Diatom monitors of close-to-pristine, very-low alkalinity habitats: three new Eunotia species from springs in Nature Parks of the south-eastern Alps

On the basis of LM and SEM observations as well as of environmental data, three species of the predominantly-acidophilous diatom genus Eunotia (E. cisalpina, E. fallacoides, E. insubrica) are described as new to science, and characterized from the ecological point of view. The three new species were not distinguished from other similar ones in the past but can be identified at the LM by careful observation of diacritical characters such as valve outline (in particular the shape of the endings), dimensions, and stria density. One of the three new species (E. insubrica) presents a very peculiar ultrastructural feature, i.e. well-developed pseudoseptum-like structures at the apices. The three new species were pointed out by detailed analyses of materials sampled in the south-eastern Alps. It is put forward that diatom investigations adopting high-resolution taxonomy are particularly opportune in habitats such as those colonized by the three new species. The three new species were found to be characteristic of low-alkalinity, naturally slightly-acidic, strictly-oligotrophic, high-mountain springs and lakes. Efficient desiccation-resistance strategies, apparently widespread in the genus Eunotia, might be supposed also for the three new species, that were found to thrive also in lowdischarge springs and in the shallow littoral waters of lakes showing seasonal or exploitation-enhanced water-level fluctuations. The diatom assemblages of these aquatic habitats possess a high species richness, and include many rare and Red List species, and are thus of prominent importance for diatom biodiversity conservation. These relatively-pristine aquatic habitats on siliceous bedrocks are however highly sensitive, and endangered because of diffuse pollution. Climate- and environmental-change driven increased release of organic acids, and contamination by airborne inorganic acids and nutrients are all potential threats to these still highintegrity but fragile systems. The detailed characterization of their diatom assemblages, that are excellent monitors of acid-base and nutrient status is thus of the foremost importance. In particular the distinction between naturally-acidic and acidified systems is a relevant topic that might benefit from detailed knowledge of taxonomy and ecology of both communities and indicative taxa of the diatom assemblages

Using different epilithic-diatom assemblage metrics for an ecological characterization of the shores of Lake Garda

It has been proved that littoral diatoms provide a useful marker for detecting localised changes resulting from neve anthropogenic disturbances or intermittent releases of sewage along the shorelines of lakes. This study tested the spatial resolution at which this general observation occurs, by selecting areas with different anthropogenic pressures (urbanization) along a latitudinal gradient in Lake Garda, a deep and wide peri-Alpine lake. The sampling design aimed to detect differences in diatom distribution in terms of species diversity, quality indices, proportion of Red List taxa, assemblages, and individual species. Because the extent to which diatom assemblages respond to these gradients was unknown, we used assemblage metrics of different sensitivities. Results showed that the most important environmental factor was the latitudinal gradient, which was revealed by almost all the assemblage metrics. This dominant trend was explained by two co-occurring environmental gradients: concentration of nutrients and thermal gradient. The importance of different levels of urbanization was unevenly partitioned among locations and latitudes because of the different intensities of urbanization pressure. Only the species Brachysira neglectissima, the quality index (Trophic Index), and to a lesser extent, the metric at assemblage level revealed significant effects. Overall, this study comes to two main conclusions: (1) different metrics are needed to detect the multifaceted effects of anthropogenic disturbances, which by their very nature are unevenly distributed and of different intensities, and therefore affect assemblages to different degrees; (2) for any monitoring program in this lake to be effective, the various gradients revealed in this work should be taken into account. Failing to include these sources of variability might lessen the benefits of monitorin

Cymbopleura pyrenaica sp. nov. (Bacillariophyceae) et d'autres espèces du même genre rarement recensées dans quelques lacs des Pyrénées françaises

Lors d’une étude des diatomées des lacs français des Pyrénées, une nouvelle espèce de Cymbopleura, C. pyrenaica sp. nov., a été mise en évidence. La morphologie détaillée de ce taxon a été examinée à l’aide du microscope photonique (MP) et du microscope électronique à balayage (MEB). La nouvelle espèce est très proche de Cymbella laevis Naegeli mais l’absence de champs apicaux de pores la place dans le genre Cymbopleura. Le caractère ultra-structural le plus frappant est la variabilité morphologique des aréoles. Cymbopleura pyrenaica sp. nov. est présente dans plusieurs lacs mais avec une très faible occurrence; elle tolère un large éventail de la conductivité. Une courte revue des autres espèces de Cymbopleura recensées dans les lacs prospectés est présentée

