MAGNETIC FLUCTUATIONS AFFECT CIRCADIAN PATTERNS OF LOCOMOTOR ACTIVITY IN ZEBRAFISH (PRELIMINARY DATA)

The locomotor activity of zebrafish (Danio rerio) has a pronounced, well-studied circadian rhythm. Under constant illumination, the period of free-running locomotor activity in this species usually becomes less than 24 hours. To evaluate the entraining capabilities of slow magnetic variations, zebrafish locomotor activity was evaluated at constant illumination and fluctuating magnetic field with a period of 26.8 hours. Lomb-Scargle periodogram revealed significant free-running rhythms of locomotor activity and related behavioral endpoints with a period close to 27 hours. Obtained results reveal the potential of slow magnetic fluctuations for entrainment of the circadian rhythms in zebrafish. The putative mechanisms responsible for the entrainment are discussed, including the possible role of cryptochromes.

NEW RECORDS OF HALIPLIDAE, DYTISCIDAE, HYDROPHILIDAE AND SCIRTIDAE (COLEOPTERA) FROM LIPETSK OBLAST

Six species of aquatic Coleoptera are recorded from the Lipetsk Oblast for the first time: Haliplus flavicollis Sturm, 1834 (Haliplidae); Agabus paludosus (Fabricius, 1801), Ilybius neglectus (Erichson, 1837), I. wasastjernae (C.R. Sahlberg, 1824), Hydroporus incognitus Sharp, 1869, Hygrotus versicolor (Schaller, 1783) (Dytiscidae), Hydrobius rottenbergii Gerhardt, 1872 (Hydrophilidae). Two species (Ilybius wasastjernae, Hydroporus incognitus), are recorded at the southernmost limits of the known range in the European part of Russia. The record of Contacyphon laevipennis (Tournier, 1868) is confirmed by provided material. For three species, original photographs of the habitus and male genitalia are provided, and for two ones – of the habitat.

SPATIAL STRUCTURE OF VEGETATION OF LARGE LAKES OF THE ONEGA PENINSULA (ON THE EXAMPLE OF MURAKANSKOE AND BOLSHOE VYGOZERO LAKE)

Studying the vegetation of freshwater lakes remains a topical subject in the national parks of the Arkhangelsk Region. It is in particular important for the Onega Pomorie National Park, which is located along the coasts of the Onega and Dvinskoy bays (of the White Sea) in the northern part of the Onega Peninsula. This article examines the spatial structure of aquatic and coastal-aquatic vegetation of Murakanskoye and Bolshoye Vygozero – two large lakes of the Onega Peninsula. The spatial structure is presented in the form of ecological series of associations of plant communities. A comparative characteristic of the lakes’ vegetation is given in the discussion of the article. The littoral zone is poorly developed in both lakes mentioned above. It depends on the openness of the water areas to the winds from the north. It is indicated that the species composition and vegetation structure of the Bolshoye Vygozero Lake mostly depends on water transparency and high acidity; these factors determine the development of the Phragmitetum australis fontinaliosum dalecarlicae, Phragmitetum australis caricosum aquatilis, Caricetum aquatilis associations. In the Murakanskoe Lake, high water transparency and slightly alkaline pH values contribute to the development of communities of pondweeds – such as Potamogeton alpinus, Potamogeton praelongus, and communities of the Lobelietum dortmannae isoëtosum echinosporae association.

FORMATION OF ZOOPLANKTON IN THE BOGUCHANY RESERVOIR DURING ITS FILLING

For the first time, we present the materials of the spatial distribution of qualitative and quantitative indicators of zooplankton in the first year of top water level (TWL) in the Boguchany Reservoir. We indicate the dynamics of the formation of the zooplankton community in the Upper section of the reservoir during its filling (from 2013 to 2015). The Irkutsk, Bratsk, and Ust-Ilimsk reservoirs influence the composition and structure of zooplankton in the Boguchany Reservoir that closes the cascade of the Angara HPPs, and there is a great similarity of the crustacean and rotifer fauna with the upstream artificial reservoirs. During the study period (from 2013 to 2017), the plankton fauna included 84 species from 49 genera and 23 families. The horizontal distribution of quantitative indicators throughout the water area of the reservoir had a mosaic pattern. The relative and absolute proportion of rotifers in the composition of zooplankton decreased from the Upper section to the Lower one, and the dominance of crustaceans was opposite. Due to this, the maximum number (129±97.8 thou ind./m3) of zooplankton was recorded in the Upper section, and the biomass (2080±676 mg/m3) – in the Lower section. The obtained unique data on the composition, structure and quantitative development of zooplankton in the Boguchany Reservoir during its formation and filling are important for further monitoring of its state, including the assessment of the feeding of planktonophagous fish and juvenilefish.

