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The present study is the first structured attempt to analyze the species composition and distribution of freshwater invertebrates in the lakes, streams, and rivers of the Shantar Islands and to compare the diversity of the hydrobiont fauna of the archipelago and the continental part of Khabarovsk Krai on the basis of the original and literature data. The research revealed 57 zooplanktonic, 47 meiobenthic, and 142 macrobenthic taxa in the waters of the island and the adjacent continental areas. Different patterns of variability in the species richness, abundance, and the community structure are observed for different groups of hydrobionts along the salinity gradient in the unique, brackish Lake Bolshoe. Zooplankton show no directional variability, reaching a maximum in a frontal zone where riverine and brackish water mix. Meiobenthos show the highest diversity in the most saline zone of the lake, where marine species are abundant. The characteristics of the macrozoobenthos gradually increase with the salinity of the lake, with a dramatic change in the dominance structure at the critical salinity threshold, where amphibiotic insects, dominant in the desalinated water zone, are replaced by amphipods. Latitudinal variability in species richness and biogeographic structure of the fauna are closely related for different groups of freshwater invertebrates. A smooth decline in species richness from southern to northern areas was observed when comparing the faunas of the Shantar water bodies with those located to the south. This trend is shown for amphibiotic insects and microcrustaceans and is most pronounced for mollusks. The fauna of the Shantar Islands is predominantly represented by species with a wide Palaearctic, Holarctic, and cosmopolitan range, with a small proportion of species restricted to the Arctic zone of Eurasia or specific to Eastern Siberia and the Far East. Only three brackish water species have a Beringian type of distribution. The assemblage structures of the zooplankton and meiobenthos communities of continental coastal and island lakes do not greatly differ. On the contrary, brackish communities are clearly distinct from the others. The taxonomic composition of macroinvertebrates differed significantly between the islands and the mainland. [ABSTRACT FROM AUTHOR]

Global climate change might result in permafrost thaw and the formation of thermokarst landscapes that release long-term carbon stocks as greenhouse into the atmosphere, thereby initiating a positive climate feedback. These processes are mediated by biological activity, including by microbes, vascular plants and animals, whereas the role of invertebrates in thermokarst ecosystems remains poorly understood. We investigated the diversity and assemblage structures of zooplankton (mainly Copepoda, Cladocera), microbenthos (testate amoebae) and meio- (Copepoda and Cladocera) and macrozoobenthos (mollusks, crustaceans, insects and annelids) from a range of water bodies representing different stages of thermokarst lake formation in the southern part of the Lena River Delta (Central Siberia). Altogether, 206 species of testate amoeba, mollusk, crustacean, insect and annelid taxa were identified. A total of 60 species of macrozoobenthos (mainly insects) and 62 species of testate amoebae were detected in the water bodies of the Lena River Delta for the first time. The species richness of zooplankton and meio- and macrozoobenthos was greater in the large thermokarst lakes than in the polygonal ponds due to the freezing of the latter in the winter. In contrast, the species richness of protists was higher in the polygonal ponds, which was related to the habitat preferences of testate amoebae. Fish grazing strongly affected the macrobenthos assemblages but not the smaller-sized organisms. Water acidity and temperature were the main environmental drivers of the assemblage structure of testate amoeba and microcrustacean. The species structure of the macroinvertebrate assemblages was significantly explained by water acidity, permafrost depth and size of the water area. It means that small size organisms with their short generation times are sensitive to more dynamic factors such as temperature and may serve as indicators of ecosystem changes due to global climate warming. In contrast, large size organisms are affected by driven factors that appear during thermokarst lakes formation and permafrost degradation. [ABSTRACT FROM AUTHOR]

Several taxa of high taxonomic rank are represented exclusively or almost exclusively by meiobenthos organisms of marine areas and freshwater reservoirs. The taxonomic articles deal with two groups of meiofauna: nematodes, whose diversity sometimes seems endless, and tardigrades. Among meiofauna groups, nematodes dominate in most biotopes. The meiofauna is currently considered to be a group of microscopic metazoans ranging in size from 30 to 1000-2000 m, forming a distinct size class [[1]]. [Extracted from the article]

