In formerly glaciated mountain regions, lacustrine sediments effectively trace landscape responses to postglacial changes. However, the sedimentary archives preserved in lakes on the southern side of the Tatra Mountains have received little attention to date, and the environmental signals they contain are poorly understood. Here, we provide a detailed characterisation of lacustrine sedimentary facies from eight lakes in the Vysoké Tatry Mountains. Multi-proxy analyses coupled with radiocarbon dating reveal lake-specific responses to environmental and climatic changes during the Late Glacial–Early Holocene, highlighting the influence of local topography and lake morphology on facies evolution. In general, the basal recovered sediments in the studied lakes are represented by minerogenic facies. The oldest minerogenic facies is commonly represented by finely and regularly laminated clay and silt, interpreted as varves and likely deposited until an estimated ~13.7–13.3 kyr BP, corresponding to the late Bølling–Allerød Interstadial. The termination of this sedimentary pattern and its transition into more homogeneous or irregularly laminated mud suggest a change in meltwater dynamics, possibly reflecting reduced stable annual meltwater contributions from persistent cryospheric sources, likely including debris-covered relict glaciers and/or rock glaciers. Gyttja represents another dominant facies overlying the minerogenic deposits. Its heterochronous onset across studied lakes, estimated to range from ~12.2 to ~8.4 kyr BP, appears to have been modulated by the termination of the Younger Dryas marginal glaciation and the volume of siliciclastic input.

Water bugs (Hemiptera: Heteroptera: Leptopodomorpha, Gerromorpha & Nepomorpha) are commonly found on the surface, margins, water column, or the bottom of water bodies globally. Most of them are generalist predators, feeding upon invertebrates or vertebrates, but the ingestion of algae and detritus has also been recorded in some species. Although most of their diversity is found in tropical areas, still significant knowledge gaps persist on the composition and distribution of this fauna in those regions. Here, we describe a new species of Tenagobia (Romanogobia) Nieser, 1977 (Nepomorpha: Micronectidae) and provide new records of 24 species of water bugs from Venezuela, Brazil, and Madagascar.

Paleoenvironmental reconstruction was conducted on a short sediment core from a subalpine lake (Low Tatra Mountains, Slovakia) spanning the past 300 years, and aimed to assess the impact of climatic oscillations and the well-documented human activities in the catchment. An analysis of subfossil chironomid remains was applied, supported by a land cover reconstruction using historical maps and orthoimagery. Two main phases of lake development were identified: the first, preceding major anthropogenic pressure and the second, which followed the opening of the first hotel in the lake vicinity in 1950, characterised by massive infrastructure and tourism expansion. The oldest assemblages date to the coldest period of the Little Ice Age (LIA) and were dominated by Derotanypus and Paratanytarsus austriacus-type, indicating very cold and oligotrophic conditions. Warming following the end of LIA caused a gradual shift in the taxonomic composition, with previously dominant taxa disappearing or decreasing in abundance. Dominance of Tanytarsus lugens-type, Zavrelimyia and Heterotrissocladius marcidus-type still reflects relatively cold temperatures and low productivity. Taxonomic composition remained mostly stable until the middle of the twentieth century, when construction work in the catchment caused deforestation, the number of year-round tourists increased, and the lake was dammed to improve conditions for boating and angling. The resulting increased nutrient loading, oxygen depletion and macrophyte development are evident from the rising abundances of taxa tolerant of high trophy. The increase of thermally plastic taxa in the twenty-first century reveals recent climate warming, which will likely only exacerbate the already considerable negative human influence, making lake recovery improbable.

Lakes at high altitudes are extremely sensitive to environmental stressors at both local and global scales, making them important sentinels of the changing world. Chironomidae, the most diverse group of benthic macroinvertebrates inhabiting mountain lakes, respond to various environmental impacts, making them important bioindicators of the lake’s ecological status. This study aimed to provide the first insight into chironomid diversity in high-altitude lakes from two mountain ranges of the Romanian Eastern Carpathians: the Maramures, and the Rodna Mountains. Floating chironomid material was collected by skimming the water surface with a hand net from 16 lakes at elevations ranging from 1378 to 1922 m a.s.l. A total of 50 species/ taxa were collected, including nine new records for Romania. Notes on newly recorded species’ distribution, ecology and taxonomy are provided. In addition, an identification key for Procladius choreus and P. sagittalis based on thoracic horn characteristics is given. With our addition, the total number of chironomid species known from Romania is now 526. The study provides a baseline for future research on chironomid diversity, ecology, and biogeography in high-altitude lakes of the Carpathian Mountains.

