Zooplankton Species Composition Research Articles

Distribution and Abundance of Zooplankton in Anthropogenic-Impacted Stream, Nsit-Ibom, Nigeria

This study aimed to investigate the distribution and abundance of zooplankton in Mbiokporo stream Nsit-Ibom Local Government Area, Akwa Ibom State, Nigeria. Samples were collected and analyzed using standard methods. The result revealed that there were 9 zooplankton taxonomic groups (namely: Arachnida, Bdelloidae, Branchiopoda, Chromadorae, Euglenoidea, Hexanauplia, Insecta, Polychaeta, Tubulinea), comprising 12 species and 91 individuals. The most abundant zooplankton species was Temora longicornis with the highest number of species across all the stations 24 > 19 > 7 for station 1, station 2, and station 3 respectively. Branchiopoda had the highest number of species (4) and highest species composition (33.33%), while Hexanauplia recorded the highest individual abundance (54.95%). The relative abundance of zooplankton phyla was as follows: (Hexanauplia, 54.95 %) > (Branchiopoda, 13.19 %) > (Bdelloidae, 8.79) % > (Chromadorae, 7.69 %) > (Polychaeta and Arachnida, 5.49 % each) > (Insecta, 2.20 %) > (Tubulinea, 1.10 %) respectively. Indices of species dominance were as follows: station 1 > station 2 > station 3, with the following values 0.4349 > 0.4235 > 0.2397 each. Meanwhile, the highest species evenness was in station 3 (0.7887), followed by station 2 (0.5495), while the lowest was in station 1 (0.486). Margalef’s species diversity was slightly higher in station 1 (1.649) than in station 3 (1.618) while the lowest was in station 2 (1.456). The equitability index among stations was as follows: 3 (0.8675) > station 2 (0.6659) > station 1 (0.6292). However, this result revealed that ongoing anthropogenic activities along the stream may resulted in the deterioration of the stream thereby leading low species composition of zooplankton as observed in this study.

Temporal variation and spatial factors affecting zooplankton communities in freshwater rock pools

Most ecological studies have focused on one snapshot in a single location and the same taxonomic group. However, relatively few studies have explored different taxonomic groups over multiple periods, particularly in ephemeral Neotropical ecosystems. This study investigates the seasonal dynamics of zooplankton communities and their responses to environmental variables in temporary pools in the Seasonally Dry Forest Ecosystem, Pernambuco, Brazil. We examined the seasonal fluctuations in species abundance, diversity, and evenness of Cladocera, Copepoda, and Rotifera in five temporary rock pools. Although these pools are meters apart, they vary considerably in size and drought sensitivity, leading to distinct seasonal dynamics mediated by water availability. We asked (i) how do species abundance, diversity, and evenness vary seasonally? (ii) Do these seasonal shifts differ between Cladocera, Copepoda, and Rotifera? And (iii) How do water environmental variables and spatial distance of pools influence zooplankton species composition? We hypothesized that Cladocera and Copepoda are positively affected by the rainy season, but Rotifera is mostly common in the dry season. Our findings underscore seasonality as the primary driver influencing the abundance and composition of zooplankton communities. We observed higher abundance of Cladocera and Rotifera during the post-rainy season, but Copepoda was dominant in the rainy season, leading to a strong seasonal variation in species evenness. These differences among groups highlight the importance of considering biological differences when understanding the ecological drivers of temporary freshwater ecosystems.

Seasonal variation in the mesozooplankton community structure and indicator species of the Yellow Sea

We investigated the mesozooplankton community structure of the Yellow Sea in four seasons, one season for each year during 2019–2022. Total abundance and biomass were highest in autumn and spring, respectively. The mesozooplankton community was dominated by small copepods such as Acartia, Paracalanus, and Oithona species throughout all seasons. Euphausiid larvae were particularly abundant in spring, whereas tunicates appeared only in autumn. In spring, summer, and winter, mesozooplankton were clustered into groups from coastal waters to the open ocean. However, in autumn, the mesozooplankton community was divided by latitude and indicator species analysis suggested the influence of a warm current in this season. A comparison of our findings with those of previous studies indicated no clear change in zooplankton species composition or its seasonality in the Yellow Sea within the past 30 years.

