Annotation of the results obtained in 2022
1. The metagenomic composition of a consortium of algae and heterotrophic microorganisms was determined in floodplain water bodies contrasting in CO2 emission, experimental microcosms, and laboratory experiments on DOM destruction. Molecular genetic studies were carried out in the laboratory of ecology, genetics and environmental protection of Tomsk State University. The data were obtained using an oxford Nanopore MinION sequencer. Data analysis was performed in the Unipro UGENE environment using the Kraken 2 programs with the MiniKraken database, CLARK with the database of bacterial and viral sequences, and DIAMOND with the UniRef50 database. It was found that the biodiversity of Cyanobacteria in water bodies with low CO2 emission is significantly higher than in water bodies with high CO2 emission. In addition, the species composition of algae was determined by classical methods by specialists from the Omsk State Agrarian University. P.A. Stolypina N.N. Barsukova and O.P. Bazhenova. It has been established that most species, varieties and forms of algae and cyanoprokaryotes of lakes belong to widespread species - cosmopolitans (15 taxa or 88.0% of the total number of species for which geographical confinement is known), which are found in reservoirs and watercourses of all latitudes. The remaining representatives, due to their small number in the composition of phytoplankton, do not play a significant role. In relation to the active reaction of water, the phytoplankton of the surveyed lakes is dominated by indifferents (4 taxa with a rank below the genus, or 44%) and alkaliphiles (3 species and intraspecific taxa, or 33%, of the total number of species with a known relationship to water pH). The number of other indicator species with a known relationship to water pH is small. In relation to saprobity, the phytoplankton of lakes is dominated by beta-mesosaprobionts (10 taxa or 53% of the total number of species for which the relation to pollution is known), which are inhabitants of waters belonging to the class of satisfactory purity and indicate a low degree of water pollution. 2. Field manipulation experiments and laboratory incubation experiments were carried out. Field manipulation experiments on OM leaching from different types of flooded vegetation and its destruction were carried out during the growing season in microcosms located at the TSU “Kaibasovo. In laboratory experiments, elecampane (Inulasa licina L.), early sedge (Carex praecox) and canary grass (Phalaris), which were collected in the floodplain of the Ob River near the research station of the National Research Tomsk State University Kaibasovo, were used. The filtrate of these herbs was prepared by reacting the dry material with sterile water. Enrichment cultures of microalgae from the floodplain of the middle Ob and some cultivated bacterial species were used for experimental work. For all filtrates of the studied plants, a significant effect of the consortium of algae common in the Ob floodplain on the electrical conductivity was noted: it significantly decreased during the experiment. Water leachates from dominant floodplain plants can act as an important source of nutrients for the consortium. The rate of biodegradation decreases in the series sedge-canary grass-elecampane. Enrichment culture of algae, common in the lakes of the Ob floodplain, significantly changes the structure of the organic matter of plant filtrates. As a result of the vital activity of cultures of microorganisms in the elecampane filtrate, the electrical conductivity of the filtrate increases, and the culture of Mycobacterium pyllosphaerae strain WK4 works more intensively, and under the influence of Pseudomonas jessenii strain WK1, the changes are not so strong. Under the influence of bacterial cultures, changes in the composition of organic matter in plant filtrates are insignificant, however, the spectral coefficient E2/E3 in filtrates with bacterial cultures placed in them was always somewhat higher than in the control, which may be a sign of biodegradation of organic substances and a decrease in the molecular weight of organic filtrates under exposure to the studied bacterial strains. 3. The contribution of phytoplankton (autochthonous OM) and terrigenous OM (allochthonous OM, including the products of its transformation in the process of microbiological decomposition) to the formation of a pool of dissolved organic matter in floodplain water bodies contrasting in CO2 emission and, to the corresponding fluxes of FCO2 into the atmosphere (based on the Killing plot) was determined). The separation of CO2 and CH4 fluxes from different sources and the quantitative assessment of the contribution of each of them is based on the approach with plotting the dependence of the ratios of stable isotopes d13C-CO2 on their reciprocal concentrations (Keeling plot). For methane, a modified method was used - the dependence of the ratio of the product of the content of stable isotopes (d13C-CH4) and the concentration of methane on its concentration - the Miller-Tans method. Based on the known value of the isotopic composition of these gases in the atmosphere, one can judge the nature of the source, its contribution and/or mineralization processes that determine the isotopic composition of produced greenhouse gases. The value of d13C for a mixed source of CO2 in the emission flux from the surface of lakes in winter was -25.0 ± 5.2‰ (-20.1 - -32.9 ‰), in spring - -26.4 ± 8.0‰ ( -20.8 - -40.4 ‰) and -21.6 ± 1.8 ‰ (-19.5 - -23.5 ‰) in autumn. However, it should be noted that, with the exception of strongly depleted values in the lake. Home in winter (-32.9 ‰) and lake. The curve in spring (-40.4 ‰) released CO2 from the water surface is more enriched in the heavy isotope (-19.5 – -24.1 ‰) than the reference value of allochthonous organic matter (-27 ‰). This fact suggests the absorption of lighter CO2 in the processes occurring in the water column. However, these values are significantly lower than global atmospheric values, ranging from -9.5 ‰ in winter to -8.8 ‰ in summer. At the local level, in the atmosphere where air samples were taken, lower values were observed - -16 ‰ in winter and -12 ‰ in summer and autumn, which indicates a significant contribution of emission fluxes. The values of d13C-CH4 in the emission flux from the surface of the lakes varied from -49.6 to -74.7 ‰. The smallest spatial variation of the lake was demonstrated in winter (-61.5 - -63.8 ‰). In spring and autumn, the amplitude of variability of the isotopic composition of methane (d13C-CH4) was -49.6 - -67.6 ‰ and -58.3 - -74.5 ‰, respectively. Obviously, the relief of δ13C-CH4 in the mixed source of methane released from the water surface of lakes is of biogenic (methanogenic) origin. Based on the dependences obtained between the isotopic composition of CO2 and CH4, one can judge about the predominantly methyl-reducing metabolic pathway of methanogenesis in lakes. Only in the autumn period, the participation of hydrogenotrophic methanogens was revealed in Lakes Inkino and Domashnoye. In the global atmosphere, δ13C-CH4 varies within -47 - - 49‰, while at the local level, extremely low values were found in winter (-59 - -83‰) and -51 - -63‰ in spring and summer.4. 4. The balance model of floodplain water bodies has been refined, taking into account water bodies with a high content of organic matter and low emissions into the atmosphere, using round-the-clock measurements. The HecRAS program, the relief model https://global.jaxa.jp/ and the information https://gmvo.skniivh.ru/ were used to build a floodplain flood model. The calculations were performed using the Spatial Analyst Tools → map algebra → raster Calculator ArcGIS 10.0 module. The model was verified on the basis of satellite images that are freely available on the portal https://earthexplorer.usgs.gov/. In the course of the work, Landsat Collection 1, 2 images from Landsat 1-8 satellites were used. The model is applicable for calculating CO2 emissions during the flood period. 5. The typification of floodplain water bodies according to their suitability for fishing and fish breeding has been carried out. When typifying floodplain water bodies, the chemical composition, size, prevailing depths, intensity of overgrowth of higher aquatic vegetation, the state of the food supply of fish, their species composition, and other indicators are taken into account.

 

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Annotation of the results obtained in 2021
As a result of the project, a set of works was carried out that combined field monitoring studies, areal mapping of the flooded floodplain of the middle Ob, field manipulation experiments and laboratory incubation experiments. All studies were carried out using the approaches and methods previously tested on various water bodies in Siberia. The assessment of the processes of CO2 production in the water bodies of the floodplain with contrasting CO2 emissions was carried out. For these purposes, the CO2 / O2 ratio was used. The data obtained indicate a different amount of РСО2 fluxes from water bodies during the period of snow melting and during the flood. During the snowmelt period, the maximum flows are typical for the daytime. During this period, the water temperature does not exceed 8 degrees Celsius, aquatic vegetation and phytoplankton are not yet developed, the processes of photosynthesis and plant respiration are poorly developed, and the dynamics of РСО2 is controlled mainly by the processes of decomposition of organic matter. The period when the fluxes of РСО2 are associated with temperature is short and corresponds to the period of snow melting. During the flood period, when the water temperature in the floodplain reaches 10 degrees or more, aquatic vegetation, phytoplankton and flooded terrestrial vegetation in the daytime enrich the water with oxygen due to photosynthesis, and at night, in the dark phase of photosynthesis, they release CO2, which leads to an increase in РСО2 at night. As shown by the data of areal mapping of the flooded floodplain, the СО2 / О2 ratio varies over a wide range. For flooded, boggy areas: sogry, boggy shrubs, boggy birch-aspen forests, sedge and reed bogs have the highest CO2 / O2 value. The average values of the indicator for these landscape elements are 5214.8, the minimum values are 2961.8, and the maximum values are 7637.0 with a standard deviation of 2055.0. The forests and shrubs of the riverbed, not swampy part of the floodplain: poplars, willows, aspen forests, as well as cereal and sedge-cereal meadows, forb-cereal, cereal boggy meadows, sedge-cereal and widespread weeds are characterized by low CO2 / O2 values. Wed value, 205.5, Min., 22.3, Max., 675.0. Art. off, 147.8076. The lower the СО2 / О2 index, the higher the productivity of the water body. As shown by our studies in 2021, phytoplankton has a significant effect on the CO2 / O2 ratio. It was revealed that the dominant phytoplankton complex in the waters of the middle Ob is represented by Aphanocapsa holsatica, Aphanocapsa incerta, Aphanocapsa planctonica, Aphanocapsa delicatissima, Chroococcus minimus, Merismopedia minima, Snowella lacustris, Aulacoseira granulate. The Shannon index, calculated on the basis of abundance, varies in the range of 2.03-3.39, averaging 2.82 ± 0.07, which indicates the average complexity of the structure of the phytoplanktocenosis. The Simpson dominance index has low values, in the range of 0.05–0.36. The relationship between the abundance of phytoplankton and the amount of dissolved CO2 