A dynamic mass-balance model has been presented for the biotic energy flux in the ecosystem of the Boguchanskoe Reservoir (Angara River, Irkutsk oblast). It has been revealed that this model is controlled by the small number of input parameters and is intended for prediction of the biomass and annual production of primary producers, reducers, and consumers from various orders, including fish. The model algorithm has been described.

Data on the species composition and development dynamics of phytoplankton complexes in the newly constructed Bureya Reservoir are given. Reservoir phytoplankton has been found to contain 119 alga species (121 taxa, considering the varieties) from nine divisions. Alga species composition, their abundance and biomass, and the saprobic characteristic of species were used to evaluate the environmental state of the reservoir. Reservoir water was classified as “nearly pure” and “weakly polluted”, belonging to the II–III purity class. The low values of phytoplankton abundance and biomass allow the Bureya Reservoir to be classified as an oligotrophic water body.

Приведены данные о видовом составе и динамике развития фитопланктонных комплексов вновь созданного Бурейского водохранилища. В фитопланктоне водохранилища обнаружено 119 видов водорослей (учитывая разновидности – 121 таксон) из девяти отделов. По видовому составу водорослей, показателям их численности и биомассы, сапробной характеристике видов оценено экологическое состояние водоема. Воды водохранилища охарактеризованы как “практически чистые” и “слабо загрязненные”, II–III класса чистоты. Низкие значения численности и биомассы фитопланктона характеризуют Бурейское водохранилище как олиготрофный водоем.

The grain size distribution and fraction composition of bottom sediments (BS) in the Amur River are studied. The total composition of sediments, their clay subfractions—water-peptizable (WPC) and aggregated (AC) clays—and residue after clay elutriation were analyzed. It has been established that contents of Fe, Mn, Zn, and Cu in the clay subfractions are 2–4 times higher than in common bottom sediments and their residue left after the extraction of clay subfractions, confirming a significant role of clay minerals in the accumulation of elements mentioned above. It is shown that diatom algae participate in the accumulation and transport of Fe, Mn, Zn, and Cu in the river water-suspended matter-bottom sediments (clay minerals) system. It has been established that high Zr concentrations in bottom sediments are related to the presence of zircon therein.

Study of the composition, structure and morphology of microaggregates less than 1 mm in size in soils of one of the Behr hillocks revealed a high share of the clay-salt segregations (microaggregates and cutans). It was established that the segregation type depends on the mud content in soil, while the packing of particles, as well as the size and morphology of microaggregates, depend on the content and properties of salts. The clay component in the microaggregates is mainly represented by smectite. Carbonate (calcitic, dolomitic, and ferruginous) clay-salt microaggregates were found in all horizons of the studied soils, except for horizon Ap on the subhillock plain in the former rice paddy. Gypsum clay-salt microaggregates were identified in the salic horizon Bs of soils. The microaggregates in solonchaks were formed with the contribution of Na-Mg-Ca chlorides and sulfates. The formation of clay-salt aggregates promoted high microstructuring of soils and stability of the Behr hillocks under arid climatic conditions.

Particle-size and microaggregate-size distributions and the morphology of aggregates <1 mm have been studied in soils of the Baer mounds. It is shown that the soil aggregates contain specific clayey-salt microaggregates and coatings. The type of the clayey-salt pedofeatures (microaggregates and/or coatings) depends on the clay content in the soils, and the size and shape of the clayey-salt microaggregates depends on the concentration and chemistry of salts participating in their formation. The clayey material of the micro-aggregates is mainly represented by smectitic minerals. Calcareous (calcitic, dolomitic, and iron-bearing) clayey-salt microaggregates have been found in all the horizons of investigated soils, except for the Ap horizon of the soil of the former rice paddy in the hollow between the Baer mounds. Clayey-salt microaggregates with simultaneous participation of several different salts (chlorides and sulfates of Na, Mg, and Ca) have been detected in the solonchakous soil at the foot of the Baer mound. For the first time, quasicrystalline formations—pentagonal NaCl crystals of up to 3 μm in size with participation of phyllosilicates and sulfates of Na and Mg—have been described under native conditions in the B2 horizon of the solonchak. It is argued that the formation of clayey-salt aggregates contributes to the good microaggregation of the soils and to the stability of the Baer mounds under conditions of the arid climate.

Water chemistry, chlorophyll “a” concentration in phytoplankton and periphyton, and the structure of bacterioplankton communities of the Zeya River and its tributaries are assessed in the construction zone of the Nizhne-Zeiskaya HPP. The results of multidisciplinary studies demonstrate the effect of natural and anthropogenic factors on the formation of water quality in the examined part of the Zeya River.

A mass balance model is applied to assess the biotic energy flux in ecosystems of the operating Zeiskoe and Bureiskoe reservoirs and the anticipated Lower Zeiskoe and Lower Bureiskoe Reservoirs. A forecast of the mean annual biomass and annual production of phytoplankton, macrophytes, epiphytes, and phytobenthos (primary producers), bacterioplankton, bacteriobenthos (decomposers), “peaceful” and predatory zooplankton, zoobenthos, plankton-feeding, benthos-feeding, and predatory fish (consumers).

The mineralogy and chemistry of the fine fractions separated from the bottom sediments (aquasols) in the Amur River were studied in the subfractions of the fractional peptization differing in the binding strength between the water-peptized and aggregated components. Detritus of quartz, field spars, and strongly degraded layered silicates mainly passes into the water-peptized state. Interstratified layered silicates with different combinations of chlorite and mica layers prevail in the aggregate subfraction. The distribution of the microelements in the bottom sediments, the water-peptized and aggregated clays, and the residues after their separation was determined. The content of iron, manganese, zinc, and copper in the clay subfractions was higher than in the bottom sediments and in the residue after the separation of the clay subfractions by 2–4 times, which confirmed the functional significance of the clay minerals. The presence of diatomic algae in the components of the bottom sediments was revealed by scanning electron microscopy. The contribution of the diatoms to the accumulation of iron, manganese, zinc, and copper was shown.