The Putorana Plateau (Krasnoyarsk Territory, Russia) is one of the largest mountainous regions of subarctic Eurasia. Studies of aquatic ecosystems of this are far from complete. In particular, microcrustaceans (Cladocera и Copepoda) of the Putorana Plateau are poorly investigated, although they are one of the main components of meiobenthic and zooplanktonic communities and a target for monitoring of the anthropogenic influence and climate change. An open question is a biogeographical status of the crustacean fauna of the plateau. Additionally, it is unknown which environmental factors significantly affect benthic and planktonic crustacean assemblages? Based on the samples collected in tundra and forest tundra ponds in the western and central parts of the plateau, analysis of the composition of crustacean fauna and factors regulating the assemblage structure was performed. In total, 36 Cladocera and 24 Copepoda species were found. Of these, 23 taxa are new for the region, and four are new to science. Species richness of Copepoda is higher in the central part and on the western slopes of the plateau than in foothills, while number of the Cladocera species in contrast decreases in mountainous areas. Variations in meiobenthic assemblages are due to the research area, type of water supply and less affected by altitude above sea level. For planktonic assemblages the size of the water body and, to a lesser degree, by macrophytes species composition was significant. Almost 12.8% of microcrustacean species of the Putorana Plateau can be attributed to glacial relics. Crustacean fauna of the Putorana Plateau has a high species richness and distinguishes significantly from the fauna of both western and eastern regions of the Arctic. The specifics of faunal composition of the region are connected to the climatic features of Middle Siberia and the retaining of the Pleistocene fauna in some glacial refugia. [ABSTRACT FROM AUTHOR]

Despite the accessibility of the Faroe Islands, faunistic research on their numerous lakes and ponds is quite rare. The biota of Faroese freshwaters is still underexplored, and its specific traits raise many questions. In the present survey, 32 microcrustacean species were observed, 8 of which were new to the Faroese fauna. The obtained species list shows that Cladocera species prevail over Copepoda here, which is not typical of northern territories. This fact is due to (1) the extraordinarily warm climate of the Faroe Islands compared to other areas at similar latitudes because of the heating effect of the surrounding North Atlantic Current and (2) the lack of calanoid species, which have never been found in the freshwaters of the Faroe Islands. The diachronic analysis of the species diversity and composition over the centuries of research on the archipelago showed no evidence of the impact of global climate change on the fauna. [ABSTRACT FROM AUTHOR]

Information on the freshwater fauna of the remote Arctic territories is very patchy, and most of the isolated islands of the Arctic Ocean remain absolutely unexplored. The pioneer data on the species composition of microcrustaceans of Shokalsky Island (northwest Siberia, Russia) is reported here. The initial three-year research revealed a total of 31 new for the area species of Cladocera and Copepoda, including new records for the whole of northwestern Siberia. Comparing the interannual differences in faunal composition, we suggested the hypothesis of the existence of a cryptic pool of species’ resting stages, which can invade the community in the event of favourable environmental conditions in the Arctic freshwaters. We also compiled all the available data from different parts of northern Siberia and compared them with the fauna of Shokalsky Island to analyse the connection between the diversity and distributional patterns of copepods and cladoceran species and the climate conditions of different territories. [ABSTRACT FROM AUTHOR]

Microcrustaceans (MCs) are an important component of freshwater ecosystems, and their local diversity is known to be driven by many factors. What are the relative contributions of these factors at the larger geographic scale? We analyzed the faunal richness and composition of freshwater Cladocera and Copepoda from 27 mainland and insular circumpolar regions (46°-85°N) to determine the main patterns of their species richness and distribution. The average warmest month air temperature was the primary factor affecting MC richness. Regional richness decreased sharply when the temperature dropped below 12-13 °C, and this effect was more pronounced for Cladocera. As a result, the Cladocera/Copepoda species ratio increased significantly with temperature. The total MC richness and cladoceran richness increased with the ice-free area of a region, while the copepod richness decreased on islands with increasing distance from the mainland. Copepod richness was lower in regions that were glaciated during the Quaternary period. Faunal composition significantly differed between cold and warm regions, as well as between the Palearctic and Nearctic, whereas it was affected by neither the glaciation history nor insularity. The contemporary climate had a stronger effect on the cladoceran distribution, whereas the copepods' ranges were often restricted to a single continent. The former parts of the intercontinental land bridges are primarily inhabited by Holarctic or cosmopolitan species, with almost equal Nearctic and Palearctic components, which indicates repeated colonization events of these regions from various sources. These findings suggest a key role of contemporary climate (especially for cladocerans) and dispersal limitations (primarily for copepods) in structuring MC faunas at high latitudes, and they may help assess possible changes due to global warming. [ABSTRACT FROM AUTHOR]

