimbabwe, with the view of stimulating research to develop improved approaches for assessing ecological integrity of lotic systems in the country. The study evaluated the relationship between measured water quality variables and diatom index scores. The study found a high degree of concordance between water quality variables and diatom index scores. Thus, the indices proved useful in providing an indication of the quality of the investigated waters. This could be attributed to the occurrence of many widely distributed diatom species that have similar environmental tolerances to t...

Diatom algae are known to play an important role as primary producers in many diverse ecosystems including artificial aquaculture ponds were they also aid in maintaining water quality by consuming excess nutrients. But factors influencing... more

Diatom algae are known to play an important role as primary producers in many diverse ecosystems including artificial aquaculture ponds were they also aid in maintaining water quality by consuming excess nutrients. But factors influencing their growth are still poorly understood. In the present study the effect of micro nutrients, N: P ratio and silica concentration on benthic diatom Synedra sp. grown in fish pond waste water was studied along with nutrient removal efficiency. We have studied 9 different treatments of which addition of micronutrient mixture Nualgi along with adjusted N:P to 6:1 has resulted in highest cell density followed by Silicate enrichment were as only N:P adjustment and Nualgi addition has no significant effect on diatom growth. At the end of growth experiment, the N removal efficiency of treatment groups (50.23%–65.44%) were significantly higher (P < 0.05) than control group (43.56%) were as phosphate removal efficiency was significantly higher (P < 0.05) with Nualgi and N:P adjustment (53.37%–68.98%). The silicate consumption was significantly higher in control group at 63.87%, than other experimental groups. These results will give us a new insight in to important factors influencing beneficial algae growth and simultaneous nutrient removal from aquaculture waste water.

Diatom assemblages in carbonate spring habitats at low elevations, with low discharge, and affected by direct human impacts were studied only recently and in some geographic areas. We describe and characterize the ecology of a new... more

Diatom assemblages in carbonate spring habitats at low elevations, with low discharge, and affected by direct human impacts were studied only recently and in some geographic areas. We describe and characterize the ecology of a new Navicula species from springs with these characteristics within the basin of the River Adige in the south–eastern Alps and Alpine foothills (Province of Verona, Italy). Navicula veronensis sp. nov. is in the group of species around N. cincta but has distinct outline, size, central area, and proximal raphe endings. The availability of data on the distribution of the new species in streams of the Island of Cyprus allowed to quantitatively compare the ecological preferences, niche position, and niche breadth of Navicula veronensis sp. nov. with those of allied species. The new species was found to be characteristic of medium–high conductivity freshwaters, rich in sulphates and chloride, often nitrate enriched and affected by marked discharge fluctuations and seasonal desiccation. Niche position however differed only slightly from those of morphologically–similar species, with the exception of Navicula dealpina that was found to be characteristic of oligotrophic, calcium– bicarbonate rich environments with medium(–low) conductivity. Canonical Correspondence Analysis clearly showed that the most influential environmental variables determining the diatom assemblages of low–elevation carbonate springs affected by anthropogenic disturbance were nitrate enrichment, spring morphology alteration (in particular for water abstraction), and low discharge.

Correct identification of diatom taxa is indispensable for diatom-based water quality studies, as well as for biotechnological applications. Biological applications of taxonomy include the identification of taxa from particular specimens.... more

Correct identification of diatom taxa is indispensable for diatom-based water quality studies, as well as for biotechnological applications. Biological applications of taxonomy include the identification of taxa from particular specimens. In this regard, identification keys, that use a predetermined set of characters to identify a given individual, are not commonly employed by diatom specialists due to the extreme biological diversity found in this group of microalgae. This chapter reviews previous attempts of using taxonomic keys for diatom identification, highlighting the pros and cons of the use of this and similar methods. The main morphological features found in common freshwater diatom genera are briefly presented, together with an account of the historical development of technologies used for species description.