Composition, Distribution, and Biodiversity of Zooplanktons in Tropical Lentic Ecosystems with Different Environmental Conditions

A study was conducted to evaluate zooplankton species composition, abundance, and diversity in both natural and artificial lakes with varying trophic levels and to determine the relationship between zooplankton community structure and lake environmental conditions. This study hypothesized that correlations exist between zooplankton community structures and environmental parameters associated with eutrophication in natural and artificial lakes. Sampling was conducted across 16 distinct freshwater lentic ecosystems in Malaysia, including natural lakes/swamps, reservoirs, constructed lakes/ponds, and old mining lakes, spanning a range of trophic levels from mesotrophic to hypereutrophic conditions. Physicochemical parameters were measured in situ, while water and zooplankton samples were collected for nutrient analyses, as well as for zooplankton identification and enumeration. Throughout this study, a total of 58 zooplankton species, consisting of 36 species of rotifers, 12 species of cladocerans, and 10 species of copepods, were recorded. The highest zooplankton density (365.7 ± 13.7 ind L−1) was recorded in constructed lakes/ponds while the lowest density was recorded in natural shallow lakes/swamps (200.5 ± 25.5 ind L−1). On the other hand, significantly higher (p < 0.05) mean species diversity was observed in natural lakes/swamps (H’ = 2.2 ± 0.0); whereas, the lowest diversity was in old mining lakes (H’ = 1.5 ± 0.1). The canonical correspondence analysis (CCA) scores indicated that Polyarthra vulgaris and Chydorus ventricosus were the discriminating species in natural shallow lakes/swamps associated with high water transparency. Meanwhile, the small-sized cladocerans (Ceriodaphnia cornuta) and rotifers (Keratella spp., Brachionus spp., and Trichocerca spp.) were the most discriminating species in lakes with high turbidity, nutrients, and chlorophyll a concentrations, which are the main features of reservoirs and constructed lakes/ponds. Low density and diversity in old mining lakes were due to a low species number and the dominance of two species, Lophocharis curvata (38.8%) and Ptygura libera (39.7%). Overall, the high dominance of a specific zooplankton species resulted in lower biodiversity in artificial ecosystems compared to natural ecosystems. This study elucidated that zooplankton community structure in lakes was significantly influenced by the environmental conditions related to the lake trophic status.

Zooplankton of Pronskoye reservoir in August 2023

The aim of this study was to investigate the zooplankton of Pronskoye Reservoir during the summer period of 2023. Sampling and processing of hydrobiological zooplankton samples were carried out using standard methods in August 2023 at six monitoring stations in Pronskoye Reservoir. A total of 15 zooplankton taxa were identified in the samples: 6 taxa of rotifers, 5 taxa of cladocerans, and 4 taxa of copepods. On average, the abundance and biomass of zooplankton (mean values across stations) in Pronskoye Reservoir in August 2023 were 928.1 thousand individuals/m3 and 3.4 g/m3, respectively. Rotifers dominated in terms of abundance (63,5%), while cladocerans dominated in terms of biomass (40,3%). Pronskoye Reservoir exhibited above-average productivity in terms of zooplankton, which is favorable from a fisheries perspective. The abundance and biomass of zooplankton for all major groups (rotifers, cladocerans, and copepods) were higher in the lower part of the reservoir, separated from the middle and upper parts by a narrow neck. The increase in the abundance of the rotifer species Brachionus angularis was particularly noticeable in the lower part of the reservoir. The lower part of the water body is classified as highly productive, while the middle and upper parts has above-average productivity. The lower part of the reservoir is characterized by lower temperatures and lower dissolved oxygen concentrations in the water. The lower part of Pronskoye Reservoir exhibits a more diverse species composition compared to the middle and upper parts. It is evident that abiotic factors, in one way or another, determine the differences in the abundance, biomass, and species composition of zooplankton between the lower and upper parts of Pronskoye Reservoir.

Current state of zooplankton and zoobenthos in the lower stream of the Chulym river (Obi river basin)

