Fishes are key component in the trophic web of Antarctic marine ecosystems, representing food for top predators, such as other fish, birds and mammals. In particular, fishes are among the most important prey of the Weddell seal, Leptonychotes weddellii. Several studies reported data on the diet and foraging ecology of Weddell seals all around the Antarctic continent, from the Ross and Weddell Seas to the South Orkney and the South Shetland Islands. In the present study we investigated the fish component in the diet of Weddell seal from the Kyiv Peninsula region, which so far represented an unexplored area. During the four-year research, a total of 16 species of fish were identified, five of them were recorded for the first time in the study area. Except for the Antarctic silverfish, which represented the most abundant prey, all other species were benthic or demersal notothenioid species. Weddell seals relied on a wide range of prey size, including both juveniles, subadult and adult ontogenetic stages. Applying a multivariate analysis of prey items, temporal factors such as month, season and year of sampling did not influence diet composition, whereas it was slightly affected on a spatial midscale. In conclusion, the food composition of the Weddell seal populations living in this area seemed to be largely determined by the local abundance of fish prey, providing evidence of a remarkable feeding plasticity of this species.

The anostracan Branchinecta granulosa Daday, 1902 is the largest invertebrate animal in Antarctic freshwater bodies. This crustacean species playing important role in Antarctic ecosystems, was first recorded in the freshwater ponds of Petermann Island (Wilhelm Archipelago, Maritime Antarctica) during the Second French Antarctic Expedition of Jean-Baptiste Charcot in 1909. More complete official information about the distribution of this crustacean within this region of Antarctica is almost absent. Thus, we investigate the current distribution of B. granulosa in the region of Argentine Islands – southern part of this archipelago. During multiyear sampling effort covering 2007, 2008, 2010 and 2020 expeditions, B. granulosa was found in 32 freshwater bodies of 12 islands of the Wilhelm Archipelago region and for the first time in reservoirs of 11 islands.

Background:Limno-terrestrial rotifers, particularly those of the order Bdelloidea, inhabit bryophytes, lichens, soils and other periodically moist terrestrial habitats. Despite their high abundance in all latitudinal zones, these rotifers remain poorly documented in biodiversity databases due to difficulties in preservation and morphological identification. As a result, the current knowledge of their global distribution is still highly fragmented and geographically biased, with the majority of species records concentrated in Europe (where the experts mostly collected material). Many regions like north-eastern Asia, North and South America, Africa and Australia remain under-represented in current knowledge on distribution of limno-terrestrial rotifers. Recent studies suggested that Bdelloidea exhibit distinct biogeographical patterns and potentially high levels of cryptic diversity and endemism, challenging the traditional view of the omnipresence of all microscopic taxa. Comprehensive, georeferenced occurrence data are essential to advance our understanding of bdelloid biodiversity and distribution, yet such data are still scarce in global platforms like the Global Biodiversity Information Facility (GBIF). New information:The dataset provides new, georeferenced data on the occurrence of rotifer species inhabiting limno-terrestrial habitats worldwide. For the first time, occurrence records for 48 rotifer species (including nominal taxonomic 'subspecies') are published in GBIF.In particular, the dataset significantly expands the information on the distribution ranges of the bdelloid rotifers (order Bdelloidea) in GBIF. We contributed 5,651 new occurrence records of bdelloids rotifers, increasing the number of records in GBIF by 47.5% (or by 61.6% when considering only previously georeferenced records).Moreover, we add 394 new records to the faunas of 49 of 56 studied countries, in 17 of which limno-terrestrial rotifers were studied for the first time.Additionally, for 19 countries, records of bdelloid rotifers are now available in GBIF for the first time.

The anostracan Branchinecta gaini is the largest invertebrate animal in Antarctic freshwater bodies. This crustacean species playing important role in Antarctic ecosystems, was first recorded in the freshwater ponds of Petermann Island (Wilhelm Archipelago, Maritime Antarctica) during the Second French Antarctic Expedition of Jean-Baptiste Charcot in 1909. More complete official information about the distribution of this crustacean within this region of Antarctica is almost absent. Thus, present work aims to investigate the current distribution of B. gaini in the region of Argentine Islands – southern part of this archipelago. During multiyear sampling effort covering 2007, 2008, 2010 and 2020 expeditions, Branchinecta gaini was found in 32 freshwater bodies of 12 islands of the Wilhelm Archipelago region and for the first time in reservoirs of 11 islands.

