No 2 (2023)

This scanning electron microscopy study of phytoplankton from the Nizhny-Tagil Reservoir has revealed a small-sized genus and species of diatoms, Brevilinea kevei, new to the flora of Russia. Small differences from the original description in the minimum values of the valve width and a higher variability range of the number of striae in 10 µm allow the authors to refine the species description. New data on the location make it possible to clarify the ecology and geographical range of Brevilinea kevei.

A description of a new species, the coastal cattail Typha litoralis, collected in the coastal areas of the Sea of Okhotsk is given. Habitually, the plants differ from T. latifolia and T. laxmannii, has been reported Sakhalin Island and the Kuril Islands. The new species is morphologically closest to T. krasnovae Doweld.

A comparative light- and electron-microscopic study of the tegument of a formed cystacanth and a mature acanthocephalan Acanthocephalus tenuirostris (Achmerov et Dombrowskaja – Achmerova, 1941) was carried out. It was shown that, in addition to morphometric differences, the tegument of cystacanth differs from that of the adult acanthocephalan by terminal expansions of invaginates of the outer tegument membrane, presumably due to the secretion of glycocalyx material. In the tegument of an adult acanthocephalan, a process of detachment from the nuclei of small fragments was found, which may be an analogue of the well-known process of nuclear fragmentation that occurs at the early stages of postembryonic development. It has been shown that in many cases tegument lacunae are not completely limited by dense formations resembling fibrils on sections.

Using the electron microscopy method, the species identity of the diatom Cerataulina pelagica, isolated in pure culture from the coastal waters of the Black Sea in September 2021, was confirmed. The range of optimal temperature values for the development of this species was identified. The impact of light and biogenic substances on its main structural and functional characteristics has been studied. Acclimation of C. pelagica to various light intensities was carried out by changing the efficiency of photosystem II, the C/Chl a ratio, and the specific growth rate. The morphometric parameters of cells (volume, surface area, and specific surface area) changed slightly in the studied light range – 8.5–510 μE/(m² · s). The transfer of C. pelagica cells, which have the maximum intracellular pool of nutrients, to seawater depleted in nutrients caused a rapid increase in the C/Chl a ratio, as well as a decrease in the efficiency of photosystem II, the relative rate of electron transport, and the specific growth rate. A high degree of toxicity with copper ion in low concentrations in relation to the studied species was shown.

The vegetation of 5 lakes and 40 springs of Western Kazakhstan was considered. The relationship between the degree of mineralization and the composition of vegetation was revealed. The anthropogenic factor influences the vegetation of lakes and springs by increasing the number of ruderal and halophytic plants. With a decrease in the water level in lakes, processes of active salinization of the water area and the coastal part are observed, an indicator of which is vegetation. In the territories adjacent to the springs, the dominant role of mesotrophs and megatrophs in the structure of the flora of the springs was noted, which indicates the predominance of soils and soils with sufficient and excessive content of nutrients in the studied area. The flora of the region’s springs has a low degree of similarity. Cluster analysis of the flora of spring tracts confirmed the heterogeneity of quantitative species composition.

The trophic status of a reservoir in the southern subtropical region of China was evaluated by non-biological environmental factors from 2011 to 2020. The relationship between the community structure of planktonic rotifers and eutrophication was examined based on the species composition, dominant species, standing crop, and biodiversity index of the planktonic rotifers in the surface water. The results showed that the reservoir was continually slightly eutrophic. The dominant species of planktonic rotifers were mesosaprobic species such as Polyarthra trigla and Brachionus angularis. The overall abundance fluctuated between 438 and 1360 ind./L; biomass fluctuated between 520 and 1613 μg/L, and the biodiversity index fluctuated between 1.27 and 2.43. Redundancy analysis showed that chlorophyll a content, water transparency, total phosphorus, and water temperature had significant impacts on the abundance of planktonic rotifers. The results demonstrate a close relationship between the community structure of planktonic rotifers and eutrophication. In other words, eutrophication was the main cause of the changes in the community structure of planktonic rotifers in surface water.

The species list and distribution of crustacean of a nearshore zone of the Valaam Island (Ladoga Lake) have been investigated by sampler-syringe, dredge and video records. On the depth 1–25 m the five species of crustacean: Asellus aquaticus (Linnaeus, 1758), Monoporeia affinis (Lindström, 1855), Pallaseopsis quadrispinosa (G.O. Sars, 1867), Gmelinoides fasciatus (Stebbing, 1899), Mysis relicta Lovén, 1862 were described. For the first time the vertical distribution of naturalized Baikal amphipods G. fasciatus were inventoried and their features of joint residence with local species were characterized. The distribution of the alien species reliably connected with wave intensity, types of grounds and depth range. The most numerous local species P. quadrispinosa distribution affects by depth range. The types of grounds do not influence on the quantity of all indigenous crustacean in the nearshore zone. In all condition the local species successfully compete with G. fasciatus. All these species inhabit of littoral have higher resistance for wave action as compared with non-indigenous species. It guarantees existence of refuges which can safe diversity of the indigenous species. The obtained data on the spatial distribution of crustaceans make possible to characterize the benthic communities of the little-studied parts of the littoral and sublittoral and, as a result, the food base of bentophagous fishes.