ZOOINDICATION OF WATER BODIES WITHIN PETROLEUM INDUSTRIAL TERRITORIES OF THE BOLSHEZEMELSKAYA TUNDRA

Intensive development of the oil and gas industry and accidents on oil pipelines become the reason of the environmental tension in the Pechora River basin (Nenets Autonomous District). Data on changes in water quality in five lakes and a small watercourse in the territory of oil fields of the Bolshezemelskaya tundra are presented. The bioindication indices (Berger-Parker (D), Shannon biodiversity (H '), Woodiwiss (W), Pantle-Buck (S), Balushkina (Kch)) were applied. The assessment of the state of water bodies in the Kolva River Basin (large lakes - Kolvaty and Nercheity), in the Laya River Basin (shallow lakes - Krugloye, Bezymyannoe 1, Bezymyannoe 2, stream) was done. The 28 samples of zoobenthos was processed by the standard method in July 2012 and 2019. A low diversity of benthic invertebrates was revealed for 5–20 taxa of the rank of families and orders. During the considered period, the changes have occurred in the structure and composition of the zoobenthos of water bodies. In 2019, the species diversity decreased in Kolvaty Lake (H'<2). There are no species of the crustacean complex (Monoporeia affinis, Mesocyclops leuckarti, Heterocope borealis) and larvae of Trichoptera. Only Sphaeriidae and Chironomidae with a predominance of Psectrocladius psilopterus (D = 55%) were recorded. The species diversity in Nercheity Lake increased (H'> 2) with a change in the dominant taxa: the larvae of the chironomids Ablabesmyia monilis (D = 44%) were found in 2012, the lower crustaceans (D = 47–51%) - in 2019. However, according to the totality of hydrobiological indicators, the quality of water in the lakes of the Kolva River Basin in 2019 compared to 2012 did not change significantly. The quality of water in the Krugloye and Bezymyannoe 1, Bezymyannoe 2 lakes (the Laya River Basin) has improved that is confirmed by a significant increase of species diversity. The most characteristic groups of benthic communities in these lakes are lower crustaceans (Cladocera, Copepoda, Ostracoda) and Chironomidae. The indicators of clean waters are o-β-mesosaprobic species Cladocera, Copepoda Heterocope appendiculata, Heterocope borealis (in the oligotrophic lakes), caddisfly Limnephilus stigma (in the Krugloe Lake), rotifer Polyarthra euryptera (in the Bezymyannoe 2 Lake), mayfly larvae Centroptilum luteolum. More resistant to organic pollution Copepoda began to prevail in abundance and diversity in Bezymyannoe 1 and Bezymyannoe 2 lakes, with a decrease in the taxonomic composition of Cladocera, which indicates the eutrophication of these water bodies. In most lakes, the water corresponds to the III quality class ("moderate pollution"), but in the Kolvaty lake and in the Bezymyanny stream (the Laya River basin) was recorded the biogenic pollution. Totally, insignificant taxonomic changes in zoobenthos structure took place in the lakes and the state of water bodies of the surveyed tundra remains relatively stable.

