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Field observations form the basis of the majority of studies on microphytobenthic algal communities in freshwater ecosystems. Controlled mesocosm experiments data are comparatively uncommon. The few experimental mesocosm studies that have been conducted provide valuable insights into how multiple stressors affect the community structures and photosynthesis-related traits of benthic microalgae. The recovery process after the stressors have subsided, however, has received less attention in mesocosm studies. To close this gap, here we present the results of a riparian mesocosm experiment designed to investigate the effects of reduced flow velocity, increased salinity and increased temperature on microphytobenthic communities. We used a full factorial design with a semi-randomised distribution of treatments consisting of two levels of each stressor (2 × 2 × 2 treatments), with eight replicates making a total of 64 circular mesocosms, allowing a nuanced examination of their individual and combined influences. We aimed to elucidate the responses of microalgae communities seeded from stream water to the applied environmental stressors. Our results showed significant effects of

Benthic diatoms have been used for decades as powerful indicators for biomonitoring lakes and rivers around the world. Due to the more than 100,000 diatom species morphological approach requires a high level of taxonomic knowledge. To overcome this obstacle, the application of metabarcoding has been developed in recent years. One of the challenges that still “forces” the simultaneous use of both approaches in biomonitoring is the incompleteness of the reference barcoding library. The diatom community from different substrates (reed, mud, artificial substrate) in Pečena Slatina has been intensively investigated in 2019, 2021-2023. One of the goals of the ongoing BIOLAWEB project, funded by the European Union, was to complement the Diat.barcode reference library for the possibility of using metabarcoding as tool in the future routine biomonitoring in Serbia. The morphological results show a similar diatom composition among different substrates with little difference in dominant taxa. Nitzschia frustulum was one of the most dominant taxa in 2022, while in 2019 it dominated together with Anomoeoneis sphaerophora, in 2021 with Navicymbula pusilla and Tryblionella hungarica, and in 2023 with Halamphora veneta. Molecular data (rbcL) have shown the dominance of T. hungarica and Nitzschia supralitorea. Anomoeoneis sphaerophora was observed in microscopy while metabarcoding data showed an unknown sequence of Anomoeoneis. Using phylogeny and p-distance calculations to compare our sequence to those present in the Diat.barcode we showed that this unknown sequence of Anomoeoneis had a high probability of matching with A. sphaerophora.

Large lowland rivers represent an important type of ecosystem that has been under a constant anthropogenic influence (industry, thermal power plants, untreated communal water, and agriculture) for centuries, which has led to most of them no longer meeting natural reference conditions. These pressures affect diatom communities which represent a reliable bioindicator of the overall degradation of water bodies. The current study provides detailed information about benthic diatoms from the large international lowland rivers Sava and Tisa, analyzed using digital microscopy. Using the digital method and the BIIGLE 2.0 image annotation system, a total of 205 and 206 diatom taxa in the Sava and Tisa rivers were identified, belonging to 65 and 63 genera, respectively. Some of the dominant genera in the Sava River were Achnanthidium, Cocconeis, Gyrosigma, and Navicula, while in the Tisa River, mostly centric diatoms (Discostella, Cyclotella, Stephanodiscus) were dominant. Most of the recorded species are alkaliphilic and characteristic of running waters with high trophic conditions. The presence of halophilic taxa was also noted (e.g. Bacillaria paxilifera, Tryblionella species, Nitzschia clausii, Navicula salinarum). These taxa are sensitive indicators of even short-term changes in lowland lotic ecosystems characterized by elevated conductivity. The diatom indices showed very consistent ecological status, mainly moderate in terms of the general pollution index IPS, and poor to bad ecological status according to trophic diatom indices (Rott TI and TDI).