Understanding the structure and diversity of high-altitude lake communities and the patterns of their altitudinal changes is important for predicting their response to ongoing climate change. We analysed littoral benthic communities of 18 mountain lakes of glacial origin distributed along a 500-m altitudinal gradient and characterized by differing topographic shading levels: unshaded lakes and shaded lakes with a substantially lower (by 1151 h) mean annual duration of direct solar radiation. We hypothesized that local topographic shading modifies diversity–altitude relationships and affects the pattern of community turnover along the altitudinal gradient. We found a decreasing trend in diversity with increasing altitude and a significant deviation from that pattern in shaded lakes. Investigated lake groups supported distinct communities in lower altitudes. However, their community composition converged towards higher altitudes in communities typical for a greater abundance of cold stenotherms. The proportion of cold-stenothermal species increased with increasing altitude in shaded lakes and was notably greater than that in unshaded lakes along the studied altitudinal gradient. The lower temperatures of shaded lakes and different temperature variabilities of the two groups of lakes likely explain the observed patterns. We hypothesize that topographically shaded lakes may provide refugia for cold-stenothermal communities threatened by ongoing global warming.

Lake sediments preserve valuable environmental data. Paleoecological studies of these archives enable the reconstruction of past ecosystem changes and improve our understanding of contemporary and future transformations. While such reconstructions are common in the Western and Southern Carpathians, the Eastern Carpathians remain a knowledge gap, despite their long history of human influence that makes them suitable for studying natural and human-driven environmental changes. To address this gap, we analyzed sediment cores from three alpine lakes in the Ukrainian Eastern Carpathians. Using subfossil chironomids, cladocerans, pollen records, and sedimentation rates, we reconstructed 200 years of lake and catchment history to assess land-use changes driven by socio-economic shifts and natural fluctuations. Aquatic proxies and catchment vegetation remained relatively stable, with slight variations across socio-economic regimes, particularly during the socialist and post-socialist periods. Despite global warming’s documented effects on high-altitude lakes, we found no clear evidence of these impacts, nor of overtourism. We attribute this to the region’s long history of human activities, particularly grazing and deforestation, which may have masked broader environmental changes. Given this extensive human influence, our 200-year study period is likely insufficient to establish true reference conditions, as a predominantly natural state may not have existed for centuries.

Diamesa species (Diptera, Chironomidae) are widely distributed in freshwater ecosystems, and their life cycles are closely linked to environmental variables such as temperature, water quality, and sediment composition. Their sensitivity to environmental changes, particularly in response to pollution and habitat alterations, makes them valuable indicators of ecosystem health. The challenges associated with the morphological identification of larvae invoke the use of DNA barcoding for species determination. The mitochondrial cytochrome oxidase subunit I (COI) gene is regularly used for species identification but faces limitations, such as similar sequences in closely related species. To overcome this, we explored the use of the internal transcribed spacers (ITS) region in addition to COI for Diamesa larvae identification. Therefore, this study employs a combination of molecular markers alongside traditional morphological identification to enhance species discrimination. In total, 129 specimens were analysed, of which 101 were sampled from a glacier-fed stream in Rotmoostal, and the remaining 28 from spring-fed streams in the neighbouring valleys of Königstal and Timmelstal. This study reveals the inadequacy of utilizing single COI or ITS genes for comprehensive species differentiation within the genus Diamesa. However, the combined application of COI and ITS markers significantly enhances species identification resolution, surpassing the limitations faced by traditional taxonomists. Notably, this is evident in cases involving morphologically indistinguishable species, such as Diamesa latitarsis and Diamesa modesta. It highlights the potential of employing a multi-marker approach for more accurate and reliable Diamesa species identification. This method can be a powerful tool for identifying Diamesa species, shedding light on their remarkable adaptations to extreme environments and the impacts of environmental changes on their populations.

Chironomids of the genus Diamesa (Meigen, 1835, Diptera: Chironomidae) inhabit cold, oxygen-rich running waters. We have investigated the presence of Diamesa and other freshwater macroinvertebrates at 22 stream sampling sites in 3 European high mountain regions (the Central Pyrenees, the Ötztal Alps, and the Tatra Mountains) to establish suitable temperature conditions for Diamesa dominance. It has been generally accepted that their high abundance was linked to the presence of glaciers; however, we have shown that in the Tatra Mountains, where there are no glaciers, the conditions for the dominance of Diamesa species are created due to permanent snowfields, the geographical orientation of the valley and shading by the surrounding high peaks. The historical connection of Diamesa to glaciers was investigated from the paleolimnological records of subfossil chironomid assemblages from the Bohemian Forest, where glaciers disappeared before or during the Late Glacial period. As expected, water temperature seems to be the main driver of Diamesa distribution, and we determined that the relative abundance of Diamesa species was significantly higher at the sites with a mean July water temperature below 6.5 °C. The Diamesa-dominated stream communities seems to be endangered due to ongoing climate warming and this assumption is supported by our paleolimnological results from the Bohemian Forest lakes, where Diamesa has disappeared due to warming of lake inflows at the beginning of the Holocene. These findings strengthen the former suggestions that some Diamesa species could be used as an indicator for tracking recent environmental changes in vulnerable ecosystems of cold mountain streams.