A comparison was made of the numerical indicators of zooplankton and zoobenthos of the Chulym River in comparison with those obtained in 1972–1973 in order to assess the transformation of the ecosystem that has occurred over 50 years. It is shown that the zooplankton of the Chulym River has undergone dramatic changes, both qualitatively and quantitatively. The number of zooplankton increased 4–5 times due to small rotifers. At the same time, the zooplankton biomass, and therefore the feed value, decreased by more than half due to a reduction in the number of large crustaceans. The species composition of structure-forming zooplankton species has changed. The number of rotifer species in the riverbed decreased from 55 rotifers to 34. The species of Trichocerca family dropped out of the dominant composition and representatives of the river began to dominate Brachionus family. There is a significant change in the structure of zoobenthos: the number of organisms in the Chulym River bed is 5 times lower than in the 1970s. The species composition in benthic communities has remained almost unchanged over 50 years, while the proportion of some heterotopic insects (caddis flies, mayflies, stoneflies) has increased, and the proportion of oligochaetes, mollusks and chironomids in the biomass has decreased by 4–5 times. In the accessory reservoirs of Chulym, the abundance and biomass of zooplankton and zoobenthos over the past 50 years have remained more or less stable, which may indicate the presence of chronic pollution that affects the ecosystem of the main river channel and does not have time to have a negative impact on the accessory reservoirs during floods. The water quality indicators of the Chulym River and its subsidiary reservoirs, according to biotic indices, are low and correspond to a low or poor water quality class. Such conditions are unfavorable for the further development of zoobenthos and, accordingly, ichthyofauna, for which bottom invertebrates are the food supply.

Natural food base of fish culture ponds and its use in growing fellow of carp

A study of the natural food supply of the nursery ponds of Ecopark LLC’s fish farm in the Moshkovsky district of the Novosibirsk region was carried out in July–August 2022. Carp fingerlings were raised in the ponds with a stocking density of 34.77 and 57.73 thousand/ha. During the growing period, carp fingerlings were fed 5000 kg of feed mixture in equal parts of crushed barley and wheat grains. The species composition of zooplankton in the studied reservoirs is monotonous and is represented by nine species. Variable species diversity was observed in all reservoirs. The number of zooplankton in July in ponds No. 5 and No. 2 was 76344.45 and 48311.11 ind./m3, in August – 56800 and 48616.67 ind./m3; biomass – in the range of 2724.88-5777.86 and 1618.65-2258.73 mg/m3, respectively. Analysis of variance showed a relationship between the mass of under-yearlings and zooplankton biomass. It is 0.70, which indicates that the mass of carp under-yearlings increases with an increase in zooplankton biomass. The identified differences in the rates of linear growth and weight depending on the stocking density make it possible to establish fish productivity - in pond No. 2. It was 806.4. In pond No. 5 - it was 878.4 kg/ha. Planting 37.33 ind./ha is more productive and gives better growth indicators (average length and weight of carp fingerlings at the end of the study are 10.91 cm and 26.96 g, respectively) than planting 57.77 ind./ha (average length and weight at the back of the study 9.70 cm and 18.67 g, respectively). The planting density of 37 thousand specimens/ha makes it possible to grow fingerlings with a standard weight of 25-26 g. The influence of the stocking density factor on the weight of fingerlings is 0.92 (at a level of P > 0.001). Fish productivity in Pond No. 2 was 806.4 kg/ha, and in Pond No. 5, it was 878.4 kg/ha.

A space‐for‐time framework for forecasting the effects of ocean stratification on zooplankton vertical habitat use and trait composition

AbstractThe effects of environmental change on zooplankton communities, and more broadly, pelagic ecosystems are difficult to predict due to the high diversity of ecological strategies and complex interspecific interactions within the zooplankton. Trait‐based approaches can define zooplankton functional groups with distinct responses to environmental change. Analyses across multiple mesozooplankton groups can help identify key organizing traits. Here, we use the pronounced cross‐shore environmental gradient within the California Current Ecosystem in a space‐for‐time substitution to test potential effects of ocean warming and increased stratification on zooplankton communities. Along a horizontal gradient in sea‐surface temperature, water column stratification, and light attenuation, we test whether there are changes in zooplankton species composition, trait composition, and vertical habitat use. We employ DNA metabarcoding at two loci (18S‐V4 and COI) and digital ZooScan imaging of zooplankton sampled in a Lagrangian manner. We find that vertical distributions of many mesozooplankton taxa shift to deeper depths in the cross‐shore direction, and light attenuation is the strongest predictor of magnitude of change. Vertical habitat shifts vary among functional groups, with changes in vertical distribution most pronounced among carnivorous taxa. Herbivorous taxa remain associated with the chlorophyll maximum, especially in clear offshore waters. Our results suggest that increased stratification of this ocean region will lead to deeper depths occupied by some components of epipelagic mesozooplankton communities, and may result in zooplankton communities with more specialized feeding strategies, increased egg brooding, and more asexual reproduction.