Project "Boosting Institute of Chemistry, Technology and Metallurgy in Water Biomonitoring" (BIOLAWEB) aims to strengthen the research and innovation capacity of the Institute of Chemistry, Technology and Metallurgy, National Institute of the Republic of Serbia, University of Belgrade (UB-ICTM) in biodiversity assessment and biomonitoring. UB-ICTM researchers made a noticeable contribution to the study of biodiversity, community ecology, and conservation of water bodies in South-Eastern Europe. However, a knowledge on index development and intercalibration following the EU standards for lakes and watercourse monitoring is still lacking in this geographic region. Similarly, there is a knowledge gap in DNA-based ecological status assessment in SEE.

Napredak u molekularnoj biologiji doveo je do snažnog razvoja molekularnih metoda u biomonitoringu. Metabarkoding je porcedura zasnovana na upotrebi DNK molekula koja može da dopuni ili čak potpuno zameni klasičan biomonitoring u skorijoj budućnosti. Sproveli smo istraživanje fitoplanktonske zajednice, važnog biološkog parametra kvaliteta, u Markovačkom jezeru sa ciljem da uporedimo tradicionalni i molekularni pristup u biomonitoringu. Ukupno smo pronašli 105 sekvenci algi i cijanobakterija, ali usled nepotpunosti baze, lista taksona dobijena metabarkodingom je nepotpuna. Iako se rezultati metabarkodinga trenutno ne mogu koristiti za procenu ekološkog statusa u Republici Srbiji, primena molekularnog pristupa u biomonitoringu je obećavajuća., The advancement in molecular biology resultet in development of molecular methods in biomonitoring. Metabarcoding is a DNA based procedure that can supplement or even replace classical biomonitoring in the near future. We conducted a study of phytoplankton, an importtant biological quality element, in Markovačko lake aiming to compare morphological and metabacoding approach in biomonitoring. In total, 105 sequences were obtained, but due to the incompletness of the reference library the metabarcoding taxonomic list was not comprehensive. Although, the metabarcoding results can not be currently used for ecological status assessment in the Republic of Serbia, its application in biomonitoring is promissing.

This paper presents new records and noteworthy data on the following taxa in SE Europe and adjacent regions: diatom algae Cyclostephanos invisitatus, Cyclotella meduanae, and Stephanodiscus lacustris, mycorrhizal fungi Alessioporus ichnusanus and Amanita mairei, saprotrophic fungi Diaporthe oncostoma, Stropharia albonitens and Pseudomassaria chondrospora, lichenised fungus Acrocordia subglobosa, stonewort Chara connivens, mosses Buxbaumia viridis, Tortella fasciculata and Tortula protobryoides, monocots Epipactis pontica Gymnadenia frivaldii, and Orchis italica and dicots Callitriche brutia, Callitriche platycarpa and Epilobium nutans are given within SE Europe and adjacent regions.

Here, we introduce a collection of more than 83,000 light microscopy images of individual diatom valves or frustules, covering a broad range of taxa and morphology by more than 320 samples from 15 different river and lake ecotypes. The diatoms were imaged at high resolution (< 0.1 µm/pixel) by transmitted light bright-field microscopy, with focus stacking to artificially increase focal depth up to 25 µm, allowing simultaneous observation of valve ornamentation and shape. Taken from a real-world setting, the images partly also include debris, mineral particles or other diatoms. Four experts identified over 500 diatom species; more than 100 species are represented by at least 100 specimens and about 150 by at least 50 specimens each. This data set is about one order of magnitude larger than previously published diatom data sets, and its high interspecies similarity makes it a valuable resource e.g. for benchmarking fine-grained out-of-distribution (OOD) detection, on which we present a new approach.

