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Our study addresses how large-scale hydrological alterations shape zooplankton biodiversity in floodplain ecosystems, which are highly sensitive to changes in river connectivity. Following the operation of the Gabčíkovo hydroelectric power plant in the Danube inland delta, we examined the long-term responses of crustacean zooplankton communities, as these organisms are key indicators of hydromorphological disturbance. Based on previous evidence that river regulation often reduces habitat heterogeneity, we hypothesized that hydrological alterations in the Danube riverscape would promote increasing taxonomic and functional homogenization within sites, while simultaneously enhancing differentiation between sites over the past three decades. A total of 121 planktonic crustacean species were recorded across six monitored sites between 1991 and 2020, comprising 49 copepods and 72 cladocerans. Communities showed rising species richness, especially during the first decade of the hydropower plant’s operation. While overall richness increased, dam-induced hydromorphological changes triggered habitat-specific community shifts. In the main channel and adjacent parapotamal arm, taxonomic and functional homogenization occurred, dominated by resilient tychoplanktonic species with a gathering or secondary filter-feeding strategy. In contrast, isolated side arms experienced gradual eutrophication, favoring euplanktonic and primary filter-feeding taxa. The observed taxonomic and functional convergence within both habitat groups reflects the loss of connectivity and the cessation of artificial flooding.

The main objective of this study is to present a new record of Tasserkidrilus cf. americanus found in a channel near the Tešmak swamp in Slovakia (Central Europe) and to compare its morphological features and habitat requirements with those of populations occurring in North America and Europe. The new specimens are similar to those found in The Netherlands and Belgium, but dissimilar to previously reported North American material of T. americanus , reopening the question of whether the European form is a separate species. The European form has the penis sheaths approximately twice as long as and wider than the North American form and may inhabit slow-flowing or standing waters of a eutrophic character, which is in conflict with the current knowledge on the morphology and ecology of North American populations. Further investigation is necessary to solve the questions about the origin and taxonomic relationship of the European population to other populations.

We present the first record of Anatopynia plumipes (Fries, 1823) from Slovakia. Larva of this species was found in a semi-permanent oxbow lake, a remnant of a plesiopotamal-type side arm of the Danube River.

The main objective of this study is to present a new record of Tasserkidriluscf.americanus found in a channel near the Tešmak swamp in Slovakia (Central Europe) and to compare its morphological features and habitat requirements with those of populations occurring in North America and Europe. The new specimens are similar to those found in The Netherlands and Belgium, but dissimilar to previously reported North American material of T.americanus, reopening the question of whether the European form is a separate species. The European form has the penis sheaths approximately twice as long as and wider than the North American form and may inhabit slow-flowing or standing waters of a eutrophic character, which is in conflict with the current knowledge on the morphology and ecology of North American populations. Further investigation is necessary to solve the questions about the origin and taxonomic relationship of the European population to other populations.The main objective of this study is to present a new record of Tasserkidriluscf.americanus found in a channel near the Tešmak swamp in Slovakia (Central Europe) and to compare its morphological features and habitat requirements with those of populations occurring in North America and Europe. The new specimens are similar to those found in The Netherlands and Belgium, but dissimilar to previously reported North American material of T.americanus, reopening the question of whether the European form is a separate species. The European form has the penis sheaths approximately twice as long as and wider than the North American form and may inhabit slow-flowing or standing waters of a eutrophic character, which is in conflict with the current knowledge on the morphology and ecology of North American populations. Further investigation is necessary to solve the questions about the origin and taxonomic relationship of the European population to other populations.