The Structure of the Zooplankton Communities in Sukhoe More Bay, Southeastern White Sea

This paper presents the results of our investigation of the zooplankton communities from Sukhoe More Bay, located in the southeastern part of Dvina Bay of the White Sea, in July−August, 2018. The species composition, quantitative characteristics and spatial distribution of zooplankton were studied. The zooplankton communities are composed of 34 species of hydrobionts. Copepods were the dominant group in the entire study area. The zooplankton communities were characterized by high quantitative indicators. Juvenile stages of copepods were a significant contribution to the formation of the total number of zoocenoses. During high water level, the abundance of zooplankton was 37 000 ind./m3, biomass, 0.6 g/m3 (wet weight). During low water level these parameters were 210 000 ind./m3 and 1.7 g/m3 (wet weight), respectively. The structure, abundance and spatial distribution of zooplankton in the bay are determined by the morphometric features of the reservoir (shallow water), the influence of a complex of environmental factors (temperature and salinity), as well as tidal phenomena.

Analisis Komposisi Jenis dan Kelimpahan Zooplankton di Perairan Kampung Nafri, Kota Jayapura

This study aimed to determine the type, composition, and abundance of zooplankton in the waters of Kampung Nafri. Zooplankton were identified using zooplankton sample identification guidelines, and zooplankton abundance analysis was performed using the Sedgewick Rafter. Purposive sampling was used in this study. Zooplankton sampling was carried out horizontally on the surface of the water using a plankton net which was carried out in the morning around 08:00 - 10:30 WIT at 3 stations. Sampling at each station was done 2 times repetition and the water parameters were done 3 times repetition. In situ measurement of water quality parameters, such as salinity, pH, current speed, and temperature Based on the identification results, there are 11 types of zooplankton that inhabit the waters of Kampung Nafri. The highest value of zooplankton species composition in Nafri Waters was Naplius sp., which was 63%, and the lowest was Temora sp. and Corycaeus sp. by 1%. The highest abundance of zooplankton species in Nafri Waters was Nauplius sp. (Copepoda larvae), with a total abundance of 9,900 ind/l, and the lowest was Corycaeus sp. and Temora sp., with a total abundance of 200 ind/l.

How do environmental variables affect the temporal dynamics of zooplankton functional groups in a hyper-eutrophic wetland?

In recent years, trait-based research on zooplankton has gained importance to enable comprehensive interpretation of ecosystem processes, but this approach is still limited in inland waters. Wetlands, one of the most important inland water resources, provide many ecological and economic services in the ecosystem, but like all other water bodies in the world, they are under threat of deterioration and depletion for various reasons. In this study, the taxonomic structure of the zooplankton community in Lake Manyas, one of the important wetlands of Türkiye, as well as their functional characteristics such as body size (small, large) and feeding strategies (microphagous, raptorials) were investigated monthly between 2019 and 2020. The hypothesis that environmental variables influence the species composition and functional groups of zooplankton was tested, given that their structure is shaped by environmental gradients. A total of 62 taxa, including rotifer-dominated, cosmopolite and eutrophication indicator species, were identified. These taxa categorized into three functional groups dominated by small microphagous. Although the zooplankton structure had a high taxonomic diversity, functional homogeneity was observed which reflected a low grazing rate in the ecosystem. Albeit water temperature and total organic carbon significantly affected the distribution of all functional groups, each dominant taxa interacted with different environmental variables. Changing environmental conditions in the lake affected the presence and/or quantity of the zooplankton functional groups (ZFGs). The results showed that ZFGs are strongly associated with environmental conditions and that the response of trait-based functional groups to environmental changes can provide useful knowledge about aquatic ecosystem's health.

A dataset of zooplankton occurrence, abundance, and biomass in the Far East seas and adjacent Pacific Ocean waters.