Soda pans located in the northern part of Serbia are alkaline and very shallow water habitats influenced by seasonal drying. Due to the rareness, vulnerability, and specific biota, these saline habitats have high conservation priority according to the EU Habitats Directive (92/43/EC). Since 2017, ten soda pans have been intensively studied with the aim to determine the diatom biodiversity and to evaluate ecological conditions. Diatom samples were collected from mud and reed, and samples for molecular analyses were additionally collected in 2021. The diatom community is mostly composed of species that prefer alkaline conditions and high conductivity. Some of the most dominant genera are Nitzschia and Navicula. Among the recorded diatoms, Mayamaea permitis and one unknown Mayamaea species were recorded in two soda pans (Okanj bara and Bela bara). The unknown Mayamaea can easily be distinguished from similar species by the valve outline and shape of the central area using light and scanning electron microscopy. In a metabarcoding (partial 18S rRNA gene sequence) data set from the same sample, we could identify two amplicon sequence variants showing affinities to the genus Mayamaea, one of them matching published sequences from M. permitis, the other without exact matches in the Diat.barcode and NCBI databases. We conclude that the latter probably belongs to the new Mayamaea species observed by microscopy, which indicates that the unknown Mayamaea species is closely related to but different from Mayamaea terrestris. Based on morphological features and molecular analyses, we consider the unknown Mayamaea species as a species new to science. Bearing in mind the vulnerability of soda pans due to anthropogenic threats and climate change, knowing which species inhabit these habitats is the first step in preserving these unique ecosystems.

The Ruhr area in western Germany is characterised by high industrialisation and population density. Located in an alluvial plain, some natural rivers have historically been coerced to carry wastewater through concrete channels, as technology has only recently allowed the use of separate sewage systems. Since the 1990s, the morphological and compositional restoration of these channelized rivers has begun and impacted their ecosystems. Our knowledge of how the restoration affects the ecosystems in general and diatoms, in particular, is still limited. Using molecular and digital light microscopy on samples collected in spring 2021 and 2022 from river sites along the Boye catchment, following a time-since-restoration-gradient, we aimed to analyse the effect of restoration on diatom diversity and community composition. Diatom species richness was not significantly higher in samples from natural urban rivers that never contained sewage or were constrained by concrete channelling than in renatured localities. However, using an 18S-V9 marker to characterise the protist biofilm composition, some differences were highlighted. Diatom communities were similar, with a predominance of Achnanthidium minutissimum (Kützing) Czarnecki, independent of local differences in hydrology and water composition. The natural sites tended to have a greater predominance of Planothidium frequentissimum (Lange-Bertalot in Krammer and Lange-Bertalot) Lange-Bertalot and other taxa. As all sites, from natural to recently restored, are urban rivers and as such are affected by anthropogenic pressures, both microscopy and molecular methods showed some degree of degradation in their ecosystems. The overall water quality of the streams ranged from moderate to very good, indicating the positive impacts of the restoration works conducted in these former sewage channels. In this first study reporting on the recovery of the diatom community in the Boye catchment after restoration following a severe anthropoge

Soda pans are restricted to the Carpathian Basin and differ from other similar saline waters mainly due to the dominant presence of Na+, HCO3–, and CO32– ions. These shallow and temporary aquatic habitats are inhabited by a number of species that can thrive in extreme environments. In Serbia, saline habitats are rare, endangered, and most common in the territory of Vojvodina. One of the most investigated group of organisms in soda pans is diatoms. Due to ecophysiological plasticity, they can survive and tolerate extreme environmental conditions which gives them a competitive advantage over other algae. Quite the opposite, prokaryotes in saline habitats are not sufficiently studied and data are scarce. Thus, samples from 6 soda pans were collected in March 2021 aiming to determine diatom (microscopic and molecular analysis, 18S rRNA gene) and bacterial community (16S rRNA gene). Most of the recorded diatom taxa are neutrophilic to alkalibiontic, mostly halophilic, and eutrophic species. The species richness diversity index was the highest in Velika Slatina and Slatina, while it was lowest in Mala Rusanda. The genus Nitzschia was one of the most represented and numerous according to morphological analyses (24 taxa, 4 dominant), while molecular analyses indicate 11 different species with low abundances and mainly with unassigned sequences. The biggest discrepancy in these two approaches was observed in Mala Rusanda and Okanj bara. Metabarcoding analysis indicated Halamphora veneta as the dominant taxa, while morphological analyses have shown a predominance of Nitzschia supralitorea and Surirella brebissonii in Mala Rusanda, and N. austriaca in Okanj bara. Estimated richness and alpha diversity indices showed the highest bacterial diversity in Velika Rusanda and Okanj bara, while the lowest richness was in Mala Rusanda. Representatives of the phylum Proteobacteria were detected predominantly in Pečena Slatina, Bacteroidota in Velika Slatina, Actinobacteria in Okanj bara

