This paper presents the results of a comprehensive monitoring study on the zooplankton community of the Ivankovo Reservoir, the largest source of drinking water supply for Moscow and one of the oldest water bodies in the Upper Volga basin. Field investigations were conducted during the growing season of 2025 at 17 sampling stations covering all four reaches of the reservoir. A total of 55 taxa were recorded, including 30 rotifers, 20 cladocerans, and 5 copepods. The mean zooplankton biomass amounted to 0.395 g/m³, which, according to the classification of M. L. Pidgayko, characterizes the reservoir as "very low-food" water body. A comparative analysis with previous data revealed a 1.5-fold decline in biomass relative to the 2013–2017 period (from 0.619 to 0.395 g/m³) and a 2.1-fold decline relative to 2021 (from 0.847 to 0.395 g/m³). Whereas in 2013–2017 the Ivankovo Reservoir ranked among the most productive water bodies in the Volga–Kama cascade, second only to the Uglich Reservoir, by 2025 its forage base had dropped to levels previously typical of the Rybinsk and Kuibyshev reservoirs. Spatial heterogeneity persisted, with maximum biomass recorded in the Middle Volga reach (0.631 g/m³) and minimum in the Upper Volga reach (0.063 g/m³). Biodiversity indices (Shannon, Simpson, and Pielou) regularly increased from spring to summer and decreased in autumn, except at station 30a, where summer was marked by strong dominance of Brachionus angularis (85 %) and autumn by maximum evenness. The obtained findings indicate a substantial decline in the reservoir's forage base over the past decade, necessitating identification of the underlying causes (winterkill phenomena, changes in trophic status, climatic factors) and a revision of the existing fishery management strategy.

The relevance of the study is due to the potential for the industrial use of a significant amount of by-product raw material – fish skin – for the production of fish collagen hydrate, which is used as a texture stabilizer in chocolate mousses. The aim of the study is to evaluate the effect of fish collagen and gelatin additives, used as stabilizers, on the textural and organoleptic properties of the resulting chocolate mousses. The nutritional value of the studied fish stabilizing additives (collagen and gelatin), as well as beef gelatin, is demonstrated. The density of chocolate mousse samples has been determined: 0,849 g/cm³ for those with beef gelatin, 0,827 g/cm³ for those with fish collagen, and 0,756 g/cm³ for those with fish gelatin. The texture parameters for chilled and defrosted mousses with fish collagen and gelatin are presented, respectively: for chilled ones – hardness (2,00±0,49 N and 1,38±0,42 N), adhesiveness (2,8±0,40 mJ and 2,40±0,40 mJ), cohesivity (0,84±0,14 and 0,74±0,21), elasticity (0,41±0,14 and 0,30±1,12), springiness (3,33±0,56 mm and 2,16±1,47 mm), chewiness (4,90±0,40 mJ and 2,10±1,20 mJ), average peak load (1,83±0,56 N and 1,26±0,14 N); for defrosted ones – hardness (3,16± 0,70 N and 1,47±0,14 N), adhesiveness (2,67±1,45 mJ and 1,70±0,70 mJ), cohesivity (0,77±0,21 and 0,72±0,35), elasticity (0,42±0,14 and 0,22±0,42), resilience (4,00± 0,35 mm and 2,49±0,70 mm), chewiness (8,33±1,20 mJ and 2,60±2,0 mJ), average peak load (2,91±0,63 N and 1.26±0,14 N). An organoleptic assessment of chocolate mousse samples using stabilizing fish additives is given, and options for their use in the production of dessert products are proposed.

Gravity flow is often used in the process of cleaning and applying fish oil (FO). Experimental studies by a number of authors have shown that the rheological properties of FO are well described by the Shvedov-Bingham viscous-plastic fluid (SBL) model. Moreover, as the rye is cleaned, the limiting stress σ and the plastic viscosity nn decrease. A special feature of the task is to reduce the pressure drop as the depth of the SBL layer in the tank decreases. As a result, the characteristics of the SBL motion (the radius and velocity of the quasi-solid flow, the Coriolis coefficient, etc.) change during the discharge process. In the general case, the dynamics of the discharge of liquid fuel from the tank through a cylindrical pipe in a non-stationary formulation is described by a system of two differential equations. Reducing this system of equations to a dimensionless form made it possible to determine 6 criteria for the similarity of the Cauchy problem: the analogue of the Strouhal number Str, the ratio of the length of the entire pipeline and its vertical part to the initial depth of the reservoir (respectively, l and a), the modified Reynolds number, the ratio of the forces of marginal tangential stress to gravity forces Θ, the ratio gravity to inertia forces. The first 3 criteria are determined by the geometric parameters of the hydraulic system, the last three depend on the rheological properties of the hydraulic fluid. The Cauchy problem has been solved numerically. The results of the numerical analysis shows that the higher the value of Str is , the lower the flow rate in the pipe can be achieved and the longer the time to achieve it. For Str < 1, the problem can be solved in the quasi-stationary approximation. As an example, the problem of dynamics of the discharge of FO samples from the tank has been solved. It has been found that the time for the complete discharge of FO from the tank decreases according to the stages of purification. Moreover, for unpeeled FO, this time is much longer than for other OF samples. In all the conditions studied, the Bingham number remained large, which indicates the impossibility of using the rheological model of a Newtonian fluid.