Planktonic animals drifting or floating in the sea have small body sizes and weights from hundreds to thousands of milligrams, and are primarily the food for other zooplankton and macrofauna: fish, cephalopods, seabirds and marine mammals, and also the larval pool of many benthic invertebrates. This paper describes a unique dataset of zooplankton collected from 1984 to 2013 in the North Pacific (the Bering Sea, Sea of Okhotsk, Sea of Japan and adjacent Pacific Ocean waters), one of the most productive and economically important regions of the world's oceans using a Juday net made of kapron sieve No. 49 (0.168 mm mesh) with a 0.1 m2 opening. The information in this dataset has already been used to quantify the inventory of marine biological resources and assess the waters of the Russian Far Eastern seas and adjacent Pacific Ocean. In 2016, five tabular reference books were printed in Russian in limited numbers containing the species composition, occurrence (number and percentage of samples), abundance and biomass (in individuals per cubic meter, milligrams per cubic meter) of zooplankton in the surveyed area. The data are grouped by species, developmental stages, size fractions (animal length of 0.6-1.2 mm "fine/small," 1.2-3.2 mm "medium" and >3.2 mm "large"), standard regions (their total area is more than 6 million km2 ), vertical layers of water, light and dark time of the day, four seasons of the year and multiyear periods, in which there were considerable changes in the biota of the region caused by global climate and oceanographic factors. This information has recently been verified, corrected, translated into English, transformed from text to digital format, and supplemented by GIS with maps of the standard regions by which data were aggregated using morphometric parameters (volume of water in cubic kilometers in the region, in its epipelagic 0-200 m, and upper epipelagic 0-50 m water layers, occupied area in square kilometers, longitude and latitude of their centroids in decimal degrees) to increase their availability to the scientific community worldwide. The data enable the evaluation of the total plankton stock of the Russian Far Eastern seas in the North Pacific (in trillions of specimens and thousands of tons), recalculate the volumetric characteristics of density into areal characteristics (in billions of specimens per square kilometer or tons per square kilometer), and, using previously published tables on calorific value and chemical composition of zooplankton, obtain their energy characteristics. Such data are crucial for the proper management of marine resources, aquaculture development, nature conservation, and the assessment of the anthropogenic impact on nature. The presented metadata provide a detailed description of how this unique dataset was created, sources and volume of gathered information, its benefits and drawbacks, some results on the quantitative inventory of marine biological resources and assessment of waters in the North Pacific, and future prospects for the use of this type of dataset in applied and fundamental research. There are no copyright restrictions on the data; please cite this data paper when the data are used in publications.

Кормление личинок судака (Sander lucioperca Linnaeus, 1758) при их подращивании в установке замкнутого водоснабжения

The article presents materials on optimizing the conditions for growing pike-perch during the larval period of development in an artificially created environment. The problems associated with the complexity of embryonic and post-embryonic development, the transition of larvae from endogenous to exogenous food, their rearing on artificial feed, and the causes of cannibalism have been described. The goal was to obtain and analyze the results of growing pike-perch larvae in conditions of closed water supply using living organisms as starter feed. The results of a study of the reproduction of pike-perch in industrial conditions of the aqua complex of the Coastal Scientific Expeditionary Base “Kagalnik” of the SSC RAS (Rostov Region, Azov District) are presented, describes the results of rearing pike-perch larvae in a recirculating aquaculture system. The values of the main hydrochemical parameters of the environment in fish tanks, necessary to ensure the normal growth and development of pike-perch larvae, as well as the characteristics of growth and survival during the experiments, are given. As a result, biotechnical standards for the reproduction of pike-perch by the intensive method have been developed. For high survival of pike-perch larvae, it is necessary to ensure timely feeding of larvae – after filling the swim bladder and switching to active feeding. The diet should be varied in terms of species composition of zooplankton. To prevent cannibalism among farmed fish, it is important to maintain the hydrochemical parameters at an optimal level, and the presence of food organisms in the fish tank is also necessary.

Роль солоноватоводной фауны и состояние биоресурса экосистемы гипергалинного озера Кулундинское в фазе трансгрессии (Алтайский край)

The results of ecological monitoring of the hypergaline lake Kulundinskoye of the Altai Territory in the period 2021-2022 are presented. The research was carried out in the form of a comprehensive study of abiotic factors of the reservoir (climatic features of the lake, temperature regime, salinity of water), biological factors (species composition of brackish-water zooplankton, its abundance), production and structural indicators of the gill-legged crustacean Artemia Leach, 1819. Desalination of water during the transgressive period of water content caused successional speciation processes. There was a change of the gill-legged crustacean as a dominant and monovid to a complex of brackish-water fauna. The artemia population developed under the influence of unfavorable salinity of water with a fluctuation in the lake from 1.9 (April) to 99.0 mg/dm3.
 The influence of the transgressive phase of water content on the biota and the extraction (catch) of a biological resource - artemia (at the stage of cysts), as well as the importance of the formation of their commercial accumulations of abiotic environmental factors, is shown. Studies have shown that the prevailing combination of factors during the transgression period – tense climatic conditions, low salinity of water (less than 100 mg/dm3), low number of artemia crustaceans, was the absence of commercial accumulations of biological resources.

