Part of the geology in the Łódź province was formed during the Upper Permian period when rich Zechstein salt was deposited. Groundwater drains the deposits and flows out in the village of Pełczyska, creating a unique hydrogeological site in Central Poland. An inland, athalassic ecosystem can be a reference site for halophile microflora. The outflow with surrounding marshes has been an algological research site since 1964. The research reveals changes recorded in diatom assemblages from athalassic habitats, characterized by a wide range of salinity levels, and verifies the tolerance of taxa to salinity. The comparative analysis was based on the diatom material sampled in 1964-1965, 1992-1994 and on recently collected samples. The analysis revealed the temporal change in assemblages caused by a change in the chloride concentration, and the spatial change from one to another habitat type, characterized by varying salinity levels. The halophilic species in the studied habitats included e.g. Halamphora dominici, H. tenerrima, Navicula digitoconvergens, N. meulemansii, Staurophora salina. The analysis of changes allowed the verification of the species’ requirements and tolerance range to the salinity factor. Therefore, in the case of Fragilaria famelica and Halamphora sydowii, we propose a change in the halobion system classification.

The benthic diatoms collected during our recent research in athalassic habitats exemplify a high morphological variability within Chamaepinnularia krookiformis lange-Bertalot et krammer. The species has already been known from freshwater ecosystems as well as from brackish waters in different regions of Europe. This variability has been also confirmed by the analysis of the literature. However, this is the first time that the morphological variability of the species has been addressed. In order to revise C. krookiformis and describe a new species, which has been distinguished on the basis of our material, we compared it with the type material of Pinnularia krookiformis krammer 1992 from the periodic saline pool in Nordrhein-Westfalen (Germany). This study deals with a morphological analysis based on a large populations of C. krookiformis from Pełczyska (Central Poland). Selected morphological features were analysed, i.e.: valve length and width, number of striae in 10 µm, apices width, constrictions width, apices/constrictions width ratio, central-area length, and valve/central area length ratio. The results of light (LM) and scanning (SEM) microscopy, supported by multidimensional scaling (MDS), allowed for the distinction of three different morphotypes. Two of them match krammer concept of Pinnularia krookiformis from 1992, while the third, occurring in our samples in three sampling sites, is clearly different. Thus, we described a new species Chamaepinnularia plinskii sp. nov., by the following major features: the valves are linear, symmetric, with rounded, capitate apices, the axial area is narrow, expanding to a wide central area forming a fascia, distal raphe endings are hooked to the same side of the valve and striae slightly radiate in the middle and in the rounded apices, becoming parallel in constrictions, 20-26 in 10 µm. This species occurs in inland waters with a wide range of chloride concentration, from 1000 to 3500 mg.l-1 .

Post iron ore mining reservoirs in Łęczyca (Poland) can be considered extreme habitats because they are characterized by high pH, conductivity, and sulfate, sodium and potassium concentrations. We observed high abundances in these water bodies of several centric diatom species that are otherwise known from less extreme environments. These included Thalassiosira duostra, Cyclostephanos dubius, Stephanodiscus binatus, Stephanodiscus invisitatus, Stephanodiscus parvus, Stephanodiscus hantzschii, Lindavia aff. balatonis, Discostella woltereckii, Discostella pseudostelligera, and Cyclotella meneghiniana, revealing the eurytopic nature of these species. Morphological differences between populations from extreme habitats and their counterparts from less extreme environments may indicate phenotypic responses of eurytopic taxa to the differing environmental regimes, or the presence of distinct, more stenotopic taxa. In both cases, this could be relevant for biomonitoring. For this reason, we carefully observed the morphological variability of our target taxa in the Łęczyca reservoir samples compared with literature accounts from less extreme habitats, and in some cases, with type material of the species concerned. Specimens similar to Aulacoseira muzzanensis α-chains were observed. Following comparison with the type material of Melosira muzzanensis Meister (≡A. muzzanensis), we concluded that the Łęczyca populations are sufficiently different to be recognized as a separate species, here described as Aulacoseira pseudomuzzanensis sp. nov. The importance of identifying centric diatoms to species level for water management surveys is emphasized, even for those taxa that are difficult to identify using only LM.