In recent years, there has been a growing interest in the development of new polymeric, non-toxic, biodegradable materials extracted from renewable resources, such as cellulose. The aim of this work is selection of rational parameters for the extraction of algal polysaccharides (including cellulose) using enzymatic hydrolysis. Extraction of polysaccharides from algal biomass has been carried out using dilute mineral acids, alkali and water. For hydrolysis, algae thalli have been divided into parts and crushed into pieces of different sizes (5–10 cm) and dried for 15 hours in an oven at 105–106 °C to facilitate fine grinding. The dried biomass has been crushed to particle sizes of 0.1; 1.0; 5.0 and 10.0 cm. A solid load with a mass fraction of 10% is effective. The hydrolysis has been performed using the enzyme «Cellulase Ultra», which is an enzymatic preparation for the breakdown of xylans and other non-starch polysaccharides. A spectrophotometric method based on the interaction of sugars with an anthrone reagent has been used to determine sugars. The polysaccharide content in extracts isolated at 100 °C ranged from 0.77±0.09 g for red algae to 1.31±0.14 g for brown algae, depending on the extraction duration. It has been established that the following rational parameters for the enzymatic extraction of cellulose are: a sample fineness of 0.1–  0.5 cm, a temperature range of 180–200 °C, and a pressure of 1.0–1.5 MPa. The selected conditions allow for the extraction of fibers ranging from light beige to brownish in color without charring. The data obtained on the enzymatic hydrolysis of algae for the decomposition of cellulose indicate that the efficiency of this process and the composition of the resulting products depend significantly on the structural properties of the raw material, the balance and activity of the cellulase enzyme complex, and the hydrolysis methods used.

The article is devoted to testing of methods for calculating indicators of the quality of arable soils at the level of municipal districts in the Kaliningrad region. The study uses a comparative analysis of samples of typical soils based on the values of the soil-ecological index, the bonitet for grain crops, and the "normative yield" of grain equivalent. The diversity of soils in agro-landscapes is stipulated by the geomorphological and lithological spatial differences. The common factor limiting the quality of grain crops is the increased hydromorphism of gley soils. To a lesser extent, light or heavy granulometric composition, stony soil, and erosion affect soil quality and crop yields. Soil acidity is the main negative factor in the Zelenogradsky Municipal District. The values of the soil ecological index are a combined reflection of the agroclimatic potential, the conservative properties of the soils, and their agrochemical state. This allows for the ranking of soils from potentially the most productive to the least productive. It has been established that the best soils are sod-podzolic non- drained and drained gleyic soils of light loamy and medium loamy composition with the maximum potential of bonitet on carbonate soilforming rocks. The values of the soil-ecological index increase due to the change in the agroclimatic potential towards an increase in the sum of active temperatures in the first quarter of the 21st century. The yield level of grain crops for 2020–2025 demonstrates the realization of soil and ecological potential, primarily on drained gleyic sod-podzolic soils in the Kaliningrad region. Despite a number of methodological difficulties, the calculated indicators of "standard yield" generally agree with the spatial patterns of soil quality variation for grain crops.

Transition to renewable energy sources, such as solar power, is critical for reducing the anthropogenic impact of maritime transport on the environment. Solar panels can optimize operating costs and significantly reduce harmful emissions, contributing to the decarbonization of the maritime industry. The lack of a systematic approach and structured data makes it difficult to optimize the design of ships with photovoltaic panels. Classification of ships according to their architectural features, as done in this article, is the foundation for formalization of the design process, organizing information, and identifying patterns. The concept of a "solar ship" is most widely used in the segment of small-tonnage passenger ships (ferries, cruise yachts), which are characterized by relatively short length, large width (catamarans, trimarans), low speed, and the use of lightweight composite materials. Five main architectural types of ships with photovoltaic panels have been identified, differing in area and placement of panels (on decks, side surfaces, external structures, vertical wing sails). Maximum relative coverage of the ship's surface with panels is achieved by using the deck and side surfaces of the superstructure, but the "effective" area can be increased by using sun tracking systems. The article high-lights the relevance and prospects of using solar energy in maritime transport, identifies existing design problems, and proposes a systematic approach to solving them through the classification of architectural types of ships with photovoltaic panels.