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The article considers the species composition, features of the spatial and trophic structure of the macrobenthos of the Nikolskaya Bay of the White Sea. Nikolskaya Bay belongs to heavily silty lagoonal ecosystems with a predominance of the trophic group of collecting the detritus feeders. The accumulation of a large amount of organic matter in the sediments of the lagoon and its desalination in the spring period contribute to the development of mainly small species of detritophagous, which are more resistant to siltation and desalination, as well as to oxygen de ciency. These processes are especially manifested in the apex region of the bay. 26 species of invertebrates and 9 species of seagrasses and algae were found in the lagoon. Analysis of the obtained data on the species composition, diversity and structure of macrobenthos communities indicate the predominantly estuarine nature of the fauna of the Nikolskaya Bay lagoon ecosystem compared to other lagoons of the White Sea, since it is well protected from sea waves and currents by islands, luds and corgi.

The purpose of the work is to discuss the main environmental problems of the state of waters in the Sevastopol Bay and to identify the causes affecting their quality. Four seasonal surveys of the Sevastopol Bay water area in 2022 confirmed the prime impact of the Black River runoff, a main source of nutrients, on the hydrochemical composition of the bay waters.At the same time, it is noted that the hydrochemical parameters of the South Bay waters are predominantly affected by freshwater runoff in the estuarine part of the area rather than by the Black River water. It is assumed that the runoff is permanent, and not emergency, as previously thought. With the winds of the southern directions, the spread of the South Bay water to the central part of the Sevastopol Bay is possible, thus affecting the state of its ecosystem.In summer an additional source of ammonium ions was recorded in the estuarine part of the Artillery Bay, next to which the Crystal city beach is located, with concentrations 80 times higher than the background. Since ammonium is a product of organic matter oxidation, its appearance may indicate the predominance of destructive processes, which affect living conditions of biological organisms and, in general, the ecological state of waters. In the warm season a constant deficiency of oxygen was observed in the bottom waters of an artificial depression under the floating dock, which in some cases leads to the formation of hydrogen sulfide. All detected threats affect the ecological state of entire ecosystem of the bay, the living conditions of biological organisms and the recreational potential of the bay

This is a rst report about the diversity of micromycetes associated with living thalli of the edible red algae Palmaria palmata (dulse). We collected samples in the Kandalaksha Bay of the White Sea at upper (10 thalli in the littoral) and lower (10 thalli in the sublittoral) lines of this species distribution. The work was carried out by cultural methods, fungi were isolated from the surface of thalli. From one thallus from 0 to 55 colonies belongs to 0-24 morphotypes were isolated. The total diversity was 52 morphotypes, of which 48 were mycelia and 4 were yeast. All identi ed yeasts belong to Basidiomycota; among lamentous fungi, 2 species belongs to Zygomycota, and the rest belongs to Ascomycota, the vast majority of which are represented by anamorphic stages. The most diverse genera were Acremonium (10 morphotypes), Penicillium (9) and Cladosporium (6); the most numerous are Acremonium (158 colonies) and Cladosporium (103 colonies). Acremonium fuci is the most common species on the studied thalli (122 colonies on 15 thalli). The most important factor for the formation of the surface mycobiota of dulse is the habitat: littoral and sublittoral algal populations di er signicantly in the fungal communities number and structure. The thalli of the littoral population are much richer in fungi. The mycobiota of littoral samples in dominated by dark-colored species, as well as Acremonium fuci and Sarocladium strictum. While the mycobiota of sublittoral samples is dominated by lightcolored species, and most of the isolated yeasts were also founded here.

We present the results of seismoacoustic works carried out in the Petrozavodsk Bay of Lake Onega, the goal was to study a near-surface geological section. Seismoacoustic investigations were presented by the reflection method in a modification ultra-high resolution seismic survey. During the office work, the data were processed and interpreted, in which five seismic complexes were identified and correlated with the information about the lake structure. The result of the work was the maps construction of all five identified reflecting horizons covering all Petrozavodsk Bay. It was possible to estimate the sediments abundance and thickness corresponding to each complex.