Today, the issue of researching reservoirs, which are an important source of human water supply and are significantly affected by anthropogenic factors, is gaining more and more relevance. Research on the Oleksandrivka Reservoir is highly important since the safety of operation of the South-Ukrainian NPP depends on the functioning of this reservoir. The research material was samples of littoral zooplankton, which is a bioindicator of changes in the aquatic environment. During the research, both classical methods and the original method of standardizing the number and localization of zooplankton sampling stations within different types of reservoir were used. As a result of original research, the species composition and structural organization of littoral zooplankton communities in different parts of the Oleksandrivka Reservoir were analyzed for the first time. A total of 126 species of zooplankton were registered, of which 96 were observed in this reservoir for the first time. The rotifer Euchlanis dapidula was discovered for the first time in the fauna of Ukraine. The peculiarities of the formation of the faunal spectrum, trophic groups, complex of dominant species, distribution of biotopes, distribution in different parts of the reservoir, density, biomass, as well as seasonal and daily dynamics of littoral zooplankton groups were also clarified. It was established that the biomass of phytoplankton has a statistically significant effect on the density and biomass of zooplankton.

provide information on new records of the Cattle Egret ( Bubulcus ibis) in the Drake Passage area and within the Argentine Islands (Wilhelm Archipelago, Antarctica). Included are notes on the peculiar behavior of and difficulties experienced by this bird in the extreme conditions of the Antarctic.

Copepod Boeckella poppei was first recorded in a freshwater body of the Wilhelm Archipelago (Kyiv Peninsula, Maritime Antarctica) in 2008. This crustacean is one of the main consumers of filamentous algae in freshwater Antarctic bodies and is used as an indicator species in freshwater ecosystems. This work aimed to research the current distribution of B. poppei within the Argentine Islands of this archipelago. The second population of this crustacean species was discovered on the Nob Island at the beginning of this research in 2010. Boeckella poppei was also recorded in 33 freshwater bodies of eight other islands in 2020. During the final stage was analyzed the adaptation of B. poppei to the extreme conditions of existence in the freshwater reservoirs of Antarctica and the main ways of the spread of this species over short and long distances in this region of the planet.

Antarctica is considered one of the most inhospitable places to life due to its low temperatures and lack of liquid water. However, meiofauna taxa such as tardigrades not only thrive, but also show remarkable biodiversity in this habitat. Tardigrades are a phylum of small animals (less than 1 mm in length) mainly known for their ability to withstand freezing and desiccation, which are common stressors in Antarctica. The tardigrade genus Mesobiotus is widely distributed and abundant in Antarctica, particularly in the Antarctic Peninsula, where it is been hypothesized it was present even before the continent froze. Different Mesobiotus species have been recorded from the Antarctic Peninsula, but most are based on DNA data and lack assignment to described species. We used integrative taxonomy methods (DNA and morphology combined) on a novel population of Mesobiotus aradasi from Antarctic Peninsula. The latter allowed us to link previous molecular and morphological records of this species and to build a comprehensive map of its distribution. We show that this species is present across almost all the Antarctic Peninsula, whereas there are no records of it for any other Antarctica region. This study highlights the importance of integrating molecular and morphological methodologies and their complementarity when working with biodiversity and distribution data. The M. aradasi distribution highlights its endemicity in the Antarctic Peninsula and calls for attention to possible future threats to this species.

We present standardized, quantitative information on the avifauna of the Drake Passage obtained during six crossings between Patagonia and the South Shetland Islands during the summer-autumn period, 1998- 2020. We compare inter-annual and seasonal patterns of species occurrence, adding to previous, published surveys, and we discuss species association with the different zones and water masses of the region.

The inshore waters off the Argentine Islands host a diversified benthic fish community largely dominated by the black rockcod, Notothenia coriiceps. Compared to other areas along the western Antarctic Peninsula, the feeding habits of this species in this location are poorly known. Hence, the aim of the study is to assess food preferences by the stomach content examination, applying a sophisticated analytical approach. As reported elsewhere, the black rockcod is omnivorous, relying primarily on algae, gastropods, amphipods, euphausiids and fishes, each consumed with different foraging strategies. Based on multidimensional scaling statistical procedures, fish size and water depth are the primarily contributers to prey resource diversification and partitioning. Overall the sampled population of the black rockcod are generalist feeders with a relatively high between-phenotype component to the niche width, consisting of specialized individuals with little or no overlap in food resource use.