Combining morphological and molecular approaches, a new diatom species is described in the genus Mayamaea from a Special Nature Reserve, Okanj bara in Serbia, an alkaline and subsaline soda pan with pronounced seasonal drying. Mayamaea pannonica sp. nov. possesses typical characteristics of the genus Mayamaea, such as uniseriate striae and hymenes that cover the areolae from the outside. It can easily be distinguished from similar species by the valve outline and shape of the central area. Although presently no culture of the species is available, we identified in an amplicon data set from the same sample a partial 18S rRNA gene sequence that is thought to represent the new species, with high probability. A comparison of our sequence to those present in the Diat.barcode and NCBI databases showed that the sequence is closely related to, but significantly different from, that of Mayamaea terrestris. Natural saline habitats in Serbia and neighbouring countries are under anthropogenic threat and climate change, so knowing which species live here is the first step in preserving these unique habitats.

In the present study, a new species, Nitzschia haloserbica Vidaković, Ector, C.E.Wetzel & Krizmanić, sp. nov., is described from alkaline saline ponds and channels from Vojvodina Province (Serbia). In 2019 the new species was found in four saline ponds: Bela Bara, Čoka Kopovo, Velika Rusanda and Slatina. The same species was recorded four years ago in saline lakes in Hungary, but the authors listed it as Nitzschia sp. 2. The sigmoid valve outline of the new Nitzschia Hassall species is similar to N. austriaca Hust. but differs in striae density and fibulae distribution. In N. haloserbica sp. nov. the transapical striae are so dense that they are not visible in light microscopy. Both species have fibulae that are quite regularly distributed along the raphe canal, but in N. austriaca the central two fibulae are more widely spaced, reflecting the presence of central raphe endings, which are absent in N. haloserbica sp. nov. At the type locality (Bela Bara) both species were found with relative abundances of 94.93 % for N. haloserbica sp. nov. and 1.21 % for N. austriaca (of the 400 valves counting per slide). The valve morphology, ultrastructure and autecology of the new species are discussed and compared with morphologically similar taxa., Une espèce nouvelle de Nitzschia Hassall (Bacillariaceae, Bacillariophyta) provenant d’étangs salins en Serbie. Dans la présente étude, une espèce nouvelle, Nitzschia haloserbica Vidaković, Ector, C.E.Wetzel & Krizmanić, sp. nov., est décrite provenant d’étangs et de canaux salins alcalins de la province de Vojvodina (Serbie). En 2019, l’espèce nouvelle a été trouvée dans quatre étangs salins : Bela Bara, Čoka Kopovo, Velika Rusanda et Slatina. La même espèce a été trouvée, il y a quatre ans, dans des lacs salins en Hongrie, mais les auteurs l’ont répertoriée comme Nitzschia sp. 2. Le contour de la valve sigmoïde de la nouvelle espèce de Nitzschia Hassall est similaire à celui de N. austriaca Hust. mais elle diffère par la densité des stries et la distribution des fibules. Chez N. haloserbica sp. nov., les stries transapicales sont si denses qu’elles ne sont pas visibles en microscopie optique. Les deux espèces ont des fibules assez régulièrement réparties le long du canal du raphé, mais chez N. austriaca les fibules centrales sont plus espacées, reflétant la présence de terminaisons centrales du raphé, qui sont absentes chez N. haloserbica sp. nov. Dans la localité type (Bela Bara), nous avons trouvé les deux espèces avec des abondances relatives de 94,93% pour N. haloserbica sp. nov. et de 1,21% pour N. austriaca (estimation à partir des 400 valves comptées par lame). La morphologie de la valve, l’ultrastructure et l’autécologie de la nouvelle espèce sont discutées et comparées à des taxons morphologiquement apparentés.