Last year (2007) in Berlin the 21. Deutschsprachiger Diatomologen Treffen became at the same time the 1st Central European Diatom Meeting. This change was underlined by an evident increase in the number of participants. This trend... more

Last year (2007) in Berlin the 21. Deutschsprachiger Diatomologen Treffen became at the same time the 1st Central European Diatom Meeting. This change was underlined by an evident increase
in the number of participants. This trend continued with the second edition of the congress: The 2nd Central European Diatom Meeting in Trento. This was somewhat unexpected since this year (2008)
also the International Diatom Symposium will take place in a few months (07-13/09/2008) in Dubrovnik, Croatia, and several delegates announced that they would not be able to attend both meetings. In spite of this, as can be seen in Fig. 1, about hundred delegates registered for the Congress. It is therefore with satisfaction that we have the possibility to observe that their nationalities are very diverse, with an important contribution from non-German speaking countries
(Italy – “location effect” -, Czech Republic, Russia). We feel very honoured in acknowledging that some participants made long journeys to join our Congress, coming e.g. from Scotland, the eastern part of Russia, Israel, and Canada! Not surprisingly most of the participants work in Universities, but a significant share carries out its diatom investigations in other research institutions (e.g. Research Councils), and in Museums and Botanical Gardens (Fig. 2). This last observation is of special interest for us, since this year the Congress is organized in a Museum. In such Institutions, fundamental research (in particular
biodiversity documentation), collections, and educational issues and popularization are topics of prominent importance.
The topics covered by the contributions of the participants are diverse, but could be grouped into the categories shown in Fig. 3. These give an idea of ongoing diatom research in Central Europe. Not surprisingly biodiversity remains an important topic. Less obvious and – in our opinion encouraging – is the attention still given to taxonomy, a discipline which has difficulties in being acknowledged as a fundamental tool of ecological and applied research by administrators and decision makers.
In thanking the participants for coming to Trento and contributing to the Congress, we are happy that the Trentino Nature & Science Museum of Trento, a town that is not German speaking but that has always been a gate for those coming from Italy and approaching the German-speaking
area, can contribute to the continuation of the Central European Diatom Meetings, formerly Deutschsprachige Diatomologen Treffen.

The biodiversity of algal communities and environmental conditions were investigated in the springs of Mt. Konjuh. The assemblages of 20 springs emerging from different lithologies (limestones and ophiolites, respectively) comprised 234... more

The biodiversity of algal communities and environmental conditions were investigated in the springs of Mt. Konjuh. The assemblages of 20 springs emerging from different lithologies (limestones and ophiolites, respectively) comprised 234 algal taxa. Diatoms and cyanobacteria were the most species-rich groups. The most common alkaliphilic, circumneutral, and eutraphentic diatoms were represented by the genera Gomphonema, Nitzschia, Navicula, Cymbella, and Achnanthidium, and by the cyanobacterial genus Phormidium. Hierarchical clustering and SIMPROF analysis based on relative algal abundance clustered springs into six groups, separating them mainly according to spring type and lithology. Indicator species for groups and springs on different litholog-ical substrata were singled out, revealing 33 taxa with preferences for ophiolites, and 20 taxa with preferences for carbonates. The values of the Shannon-Wiener diversity index were moderately high per spring location, and similar for the two groups of springs on different lithologies. A higher similarity in species composition was noted between springs on ophiolites and limestones than between springs on ophiolites and other types of siliceous sub-strata. The present study suggests that algal assemblages in springs emerging from ophiolites, even those made up by a preponderance of silicates, should be analyzed separately from those related to springs on other siliceous substrata. The results obtained showed that most of the springs studied are affected by anthropogenic impacts and morphological alterations leading to the dominance of highly competitive meso-and eutraphentic algal species, thus emphasizing the importance of further investigation and conservation of these habitats.