Background: The ecological state of surface waters is typically assessed by a multi-aspect approach based on a determination of its chemical and physical parameters, by hydromorphology and the use of indicator organisms such as benthic diatoms. By assigning ecological indicator values, it is possible to create diatom indices which serve as the basic tool in assessing the ecological status of surface waters. These ecological indicator values are set according to classification systems, such as the Van Dam, Mertens & Sinkeldam (1994) system, which classifies species of diatoms according to seven different ecological factors. However, recent studies on the autecology of diatoms have shown the need to verify and establish new ecological indicator values. To this end, aquatic ecosystems are good environments to observe the range of tolerance of benthic diatoms to environmental conditions due to their unique physical and chemical parameters. The aim of the present study was to propose the establishment of new, or altered, ecological indicator values, according to the Van Dam, Mertens & Sinkeldam (1994) classification, of species of diatoms characteristic of three post-mining aquatic ecosystems. Methods: In total, 36 species were identified that were characteristic of three waterbodies: a salt aquatic complex (water outflow, a drainage ditch and a pond), mined iron ore reservoirs and a mined lignite reservoir. Their ecological indicator values were specified using OMNIDIA software, and the environmental conditions prevailing in the studied ecosystems were determined. Of the 36 characteristic species, 16 lacking at least one assigned ecological indicator value were analyzed further. The analysis identified three groups of selected characteristic species which showed a correlation, or lack of such, to the tested physical and chemical parameters. Results: Based on this multistage study of the autecology of characteristic diatoms, comprising an analysis of environmental conditions, literature analysis and reference ecological indicator values of other species, it is proposed that 32 ecological indicator values be established or adjusted for 16 species, and that Planothidium frequentissimum be excluded from water quality assessments.

Post-mining reservoirs are distinguished by characteristic environmental conditions where specific diatom communities can be observed. Reservoirs created as a part of the reclamation plan after human mining activities are marked by unique chemical and physical water parameters. In the course of research on the diatoms from Bogdałów reservoir, we examined the taxonomic and morphological diversity of Nitzschia taxa from the section Lanceolatae occurring in a post-mining lignite reservoir. Our study describes a new species of Nitzschia from a post-mining reservoir, Nitzschia nandorii Olszyński, Zakrzewski & Żelazna-Wieczorek, sp. nov. Morphometry and morphology analyses of new species were performed with light and scanning electron microscopy. Chloroplast morphology analysis was conducted with differential interference contrast microscopy and confocal laser scanning microscopy. Molecular data from SSU 18S, rbcL and psbC sequences were obtained from cultures of this taxon. Differential diagnosis of Nitzschia nandorii Olszyński, Zakrzewski & Żelazna-Wieczorek, sp. nov. with co-occurring taxa: N. lacuum and N. alpinobacillum was performed using morphological traits and nMDS analysis of the valves’ morphometry.

Tryblionella (Bacillariaceae) was described by Smith in 1853, and for many years, the diagnosis of this genus was questionable. Recent molecular analysis based on the rbcL gene marker suggests that Tryblionella is a polyphyletic genus with T. apiculata, T. hungarica, and T. gaoana forming a distinct group from other Tryblionella representatives. Therefore, this study aimed to clarify the diagnosis of Tryblionella as a genus. The focus of this study was a selected group of species previously categorized within Grunow's section Apiculatae, which includes the type species T. acuminata. This classification serves as a foundation for conducting morphological and molecular comparisons with taxa of Tryblionella sensu lato, which are likely to represent distinct and highly diverse genera. Our review includes a detailed examination of frustule ultrastructure and ontogeny combined with a new molecular phylogenetic analysis derived from a three‐gene concatenated dataset. The results of our research indicated that among Tryblionella, several monophyletic groups of taxa can be distinguished, including Tryblionella sensu stricto (s.s.), by three key characters: a porose valve cross‐section; longitudinal valve undulation, where the peak of the undulation is located on the proximal side of the valve; and the presence of an axial sternum with thickened and relief virgae. Tryblionella s.s. taxa share a similar girdle structure: The girdle is graded, except that the first band bears a single row of poroids in the pars exterior and a crenulate margin on the side corresponding to the distal valve mantle.