The paper summarizes data on the lithological and elemental composition of bottom sediments and permafrost from boreholes 1D-14, 3D-14 and 1D-15 drilled in Buor-Khaya Bay in 2014-2015. Based on the results of determining the percentage content of SiO2, Al2O3, Fe2O3, TiO2, MgO, Na2O, K2O, CaO, MnO, P2O5, Cl, Cr, S, Ni, Cu, Zn, Rb, Sr, Ba, Y, Zr, organic carbon in sediments, lithochemical modules values were calculated and comparative analysis of the lithological and geochemical composition was performed. Principal differences between near-continental (1D-14 and 3D-14) and relatively distant from land (1D-15) strata were established, which is explained by spatial and temporal variability in sedimentary fluxes and weathering crust activity in the studied area of the Laptev Sea. The results of the study allowed to conclude that the basis of the petrofund of the studied deposits are most likely sedimentary rocks of the Kharaulakh ridge of the Verkhoyansk mountain system (sandstones, siltstones and mudstones). The contribution of igneous and metamorphic rocks to the sedimentary supply in the strata uncovered by drilling was insignificant.

To determine the risks for mariculture farms, the intra-annual change of dissolved О2 concentration was simulated for five zones in the Aniva Bay using the CNPSi model. Zone 1 differed sharply from other zones as the most shallow and freshened. Zone 2 is characterized by a pronounced water exchange with Zone 3 and Zone 4: during spring two layers were formed and stood out in these zones, in the summer the water column was homogeneous. Zone 3 has free water exchange with the open waters of the La Perouse Strait. An outstanding feature of Zone 4, in the deep-water part of the bay, was a distinctive subsidence of waters in the centre of the anticyclonic circulation and the maximum thermocline depth (up to 60-70 m). Zone 5 extends along the western coast of the Tonino-Aniva Peninsula and is characterized by the constant upwelling of waters during the icefree period, which is clearly expressed by lower water temperatures. The calculation showed that in the areas suitable for mariculture farms coastal waters were provided with oxygen throughout the year. Anaerobic conditions developed in spring only in the deepest parts of the bay. An additional source of oxygen in the Aniva Bay is natural thickets of macrophytes, among which the Japanese saccharin (Saccharina japonica) dominates in terms of biomass and area. Annually, Japanese saccharin itself absorbed at least 1200 tons of C in its biomass and supplied at least 3100 tons of О2. Unlike the artificially grown biomass, the biomass of all macrophytes would remain in the system and be destroyed during the life cycle, and the oxygen would be consumed for oxidation. The carbon accumulated in the biomass would again return to the rapid cycle, with the exception of the amount transported to the deep central part of the bay, where it would slowly decompose under nearly anaerobic conditions. It would be possible to place additional algae plantations in the bay, which could absorb up to 49 500 tons of C annually, while supplying up to 132 000 tons of О2. The obtained model estimates could be a starting point for determining the "baseline" of the content of dissolved oxygen and compiling balance equations for gas flows in the ocean-atmosphere system in the Aniva Bay before the development of seaweed plantations, which simultaneously act as carbon farms.

The paper presents data on the spatial distribution of activity concentration of natural (232Th, 226Ra, 40K) and anthropogenic (137Cs) radionuclides in the surface layer of bottom sediments of the Chaun Bay of the East Siberian Sea. The measured activity of 232Th and 226Ra is typical for bottom sediments of the Arctic coastal zone and corresponds to the global level. The level of 137Cs activity in bottom sediments showed the absence of local sources of anthropogenic contamination in Chaun Bay, while the mean 40K activity concentration was 1.8 times higher than the global average. The results of statistical analysis showed that the dynamics of riverine run-off, thermoabrasion and currents, as well as aeolian and sea ice transport of sedimentary matter, are the main factors that determined the differences in the behaviour of the studied radionuclides in the surface bottom sediments of the Chaun Bay.