The composition and seasonal variations of benthic diatoms of Yedikir Dam Lake were studied using samples collected from two stations between November 2004 and April 2006. The diatom communities were diverse: 81 taxa were found, belonging... more

The composition and seasonal variations of benthic diatoms of Yedikir Dam Lake
were studied using samples collected from two stations between November 2004 and
April 2006. The diatom communities were diverse: 81 taxa were found, belonging
to the Bacillariophyta. In two sampling stations, the most important occurrence was suddenly the increase of epipelic diatoms in May 2005. It was drived from especially three species; Nitzschia fonticola, Navicula veneta and N. capitata var. hungarica.
Trophic Diatom Index (TDI) provides information about trophic levels of the aquatic ecosystem. The water quality of Yedikir Dam Lake in terms of trophic levels was determined according to these 81 diatom taxa by calculating TDI. In particular, it is important that sites in the ‘station 2’, where the water enters dam from Tersakan stream, are chosen so that the influence of the gross effects of organic pollution on the index is minimised.
According to Trophic classification and diversity (TSI, TDI), respectively, ascribed
Yedikir Dam Lake to the eutrophic range. Multivariate analyses indicated that both the regional distribution and seasonal variation of benthic diatoms are mainly driven by nutrient concentration. Diatoms are predominantly affected by geochemical characteristics including pH and mineralisation level.

Algal flora of the sandy substrate and faeces of clypeasteroids Scaphechinus mirabilis and Echinarachmus parma in Troitsa Bay Japan Sea are studied. 52 microalgae species, among which was dominated by representatives of Bacillariophyta... more

Algal flora of the sandy substrate and faeces of clypeasteroids Scaphechinus mirabilis and Echinarachmus parma in Troitsa Bay Japan Sea are studied. 52 microalgae species, among which was dominated by representatives of Bacillariophyta (44), was registered. More low composition species of diatoms faeces (29 species), compared with a sandy substrate (52), as well as the predominance of their cells with chloroplasts, testifies about selective in clypeasteroids feeding. High similarity of algae flora in S. mirabilis and E. parma faeces (0.97) indicates the similarity in food specialization of these clypeasteroids living in the same ecological niche. Largely confirmed the assumption about essential role of diatoms in feeding clypeasteroid S. mirabilis.

Since several decades diatoms are increasingly used for the assessment of the trophic status of different freshwater ecosystems. However, spring habitats have been only marginally considered concerning this topic. The purpose of this... more

Since several decades diatoms are increasingly used for the assessment of the trophic status of different freshwater ecosystems. However, spring habitats have been only marginally considered concerning this topic. The purpose of this research was to compare the diatom assemblages of two groups of carbonate, low–altitude springs, affected by different levels of anthropogenic disturbances. Between 2005 and 2008, diatoms were sampled in 57 low–altitude, carbonate springs, keeping separate the main microhabitats (stones and bryophytes), and assessing an extensive number of morphological, physical, and chemical variables. Two datasets were considered for the present paper: the first (CESSPA, N = 25) includes carbonate springs located within the River Adige catchment, the second (CRENODAT selected springs, N = 32) includes springs located not exclusively within the same basin, and very similar to the previous ones as regards lithological substratum, altitude range, shading. Trophic and saprobity indices, together with multivariate techniques, were used to assess differences between the diatom assemblages in the two datasets. Indices revealed higher trophic and saprobic levels for the CESSPA springs than for the other group (CRENODAT). Values of the Shannon–Wiener diversity index were similar for the two groups while the average richness was slightly higher in nature–near springs (CRENODAT); higher percentages of endangered or rare taxa (Red List) were found only in the nature–near springs. The main impacts affecting the CESSPA springs were found to be both anthropogenic disturbances, such us water abstraction and spring–bed modification, and higher nitrate values. The importance of the fine tuning of diatom–based bioassessment methods in spring habitats is stressed.

– Springs are unique but understudied habitats. Diatom communities have received some attention but have remained largely unknown in the southwestern Alps. We therefore studied the springs of the southwestern extreme of the Alpine... more