ABSTRACT While humic lakes are common in northern Europe, in central Europe they are rare and our understanding of their ontogeny is insufficient. Here, we present the reconstruction of the development of a humic lake in the Tatra Mountains (Slovakia) over the last 8000 years using chironomids along with diatoms, pollen and non‐pollen palynomorphs. The compositional changes in aquatic proxies suggest three developmental stages. Since its formation the lake has been oligotrophic (phase 1), and its chemistry was controlled by subsurface waters rich in base cations buffering the effect of acid humic substances from forest and peat that were already present in the catchment. The beginning of the transition to phase 2 (~4400 cal a bp ) is marked by simultaneous alterations in all proxies. Climate change combined with the local geochemistry was able to alter the limnological conditions supporting unique chironomid assemblages that have no analogues in recent Carpathian lakes. At ~ 3400 cal a bp the lake shifted to a phase when acidophilic/acidotolerant taxa indicate characteristic humic lake conditions (phase 3). Some chironomid taxa appearing ~ 2000 years ago for the first time indicate a dystrophic state in which the lake has remained until now. Human activities have been detected in the area since the Aeneolithic but had no direct influence on the lake.

AbstractPonds are common freshwater habitats in the European landscape that substantially contribute to local and regional biodiversity. Chironomids often dominate invertebrate communities in ponds but are usually disregarded in ecological studies due to relatively complicated taxonomy and identification issues. We present a comprehensive overview of the chironomid diversity in 246 ponds spanning a wide range of conditions extending from the Pannonian Plain to the Carpathians. Altogether, we recorded 225 taxa including 192 species from six subfamilies (Podonominae, Tanypodinae, Diamesinae, Prodiamesinae, Orthocladiinae and Chironominae). However, the chironomid taxa inventory is far from complete and about 16% of the total diversity of pond‐dwelling chironomids remains undetected. Chironomid alpha diversity showed a significant unimodal pattern along the elevation gradient with the highest number of taxa per pond expected around 790 m a.s.l. Gamma diversity also peaked in mid‐elevations (600–800 m), and the common chironomid taxa partitioned the 2100‐m long altitudinal gradient relatively evenly. The heterogeneity of chironomid communities among ponds measured as beta diversity was significantly higher in elevations below 800 m. Temperature and the proportion of surrounding forests significantly influenced alpha diversity of chironomid communities, while urban land cover and pond size had no significant effect. Ponds with a mean annual air temperature of approximately 4.8°C and a low proportion of surrounding forests are expected to harbour the most diverse chironomid communities. Our study showed that chironomids represent a very diverse and often exceptionally rich group of pond‐dwelling macroinvertebrates. Given the high diversity and broad range of occupied niches, chironomids should not be overlooked in pond ecology studies. On the contrary, they should be considered a potential model group.

The aquatic insect fauna of the Eastern Carpathians is poorly known, especially in Ukraine. To address this knowledge gap, we conducted faunistic surveys of Chironomidae and Chaoboridae in 2018 and 2021. The study involved sampling of 11 watercourses and 10 mountain lakes situated in the Ukrainian part of the Eastern Carpathians. A total of 101 taxa were identified, including 40 chironomid species and one genus that have been recorded for the first time from Ukraine. The occurrence of one species previously considered as “doubtfully present” in Ukraine was confirmed by this study. One of the two identified phantom midge species, Chaoborus (s. str.) obscuripes (van der Wulp, 1859), is recorded for the first time from Ukraine. The most intriguing records are chironomid species Cricotopus (s. str.) beckeri Hirvenoja, 1973, Eukiefferiella bedmari Vilchez-Quero & Laville, 1987, and Pseudorthocladius (s. str.) berthelemyi Moubayed, 1990. These species have Mediterranean distribution and their occurrence in the Eastern Carpathians could be remains of once-widespread populations that currently survive in the Carpathian refugia due to adverse climatic conditions in the former distribution area. The high number of first records from a relatively small number of sites indicates a great gap in the knowledge of the Ukrainian chironomid fauna.

We analysed a 24 cm long sediment sequence (past ~200 years) from an alpine lake (Tatra Mts., Slovakia) for chironomids, cladocerans, and diatoms to reconstruct the effects of a historically documented fish introduction. Our results indicate that fish introduction predated the age of the sequence, and thus, we did not cover the lake’s fishless period. The individual proxies coincide in showing two main lake development stages. The first stage lasted until ~1950 CE and was interpreted as the stage when brown trout and alpine bullhead co-occurred. The extremely low concentration of cladocerans, the dominance of small-bodied chydorids, and the low share of daphnids, together with the low proportion/absence of large-bodied tanypod chironomids, suggest a strong effect of both species. The beginning of the next stage is probably related to the ban on fish manipulations and grazing in the catchment. A significant increase in the total abundance of cladocerans and of daphnids may indicate the extirpation of trout. The steep increase in thermally plastic chironomid taxa since the end of the 20th century indicates climate warming. Generally, while cladocerans primarily indicate fish manipulations, chironomids and diatoms mainly reflect other local and global environmental stressors.