This paper presents new records and noteworthy data on the following taxa in SE Europe and adjacent regions: diatom alga Cylindrotheca gracilis, fungi Laccaria macrocystidiata, liverworts Riccia canaliculata, Riccia cavernosa, and Riccia frostii, mosses Dicranum viride, monocots Arundo donax, Cephalanthera rubra, Epipactis palustris, and Sternbergia colchiciflora and dicots Aconitum anthora and Cephalaria pastricensis are given within SE Europe and adjacent regions.

In 2021 a charophyte survey was conducted in the southern part of the Carpathian Basin, the Vojvodina province (Serbia). We investigated 14 waterbodies that were different in origin (natural, natural degraded, artificial) and were chosen along the gradient of salinity. Furthermore, waterbodies were characterized according to their ion composition: cations (potassium, sodium, calcium, magnesium) and anions (carbonate, bicarbonate, chloride, sulfate). Several other environmental parameters were investigated, such as temperature, pH, conductivity, nutrient content (ammonia, nitrites, nitrates, total phosphorus) and chlorophyll a. A gradient of salinity, calculated from electrical conductivity (Boros et al. 2013), ranged from freshwater to mesosaline (Hammer 1986). Magnesium was the dominant cation in seven waterbodies, frequently in combination with calcium, while sodium prevailed in three waterbodies. Bicarbonate made up a major portion of anions in nine, sulfate in three, and chloride in two waterbodies. Altogether, seven charophytes species were found: Chara canescens, Chara tenuispina, Chara connivens, Chara vulgaris, Chara globularis, Chara hispida and Chara papillosa. All species were found in subsaline waters, except C. papillosa, found only in freshwaters. Only three species, C. tenuispina, C. vulgaris and C. canescens, were found in hyposaline waters. We found no charophytes in mesohaline waters. Extremely rare male individuals of C. canescens were found in Pečena Slatina, a natural saline pond. This species showed a preference for hypertrophic and alkaline hyposaline aquatic habitats, with a different pattern of ionic predominance (sodium, magnesium, sulfate, bicarbonate, chloride). All species but C. connivens and C. papillosa were found in eutrophic waters. In addition, two species, C. hispida and C. canescens, showed tolerance to higher values of nitrates (> 3 mg L–1). In conclusion, we could state that inland saline habitats, despite their high productivi

During a survey of diatoms in the artificial sandpit lake “Peskara” in the protected zone of the Rusanda Nature Park, a large number of brackish taxa at epipsamic and epiphytic communities were recorded (e.g. Bacillaria paxillifera, Caloneis permagna, Ctenophora pulchella, Entomoneis costata. Haslea duerrenbergiana, Navicula salinarum, Nitzschia agnita, N. filiformis, Staurophora brantii, Seminavis strigosa, Tryblionella apiculata). One new genus Seminavis and 15 diatom species were noted for the first time for the diatom flora of Serbia. Dominant taxa changed over seasons without any regularity. In spring 2021, we have observed an increased abundance of centric species Thalassiosira pseudonana and Stephanodiscus parvus while in other seasons it was difficult to discern a pattern of dominance among benthic diatoms. Metabarcoding analysis of the same sample using 18S rRNA as a gene marker confirmed the dominance of centric diatoms. This study contributes to a better understanding of brackish diatom taxa found in inland habitats, many of which can be utilized as useful tools for the ecological status assessment.