– Springs are unique but understudied habitats. Diatom communities have received some attention but have remained largely unknown in the southwestern Alps. We therefore studied the springs of the southwestern extreme of the Alpine mountain range. We analysed epilithic and epiphytic assemblages in 48 springs of different ecomorpho-logical types, located on contrasting lithological substrata (carbonate/siliceous). Moreover , phytosociological relevés were carried out for carbonate springs. The diatom fl ora consisted of 223 taxa. Most (198) of the taxa were included in the Red List, and 12.5% belonged to threatened categories. Characteristic spring taxa (crenophiles) were present. The ecological preferences of crenophilous diatom species described in the eastern Alps were confi rmed. Diatom species characteristic of the lake-littoral zone were found in pool springs. We observed no signifi cant differences in species richness and diversity between epilithic and epiphytic assemblages, but some species showed a preference for bryophytes, and fi ve occurred in the epibryon only. As regards moisture conditions, 15% of the taxa occurred on wet or temporarily dry sites, and 4% lived mostly outside water bodies. The main environmental factors infl uencing diatom assemblages were pH, conductivity, altitude , and shading. The carbonate-substratum crenic vegetation was composed of a mixture of vascular plants and bryophytes, which fi nd their ecological optimum in springs. Bryo-phyte cover was dominant, with the most abundant taxa belonging to the genus Palustri-ella. The vegetation corresponded to the Cratoneuretum commutati association.

We investigated the ultrastructure of Achnanthes delicatissima Simonsen in materials collected from the Swedish Baltic coast. Valve structure differs markedly from that of Achnanthes sensu lato, particularly in the absence of cribrate... more

We investigated the ultrastructure of Achnanthes delicatissima Simonsen in materials collected from the Swedish Baltic coast. Valve structure differs markedly from that of Achnanthes sensu lato, particularly in the absence of cribrate areolae which separates Achnanthes from all other members of the family Achnanthaceae. Comparing this species with those recently described achnanthoid genera, such as Scalariella Riaux-Gobin & Witkowski and Madinithidium Witkowski, Desrosiers & Riaux-Gobin revealed morphological differences that warrant the erection of a new genus, Navithidium. Owing to the small size of the frustules, it is difficult to identify Navithidium delicatissima in light microscopy due to similarities with some closely related taxa like Achnanthidium pseudochamaepinnularia (which is here transferred to Navithidium). A comparison with related genera is provided and discussed.

Diatoms, a kind of algae microorganisms with several species, are quite useful for water quality determination, one of the hottest topics in applied biology nowadays. At the same time, deep learning and convolutional neural networks (CNN)... more

Diatoms, a kind of algae microorganisms with several species, are quite useful for water quality determination, one of the hottest topics in applied biology nowadays. At the same time, deep learning and convolutional neural networks (CNN) are becoming an extensively used technique for image classification in a variety of problems. This paper approaches diatom classification with this technique, in order to demonstrate whether it is suitable for solving the classification problem. An extensive dataset was specifically collected (80 types, 100 samples/type) for this study. The dataset covers different illumination conditions and it was computationally augmented to more than 160,000 samples. After that, CNNs were applied over datasets pre-processed with different image processing techniques. An overall accuracy of 99% is obtained for the 80-class problem and different kinds of images (brightfield, normalized). Results were compared to previous presented classification techniques with different number of samples. As far as the authors know, this is the first time that CNNs are applied to diatom classification.

As first observed on a group of taxa related to Cocconeis peltoides Hustedt, several other Cocconeis eHRenbeRG (Bacillariophyta) taxa possess a row of minute marginal pores on the external side of their sternum valve (SV) connected to... more

As first observed on a group of taxa related to Cocconeis peltoides Hustedt, several other Cocconeis eHRenbeRG (Bacillariophyta) taxa possess a row of minute marginal pores on the external side of their sternum valve (SV) connected to small and simple internal portules, or processes. These processes are often located in continuity with the striae, but can also be slightly shifted or distant from the distal areola of the striae. The row of pores is often, but not always, externally separated from the stria by a crista marginalis. Within Cocconeis, and possibly all raphid diatoms, these processes seem unique and restricted to a few taxa. A list is presented of the taxa pertaining (or close) to Cocconeis that are actually known to share these micro–structures. In addition, the morphological variability of the processes is described in detail and a morphological comparison of the taxa is provided. The characteristic features of taxa showing a row of SV processes permit the tentative definition of several morphological groups. It is difficult to prove the taxonomic affiliation of these taxa and demonstrate or refute that these processes are ancestral characters. Some of these taxa are rare and restricted to low latitudes (e.g., tropical taxa) while others are frequent and ubiquitous.