The crustaceans of the fresh waters of Bering Island and their link to the fauna of adjacent regions were studied. Based on original data and existing literature, the species composition of Cladocera and Copepoda was described. The compiled list includes 22 species of Cladocera and 30 species of Copepoda. In the original data, 35 species native to the Commander Islands were reported for the first time. Six species were newly reported in the Far East, and two were newly reported in Russia. The ecological peculiarities of several species and some biogeographical features of the freshwater zooplankton of the island are discussed. The main part of the fauna of the island form Holarctic widespread species (64.3%), another slightly smaller group of the fauna is comprised of Palaearctic species (20.1%), and the remainder comprise Nearctic (6.7%) and Beringian species (8.9%). Particular patterns in the distribution of freshwater zooplankton and the factors underlying the occurrence of these species on the island are considered. [ABSTRACT FROM AUTHOR]

Information on the freshwater microcrustaceans of the remote arctic islands is very limited. The species composition of freshwater zooplankton and meiobenthos of Wrangel Island (Russia) is reported here for the first time. We identified five species of Cladocera, and 20 species of Copepoda. Twenty-three taxa are new records for the island. Additionally, we discuss the taxonomy of some species with doubtful taxonomical status. We also analysed data from other arctic and subarctic territories to compare with that of Wrangel Island and evaluate the latitudinal trends of species richness and distribution of Cladocera and Copepoda and their relation to environmental factors. The effects of different environmental factors were statistically examined to establish which are important in controlling distributional patterns and diversity of species. On Wrangel Island the fauna of microcrustaceans is primary controlled by three factors: low temperatures, the remoteness from the nearest mainland and geological history of the island – its relation to ancient Beringia and lack of Pleistocene glaciation. [ABSTRACT FROM AUTHOR]

Of the many types of freshwater bodies across Iceland (e.g., lakes, springs, rivers, and ponds), greater effort has been invested in researching the freshwater Crustacea (Cladocera, Copepoda) of more permanent, larger, and deeper water bodies than on smaller or more ephemeral sites. To address this, we described the fauna of 12 shallow freshwater bodies distributed from the coast to the central highlands of Iceland. We identified 16 species in 11 genera belonging to six families of Cladocera, and 12 species in eight genera belonging to four families of Copepoda. Five of the species we identified ( Alona werestschagini, Cyclops vicinus, Daphnia cristata, Diacyclops abyssicola, and Heterocope borealis) represent new distribution records for Iceland, increasing the number of species now known from this region to 34 Cladocera and 38 Copepoda taxa. Additionally, we discuss the taxonomy of some species with doubtful taxonomical status. Six crustacean taxocenes are described, each characterized by the dominance of different taxa, with bottom sediment characteristics best explaining species assemblage structure. We evaluated the relationships between Icelandic Cladocera and Copepoda faunas and those of the adjacent Svalbard, Faroe, and Shetland Islands, Greenland, and the mainland Norway. The taxonomic composition of the Icelandic fauna is dominated by widely distributed Holarctic, and secondarily Palaearctic and Nearctic species, and is more similar to the faunas of the major North Atlantic islands (64.2-71.8 % similarity) than it is to that of continental Norway. [ABSTRACT FROM AUTHOR]