The results of studies of the current state of zoobenthic communities of lakes Sukkozero and Gimolskoye, located in the western part of the Republic of Karelia (Muezersky district), are presented. Under conditions of high color and low mineralization of waters, communities are formed with a predominance of chironomid larvae, caddisflies, mayflies, and oligochaetes. Biomass and abundance indicators in 2017–2018 were within 0.41–0.75 g/m² and 315–685 ind./m² in the lake Sukkozero and 0.41–0.93 g/m² and 220–346 ind./m² in the lake Gimolskoye. The highest values of abundance and biomass were noted in biotopes of silty soils (overgrown littoral and profundal), the lowest values in the biotope of sandy littoral. According to the level of quantitative development of zoobenthos, Sukkozero belongs to oligotrophic water bodies; Gimolskoye – mesotrophic. The experience of using common biotic indices for assessing the ecological quality of waters (Mayer, oligochaete, saprobity, chironomid) indicates that low mineralization and high humus content can affect their performance and distort the assessment of real organic pollution.

The problem of salt water intrusion into the Mekong Delta is a research topic involving various branches of science. Among the causes of this phenomenon are global sea level rise and regulation of the natural river discharge due to hydropower dam construction. The scale of the delta and its water dynamics complicate instrument-based observations. Meanwhile, communities of living organisms can serve as indicators of environmental heterogeneity. This study aimed to analyze the spatial variability of fish assemblage organisation in the Mekong Delta for use as an indicator of salt water intrusion. The composition of fish assemblages in different parts of the delta were determined by midwater trawl catches during January and April 2021. A total of ~15 thousand individual fish from 74 trawl hauls were captured and analyzed. The null hypothesis was that the fish assemblages in the Mekong Delta are represented by three taxonomic complexes that are localized in the upper course (freshwater), the lower course (brackish) and the middle course (zone of the contact of the fresh and brackish waters) of the delta. The taxonomic composition of the freshwater complex is the most poor and is represented by 9 families. Meanwhile, marginal (the contact zone) and brackish complexes include 26 and 23 families, respectively. Specimens of families Cobitidae, Eleotridae, Plotosidae and Siluridae that are only found in the zone of contact of fresh and brackish waters could be considered as indicator species of its position. The actual boundaries of the brackish and freshwater complexes were determined and the distance from them to the marine delta edge equals 34 and 78 km, respectively. Assessment of the salinity values that correspond to the complex boundaries is a task for future investigation. The position of the boundaries of freshwater and brackish fish taxonomic complexes has a biological basis and could be used as an indicator of salt water intrusion into the Mekong Delta.

In the last 30 years, the natural life in the inland waters of the Turkish Thrace has been threatened by water pollution, deterioration of river continuity, the presence of non-native or invasive fish, and drought. The aim of the present study was to determine the recent status of fish fauna in the river systems lying at the Turkish Thrace, under these threats. The field surveys were conducted in a total of 164 sampling sites in both Marmara and Meriç-Ergene water basins between July and August 2017. A total of 36 freshwater fish species representing 12 families (Acheilognathidae, Atherinidae, Centrarchidae, Cobitidae, Cyprinidae, Esocidae, Gobiidae, Gobionidae, Leuciscidae, Percidae, Poeciliidae, and Salmonidae) were determined. The most widespread species of the region was Cobitis strumicae and it was followed by Rhodeus amarus and Squalius orpheus. This study provides first detailed information on the distribution of the species of Barbus tauricus, Chondrostoma vardarense, Cobitis strumicae, Squalius orpheus, and Vimba melanops.

The ecological analysis of the helminth fauna of the Dice snake Natrix tessellata from different habitats of the Astrakhan region in 2004, 2005, 2008 was carried out. The helminth community of the reptile includes 21 species of parasitic worms: 11 trematodes, 1 cestode, 8 nematodes and 1 acanthocephalan. Of these, 11 species are found in all the studied localities and form the basis of N. tessellata helminth fauna. Dominant and subdominant helminth species are found in snakes in all habitats as a result of the implementation of its main trophic relationships. Comparison of the helminth composition from different study sites showed a relatively high degree of similarity. Differences in the helminth fauna of the dice snake from different habitats are insignificant and relate to rare and accidental parasite species. Significant differences in the infection level of snakes with certain species of helminths were revealed. Most of the helminth species that parasitize the water snake have a complex life cycle. The infection of reptiles by them is determined to a large extent by biotic factors: fauna and the number of invertebrates (intermediate hosts of helminths) and vertebrates (paratenic and final hosts) in biocenosis.