A population of an unknown Psammothidium species (Bacillariophyta, Achnanthidiaceae) was found in core sediments collected from Cimera Lake, an oligotrophic, undisturbed mountain lake in Central Spain (Gredos mountain range). The... more

A population of an unknown Psammothidium species (Bacillariophyta, Achnanthidiaceae) was found in core sediments collected from Cimera Lake, an oligotrophic, undisturbed mountain lake in Central Spain (Gredos mountain range). The morphology and ultrastructure of this taxon is hereby documented in detail by means of light (LM) and scanning electron (SEM) micrographs. Morphologically, the closest taxon is P. levanderi, and the type of this species is analyzed here to provide a differential diagnosis. A comparison with other similar small Psammothidium species with an elliptic outline show that the combination of features exhibited by this taxon is unique and it is thus described here as Psammothidium toroi sp. nov.

In situ effect of heavy metal enrichment on periphytic diatom community of a river was studied using metal diffusing substrates. Periphytic algae growing on these substrates showed intracellular accumulation of test metals (Cu, Zn and Pb)... more

In situ effect of heavy metal enrichment on periphytic diatom community of a river was studied using metal diffusing substrates. Periphytic algae growing on these substrates showed intracellular accumulation of test metals (Cu, Zn and Pb) which inhibited growth, as evidenced by reduced cell number, and increased morphological abnormalities in diatoms. In the case of Cu and Zn, percent deformed diatom frustules showed a strong relationship (r 2 > 0.80) with intracellular metal content and metal release from the substrate. Frustule deformity was evident in 15 of the 19 common diatom taxa, occurring frequently in Fragilaria capucina, Gomphonema parvulum, Nitzschia palea, Pinnularia conica and Ulnaria ulna. Altered pattern of striations and changed outline of frustules were the only deformities in the control; however, raphe modification and mixed deformities (several deformities in the same frustule) were additionally observed under metal stress. Raphe modifications were more frequent in the case of Cu exposure, while abnormalities in striations and mixed deformities were more prevalent in diatoms exposed to Zn or Pb. The present study shows the utility of morphological abnormalities in diatom frustules as an effective tool for biomonitoring of heavy metal pollution in waterbodies.

This study presents investigations of the periphytic diatoms on artificial (glass slides) and natural substrates in the karstic, limnocrene spring of Bunica situated in the south of Bosnia and Herzegovina. Investigations were performed in... more

This study presents investigations of the periphytic diatoms on artificial (glass slides) and natural substrates in the karstic, limnocrene spring of Bunica situated in the south of Bosnia and Herzegovina. Investigations were performed in summer 2010. Samples were collected every seven days for eight weeks. Physical and chemical characteristics of water, temperature, oxygen saturation, dissolved oxygen, electric conductivity and nutrients as well as flow velocity at sample site, were measured simultaneously with each sampling. Physical and chemical characteristics showed low temperature oscillations, good aeration and oligotrophic conditions. In general, greater diatom diversity was noted on natural substrate. A total of 104 diatom species were found on natural substrate and 82 on glass slides. The best represented genera on both types of substrate were Gomphonema and Navicula (each with eight species), Nitzschia (with six species), and Cocconeis (with five species). Achnanthidium exiguum, Achnanthidium minutissimum, Amphora pediculus, Cymbopleura amphicephala and Surirella minuta were recorded in all samples of natural substrate and Gomphonema minutum in artificial substrate samples.

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,... more

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.

Comparative morphological (including plastids) and ultrastructural (frustule) analyses of numerous taxa within the established diatom genus Neidium Pfitzer led to the conclusion that N. binodiforme Krammer and N. binodis (Ehrenberg)... more

Comparative morphological (including plastids) and ultrastructural (frustule) analyses of numerous taxa within the established diatom genus Neidium Pfitzer led to the conclusion that N. binodiforme
Krammer and N. binodis (Ehrenberg) Hustedt can be identified as striking exceptions. They would be more coherently allocated in a new freshwater benthic diatom genus, Neidiomorpha gen. nov. This proposed genus differs from Neidium mainly by the longitudinal structures (shallow “caves” in the mantle instead of distinct
canals at the junction between valve face and mantle), by areolation pattern (including the absence of renilimbi on the internal valve surface), and raphe endings (no silica flaps causing a bifurcate appearance of the polar endings and no central endings deflected towards opposing directions). Chloroplast number and arrangement (two valve- and girdle-appressed chloroplasts placed fore and aft in the two halves of the cell), overall valve outline, and ecology (preference for medium to high conductivity freshwaters) are likely to be further relevant distinctive elements. Observations on the distribution, and habitat and choriotope preference of the two species combined with the new genus are also provided.