The effect of longitudinal zonation patterns and macroinvertebrate responses to changes in habitat characteristics have been given a lot of attention. But studies of changes in macroinvertebrate assemblages along small upland undisturbed watercourses are still lacking. The aim of the study is to analyse variability in macroinvertebrate communities between two different habitats/morphological sequences – shallow (riffle/run/step/) and deeper (pool) channel-bed morphological units on the background of the environmental parameters (local relief, slope, channel confinement ratio, channel-valley walls connectivity, floodplain continuity and channel abut, channel sinuosity and predominant land cover of riparian zone) of seven valley segments (functional process zones) in two seasons of the year (spring and autumn). The longitudinal-downstream gradient research was conducted on the semi-natural upland headwater brook in the Little Carpathians (9,330 m long, average gradient 2.8%) at 15 morphological sequences (30 sampling points). Each sampling point in spring as well as in autumn was characterised by mean flow velocity, discharge, water depth, channel width, channel bottom particle size, and flow types. Selected physico-chemical variables: pH, dissolved oxygen content (DO), oxygen saturation (DO %), temperature (t) conductivity and total dissolved solids (TDS) were measured directly in the field using the multisonde measuring device. Organisms were identified into the family level. The results showed that differences in zonation of benthic invertebrates between seasons are more apparent than seasonal variability between pools and riffles. Spring samples followed the increasing gradient of total dissolved solids downstream with characteristic families for upper and lower stretch. The disruption of macroinvertebrates zonation was more evident in autumn samples with greatest effects in pools. Based on RDA, the distribution of families was driven by three significant variables in riffles and four in pools. Alike environmental factors of pool sequences in the middle and upper reaches were responsible for similarity in macroinvertebrate structure. In conclusion, the distribution pattern of benthic invertebrates of the natural part of the small headwater stream in terms of abundance of macroinvertebrate families followed the longitudinal zonation in spring, but in autumn were the local habitat conditions more important.

The distribution and diversity of insects are crucial conservation issues. The order Trichoptera is comprised of numerous endangered species, but the rarity of some makes it challenging to determine their conservation priority. In recent decades, data based on caddisfly larvae have become more frequent in limnological research in Slovakia. Our research, focusing mainly on adult caddisflies, has led to more reliable and accurate identification of many species that cannot be identified with certainty in the larval stage.We combined several entomological methods, including sweeping, Malaise traps, and UV light attraction, to increase the likelihood of catching rare species. The text lists and discusses the discoveries of caddisfly species that are particularly important for faunistics or biodiversity in Slovakia, as well as in the Central European context. Enoicyla reichenbachii (Kolenati, 1848), Limnephilus incisus Curtis, 1834, Ptilocolepus granulatus (Pictet, 1834) and Oecetis testacea (Curtis, 1834) were recorded for the first time in Slovakia. The rare species Hagenella clathrata (Kolenati, 1848) and Adicella balcanica Botosaneanu and Novák, 1965, previously found in Slovakia, were also recorded. Additionally, a new locality of Adicella syriaca Ulmer, 1907 indicates a further northward shift of this Mediterranean species. We further discussed the faunistically important records of Beraeamyia hrabei Mayer, 1937, Allotrichia pallicornis (Eaton, 1873), Ceraclea riparia (Albarda, 1874), Grammotaulius nitidus (Müller, 1764) and Limnephilus fuscicornis Rambur, 1842 from Slovakia. The conservation status of each species is proposed and discussed on the basis of our faunistic records, in accordance with the forthcoming update of the Slovak Red Book.

We present the first record of the caddisfly species Adicella syriaca Ulmer, 1907 from Slovakia, which is also the northernmost record of the species so far. Based on the literature data, we can conclude that the species spread 250 km northwards, compared to the previous records, inhabiting north Pannonian rivers, including the Danube floodplain (the Upper Danube). We suppose that a possible explanation for the species range shift is the climate change, since this can lead to changes in species distribution. For aquatic invertebrates, more studies predicted occurrence shifts, but specific examples are not common.

