The dynamics of the layered hydrological structure was monitored in the meromictic Lake Elovoe, which was separated from the subarctic White Sea due to postglacial uplift. Within its water column, the following layers were identified: freshwater mixolimnion, brackish aerobic layer, chemocline, and anaerobic monimolimnion. The taxonomic composition of phytoplankton, its carbon biomass in different layers, and seasonal dynamics of biomass were investigated from March to October 2021. The chemocline exhibited the highest phytoplankton biomass throughout the year. In the surface water layer biomass peak occurred in summer, when diatoms proliferated en masse. The seasonal dynamics of phytoplankton abundance showed two increases: a spring increase in late May and a summer-autumn increase in late August-early September. The seasonal trend of integrated biomass dynamics and changes in predominant feeding modes were mainly shaped by the predatory dinoflagellate Oxyrrhis marina, which developed in the chemocline during winter, spring, and autumn. Autotrophic algae predominated in summer in both the surface layer and in chemocline. This is consistent with the data of underwater illuminance: conditions were dark under the ice in winter whereas during the polar day (June–July), light conditions favored autotrophs. In the chemocline, where always less than 1

Естественное или искусственное отделение водоема от материнской акватории ведет к стратификации его водной толщи и развитию вертикальной последовательности планктонных сообществ. Данные по сукцессии водорослевых сообществ единичны. В работе представлено исследование сезонной изменчивости состава и обилия микроводорослей в разных слоях водной толщи полузамкнутой лагуны под названием «Озеро Кисло-Сладкое» в 2021 г. в период устойчивой стратификации с придонной аноксией. Определены видовой состав и углеродная биомасса на разной глубине, интегрированная биомасса фитопланктона (ФП) в водном столбе (Bint). Проведен анализ сходства структуры ФП для разных слоев воды. Выявлено 53 вида и/или рода с преобладанием морских форм и 11 таксонов более высокого ранга. В период ледостава большая часть водной толщи была анаэробной, подо льдом доминировала пресноводная цианобактерия Microcystis ichthyoblabe. После схода льда максимум углеродной биомассы переместился к границе сероводородной зоны. В мае – начале июня наибольшие значения Вint определяла зеленая водоросль Chlamydomonas sp., в июне – июле – диатомовая водоросль Cyclotella choctawhatcheeana. Тип питания ФП с преимущественно автотрофного в начале сезона (март – июль) сменился на преимущественно гетеротрофный (август – октябрь). Наибольшие значения Bint отмечены в июле–сентябре (149,8 мг С/м2) при доминировании хищной динофлагелляты Oxyrrhis marina. Проведено сравнение полученных результатов с данными по водоемам подобного типа.

The seasonal succession of phytoplankton species composition and biomass plays a pivotal role in driving the seasonal variations in zooplankton community structure and biomass. Our study focused on the seasonal dynamics of planktonic communities in the Chupa Inlet (Kandalaksha Bay, White Sea) to determine if there are distinct complexes of phyto- and mesozooplankton species associated with different seasons, and whether these complexes are interconnected. Four seasonal groups of phyto- and zooplankton samples were revealed, each characterized by a specific composition of typical species. The winter and spring groups of phytoplankton and zooplankton corresponded to each other in their temporal span. Later in the year, this temporal correspondence was disrupted as early copepodite stages of Calanus glacialis dominated the community briefly in late spring, forming the basis of a separate seasonal group. From July until the end of the study period, warmer-water species constituted the community core, shaping the summer-autumn seasonal group. The role of smaller species in both phyto- and zooplankton communities increased during summer and autumn. The size structure and motility of the phytoplankton were found to significantly influence the seasonal succession of the zooplankton. This apparently contributes to better trophic coupling between phyto- and zooplankton throughout the seasonal cycle.

Natural or artificial separation of a water body from its parent water area leads to stratification of its water column and the development of a vertical sequence of planktonic communities. Data on succession of algal communities are sparse. Seasonal variability in the composition and abundance of microalgae in different water layers of the semienclosed lagoon called Lake Kislo-Sladkoe in 2021 was studied during stable stratification and bottom anoxia. Species composition and carbon biomass at different depths, as well as the integrated phytoplankton biomass in the water column (Bint), were determined. An analysis of the similarity of the phytoplankton structure in different water layers was carried out. A total of 53 species and/or genera with a predominance of marine forms and 11 higher rank taxa were identified. During the ice-covered period, most of the water column was anaerobic, and the freshwater cyanobacterium Microcystis ichthyoblabe dominated under the ice. After ice thaw, the biomass maximum shifted towards the boundary of the sulfide zone (into the chemocline). In May–early June, the highest biomass was determined by green alga Chlamydomonas sp., while that in June-July was by the diatom Cyclotella choctawhatcheeana. The type of nutrition changed from predominantly autotrophic at the beginning of the season (March–July) to predominantly heterotrophic (August–October). The highest biomass values were recorded in July–September (149.8 mg С/m2) due to the dominance of the predatory dinoflagellate Oxyrrhis marina. A comparison was made with water bodies of a similar type.