Metal pollution of aquatic habitats is a major and persistent environmental problem. Acid mine drainage (AMD) affects lotic systems in numerous and interactive ways. In the present work, a mining area (Roșia Montană) was chosen as study... more

Metal pollution of aquatic habitats is a major and persistent environmental problem. Acid mine drainage (AMD) affects lotic systems in numerous and interactive ways. In the present work, a mining area (Roșia Montană) was chosen as study site, and we focused on two aims: (i) to find the set of environmental predictors leading to the appearance of the abnormal diatom individuals in the study area and (ii) to assess the relationship between the degree of valve outline deformation and AMD-derived pollution. In this context, morphological differences between populations of Achnanthidium minutissimum and A. macrocephalum, including normal and abnormal individuals, were evidenced by means of valve shape analysis. Geometric morphometry managed to capture and discriminate normal and abnormal individuals. Multivariate analyses (NMDS, PLS) separated the four populations of the two species mentioned and revealed the main physico-chemical parameters that influenced valve deformation in this context, namely conductivity, Zn, and Cu. ANOSIM test evidenced the presence of statistically significant differences between normal and abnormal individuals within both chosen Achnanthidium taxa. In order to determine the relative contribution of each of the measured physico-chemical parameters in the observed valve outline deformations, a PLS was conducted, confirming the results of the NMDS. The presence of deformed individuals in the study area can be attributed to the fact that the diatom communities were strongly affected by AMD released from old mining works and waste rock deposits.

Fragilaria candidagilae Almeida, C. Delgado, Novais & S. Blanco is a new araphid diatom species, described from samples collected in central and southern Portugal (SW Europe). Fragilaria candidagilae has linear-lanceolate valves with... more

Fragilaria candidagilae Almeida, C. Delgado, Novais & S. Blanco is a new araphid diatom species, described from samples collected in central and southern Portugal (SW Europe). Fragilaria candidagilae has linear-lanceolate valves with strongly capitate apices, without spines, and alternate punctate striae. This taxon presents siliceous plaques on the valve mantle edge, two apical pore fields in the poles and siliceous depositions on the outer areolar openings in the form of rounded floating disks. The morphology of the new diatom species is documented by light and scanning electron micrographs and discussed in detail, including a morphological comparison with the type material of similar taxa such as Fragilaria recapitellata, F. capucina, F. intermedia, F. neointermedia and F. perminuta to confirm it as a new species. Statistical comparison of morpho-metric characters and valve shape analysis were based on at least 20 valves. Ecological notes were also included. Considering morphology and morphometry, together F. candidagilae is clearly different from other species.

Ultrastructural observations of one previously misidentified freshwater species of a Cocconeis (Bacillariophyceae) from the Crozet Archipelago, Indian Sector of the Southern Ocean, are presented. Cocconeis crozetensis sp. nov. possesses... more

Ultrastructural observations of one previously misidentified freshwater species of a Cocconeis (Bacillariophyceae) from the Crozet Archipelago, Indian Sector of the Southern Ocean, are presented. Cocconeis crozetensis sp. nov. possesses small valves (apical axis: 10–13μm; transapical axis: 6.7–8.4μm). The main frustule features that distinguish the proposed new species are: (1) the sternum valve (SV) areolae with an external vola and the internal vela, (2) the submarginal area of the raphe-sternum valve, and (3) the mor- phology of valvocopula and fimbriae of the SV. Possible morphological relationships with several other small Cocconeis, such as C. neodiminuta, C. neothumensis, C. placentula var. pseudolineata and C. pseudothumensis, as well as its morphological similarities with placentuloid Cocconeis are discussed. Reliable identification of C. crozetensis sp. nov. under light microscopy can prove diffi- cult for less-experienced diatomologists and ecologists, and the use of electron microscopy proves to be unavoidable for its correct identification.