We analysed the pattern of spatiotemporal distribution of harpacticoid assemblages of 106 plankton samples collected in May–August of 2013–2015 in Prostor Bay, South Kuril Islands (Sea of Okhotsk). Taxonomically and ecologically diverse harpacticoid assemblages were found in the water column. Among the 49 species identified, only one was truly planktonic, while the others were typically benthic, mainly phytal-dwelling forms. The most abundant and rich (42 species) assemblage occupied the shallow (10 m depth) area in the western, stone-bottomed part of the bay with a well-developed phytal zone. In deeper areas, the abundance and diversity of harpacticoids in plankton samples decreased steeply. There was a clear seasonal pattern of abundance, diversity and composition, with a peak in spring and then a decrease. On average, the total abundance was low (64 ind/m2). Neither interannual variations contributed significantly to the harpacticoid distribution. The analysis of the gut contents suggests that the harpacticoids feed on planktonic diatoms in the water column, but their residence time in the water column was short, and their feeding rate was low. In turn, the harpacticoids constituted a permanent but relatively minor fraction of the salmon fry diet. Thus, in quantitative terms, harpacticoids contribute relatively little to benthopelagic coupling in the Prostor Bay ecosystem. [ABSTRACT FROM AUTHOR]

Climate warming and subsequent landscape transformations result in rapid ecological change in Arctic freshwaters. Here we provide a synthesis of the diversity of benthic diatoms, plankton, macrophytes, macroinvertebrates, and fish in Arctic freshwaters.We developed a multi‐organism measure of α diversity to characterise circumpolar spatial patterns and their environmental correlates, and we assessed ecoregion‐level β diversity for all organism groups across the Arctic.Alpha diversity was lowest at high latitudes and elevations and where dispersal barriers exist. Diversity was positively related to temperature, and both temperature and connectivity limited diversity on high latitude islands. Beta diversity was highly variable among ecoregions for most organism groups, ranging from 0 (complete similarity) to 1 (complete dissimilarity). The high degree of dissimilarity within many ecoregions illustrates the uniqueness of many Arctic freshwater communities.Northward range expansion of freshwater taxa into Arctic regions may lead to increased competition for cold‐stenothermic and cold‐adapted species, and ultimately lead to the extinction of unique Arctic species. Societal responses to predicted impacts include: (1) actions to improve detection of changes (e.g., harmonised monitoring, remote sensing) and engagement with Arctic residents and Indigenous Peoples; and (2) actions to reduce the impact of unwanted changes (e.g., reductions of CO2 emissions, action against the spread of invasive species).Current Arctic freshwater monitoring shows large gaps in spatial coverage, while time series data are scarce. Arctic countries should develop an intensified, long‐term monitoring programme with routine reporting. Such an approach will allow detection of long‐term changes in water quality, biodiversity, and ecosystem services of Arctic freshwaters. [ABSTRACT FROM AUTHOR]

Warming in the Arctic is predicted to change freshwater biodiversity through loss of unique taxa and northward range expansion of lower latitude taxa. Detecting such changes requires establishing circumpolar baselines for diversity, and understanding the primary drivers of diversity.We examined benthic macroinvertebrate diversity using a circumpolar dataset of >1,500 Arctic lake and river sites. Rarefied α diversity within catchments was assessed along latitude and temperature gradients. Community composition was assessed through region‐scale analysis of β diversity and its components (nestedness and turnover), and analysis of biotic–abiotic relationships.Rarefied α diversity of lakes and rivers declined with increasing latitude, although more strongly across mainland regions than islands. Diversity was strongly related to air temperature, with the lowest diversity in the coldest catchments. Regional dissimilarity was highest when mainland regions were compared with islands, suggesting that connectivity limitations led to the strongest dissimilarity. High contributions of nestedness indicated that island regions contained a subset of the taxa found in mainland regions.High Arctic rivers and lakes were predominately occupied by Chironomidae and Oligochaeta, whereas Ephemeroptera, Plecoptera, and Trichoptera taxa were more abundant at lower latitudes. Community composition was strongly associated with temperature, although geology and precipitation were also important correlates.The strong association with temperature supports the prediction that warming will increase Arctic macroinvertebrate diversity, although low diversity on islands suggests that this increase will be limited by biogeographical constraints. Long‐term harmonised monitoring across the circumpolar region is necessary to detect such changes to diversity and inform science‐based management. [ABSTRACT FROM AUTHOR]