Проєктуючи дерев’яні конструкції, необхідно забезпечувати їх довговічність з урахуванням тривалості дії навантажень і особливості природної структури деревини. У період експлуатації в матеріалі будівельних конструкцій відбуваються зміни, спричинені появою, розвитком та накопиченням ушкоджень структури. Ці ушкодження викликають субмікро- і макротріщини, які, з’являючись у результаті зовнішніх механічних навантажень на конструкцію, впливають на зміну несучої здатності та перехід її в граничний стан, що є результатом поступового нагромадження ушкоджень. Розробивши методику реєстрації ушкоджень, можна одержати інструмент, який дозволяє не тільки контролювати поточний стан конструкції, а і прогнозувати зміну несучої здатності її в часі. У дослідженні несучої здатності будівельних конструкцій застосовують механічні та електричні прилади. Але вони придатні для реєстрації мікроушкоджень структури матеріалу. Сьогодні в Україні та за кордоном розроблено цілу низку методів неруйнівного дослідження і контролю за утриманням та експлуатацією дерев’яних конструкцій. Таким методом є і акустична емісія. Усі неруйнівні методи мають основні принципи: відмова від завдань дефектоскопії або нітроскопії як внутрішньої або поверхневої; обов’язковість принципу кореляції (міцності); порівняльна простота і перспективність їх використання; наявність прецендетності їх апробації для дерев’яних конструкцій у військових містечках як Державної прикордонної служби України, так і інших видів Збройних Сил України. У переважній більшості військових містечок експлуатуються будинки та споруди військового призначення, вік яких сягає більше 50 років. До дерев’яних конструкцій будівель і споруд належать: покриття; перекриття; утеплене покриття без горища; покрівля; пароізоляція тощо. Вони піддаються гниттю. У старих будинках покрівля завжди має проблеми – протікання і вологість у житлових приміщеннях. Балки перекриття та крокви згнивають і пошкоджуються грибком або комахами. У разі пошкодження механічним шляхом через надмірні навантаження виникають провислі хвилеподібні деформації балок уздовж усієї довжини споруди. За експлуатацію та утримання в належному стані споруд та конструкцій у військових містечках Державної прикордонної служби України та інших видах Збройних Сил України, правильну технічну експлуатацією казармено-житлового фонду, комунальних споруд і обладнання, територій військових містечок відповідає начальник квартирноексплуатаційної служби, який повинен організовувати та забезпечувати огляд дефектних конструкцій у таких будинках і спорудах відповідними фахівцями та планувати проведення поточного або капітального ремонту. У роботі проведено експериментальне дослідження матеріалу дерев’яних конструкцій будинків і споруд військового інфраструктурного комплексу та процесів накопичення ушкоджень у матеріалі конструкції за допомогою метода акустичної емісії.

In a saline semi-isolated lagoon on Cape Zeleny (White Sea), the annual dynamics of the vertical hydrological structure and the seasonal dynamics of phytoplankton were traced. Species composition, vertical distribution, abundance, nutrition type, and biomass were analyzed. In total, 293 species and supraspecific taxa of algae and cyanobacteria were found. Most of the identified species are marine, and 38 species are freshwater. Taxonomic composition changed in the lagoon throughout the year. Dinoflagellates dominated in winter and early June; unidentified cocci and flagellates in July; diatoms, dinoflagellates, and unidentified cells in August; dinoflagellates in September; and unidentified cocci and flagellates in October–November. The abundance of algae also changed in the lagoon throughout the year. The integrated biomass in the water column varied from 0.01 g C/m2 in January to 0.78 g C/m2 in early September. According to the environmental parameters, the water column of the lagoon was subdivided into several zones with different environmental conditions and corresponding phytoplankton communities. The similarity between the communities of different horizons was 32–46% in summer and 7% in winter. The chemocline layer was the most populous. It contained a maximum of phytoplankton biomass, 1–2 orders of magnitude higher than that in the overlying horizons. Despite the connection to the sea, the phytoplankton structure in the surface water layer in the lagoon and in the sea differed significantly in composition, quantitative parameters, and seasonal dynamics. The similarity between the communities never exceeded 50%. In terms of biomass dynamics, the lagoon lagged behind the sea until mid-summer, but, starting from August, it outnumbered it, and the phytoplankton development in the lagoon lasted longer, until late autumn. According to sequential tests DistLM, the phytoplankton structure and dynamics in the lagoon and in the sea were related to the daylength, water salinity, oxygen content, and pH by 24.5%. At the same time, the PhP structure did not depend on water temperature, underwater illuminance, or depth. Oxygen content and pH were defined by PhP activity. Salinity serves as a vector of the vertical sequence of ecological niches. The day length seems to be the crucial factor of the seasonal PhP dynamics in the semi-isolated coastal stratified lakes and lagoons.