New Amphora and Halamphora (Bacillariophyta) species from springs in the northern Apennines (Emilia-Romagna, Italy)

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

Navicula pierre-comperei sp. nov. (Bacillariophyta), a small benthic diatom recently observed in several Central European rivers

Background and aims – An unidentifiable naviculoid diatom was found in several small rivers of Germany over some years of routine water monitoring. Since it occurred rather abundantly in places taxonomical and ecological definition is required. Methods – Acid-cleaned diatom material, mounted in Naphrax, was observed and photographed in a light microscope with PlanAPO objectives, for SEM analysis gold-sputtered on stubs using Hitachi S 4500 field emission techniques. Key results – Navicula pierre-comperei is described and proposed as a new species. It is compared in particular to Navicula claytonii J.R. Carter, a similar taxon from the British Isles, currently absent from Central Europe

Kieselalgen als Indikatoren für Gewässerqualität : wie sich die Gewässergüte des Mains im Verlauf der vergangenen zwei Jahrzehnte verändert hat

Einzellige, mikroskopisch kleine, pflanzliche Organismen erweisen sich als ideale Bioindikatoren, um den Verunreinigungsgrad von Gewässern zu bestimmen: Diese Kieselalgen finden sich in den verschiedensten Gewässern - von reinsten Quellbächen bis zu Abwasserkanälen; die Artenzusammensetzung der Kieselalgen ist je nach Gewässerzustand sehr unterschiedlich. Auf jede Veränderung der Qualität folgt schnell ein charakteristischer Artenaustausch. Seit 1972 untersucht der Biologe Horst Lange-Bertalot mit dieser Methode die Wasserqualität des Mains, die sich wesentlich verbessert hat. Über Ergebnisse berichtet er gemeinsam mit Christine Schmidt

Navicula pierre-comperei sp. nov. (Bacillariophyta), a small benthic diatom recently observed in several Central European rivers

Background and aims – An unidentifiable naviculoid diatom was found in several small rivers of Germany over some years of routine water monitoring. Since it occurred rather abundantly in places taxonomical and ecological definition is required. Methods – Acid-cleaned diatom material, mounted in Naphrax, was observed and photographed in a light microscope with PlanAPO objectives, for SEM analysis gold-sputtered on stubs using Hitachi S 4500 field emission techniques. Key results – Navicula pierre-comperei is described and proposed as a new species. It is compared in particular to Navicula claytonii J.R. Carter, a similar taxon from the British Isles, currently absent from Central Europe

Quatre nouvelles espèces de <I>Navicula</I> (Bacillariophyta) provenant de rivières en Suède

Durant une analyse des diatomées lotiques des rivières en Suède, plusieurs nouvelles espèces de Navicula (Bacillariophyceae) ont été trouvées : Navicula antonioides sp. nov., N. ireneae sp. nov., N. scaniae sp. nov. et N. ceciliae sp. nov. Les nouvelles espèces sont décrites à partir d’observations en microscopie optique et à balayage. Chaque nouvelle espèce présente une combinaison unique de caractères morphologiques comme la structure des terminaisons centrales du raphé, la striation, les dimensions des valves et la forme générale des valves qui permet de les séparer d’autres espèces semblables du genre Navicula comme N. cryptocephala, N. radiosafallax ou N. antonii. Les préférences écologiques de chaque espèce sont brièvement discutées. Enfin, la distribution des Navicula s.s. dans les eaux continentales d’Europe est brièvement discutée.During an extensive survey of the diatoms of Swedish rivers, four new Navicula species (Bacillariophyceae) were found: Navicula antonioides sp. nov., N. ireneae sp. nov., N. scaniae sp. nov. and N. ceciliae sp. nov. The new species are described formally using light and scanning electron microscopy. All four species possess a unique set of morphological characters including the structure of the central raphe endings, the striation pattern, the valve dimensions and outline, which make it possible to separate them from similar Navicula taxa such as N. cryptocephala, N. radiosafallax or N. antonii. The ecological preferences of each species are briefly discussed. Finally, the distribution of Navicula s.s. taxa in European inland waters is briefly discussed.</p