TO THE QUESTION OF MORPHOLOGY OF MYRICA GALE L. GENERATIVE PLANTS

The distribution of Myrica gale on the coast of the Gulf of Finland is confined to regularly flooded coastal habitats, characterized by milder environmental conditions compared to the uplands and under the residual influence of the Gulf Stream. In Russia, M. gale is located on the northeastern border of the range. The study of the features of the species that contribute to the dispersal in the northern direction, and the properties of the environment that prevent such dispersal, is always of great interest. Growth in colder conditions in comparison with other members of the family, mainly inhabitants of the tropical and subtropical areas, affected the formation of such adaptations as deciduousness, changes in the structure of flowers and bark, as well as the presence of a large number of protective leaf organs. Their quantitative and qualitative analysis made it possible to establish the presence of 4 lignified parchment-like scales that do not fall completely and 6 membranous with partially lignified tops scales that stretch out while unfolding. An attempt was made for the first time to analyze the spatial structure of the shoots of the species. A sympodial growth of shoots and the phenomenon of acrotonia, as well as a spiral formation of lateral shoots, were established. In the structure of the mature generative branch of M. gale there were identified 3 types of shoots: long growth, medium and short, and also their leaf series were analyzed. Leaf series of short and medium shoots are characterized by significant asymmetry compared to leaf series of long shoots and are incomplete. The curves were constructed on the basis of such characteristics of leaf organs as their total number, length along the central vein, including the petioles (if they are presented), and internode lengths. A large number of rudiments of leaf organs determines the gradual formation of the buds, and the imperfection of the structure of the scales reflects the weak protective ability of these organs. Both features indicate the deep ancientness of the species and the difficulty in adapting to cold environmental conditions. Mature generative branches of M. gale are similar in habit to small trees, which is of particular interest in the context of modeling possible directions of adaptation during the spread of species of subtropical origin to more northern regions.

POLYPLOIDY OF NORTH EAST ASIA AQUATIC AND SEMIAQUATIC VASCULAR PLANTS

The chromosome numbers of aquatic and semiaquatic vascular plants growing in extreme North-East Asia, east of the Lena River, were analyzed. We have reviewed the information about the karyological peculiarity of the aquatic flora based on published data, including our own definitions. The karyological data are considered depending on the taxonomic position, distribution and ecological characteristics of the species. The chromosome numbers are known for 119 out of 123 species. There is no data on Zannichellia komarovii, Eleocharis termale, Stuckenia subretusa and Potamogeton sibiricus. In the aquatic flora of North-East Asia, the proportion of polyploids is higher (79%) than that reported for the entire Beringian flora (69%). We analyzed species for the presence of polyploidy depending on the type of area. Analysis by latitudinal groups revealed that all Arctic and hypoarctic species of aquatic plants are polyploids. The minimum proportion of polyploids is observed among arctoboreal species. Analysis by longitudinal groups revealed that the lowest proportion of polyploids was noted among species found only in Eurasia and absent in North America (61%), and it was the highest among pluriregional species (96%). The species of the families Cyperaceae, Lemnaceae, Ranunculaceae and Poaceae are characterized by a high level of variability in the number of chromosomes. The greatest variety of chromosome numbers is observed in the polymorphic species Caltha palustris s. l., Agrostis stolonifera, Dupontia fisheri s. l., Phragmites australis, in all species of the genus Eleocharis, and in Nymphaea tetragona, Acorus calamus, Calla palustris. The isolated cases of a high level of ploidy were found in the extreme northeast, at the northern borders of ranges, in 3 species - Hippuris vulgaris, Arctophila fulva and Beckmannia syzigachne. Only diploids are known in the families Equisetaceae, Typhaceae, Zosteraceae from the flora of North East Asia. We revealed the existence of several chromosomal races in Ranunculus gmelinii and Caltha palustris (Ranunculaceae) in the Magadan region; the distribution of chromosomal races is partly related to geographic location and partly to plant habitats. Rare karyotypes in these species are observed in aquatic forms with mainly vegetative reproduction, growing in non-freezing watercourses.