Two Mastogloia Thwaites ex W.Sm. taxa were found during a survey of the diatom flora of Lac de Guiers, Senegal. Based on all currently available literature, one taxon could be identified as M. belaensis M.Voigt, a species formerly... more

Two Mastogloia Thwaites ex W.Sm. taxa were found during a survey of the diatom flora of Lac de Guiers, Senegal. Based on all currently available literature, one taxon could be identified as M. belaensis M.Voigt, a species formerly described from Pakistan. The second species showed some resemblance to M. braunii Grunow. Analysis of the type of M. braunii revealed, however, important morphologic differences, leading to the description of a new species from the Senegal population: M. senegalensis Van de Vijver, Fofana, Sow \& Ector sp. nov. The present paper describes this new species and discusses and illustrates the morphology of M. belaensis and the type of M. braunii. All taxa are discussed with morphologically similar taxa.

A new freshwater benthic diatom genus, Microfissu-rata gen. nov., was identified from light and scanning electron micrographs. The most characteristic morphological feature (referred to also by the name of the new genus) is the structure... more

A new freshwater benthic diatom genus, Microfissu-rata gen. nov., was identified from light and scanning electron micrographs. The most characteristic morphological feature (referred to also by the name of the new genus) is the structure of the striae ⁄ alve-oli, which are simple, mostly uninterrupted, trans-apical slits. The combination of characteristics of the new genus is unique. It includes two new species: Microfissurata paludosa Cantonati et Lange-Bert. sp. nov. and M. australis Van de Vijver et Lange-Bert. sp. nov., distributed in Europe and on an austral island, respectively. The new genus occurs in freshwater dystrophic lakes, pools, seepage springs, mires, and in intermittently wet terrestrial habitats. It is not abundant but widespread wherever these habitat types are well developed, in Nordic-alpine and sub-Antarctic areas. Overall, the new genus appears to be mostly epiphytic (bryophilous) and capable of tolerating a wide range of moisture conditions (xerotolerant). The finding of the type species (M. paludosa) in a well-investigated area like central Europe highlights the diatom species richness of dystrophic habitats and their importance for diatom biodiversity conservation.

Achnanthidium sinense sp. nov., a new diatom species from the Wuling Mountains Area, central China, was studied by light and scanning electron microscopy. The valvar dimensions of this species are relatively large with respect to average... more

Achnanthidium sinense sp. nov., a new diatom species from the Wuling Mountains Area, central China, was studied by light and scanning electron microscopy. The valvar dimensions of this species are relatively large with respect to average Achnathidium taxa. The valves are narrowly lanceolate with round, acute apices. Only a few striae in the middle part of both valves can be resolved under light microscopy. The axial area of raphe valve is linear-lanceolate and the distal raphe fissures hook towards the same side of the valve. Striae are slightly radiate throughout both valves except at the apices of the raphe valve, where they become parallel or slightly convergent. The number of areolae in each stria on the rapheless valve is usually greater than that on the raphe valve (1–7 vs. 1–6). Around the central areas of both valves, sometimes short marginal striae composed of 1–3 areolae are present. Valve mantle possesses a row of slit-like areolae and 2–3 notches. A. sinense is compared with the similar species A. exile and other large species. A. sinense is epilithic and lives in freshwater habitats.

ABSTRACT The augmentation of fine particles and water velocity may have important effects on river biota, which have not been fully clarified. The aim of this study is to relate the removal of diatoms to changes in environmental variables... more

ABSTRACT The augmentation of fine particles and water velocity may have important effects on river biota, which have not been fully clarified. The aim of this study is to relate the removal of diatoms to changes in environmental variables during high-stage flow in alpine streams.

