Morphology and distribution of Brevilinea kevei sp. nov. (Bacillariophyceae), a new diatom from Europe

An unknown small naviculoid diatom was found in the epiphyton samples from Hungary (in Kanyari Holt-Tisza oxbow) and in the epilithon samples from France (Canal de Berry at Épineuil-le-Fleuriel). Detailed observations using light and scanning electron microscopy were used to describe Brevilinea kevei Ács &amp; Ector sp. nov. It can be separated from Brevilinea pocosinensis Siver et al. (which was the only described species in the genus) by its size (smaller than B. pocosinensis), shape (elliptic valve, never capitate) and ecological requirements. Brevilinea pocosinensis lives in acidic conditions while B. kevei in neutral ones. Differential diagnostic criteria with respect to similar taxa, especially Fallacia indifferens (Hustedt) D.G. Mann, together with ecological implications of this finding are briefly discussed.</jats:p

Interesting diatoms from a special habitat

The epiphytic diatoms of the soda ponds of bomb craters were sampled in 2014. The small ponds (area: 7.1-86.5 m2, depth: 4 to 60 cm) are located in the northern part of the Kiskunság National Park (47°7.403 'N, 19°8.187'E), near the village of Apaj in Hungary. Their salinity ranges from fresh water to moderately saline levels (conductivity of 1.3 to 7.1 mS cm-1). This area has patchy surface salinization, because the flow pattern of groundwater results extensive surface salinization in those discharge areas where the infiltrating freshwater does not superimpose the upwelling saline water. The salts origin from the overpressured NaCl-type water of the Pre-Neogene basement and the NaHCO3-type water of the Neogene sediments. The ponds can be characterized by different areal extent, depth and salinity, various conductivity, hydroperiod (1–9 months, the deepest ones do not dry out in years with high amount of precipitation due to probably more or less continuous supply by groundwater), plant coverage and width of macrophyte belt. All of the ponds were sampled except for the ones with very short (shorter than one month) hydroperiod. A total of 80 diatom taxa, representing 33 genera, were identified in these ponds. The genus Nitzschia was represented by the largest number of species (16), followed by the genus Gomphonema with 9 taxa. IndVal analysis identified 15 species with significant indicator values for ponds. Some interesting, rare or new diatoms for Hungarian flora have also been recorded, including Gomphonema jadwigiae, Halamphora dominici, Navicula wiesneri, Nitzschia austriaca, N. vitrea, Surirella peisonis

Nitzschia austriaca Hustedt: a characteristic diatom of Hungarian inland saline waters including a morphological comparison with the type material

A detailed scanning electron microscopic investigation was carried out to clarify the taxonomic status of a small sigmoid Nitzschia species, a potential indicator of Central European soda waters. We found this taxon to be one of the dominant epiphytic diatoms collected from sodic bomb crater ponds at Apaj (Hungary). The large population allowed for a morphometric comparison based on frustule ultrastructure with the type material of the most similar species, Nitzschia austriaca Hustedt that was originally described from a soda pan in the region. The results clearly demonstrated an overlap between the Apaj population and the type material of N. austriaca (based on NMDS analysis), therefore we argue that they represent the same taxon. An emended diagnosis of N. austriaca is given. Total suspended solids and total phosphorous proved to be the most important factors predicting the occurrence of the species, with possible interactive effects of conductivity and pH. We then expanded the distribution of the species by revisiting data originating from previous large-scale surveys targeting sodic habitats in Hungary. On the basis of our results, N. austriaca is a characteristic species for Central European soda waters, including the protected astatic soda pans, indicating their typical chemical and physical characteristics.</jats:p

Biogeography and morphology of a poorly known diatom Dorofeyukea rostellata (Hustedt) Kulikovskiy & Kociolek = Biogeografía y morfología de una diatomea poco conocida Dorofeyukea rostellata (Hustedt) Kulikovskiy & Kociolek

Dorofeyukea rostellata is a rare and poorly known representative of Dorofeyukea genus. To date, this taxon has only been recorded only outside of Europe. In two Croatian lakes, we found a diatom in appearance similar to Dorofeyukea rostellata and within corresponding physical and chemical conditions. Due to the uncertain taxonomical position of this taxon, type material of Dorofeyukea rostellata and a closely related species, Navicula grimmeioides, were analysed by means of light and scanning electron microscopy. Upon a detailed investigation, we could clearly distinguish the Croatian population from N. grimmeioides. However, the Croatian population and the type material of D. rostellata differed only in minor characteristics. The most obvious difference is the shape of areolae. Nevertheless, differences between the shapes of the areolae can be caused by the degree of silicification, which often depends on the environmental conditions. Since almost every other characteristic of the Croatian population overlapped with that of the type material of D. rostellata we identified it as D. rostellata. Additionally, scanning electron microscopy analyses also revealed that N. grimmeioides belongs to the genus Dorofeyukea, so its new combination was proposed

Effect of Land Use on the Benthic Diatom Community of the Danube River in the Region of Budapest

(1) Urbanization significantly influences the ecosystems of rivers in various ways, including the so-called loading effect of wastewater production. Benthic diatoms are used in ecological status assessments of waters. Beside species composition, traits can be used as indicators. We aimed to evaluate how the loading of the large city of Budapest manifests in the physico-chemical variables of the River Danube and what species composition and trait response this loading results in for the benthic diatom communities. (2) Weekly samplings were performed at points upstream and downstream of Budapest on both riverbanks. Samples were compared, based on general physical-chemical variables and the concentration of thirty-four elements, as well as species composition and seven traits of species of diatom communities. Ecological status was assessed using the Specific Pollution Sensitivity Index (IPS). (3) Only a few measured environmental variables showed differences between the sampling points, suggesting that the nutrient loading has significantly decreased due to the installation of several efficiently working wastewater treatment plants since the introduction of the European Union Water Framework Directive. In contrast, the species composition and traits of species showed the effect of land use. Benthic diatoms indicate the environmental changes caused by land use in the longer-term, while chemical measurements reflect instantaneous status