Alkaline soda lakes are unique habitats found in specific geographic regions, usually with dry climate. The Carpathian Basin is one of those regions very important for habitat and biodiversity conservation in Europe, with natural soda lakes found in Austria, Hungary and Serbia. In comparison to other two countries from Central Europe, algal biodiversity studies of saline soda lakes in Serbia are scarce. Lake Velika Rusanda has the highest measured salinity of all saline lakes in the Carpathian Basin and there were no reports of its diatom species richness and diversity till now. We conducted 2-year investigation programme to study biodiversity and seasonal dynamics of diatoms in this lake. A total of 27 diatom taxa were found, almost all of them attached to reed and much less in benthos and plankton. Five new diatom species for Serbia were recorded, Craticula halopannonica, Navicymbula pusilla, Hantzschia weyprechtii, Nitzschia thermaloides and Navicula staffordiae. The last mentioned is new for Europe as well. Lake Velika Rusanda is inhabited mostly by alkaliphilous and halophilic diatoms. Since diatoms are used as bioindicators in soda lakes, our results will improve their further application in ecological status assessment of these fragile habitats in the Carpathian Basin.

The main aim of this study was to investigate the application of benthic diatoms and the efficiency of diatom indices in water ecological assessment of rivers in Serbia, as well as the influence of trout farms on rivers water quality. Research was conducted in one year period along the Crnica and Radovanska rivers (Eastern Serbia), in 11 sampling sites (taking into account the position of trout fish farms that are built on both rivers). Results showed that fish farms affect the physical and chemical parameters, as well as diversity of the epilithic diatom assemblage along the rivers. Canonical correspondence analysis (CCA) indicated that among tested physical and chemical parameters, conductivity “EC”, water hardness “WH”, sulfates “SO42-”, ionized ammonia fraction “NH4+”, nitrates “NO3–“, “pH”, mud, stone and depth were the most important variables affecting the distribution of diatom species. A total of 206 epilithic diatom taxa were recorded in the Radovanska and 170 in the Crnica River. Based on diatom indices, trout fish farms have no significant negative impact on the water quality of the investigated rivers (indices are not enough sensitive). Redundancy analysis (RDA) showed a high degree of correlation between the majority of indices which mostly indicated to good water quality of studied rivers. TID and TDI were the only two indices indicating moderate and poor water quality of both rivers. Water quality based on the TIDRS, the first proposed diatom index for Serbia was differ in two classes in most sites compairing with TID.

Soda pans are protected in the EuropeanUnion as Natura 2000 areas in the category of‘‘Pannonic saline steppes and marshes’’. There are atleast six soda pans of reference status in Serbia andonly a half have strict legal protection. The number ofsimilar, but disturbed (modified) habitats that could bereconstructed is still unknown. We conducted samplingin five natural and two disturbed soda pansaiming to compare a difference in physical andchemical water properties and benthic diatom communities.In addition, we tried to apply recentlydeveloped Diatom Index for Soda Pans (DISP) andTrait-based index (TBI) to test the applicability oftaxonomic and trait-based approaches in ecologicalstatus assessment of soda pans in the southern part of the Carpathian Basin. In contrast to natural soda pans,lower pH and nutrients levels were recorded indisturbed pans. A total of 86 taxa of benthic diatoms,including 11 new for diatom flora of Serbia, wereidentified. A lower species richness and Shannonindex was recorded in natural soda pans. Nitzschiaaustriaca, N. supralitorea, Navicula veneta and N.wiesneri were dominant diatoms in soda pans of thereference status. Both diatom indices were in averagelower in disturbed pans, and this difference wasstatistically significant for DISP index. We concludedthat two indices, supplemented with indicator valuesfor some local diatom species, can be a promising toolfor soda pan conservation in this part of the CarpathianBasin.