Arctic freshwaters are facing multiple environmental pressures, including rapid climate change and increasing land___use activities. Freshwater plankton assemblages are expected to reflect the effects of these stressors through shifts in species distributions and changes to biodiversity. These changes may occur rapidly due to the short generation times and high dispersal capabilities of both phyto___ and zooplankton.Spatial patterns and contemporary trends in plankton diversity throughout the circumpolar region were assessed using data from more than 300 lakes in the U.S.A. (Alaska), Canada, Greenland, Iceland, the Faroe Islands, Norway, Sweden, Finland, and Russia. The main objectives of this study were: (1) to assess spatial patterns of plankton diversity focusing on pelagic communities; (2) to assess dominant component of __ diversity (turnover or nestedness); (3) to identify which environmental factors best explain diversity; and (4) to provide recommendations for future monitoring and assessment of freshwater plankton communities across the Arctic region.Phytoplankton and crustacean zooplankton diversity varied substantially across the Arctic and was positively related to summer air temperature. However, for zooplankton, the positive correlation between summer temperature and species numbers decreased with increasing latitude. Taxonomic richness was lower in the high Arctic compared to the sub___ and low Arctic for zooplankton but this pattern was less clear for phytoplankton. Fennoscandia and inland regions of Russia represented hotspots for, respectively, phytoplankton and zooplankton diversity, whereas isolated regions had lower taxonomic richness. Ecoregions with high __ diversity generally also had high __ diversity, and turnover was the most important component of __ diversity in all ecoregions.For both phytoplankton and zooplankton, climatic variables were the most important environmental factors influencing diversity patterns, consistent with previous studies that examined shorter temperature gradients. However, barriers to dispersal may have also played a role in limiting diversity on islands. A better understanding of how diversity patterns are determined by colonisation history, environmental variables, and biotic interactions requires more monitoring data with locations dispersed evenly across the circumpolar Arctic. Furthermore, the importance of turnover in regional diversity patterns indicates that more extensive sampling is required to fully characterise the species pool of Arctic lakes. [ABSTRACT FROM AUTHOR]

Climate change is predicted to have dramatic effects on Arctic freshwater ecosystems through changes to the abiotic template that are expected to influence biodiversity. Changes are already ongoing in Arctic systems, but there is a lack of coordinated monitoring of Arctic freshwaters that hinders our ability to assess changes in biodiversity.To address the need for coordinated monitoring on a circumpolar scale, the Arctic Council working group, Conservation of Arctic Flora and Fauna, established the Circumpolar Biodiversity Monitoring Program, which is an adaptive monitoring program for the Arctic centred around four ecosystem themes (i.e., Freshwater, Terrestrial, Coastal, Marine). The freshwater theme developed a monitoring plan for Arctic freshwater biodiversity and recently completed the first assessment of status and trends in Arctic freshwater biodiversity.Circumpolar Biodiversity Monitoring Program–Freshwater has compiled and analysed a database of Arctic freshwater monitoring data to form the first report of the state of circumpolar Arctic freshwater biodiversity. This special issue presents the scientific analyses that underlie the Circumpolar Biodiversity Monitoring Program–Freshwater report and provides analyses of spatial and temporal diversity patterns and the multiple‐stressor scenarios that act on the biological assemblages and biogeochemistry of Arctic lakes and rivers.This special issue includes regional patterns for selected groups of organisms in Arctic rivers and lakes of northern Europe, Russia, and North America. Circumpolar assessments for benthic diatoms, macrophytes, plankton, benthic macroinvertebrates, and fish demonstrate how climate change and associated environmental drivers affect freshwater biodiversity. Also included are papers on spatial and temporal trends in water chemistry across the circumpolar region, and a systematic review of documented Indigenous Knowledge that demonstrates its potential to support assessment and conservation of Arctic freshwaters.This special issue includes the first circumpolar assessment of trends in Arctic freshwater biodiversity and provides important baseline information for future assessments and studies. It represents the largest compilation and assessment of Arctic freshwater biodiversity data to date and strives to provide a holistic view of ongoing change in these ecosystems to support future monitoring efforts. By identifying gaps in monitoring data across the circumpolar region, as well as identifying best practices for monitoring and assessment, this special issue presents an important resource for researchers, policy makers, and Indigenous and local communities that can support future assessments of ecosystem change. [ABSTRACT FROM AUTHOR]