Belgica antarctica is one of the two native chironomid species of the Antarctic Peninsula. In this species, adult males and females are considerably different, yet the question of larval sex differences in morphometric parameters remains unanswered. In this paper, we analyze five morphometric parameters: head capsule length, head capsule width, mandible width, mandible length, mentum length of 140 fourth-instar larvae of B. antarctica from seven study plots in the south of Petermann Island, Wilhelm Archipelago, Antarctic Peninsula. To infer possible sexual dimorphism, we use the methods of unsupervised analysis (PCA and hierarchical clusterization). Our results suggest that the selected morphometric features of width and length are highly intercorrelated and cannot differentiate sex in the sampled larvae of B. antarctica.

In the last three decades, several interdisciplinary studies investigated the marine ecosystems off the West Antarctic Peninsula (WAP), one of the most impacted areas of the Southern Ocean by the global warming. Although the extent of near-shore habitats along the WAP is wider than elsewhere in Antarctica, the coastal fish communities have been rarely studied. Complementing these previous studies, we provide new data on the species composition, population structure and relative abundance of the inshore fish community living off the Argentine Islands (Bellingshausen Sea). Fish samples were caught all the year round during four different periods spread over ten years (from 2006 to 2017). The fish fauna consisted of fourteen high-Antarctic and low-Antarctic species of notothenioids, most of them belonging to the Nototheniidae. Notothenia coriiceps was by far the most abundant species, followed in decreasing abundance by Chaenocephalus aceratus , Notothenia rossii , Trematomus newnesi and Trematomus bernacchii . Our findings provide context for future ecological studies as this area represents either a spawning and nursery area for multiple species in this study. More generally, the inshore waters off the Argentine Islands represent the southern limit of distribution for several low-Antarctic species, and our results provide critical baseline data for assessing possible disruptions in population dynamics driven by the ongoing climate change.

The maritime Antarctic is one of the most interesting regions on planet where climate change can be observed to impact all components of its poor flora. Boeckella poppei is common in the maritime and continental Antarctic species of the copepod. The aim of the study was to check the local trends in the copepod's population density over summer. The samples were collected 23.12.05, 03.01.06 and 10.01.06 at the King George Island from the lake near the Polish Antarctic Station. The population density varied with strongly fluctuating ratios of different juvenile and generative developmental stages. We also analyzed the regularities reported by other authors. The sex structure of the population did not change during the study period with females much more numerous than males. The article discusses possible causes of this phenomenon.

Given the recent climate changes and their impact on the Antarctic Peninsula ecosystems, the emergence of invasive species, and increased tourism activity in this region, monitoring changes in the habitats of species native to the Antarctic Peninsula region is necessary. One such species is the Antarctic midge Belgica antarctica (Chironomidae). This insect is endemic to the Antarctic Peninsula and adjacent islands. Thorough studies of changes in the range of this species have not been performed in recent decades. In this study, we present the area of Belgica antarctica according to the collections of biological samples during 2007–2021 (XII, XIV, XVI, XXIV, and XXV Ukrainian Antarctic Expeditions). This Antarctic midge was recorded at 26 localities on the Antarctic Peninsula and 212 localities on 55 surrounding islands between 66°08′38.4′′ S, 65°43′37.1′′ W (Cape Evensen, Stresher Peninsula, opposite the Marie Island, west coast of Graham Land) and 62°11′44.7′′ S, 58°57′40.6′′ W (King George Island, South Shetland Islands) from south-west to north-east.