Supplementary table 1. The relative abundance (%) of recorded diatom species in seven soda pans

Aerophytic phototrophs, colonizers of different substrates exposed to air, among which are rock substrates in cave habitats, are in general not sufficiently investigated and studied. From the ecological point of view, seasonal/temporal variations and parameters that influence aerophytic phototrophic communities through seasons still remain largely unknown. Seasonal analysis of phototrophic microorganisms from biofilms developed at entrances of Samar and Jezava caves in Eastern Serbia was performed four times a year. All identified phototrophic representatives were assigned to a certain division or group. The relationship between documented groups and different measured, determined and observed ecological parameters was illustrated using principal component analysis (PCA). A high diversity of cyanobacteria and algae was observed as a result of seasonal sampling: 141 taxa in Samar and 61 taxa in Jezava Cave. Cyanobacteria were dominant in both caves (coccoid forms prevailing) and were followed by Bacillariophyta. Bacillariophyta were positively correlated with light intensity and sites where seeping water was present, and cyanobacteria with water content in biofilm, Chl a and relative air humidity. Higher diversity of phototrophs was documented in December and March, and lower in May and August in both caves with Chl a values having the same trend as the diversity of phototrophic microorganisms. This was especially the case with biofilms in which diversity was more prone to seasonal changes and where Cyanobacteria dominated. Only 24 taxa were documented during all four seasons in Samar Cave (Cyanobacteria, Bacillariophyta and Chlorophyta representatives) and three in Jezava Cave (Cyanobacteria only).

A total of 15 Navicula taxa were recorded in epilithic communities occurring in seven rivers of Serbia, all of which are new to the diatom flora of Serbia. The most interesting of them are N. splendicula and N. moskalii. When observing N. splendicula specimens under SEM, we noticed a characteristic silicate tongue in the center of raphe ends, which had not been previously reported in the available literature. The insufficiently researched distribution of N. moskalii and scarce autecological information on the taxon prompted us to provide new details about the species in this study. These findings clearly indicate the need for further comprehensive research that would provide new information on rare taxa.

Phototrophic microorganisms can be found in biofilms at entrances to caves where they have access to sufficient sunlight, water and nutrients; however, they can also be found inside caves, where they are carried by animals and people, and can proliferate in the presence of artificial light. Although the genus Humidophila includes some well-known cosmopolitan species, further exploration of its rare, insufficiently investigated representatives in different geographical areas and unusual habitats is necessary. Caves remain unknown, little-explored habitats, and many species currently known to science were recorded for the first time. This study aimed to report species belonging to the genus Humidophila that were identified in 19 caves in Serbia. A total of ten species of this genus were recorded and some of them are documented for the first time in Serbia. The most abundant species were H. contenta (found in 16 caves), H. paracontenta, and H. aerophila (found in 13 caves), whereas H. pyrenaica was identified in only one cave. The rare species, H. brekkaensoides and H. vidalii, were also documented and described, but with different dimensions from those provided in current identification keys.

Salt habitats are extreme and unique environments found from Austria through Hungary to the Vojvodina Province in Serbia. In our study, we investigated eight saline habitats (channeled salt marshes, moist salt meadows and saline ponds), from which we collectedplankton, epipelic and epiphytic diatoms. Seventeen diatom taxa new for the Serbian diatom flora were recorded. In addition, the genus Haslea, with one species (H. spicula), was recorded for the first time in Serbia. The identified taxa were sporadic or rare in the samples., Alkalna slana jezera, bare i močvare su ekstremna i jedinstvena staništa rasprostranjena u Austriji, Mađarskoj i Srbiji (Vojvodina). Istraživanje je obuhvatilo osam slanih staništa različitog tipa: kanalizovane slatine, zabarena slana staništa i slane bare. Uzorci obuhvataju različite zajednice silikatnih algi: plankton, bentos i epifite. Utvrđeno je prisustvo 17 taksona silikatnih algi po prvi put zabeleženih na teritoriji Srbije, a među njima prvi put i rod Haslea Simonsen sa jednom vrstom, H. spicula. Identifikovani taksoni su retki i sporadično nalaženi u uzorcima.