The article presents data on the composition and abundance of algal flora in the coastal stratified Kislo-Sladkoe Lake (the Karelian coast of the White Sea) after its flushing with seawater in autumn. The seasonal dynamics and vertical structure of the phytoplankton were monitored from March 17 to October 3, 2019. We also studied ice flora on March 17 and April 1. The largest carbon biomass of ice algae (0.79 g C/m(3)) dominated by Nitzschia frigida was recorded in April. The integrated biomass of phytoplankton in the water column varied from 0.01 g C/m(2) in March to 5.83 g C/m(2) during spring bloom in late May (when it was dominated by Chaetoceros invisibilis) and remained at the level of 0.07 to 0.29 g C/m(2) until October; heterotrophic forms replaced autotrophic algae during this period. A regression analysis has shown that the structure of the phytoplankton was influenced by length of daylight, water temperature, dissolved oxygen level, depth, pH, salinity, and illuminance.

After a long break since 1994, the dynamics of the structure and abundance of phytoplankton was studied again at different depths in the White Sea in March–November 2017. The microalgae abundance varied from 3.8 × 106 to 3519 × 106 cells/m3. Phytoplankton biomass ranged from 0.2 to 90 mg C/m3; it was the highest in the surface layer of the water column (0–5 m) with some exceptions. The algal abundance and biomass, integrated throughout the water column, varied from 0.2 × 109 to 68.5 × 109 cells/m2 and 0.01 to 1.38 g C/m2, respectively. Two peaks of phytoplankton biomass were identified, in early May after the ice melting and in early September. The summer peak of phytoplankton biomass, reported by previous studies in July in the surface layers, was not observed in 2017. This was caused by the dominance of smaller groups of nanoplanktonic prasinophytes, cryptophytes, and dinoflagellates. The change of dominant species may be related to the general tendency of decreasing the contribution of large species and increasing the share of heterotrophic taxa in the phytoplankton community due to more pronounced stratification of the water column caused by the climate warming.

The spring blooms of phytoplankton play a key role in the functioning of marine ecosystems in the polar regions. A spring bloom in the Subarctic White Sea was observed in order to determine the effect of ice cover on the distribution, composition, and temporal changes of phytoplankton communities. The obtained results clearly show that in the White Sea, as in other freezing Arctic seas, ice melting and ice removal both play an essential role in the onset and development of spring phytoplankton blooms. This facilitates the release of ice algae and ice-pelagic algae into the water, as well as the rapid development of true planktonic taxa within the euphotic zone. One major peak of algal biomass is associated with ice removal while the other is recorded in the early summer. Comparison of our results with earlier data from 1960s to 1990s indicated strong year-to-year variation in terms of ice removal, the onset of the spring bloom, and the abundance and composition of the dominant phytoplankton taxa.

Paper examines ice algae and phytoplankton species composition and abundance in a stratified salt lake separated from the White Sea, in spring after a complete winter washing.

Abundance and biomass of small photosynthetic flagellates (SPF; 3–10 µm), chlorophyll a, and the contribution of SPF to total phytoplankton biomass in different stages of seasonal succession in ice and the surface water were studied in Kandalaksha Bay of the White Sea in September 2016, February and July 2017. In summer SPF biomass in the photic layer averaged 38.36±9.77 mg С/м 3 , in autumn – 2.22±1.43 mg С/м 3 , in under-ice water – 2.6±1.72 mg С/м 3 , and in ice – 14.79±11.25 mg С/м 3 . The contribution of SPF to total phytoplankton biomass depends of the season and ranged from 29% to 95%, the contribution to sympagic communities averaged 66%. The size structure of photosynthetic flagellates varied by seasons. Flagellates with cell size 6–10 µm dominated in summer plankton and in the ice. Flagellates with cell size 3–6 µm prevailed in autumn and in the under-ice water. The obtained data of SPF abundance gave higher values of the total phytoplankton biomass of the White Sea in the autumn-winter period compared with the estimates obtained previously. Applying the method of epifluorescence microscopy confirms the assumption that photosynthetic flagellates are the main producers in the winter period, as well as in the summer when the biomass of planktonic algae with cell size more than 10 µm is low.more than 10 µm is low.