Fish diets are important indicators of ecosystem change. This aspect of the ichthyofauna of the coast of the Argentine Islands has been insufficiently studied in comparison with other regions. This article presents the results of comparison of dietary and somatic parameters of the dominant species Notothenia coriiceps depending on the point, depth and season of catch. The sample was collected between February 2006 and February 2007. In the year of study, N. coriiceps, Trematomus bernacchii, Chaenocephalus aceratus (common species), Harpagifer antarcticus and Pagothenia borchgrevinki (rare species in this region) were caught. The average fish size in this region does not differ from other places in the Southern Ocean. In Cornice Channel and Stella Creek, N. coriiceps was smaller than at other points due to the narrowness and shallow depth of these places. In winter, large individuals apparently migrated from the coast. The diet of N. coriiceps consisted mainly of crustaceans and seaweeds, with a small number of mollusks (especially limpets), which are common. The number of fish in the diet of N. coriiceps is relatively low for this region. Access to food was relatively the same at different points and depths of the catch. The lowest amount of food was in the fall, the highest amount of food was in the spring and summer. The condition and hepatosomatic index also did not change depending on the point and depth of the catch, but they were low in spring and high in summer. Perhaps this is due to the low energy value of food, which is not compensated by the amount. It is necessary to conduct studies of the diet of N. coriiceps in other years to clarify the specificity of fish in the diet and phenological changes in somatic parameters. Similar studies are needed for other species in the region if catches are sufficient to collect a representative sample.

The analysis results of the structural-functional organization of littoral zooplankton community of the upper Kremenchug Reservoir in the territory of Kaniv Nature Reserve during the summer of 2015 are presented. Diversity of zooplankton was presented with 34 species: Monogononta rotifers, cladocerans, copepods. The rotatoria-cladoceran zooplankton complex dominated in the taxonomic composition. Zhakkara dominant index for the comparison of the dominant species complexes was used, and it was the low number of similarities within the various biotopes of the six research stations (J = 7,1-28,6). This can be explained by the formation of higher aquatic plants.This led to the formation of specific zooplankton groups in overgrown biotopes.The ecological spectrum of the different groups of the upper Kremenchug Reservoir littoral zooplankton in the summer was characterized by the predominance of the phytophilic groups: phytophilic – 18 species (53 % of all zooplankton species). Depending on the feeding type the largest part was made by the peaceful group – 73,3 % (25 species). Summer littoral zooplankton in quantitative terms was characterized by very low development in both biotopes. Its density varied within 4077± 2098 ind./m³ and biomass 0,07 ± 0,04 g/m for overgrown biotopes, and 4123 ± 3929 ind./m³ and 0,054 ± 0,038 g/m³ for freshwater ones. Among the quantitative indicators, the species of Copepoda dominated, what was associated with the development of their larval stages (Nauplia, Сalanoida juv., Cyclopoida juv.) in the summer period.

The increase in anthropogenic impact on aquatic ecosystems causes significant alterations in the composition and structure of hydrobiont groups. These processes are characteristic of the hydrobiocenoses of the Uday River, the valley of which lies within the National Nature Park "Pyryatynsky", established in 2009 in the Pyryatyn district of Poltava region. Within this protected area it is convenient to carry out continuous monitoring of changes in anthropogenic load on shore ecosystems of the river. One of the most convenient monitoring groups is zooplankton, which is one of the essential components of the trophic networks of aquatic ecosystems and which is the feeding basis of planktonophagous and young fish. The object of this research was the major groups of zooplankton: rotifers (class Eurotatoria), cladocerans (class Branchiopoda, order Cladocera), different age stages of copepods (class Copepoda), ostracods (class Ostracoda). Zooplankton were collected in the daytime in spring (mid April), summer (end of July) and autumn (late September) 2016 within eight research stations. As a result of the conducted research, 69 species of zooplankton were registered within the littoral water area of the Uday River. Monogonont rotifers numbered 19 (27.5%) species, bdelloid rotifers (subclass Bdelloidea), cladocerans – 33 (47.9%) species, copepods – 17 (24.6%). According to the faunal spectrum in the zooplankton groups, representatives of the cladoceran complex predominated. This is due to the favourable conditions for the development of filtrators, of which a considerable part is cladocerans. Three species of rotifers were identified in Poltava region for the first time: Beauchampiella eudactylota (Gosse, 1886), Dipleuchlanis propatula (Gosse, 1886), Mytilina acanthophora (Hauer, 1938). During the spring, 33 species of zooplankton were collected: rotifers – 10 species, cladocerans – 14, copepods – 9 species. In summer 41 species were registered, including rotifers – 10, cladocerans – 18, and copepods – 13. In autumn 37 species were found: 6 species of rotifers, cladocerans – 21 and copepods – 10. The species composition of the zooplankton in different seasons had a low similarity, as evidenced by Jaccard index: spring and autumn (J = 25.4), spring and autumn (J = 34.5), and summer and autumn (J = 34.6). In the spring, pelagic (36.3%) and phytophilic (45.6%) groups prevailed, and phytophilic dominated in summer (41.4%) and autumn (48.7%). Of the various groups classified according to feeding type, representatives of the peaceful group dominated in all the studied seasons, in spring comprising 69.7%, in summer – 65.8%, and in autumn – 73%. The density and biomass of zooplankton of the Uday River were “low” in spring and summer, and "very low" – in autumn.