In this study on benthic diatoms from Mona Island, Puerto Rico one hundred forty-eight taxa are reported. Sixteen are new records for Puerto Rico; eleven are new for the Caribbean Sea and one for the Caribbean Sea and Atlantic Ocean. A... more

In this study on benthic diatoms from Mona Island, Puerto Rico one hundred forty-eight taxa are reported. Sixteen are new records for Puerto Rico; eleven are new for the Caribbean Sea and one for the Caribbean Sea and Atlantic Ocean. A new variety, Lampriscus shadboltianus var. tricrenulata, and a new combination, Haslea quarnerensoides, is presented. Each species displays its main references, measurements, distribution on the Island, and photographs, in some cases, with light and/or scanning electron microscope.

Gomphonema alavariense sp. nov. is a new freshwater diatom described in Portugal from phytobenthos samples in an urban pond located in Aveiro (Portugal). This new diatom is illustrated and discussed based on different samples collected in... more

Gomphonema alavariense sp. nov. is a new freshwater diatom described in Portugal from phytobenthos samples in an urban pond located in Aveiro (Portugal). This new diatom is illustrated and discussed based on different samples collected in July August 2017 from Santo Ant{\'{o}}nio Park pond in the city centre. This taxon was compared with other Gomphonema taxa and the morphological features are documented through light and scanning electron micrographs. Gomphonema alavariense sp. nov. is characterized by showing solitary cells, rhombic-lanceolate to lanceolate valves with rounded apices, a narrow, linear axial area, and slightly asymmetrical central area. This taxon may be confused with G. affine var. rhombicum in terms of length, striae density and outline. Gomphonema alavariense sp. nov. was present in freshwater with low dissolved oxygen concentrations, high conductivity, neutral to slightly alkaline pH and high nitrate concentrations.

Background and aims-The detailed analysis of algae and cyanoprokaryotes in a heterogeneous group of spring habitats (including all the different typologies) of the northern Apennines (Emilia-Romagna Region, Italy) revealed a new Amphora... more

Background and aims-The detailed analysis of algae and cyanoprokaryotes in a heterogeneous group of spring habitats (including all the different typologies) of the northern Apennines (Emilia-Romagna Region, Italy) revealed a new Amphora species in a small mountain flowing spring with low conductivity, and a new Halamphora species in a large, inland-saline (Triassic gypsum), fast flowing spring (Poiano spring). The present study aims to describe in detail these two new species found in contrasting spring types. Methods-This study is based on light microscopy (both fresh-for plastids-and prepared materials) and scanning electron microscopy observations, as well as a thorough morphological, physical, chemical, and biological characterization of the habitats. Key results-Amphora eileencoxiae sp. nov. is most similar to A. vetula (and allied taxa), and is characterized by the outline with acutely rounded, moderately ventrally bent ends, by the dimensions, and by the well-defined, semi-elliptic dorsal area. Halamphora poianensis sp. nov. is most similar to H. gasseae but differs by the higher stria density, the clearly ventrally bent ends, and the strongly developed dorsal raphe ledge. Conclusions-This is a contribution to the knowledge of the genera Amphora and Halamphora in mountain springs in understudied geographic areas and inland-saline springs, the species communities of which are likely insufficiently explored.

This paper presents light (LM) and scanning electron microscopic (SEM) observations on two small Cocconeis taxa from Kerguelen Archipelago (Indian Sector of the Southern Ocean). The new species Cocconeis germainii sp. nov. is described.... more

This paper presents light (LM) and scanning electron microscopic (SEM) observations on two small Cocconeis taxa from Kerguelen Archipelago (Indian Sector of the Southern Ocean). The new species Cocconeis germainii sp. nov. is described. Previous works show that this species, or morphologically similar varieties with lower striae density, have already been illustrated and briefly described under various names. Most of these descriptions are based either on incomplete frustules or probably juxtaposed sternum and raphe valves. Several other taxa showing a certain degree of morphological affinity with the sternum valve of C. germainii are discussed. Included in this group are Catillus subimpletus Hendey and a so-far unidentified Cocconeis sp. [aff. C.peltoides Hustedt]. The generic status of Catillus, established by N.I. Hendey, is briefly discussed.