The fauna of the stream water in the Lower Shakuranskaya Cave in central Abkhazia, western Caucasus, was studied. This cave has a large inlet and an extended entrance ecotone area of approximately 60 m, which makes it a convenient area for studying macrozoobenthic assemblages across a gradient of environmental factors. The cave has 13 species of stygobionts, 10 species of stygophiles and 18 species of stygoxenes. The number of species and the abundance and biomass of stygobionts per station were the highest near the boundary of the photic zone, at a distance of 50-60 m from the entrance to the cave, and gradually decreased toward both the remote parts of the cavity and the cave exit. The most abundant stygobionts were gastropod mollusks of the Hydrobiidae family, and Xiphocaridinella shrimp comprised the main part of the biomass. It has been shown that the main environmental factors determining the distribution of macrozoobenthos are luminosity and distance from the entrance to a cave. According to the differences in their reactions to these environmental factors, several groups of species were identified. In addition, three main assemblages of macrozoobenthic species were described: (1) an assemblage of epigean species near the cave entrance area; (2) stygobionts in remote parts of the cave outside the photic zone; and (3) a mixed assemblage in the cave ecotone, where a faint light penetrates. The specific details related to the faunal structure in the ecotone of the cave are discussed, as well as active and passive methods by which stygoxenes invade underground cavities. [ABSTRACT FROM AUTHOR]

The high Arctic, including the Svalbard archipelago in the North Atlantic, has been exposed to direct and indirect drivers of climatic change such as rising temperatures and associated changes in hydrology and nutrient fluxes. In addition, the number of migrating birds, particularly geese, increased remarkably in the Svalbard archipelago during the second half of the last century. The higher number of breeding birds potentially affects water quality and the biota in ponds and lakes.We aimed to investigate the potential influence of increasing goose abundance on trophic state, taxon richness, and species composition of freshwater communities in the high Arctic. We hypothesised that higher goose abundance affects the trophic state of shallow lakes and ponds and their taxon richness and species composition. We conducted a survey of selected ponds at Svalbard along a goose abundance gradient. We used the number of area‐specific goose droppings (range of 0–94 droppings m2) as a proxy of goose presence and measured proxies for productivity as well as taxon richness and composition of phytoplankton and invertebrate communities.Presence and abundance of geese were associated with higher productivity of ponds. Invertebrate and phytoplankton taxon richness correlated (positively) with goose abundance. Both phytoplankton and invertebrate taxon richness increased with increasing nitrogen (N) concentrations. Goose abundance significantly affected phytoplankton species composition, while concentrations of total‐N and total phosphorus (P) did not. Species composition of aquatic invertebrates was most strongly affected by goose abundance, but the effect of total‐N concentration was also significant.Increased goose abundance was associated with bird driven nutrient enrichment, increased phytoplankton and invertebrate taxon richness and changes of these biological communities. Thus, in addition to climate change, the higher abundances of large migratory water fowl in many polar areas may pose a major additional stress to arctic lakes and ponds. In fact, climate change and bird impact may interact, accelerating ongoing environmental change of arctic freshwater ecosystems. [ABSTRACT FROM AUTHOR]

The high Arctic is in a rapid transition due to climate change, and both direct effects due to warming and an extended growing season, as well as an indirect effect caused by increased bird activity and density (notably geese), strongly affect ponds and lakes. Our study presents the hitherto most comprehensive data on invertebrate freshwater diversity at Svalbard and had three main purposes: to provide a current “baseline” of community composition, to compare current species distribution and occurrence with older data to identify changes that have already occurred, and finally to identify how diversity and community composition are related to the age of localities. To address these aims, we conducted a survey of freshwater invertebrates in 75 ponds and lakes at Svalbard in August 2014 and 2015. We provide a full report of the species’ inventory data for zooplankton, benthos, and meiofauna. We also provide data for species that have likely colonized the sites over the previous decades. Finally, our study also clearly demonstrates a diversity gradient related to ecosystem age and/or parameters confounded with age (e.g., productivity), which may hint at the rate of colonization over the time span from the oldest to the youngest localities. [ABSTRACT FROM AUTHOR]