Diversity and distribution pattern of copepods in Palk Bay coastal waters of India

The aim of this study was to find the species abundance and composition of copepod zooplankton in four selected sites such as Karangadur, Thevipattinam, Athangarai and Mandapam in Palk Bay region during February 2022 to January 2023. There is no significant difference (P<0.05) in water temperature, salinity, DO and pH values between the sites during this study period. In this study, we have observed 46 species of copepods belongs to 30 genus, 20 families and four orders. The overall percentage of copepod species composition in the four collection sites was: Calanoida (58.7%), Poecilostomatoida (17.4%), Harpacticoida (15.2%) and Cyclopoida (8.7%). In Athangarai site, a maximum of 40 copepod species were recorded. In Karangadu site, 34 species, in Devipattinam site, 28 species and in Mandapam site only 25 species were observed. In calanoid copepods, Acartia, Calanopia and Temora was the dominant genus which representing three species. In Poecilostomatoida order, four families, seven genus and eight species were observed. Out of the seven genus, Corycaeus was the dominant genus which comprises two species such as Corycaeus crassiusculus and C. speciosus. In Harpacticoida order, six families, six genus and seven species were recorded. Among the six genus, Longipedia represents two species (Longipedia coronata and L. weberi). The order Cyclopoida, has only one family, two genus and four species. Among the genus, Oithona was the dominant genus which contains three species. Among the 20 families, Pontellidae was the dominant one includes six species.

Environmental Factors Controlling Zooplankton Communities in Thermokarst Lakes of the Bolshezemelskaya Tundra Permafrost Peatlands (NE Europe)

Environmental physical and chemical factors controlling the abundance and biodiversity of zooplankton in permafrost-affected lakes are poorly known yet they determine the response of aquatic ecosystems to on-going climate change and water warming. Here, we assess the current status of zooplankton communities in lakes of the Bolshezemelskaya Tundra (permafrost peatlands of NE Europe), and provide new information about the composition and structure of zooplankton. The results demonstrate that the structure of zooplankton communities is influenced by the morphometric features of lakes and the degree of lake overgrowth by macrophytes. According to the level of quantitative development of zooplankton, most tundra lakes were of the oligotrophic type with an average wet biomass of up to 1 g/m3. The largest number of species was observed in zooplankton communities of small thaw ponds with an area of up to 0.02 km2 and overgrown with macrophytes. The analysis of factors that influence the formation of the lake zoocenosis demonstrated that the species composition and quantitative characteristics of zooplankton are chiefly controlled by pH and water mineralization. A comparison of the results obtained with the literature data on the lakes of this region collected 60 years ago suggests that the ecosystems of these lakes are in a stable state. Overall, these new insights will improve our knowledge of factors controlling the zooplankton spatial dynamics in unique but quite abundant thermokarst lakes of NE European Tundra, subjected to on-going climate warming.

Under-ice observations by trawls and multi-frequency acoustics in the Central Arctic Ocean reveals abundance and composition of pelagic fauna

The rapid ongoing changes in the Central Arctic Ocean call for baseline information on the pelagic fauna. However, sampling for motile organisms which easily escape vertically towed nets is challenging. Here, we report the species composition and catch weight of pelagic fishes and larger zooplankton from 12 trawl hauls conducted in ice covered waters in the Central Arctic Ocean beyond the continental slopes in late summer. Combined trawl catches with acoustics data revealed low amounts of fish and zooplankton from the advective influenced slope region in the Nansen Basin in the south to the ice-covered deep Amundsen Basin in the north. Both arctic and subarctic-boreal species, including the ones considered as Atlantic expatriate species were found all the way to 87.5o N. We found three fish species (Boreogadus saida, Benthosema glaciale and Reinhardtius hippoglossoides), but the catch was limited to only seven individuals. Euphausiids, amphipods and gelatinous zooplankton dominated the catch weight in the Nansen Basin in the mesopelagic communities. Euphausiids were almost absent in the Amundsen Basin with copepods, amphipods, chaetognaths and gelatinous zooplankton dominating. We postulate asymmetric conditions in the pelagic ecosystems of the western and eastern Eurasian Basin caused by ice and ocean circulation regimes.