Abundance and biomass of small photosynthetic flagellates (SPF; 3–10 µm), chlorophyll a concentration, and the contribution of SPF to total phytoplankton biomass at different stages of seasonal succession in ice and in surface water were studied in Kandalaksha Bay of the White Sea in September 2016 and February and July 2017. In summer, SPF biomass in the photic layer averaged 38.36 ± 9.77 mg C/m3, 2.22 ± 1.43 mg C/m3 in autumn, 2.6 ± 1.72 mg C/m3 in under-ice water, and 14.79 ± 11.25 mg C/m3 in ice. The contribution of SPF to total phytoplankton biomass depended on the season and ranged from 29 to 95%; the contribution of SPF to sympagic communities averaged 66%. The size structure of photosynthetic flagellates varied by seasons. Flagellates with a cell size of 6–10 µm dominated in summer plankton and in the ice. Flagellates with a cell size of 3–6 µm prevailed in autumn and in the under-ice water. The obtained data of SPF abundance showed higher values of the total phytoplankton biomass of the White Sea in the autumn–winter period compared with the estimates obtained previously. Applying the method of epifluorescence microscopy confirmed the idea that photosynthetic flagellates were the main producers in the winter period as well as in the summer when the biomass of planktonic algae with cell size exceeding 10 µm is low.

The species composition and biomass of the phytoplankton (Ph) as well as hydrological characteristics were estimated in 4 spatial surveys in the subarctic tidal estuary of the Kem’ River and adjacent area of Onega Bay (White Sea, Russia) in June–July 2008–2011. The study area was divided into 3 zones (the river zone, the gradient zone and the marine zone), based on the salinity variation of the surface layer. In total, 318 species of Ph were registered, 143 species are found in the river zone, 225 — in the gradient zone, 106 — in the marine zone. The greatest number of species in all zones was represented by diatoms. The highest biodiversity of Ph in the surface layer was detected in the gradient zone. The averages of total biomass of the Ph in the surface layer (Bo) at different years varied in range 2.8–16.9 mg C/m3. Although Bo did not differ significantly between zones, with the exception of 2011, when Bo was the highest in the river zone, dissimilarity in the structure of the Ph in the river, gradient and marine zones were 61–95%. The similarity of the Ph at the stations of each zone was poor (22–53%) with the lowest values in the gradient zone. It is postulated that the tidal cycles determine the spatial and temporal heterogeneity of the composition, structure and abundance of Ph in the Kem’ river estuary in summer.

Видовой состав и биомасса фитопланктона, а также гидрологические характеристики были оценены в ходе четырех пространственных съемок в субарктическом эстуарии р. Кемь и соседних районах Онежского залива (Белое море) в июне–июле 2008–2011 гг. С учетом пределов варьирования солености поверхностного слоя выделены три зоны эстуария — речная, градиентная и морская. Из 318 идентифицированных видов фитопланктона в речной зоне обнаружено 143, в градиентной — 225, морской — 106 видов. Наибольшим числом видов (48–58%) во всех зонах были представлены диатомовые водоросли. Средние значения суммарной биомассы фитопланктона в поверхностном слое ( B o) всей акватории в разные годы составляли 2.8–16.9 мг С/м3. Средние по зонам значения B o достоверно не отличались, за исключением 2011 г., когда B o была наиболее высокой в речной зоне, при этом отличия в структуре фитопланктона в речной, градиентной и морской зонах составляли 61–95%. Сходство структуры фитопланктона на станциях одной зоны было невысоким (22–53%) с наименьшими значениями в градиентной зоне. Показано, что в летний период именно приливы определяют пространственно-временную неоднородность состава, структуры и обилия фитопланктона в эстуарии реки Кемь.

Forest–steppe and the southern forest ecotones of European Russia (ER) are the most productive agricultural areas in Russia. Both climate and land use changes have occurred within the ER during last 30 years. These changes can lead to changes in the timing, magnitude, and spatial distribution of soil erosion rates on cultivated lands. The objective of this research was to assess the trends in soil erosion rates since the 1960s for two agricultural regions of ER.

The data on the species composition of the White Sea phytoplankton are presented; the size spectrum of algae and their trophic status are considered. The spatiotemporal variability of the species composition and biomass of plankton algae is examined. Estimations of vertical fluxes of phytoplankton are presented.

Species composition and biomass of phytoplankton (Bsum), concentration of chlorophyll “a” and nutrients, and hydrophysical conditions were studied on July 5–12, 2011, at 29 stations in the White Sea. The chlorophyll “a” concentration and Bsum in the surface water layer corresponded to the level of phytoplankton bloom (>1 mg/m3 and >30 mg C/m3, respectively), except for two stations. For the first time, the dominance of diatom Thalassiosira angulata by biomass was recorded for a vast area of the White Sea; in the surface layer, the abundance and biomass of this species reached up to 24 × 103 cells/L and 34.56 mg C/m3, respectively. Even higher values (179 × 103 cells/L and 258 mg C/m3) were noted at one of the coastal stations at a 3-m depth. The stability of the water column (positive relation) and salinity (negative relation) were the main factors affecting the spatial variability of the T. angulata biomass.