THE EFFECT OF CLIMATE CHANGE ON THE THERMAL REGIME IN THE RYBINSK RESERVOIR

According to the data of the Rybinsk Hydrometeorological Observatory (HMO) and archival data of the Laboratory of Hydrology, Papanin Institute for Biology of Inland Waters, Russian Academy of Sciences, the seasonal variability of the main climate parameters, air temperature (Rybinsk HMO) and water temperature in the Rybinsk Reservoir have been studied at the modern stage of global warming (2001–2019). Over the period of 1976–2019, the rate of an increase in the average annual air temperature was 0.50°C /10 years in the littoral zone of the Rybinsk Reservoir. Changes in the timing of the onset and end of the climatic seasons of the year and an increase in their duration have been determined. It is found that during the modern period the average surface air temperature was higher than the climatic norm in all months of the year (1960–1990). During the growing season (conventionally May–October), its maximum increase was recorded in July, 1.5°C, May and September, 1.2°C. It is shown during the modern period of intensive global warming the average decadal water temperature in the spring, summer, and autumn seasons increased compared to the norm. The maximum positive anomalies were recorded in the second-third decade of May, 2.8–2.3°C and July, 2.0°C. According to observations at the standard stations, significant differences were recorded in water mass heating: in July in anomalously warm summer of 2010 the average water temperature was 27°C in the surface layer and 18.5°C in the near bottom layer; in the cold summer of 2017, the temperature was 18.5 and 16.0°C, respectively. The monitoring data on the water temperature in the reservoir indicate an increase in the number of years with anomalous thermal conditions as a result of climate change. The earlier temperature stratification of water masses (the end of May) and decrease in the difference in the temperature between the surface and near-bottom water layers have been observed.

MACROBENTOS OF VOZHE AND LACHA LAKES

The taxonomic composition of macrozoobenthos in lakes Vozhe and Lacha and in some sections in the Svid and Onega rivers is presented. The dominant complex in the lakes was formed by representatives of chironomids. Two species of oligochaetes and a gastropod were dominant in the rivers. The index of faunal similarity of macrobenthos between the lakes was rather high and amounted to 70%, while the similarity between the river and lake benthos was less than 30%. In the lakes, only two taxonomic groups were recorded, oligochaetes and chironomids that formed the basis of the benthos abundance: 87–93% of the average abundance and 92–95% of the average biomass in the lake. Oligochaetes and mollusks played a significant role in the river communities; in total, they formed 76% of the total abundance and 98% of the biomass. The trophic structure of macrobenthos in the lakes was almost similar, except the appearance of the group of phytodetritophages- filter-feeders in Lake Lacha. Detritophages-swallowers dominated in the river communities. In the previous studies of the lakes, the species richness of benthos both in Lake Vozhe and Lake Lacha was much higher. A decrease in the number of taxonomic groups and decrease in their abundance were observed in Lake Vozhe. At the same time, the role of chironomids in the formation of benthos in the lake was still significant. In general, changes in the taxonomic structure and abundance of benthos in lakes Vozhe and Lacha may be caused by a complex effect of environmental factors and long-term and intra-annual dynamics of dominant (cenose-forming) representatives of the main groups of macrobenthos. The simplification of the structure of the bottom communities, the inclusion of species with wide ecological spectra, the predominance of eurybionts among the dominants, may indicate pollution, eutrophication, and contamination of water bodies. According to the indicator species both lakes may be regarded as mesosaprobic water bodies.

STRUCTURE AND DYNAMICS OF PHYTOPLANKTON OF LARGE SHALLOW-WATER OVERGROUND LAKES (VOZHE AND LACHA, VOLOGDA AND ARKHANGELSK REGIONS, RUSSIA)

A comparative analysis of the diversity, abundance, biomass, composition of dominant species, size characteristics of phytoplankton and saprobity of the waters of shallow large overgrown lakes Vozhe, Lacha, as well as the rivers Svid and Onega in June 2015 is presented. The data obtained are compared with the results of previous studies in the 1970s years. It was found that in the 2000s, there was a significant increase in the number of phytoplankton in lakes and a change in the composition of dominant species. Non-heterocyst cyanoprokaryotes (Aphanocapsa holsatica, Planktolyngbya limnetica) began to dominate in phytoplankton, which is associated with increase of ammonium concentration. The average biomass of phytoplankton in lakes (2.6 g/m3) has remained practically unchanged since the 1970s and was typical for mesotrophic type waters. In the Lacha Lake characterized by lower transparency, high degree of overgrowth, salinity and saprobity of waters, phytoplankton was distinguished by lower floristic diversity, higher abundance, dominance level, and the smallest cell sizes.