The structure of zooplankton community in different biotopes of small rivers in the Kologrivsky cluster of the Natural State Reserve “Kologrivsky Forest”

Structure of zooplankton community was studied in different biotopes of streams and beaver ponds in the Kologrivsky cluster of the State Nature Reserve “Kologrivsky Forest” named after M.G. Sinitsyn. Forty-five zooplankton species were recorded, namely, Cladocera (20), Rotifera (17), and Copepoda (8). Zooplankton was represented mostly by phytophilic ecological group (46-61% of the total number of species). Species composition of zooplankton, trophic group ratio, zooplankton abundance and biomass differed in the medium-small river, the smallest and most insignificant watercourses. In near-shore river area (ripal) and beaver ponds, overgrown by macrophytes, higher quantitative indicators of zooplankton were registered comparing to central area of the river. In addition, high zooplankton abundance and biomass were observed in permanent beaver ponds at streams.

SEASONAL DYNAMICS OF ENVIRONMENTAL VARIABLES AND ZOOPLANKTON STRUCTURE IN WASTEWATER RESERVOIRS OF THE RIGHT-BANK SORBULAK CANAL SYSTEM

The annual increase in wastewater volumes necessitates comprehensive studies of water bodies subsidized by anthropogenic activities. An example of such reservoirs is Sorbulak and a system of shallow ponds into which pre-treated wastewater from Almaty and its environs is discharged. The published works provide fragmentary data on the hydrochemical and hydrobiological regimes of Sorbulak and ponds. There is no information on the seasonal dynamics of these variables. Our paper, aimed at studying the seasonal dynamics of pollutants and the zooplankton structure, partially fills this gap. Environmental and biological samples were taken in Sorbulak and two ponds by standard methods once a month, from April to September of 2021. The content of nutrients was high, and the heavy metals concentrations, except for copper, were low. The seasonal dynamics of pollutants in reservoirs were determined mainly by their entry from wastewater, with a more negligible contribution of natural factors. Zooplankton was represented by 80 species with an average abundance of 177.3-834.4 thousand ind./m3 and average biomass of 9.6-10.4 g/m3. The values ​​of the Shannon index were 1.98-2.12 bit/ind and 0.88-1.76 bit/mg, the average mass of an individual was 0.0140-0.0853 mg. The seasonal dynamics of zooplankton in the surveyed water bodies were different. The obtained results and comparison with the data of previous studies testified to the instability of the species composition of zooplankton communities both during one year and in individual years. Contradictions between the structure of zooplankton communities and the chemical variables of the studied reservoirs were identified. The results obtained to make a theoretical and practical contribution to understanding the formation of water quality in reservoirs with mixed pollution emphasize the need for further comprehensive studies of reservoirs of this type, and show specific differences between anthropogenic and natural successions of aquatic ecosystems.

Zooplankton Composition in Super-Intensive Whiteleg Shrimp, Litopenaeus vannamei (Boone, 1931) Culture Tanks

This study aimed to determine the zooplankton species composition in super-intensive whiteleg shrimp, Litopenaeus vannamei (Boone, 1931) tanks. The research was conducted from January to May 2021 in Bac Lieu City, Bac Lieu province, Vietnam. Eleven sampling times were divided into two periods, the nursery phase (six times) and the grow-out phase (five times) of shrimp culture. The results showed that water quality parameters fluctuated dramatically during the culture period, in which some nutrient concentrations tended to increase at the end of the shrimp culture period. Nine zooplankton species were recorded, of which five species belonged to Protozoa, three Rotifera species, and one Copepoda species. The number of zooplankton species did not differ significantly among the sampling periods. Protozoa had the highest species composition and density during most of the shrimp culture period. Copepoda was only identified in the nursery stage of shrimp culture. The species component of zooplankton had a close positive correlation with temperature, but their abundance did not have a significant relationship with water quality parameters because each species was affected by the different water quality parameters. Zoothamnium sp. had significantly positive correlations with total ammonia nitrogen (TAN), nitrate (NO3)-, total phosphorus (TP), and total nitrogen (TN) concentrations. The rotifer Brachionus plicatilis had a strong relationship with TP content, whereas Dartintinnus alderae had a strong relationship with alkalinity. Protozoa dominance in shrimp tanks could affect shrimp growth, decreasing the economic efficiency of shrimp farming. Therefore, the results of this study contribute to water quality and natural food management to improve shrimp productivity.