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

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

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

Reaction of biofilms (cyanobacterial, diatom and green algae) from lake Balaton and river Danube to herbicide preparation ROUNDUP and its components (glyphosate, POEA)

The behavior of biofilms developing during 6 weeks on sheets of glass fixed to AKK-1® type carrier buoy in River Danube (Green Island, Budapest) and in Lake Balaton (Tihany Bay) in spring time was investigated in aquaria exposed to glyphosate at concentrations of 100 and 1000 µg/l for 6 and 4 weeks, respectively. The effects of adjuvant POEA and formulated herbicide ROUNDUP® at glyphosate equivalent concentrations were also tested. Sensitivities of biofilms from River Danube and Lake Balaton were different under laboratory conditions. No adverse effects of POEA were determined on the well-estimable biofilm originated from River Danube, while glyphosate caused a 30% decrease in 10 weeks. Realignment of biofilms was typical, the initial ratio of diatom (Bacillariophyceae) and cyanobacteria (Cyanobacteria) decreased, and these species were replaced by a filamentous green alga (Chlorophyta) population