From the family Athericidae, only three species (Atherix ibis, Ibisia marginata, Atrichops crassipes) are widespread in Central and Western Europe. Although predatory larvae of these species are an important component of many benthic communities, little is known about their distribution and ecological preferences. Aiming to fill these gaps, the distribution and ecological preferences of these species were studied in three ecoregions of central Europe (Central highlands, The Carpathians, Hungarian lowlands). We found that A. ibis was present in the most streams in all of the studied ecoregions. I marginata clearly preferred the streams of the Carpathians ecoregion, whilst A. crassipes was more frequent in the Central highlands and Hungarian lowlands and it occasionally inhabited streams in the Carpathian ecoregion. The occurrence of the species was explained by the physico-chemical parameters of water (explained variability = 18.6%), site characteristics (3.8%), as well as catchment characteristics (3.3%). Four environmental variables (temperature, conductivity, percentage of agricultural land, catchment area) from three defined groups represented significant gradients, which explained species distribution in running waters of Central Europe. For the Central European streams, a correction of the saprobic index of the species was made, and the altitudinal, temperature, current and pH preferences for each species were also calculated. These values can be used for completion of the “freshwaterecology.info” database, which includes several biological and ecological traits of most European benthic species.

The number of studies assessing the downstream effects of multiple reservoirs on benthic communities over a large spatial scale has been disproportionally less compared with studies of the effects of a single reservoir, while even fewer studies have examined the responses of non-insect macroinvertebrates on the impact of river discontinuity. The main objective here is to present the effect of seven large reservoirs in a 364-km long stretch of the Váh River, which is the longest river in Slovakia. We assessed the longitudinal changes in environmental variables to identify their possible cumulative effect and recovery distance. Moreover, the spatial variability in the taxonomical and functional structure of the non-insect benthic invertebrate community was evaluated. We do not detect the true cumulative effect of any variable, because of the apparent recovery before reaching the next reservoir. Although the environmental variables closely match with the division of the river based on the river network development, the non-insect community indicates a more extensive disruption of the river environment. On the basis of species data clustering, three groups of sites (stretches) are found to reflect their longitudinal position in the river rather than their position relative to the reservoir (upstream, downstream and in-between sites). The difference between these groups also mirrors the functional structure of the benthic community. Water temperature, conductivity and chemical oxygen demand create a significant gradient causing shifts in taxonomical, as well as functional community composition. The canonical correspondence analysis shows that all reservoirs cause a shift in the structure of benthic communities as they are similar to communities at more distant sites downstream. Moreover, the reservoirs situated in the upper and middle stretch of the river were detected to have the most impact on the ecological attributes of the community. The multi-level pattern analysis reveals 31 non-insect taxa and four functional traits associated with one or two river stretches in a longitudinal profile of the Váh River. Of the indicator species, Stylaria lacustris, Nais christinae, Ophidonais serpentina and Limnodrilus claparedeianus are found to be associated with the severe downstream modification (potamalization) of the river environment induced by reservoirs.

In spite of many investigations about the impact of reservoirs on river continuum, the downstream effects of a pumped-storage hydropower plants (PSHP) still have been less known. The aim of the study was to evaluate the downstream effect of the PSHP Čierny Váh in regard to the Serial Discontinuity Concept assumptions or studies assessing more frequent types of hydropower reservoirs. We predicted that the increase of water temperature and the alteration of food sources will hierarchically be the most relevant factors determining macroinvertebrate community composition. We focused on mayflies, caddisflies and non-insect benthic invertebrates due to their appropriate responses to discontinuity. We also determined the influence of the hydropower plant on life cycles and productions of the most abundant species of mayflies and caddisflies. We recorded the unique effect of the PSHP Čierny Váh on its downstream environmental variables. According to the nested ANOVA results, temperature regime, transported organic matter, benthic fine particulate organic matter and periphyton biomass were the environmental variables significantly modified by the river discontinuum. Significant differences were also found in the case of macroinvertebrate species richness, density and diversity. Nevertheless, based on the forward selection test for predictor effects, none of the environmental variables affected the macroinvertebrate assemblages significantly. However, the redundancy analysis revealed a separated group of macroinvertebrates preferring conditions characteristic for the site immediately below the reservoir. Regarding the impact of the reservoir on life histories, we revealed the shift in hatching, emergence and duration of life cycles of the abundant mayflies (except Baetis rhodani ) and caddisfly Ecclisopteryx dalecarlica . Total annual production of mayflies as well as caddisflies was several times higher at the site immediately below the reservoir. Although PSHP Čierny Váh matches the SDC assumptions (except thermal stratification), the downstream impact resembles much more the effects of small reservoirs or epilimnetic-release reservoirs.