The analysis results of spatio-temporal dynamics of zooplankton communities from littoral of the Oleksandrivka reservoir are presented. The features of the seasonal changes in species composition, faunal and ecological spectrums, quantitative indicators (density and biomass) and the dominant species complexes of littoral zooplankton was revealed. The analysis of seasonal dynamics of qualitative and quantitative development of zooplankton in the littoral zone within the upper, middle and lower parts of the Oleksandrivka reservoir was conducted.

In recent decades, the influence of anthropogenic impact on aquatic ecosystems has increased. This has led to a restructuring of aquatic ecosystems and affected the structural and functional organization of groups of aquatic organisms, causing qualitative and quantitative changes. Particular attention is drawn to the different types of water bodies of protected areas like IchnyanskyNational Park, which is located in Ichnyansky district of Chernihiv region. This park is a newly created one, so the reduction in intensity of anthropogenic pressure can be traced within its waters. Zooplankton plays an important role in the functioning of trophic networks because it transfers energy from producers and primary consumers to young fish and planktonophagous fish. Therefore, three main groups of zooplankton were chosen as the object of study: rotifers (class Eurotatoria), cladocerans (class Branchiopoda, order Cladocera), different age stages of copepods (class Copepoda), and also ostracods (Class Ostracoda). The zooplankton used as research material was collected in the daytime in spring (April), summer (late July – early August) and autumn (late September – early October) in the years 2015–2016 from ten experimental stations. During this period 81 species of zooplankton were recorded within heterogeneous reservoirs of IchnianskyNational Park. Monogonont rotifers (subclass Monogononta) included 35 species (43% of all species) and bdelloid rotifers (subclass Bdelloidea), cladocerns, comprised 28 species (35%), and copepods included 18 species (22%). The faunal range of zooplankton over different years and seasons was characterized by the predominance of the rotator complex in spring, rotator-cladocerans and cladocerans in summer, and of the cladocerans complex in autumn. This was due to the formation during spring and summer of favourable conditions in the waters for filter feeders, which consist generally of rotifers and cladocerans. In autumn the water released large amounts of organic matter that caused a reduction in the species diversity of rotifers. Zooplankton also is characterized by the considerable ecological diversity. The range of environmental groups of zooplankton over two years was characterized by a predominance of the pelagic and benthic group of phytophiles. Pelagic representatives included 35 (43%) of 81 species, the bottom group – 20 (25%), phytophiles – 26 (32%). Rotifers dominated in the pelagic group – 18 (51%) species out of 35, and cladocerans – among the bottom group – 10 (50%) species out of 20. Zooplankton species also are distinguished by their feeding type. They represented three trophic groups: peaceful – 64 (79%) out of 81 species, omnivorous – 6 (7%) and predators – 11 (14%). Quantitative indicators of zooplankton at most stations in different seasons were defined as “very low” (less than 5,000 ind./m3 and less than 0.3 g/m3), “low” (5,000–50,000 ind./m3 and 0.3–1.0 g/m3), “below average” (5,000–50,000 ind./m3 and 0.3–1.0 g/m3) rates, occasionally – "average" (51–250,000 ind./m3 and 1.1–5.0 g/m3), “medium high” (501,000–1,000,000 ind./m3 and 1.1–5.0 g/m3). High densities of zooplankton were recorded in spring for a temporary reservoir and amounted to 3,016,000 ind./m3.

Results of the investigation of the littoral zooplankton's structural and faunistic organization of the Uday river are presented. The research was conducted in the National Nature Park "Pyriatynskiy" in summer 2015. As the result of research 58 zooplankton's species were established. Their density, biomass, ecological spectrum of the community, type and way of the feeding were analyzed.