was established, as well as the relationship between the abundance of phytoplankton and the properties of surface waters of the middle Ob. For the waters of the middle reaches of the Ob River, the relationships between the content of dissolved CO2 and the content of organic and inorganic carbon, the structure of organic matter, the elemental composition of waters, as well as the abundance, biomass and composition of phytoplankton were revealed. Indicative signs of water bodies of the floodplain, characterized by reduced values of emission fluxes of carbon dioxide, have been established. UAV photography in the optical range made it possible to reveal the relationship between the CO2 flux and the relative optical density of the images obtained, that is, the intensity of dark tones in the image may indicate the amount of CO2 emission. The results of thermal imaging obtained with the UAV are comparable to the temperature measured in the field (r = 0.83). It should be noted that according to the data of our field measurements of the CO2 flux, the relationship between the flux and the temperature of the water body has not been established. However, according to thermal imaging data, the tendency for an increase in the CO2 flux with an increase in the temperature of water bodies can be traced and may be promising for further research. The most reliable indicator of an FCO2 flux is the CO2 / O2 ratio. The larger the logarithm of the CO2/O2 ratio, the greater the CO2 flux from water bodies into the atmosphere (r = 0.75). The CO2 flux into the atmosphere is described by the equation: РCO2 = [Ln (CO2 / O2) -4.6546] /2.5512. Relationships between the water balance and the dynamics of dissolved forms of organic matter and FCO2 fluxes into the atmosphere have been established. Based on the data of satellite images and hydrological modeling of the floodplain, a flood duration map was created, on the basis of which the area of the water surface was determined at characteristic levels. It was revealed that the highest FCO2 fluxes are characteristic of water bodies with the smallest depth. It was also found that the largest amount of dissolved РСО2 is observed during the summer dry season, in the fall the amount of dissolved СО2 is minimal. The relationships between the water balance and the dynamics of dissolved forms of organic matter and FCO2 fluxes into the atmosphere have been established, and the duration of different levels of flooding of the floodplain has been calculated. The maximum emission of FCO2 is typical for floods, at the water level in the river. Ob is more than 900 cm. Such levels are observed on average long-term observation for 21 days a year. On the basis of field manipulation experiments and laboratory incubation experiments, new data were obtained on the factors determining the FCO2 fluxes in floodplain waters. The specificity of the rate of organic matter leaching and FCO2 flows has been established. The FCO2 fluxes increase in the sequence bonfire-bluegrass-canary grass-northern lover-tansy-basil. On average, during the destruction of plant litter, cereals emit less CO2 than representatives of large grasses. The highest FCO2 emission was noted in the first days of the experiment for all studied plants. Starting from the third day, there has been a sharp decline in CO2 emission. When the litter of most plant species is leached, an increase in temperature leads to an increase in pCO2, the value of the relationship “water temperature - pCO2” increases in the series willow-birch-reedhead-reed-aspen. The qualitative characteristics of the dissolved organic matter in the studied water bodies have been established. A significant range of variations in the isotopic composition of water in floodplain water bodies and watercourses was revealed. According to the results of the work, it was found that in atmospheric precipitation the average value of d (18_16) is -6.33, the minimum is -17.18, the maximum is -4.11 with a standard deviation of 4.89, the average value of d (D_H) is -64.12, the minimum is -132.22, the maximum is -59.06 at the standard deviation is 24.36. It should be noted that the isotopic composition of atmospheric precipitation in the middle Ob floodplain is heavier than in the watershed area. Differences in δ18O, ‰ can reach 20 ‰. When studying the dynamics of the isotopic composition of precipitation, it was revealed that the lowest concentrations of deuterium and oxygen-18 are characteristic for winter precipitation, and the highest for summer. In groundwater, the average value of d (18_16) is -16.15, the minimum is -15.33, the maximum is -14.98 with a standard deviation of 0.456, the average value of d (D_H) is -117.27, the minimum is -122.21, and the maximum is -116.32 with a standard deviation of 1.99. In floodplain lakes, the average d (18_16) is -13.01, the minimum is -18.17, the maximum is -9.81 with a standard deviation of 2.998, the average d (D_H) is -99.29, the minimum is -125.43, and the maximum is -80.07 with a standard deviation of 15.242. Differentiation of the water composition of the floodplain waters according to the seasons of the year was noted, the waters in the winter low-water period are characterized by a heavier isotopic composition than during the flood period; in the summer period, an increase in the isotopic composition of the waters was also noted. In general, the studies carried out on the territory of the middle Ob floodplain made it possible for the first time to obtain unique materials that explain the reasons for the discrepancy between the values of dissolved РСО2 and FCO2 fluxes in water bodies. Analysis of the obtained materials suggests that the processes found in the floodplain are characteristic not only of floodplain ecosystems.

 

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