Long-Term Dynamics of Chlorophyll in Plankton of Different Sites in a Large Plain Reservoir

On the basis of field observations in 2009–2019, the seasonal and long-term dynamics of chlorophyll at six standard stations of the Rybinsk Reservoir is considered. The fluorescence method is used to determine chlorophyll. The average chlorophyll content at stations varies from the minimum 3.5–10.8 to the maximum 16.9–40.5 μg/L in different years and from 12.0 at station 5 (Sredny Dvor) up to 21.6 μg/L at station 2 (Mologa) on average for the entire period. The seasonal dynamics of chlorophyll is characterized by spring; summer; and, in some years, autumn maxima. With the same type of seasonal dynamics, the change in chlorophyll at the stations is to varying degrees coupled in the years of observation and is most often correlated in neighboring areas. Significant differences in the amount of chlorophyll at the stations are observed during surveys carried out within one day and are determined by the complex hydrological structure of the reservoir; active dynamic processes; and, in the spring, by the thermal regime. The presence of stable large circulation zones smoothes out the spatial differences of chlorophyll, the average seasonal concentrations of which do not differ significantly at all six stations in years with an average water level, and at four stations of the Main Reach in extremely high-water years. A close correlation in long-term dynamics is revealed for the average chlorophyll concentrations for the growing season at six stations, as well as at each station and the reservoir as a whole. The results of the work confirm the reliability of the data obtained for assessing the ecological state of the Rybinsk Reservoir.

Modeling of the upper ocean winter (sub)mesoscale variability in the central Arctic Ocean during the MOSAiC drift.

<p>The dynamics of the boundary layer of the ocean significantly affect the interaction between ocean and atmosphere and, as a result, global climate. The sub-ice boundary layer of the ocean and its dynamics have not been thoroughly studied because of the extremely difficult conditions for observation, in particular during winter. Current understanding of spatial-temporal variability of (sub)mesoscales of the upper Arctic Ocean is extremely limited.<br>At the same time, one of the most important features of the upper ocean layers are the small-scale processes that influence and possibly determine the vertical and horizontal transport of heat, salt, and biologically relevant substances. As a consequence, mathematical models, in particular climate models, experience serious difficulties in parameterization of processes not resolved by the models because of the lack sufficient knowledge to detail the spatial variability at the (sub-)mesoscale.<br>To a better characterization and understanding of (sub)mesoscale dynamics and its role in vertical transport of energy and mass we apply a 3D regional ocean model FESOM-C. The observed vertical hydrological structure and a corresponding reconstructed horizontal temperature and salinity fields were imposed as a part of the forcing for the numerical model. These fields and information about the vertical hydrological structure were utilized by the model as initial conditions and for constraining (nudging) during the spin-up period. After the initial spin-up period, once the model had adjusted to our initial conditions, we performed several free runs.<br>We expect that our 3D numerical studies of eddy properties will contribute to a better characterisation and understanding of (sub)mesoscale dynamics in the Arctic Ocean and its role in the vertical transport of energy and mass.</p>

On the relation of bottom valley-type reservoir hydrocarbon carbon flux and hydrological structure of water body

Circulation of carbon in water bodies is fundamental process of nutriens cycle in water ecosystems. Carbon flux from bottom sediments is the less studied chain of this circulation nowdays. The aim of investigation was the study of HCO3 flux from bottom sediments in the valley-type reservoir and identification of their relation with hydrological structure of water body. Field works and laboratory experiments were fulfilled at Mozhaisk reservoir in 2017-2019. These years differed by weather conditions, level regime and stability of water masses. Hydrological surveys were fulfilled three times during summer period of each year. They included measuring of vertical distribution of hydrological characteristic and sampling of water and bottom sediments. The Kuznetsov-Romanenko tube method was used to study exchange processes. Hydrocarbonate carbon flux from sediments into the water may have a wide range (50-900 mgC/m2day). By comparison of HCO3 flux with hydrological structure it was revealed that in deep (>8 m) regions it depends on stratification and thickness of uniform hypolymnion, where seiches and compensation currents may promote transsedimentation from shallow places to flooded river bed. At the regions with depth <8 m hydrocarbonate carbon flux from sediments depends much more from autochthonic organic matter, produced by phytoplankton. The relationship of the HCO3 flux with the content of organic matter in the soil and its hygroscopic humidity is insignificant.

Integrated Russian-Vietnamese geological-geophysical and oceanographic expedition in the South China Sea (R/V “Akademik M.A. Lavrentyev”, cruise 88, 2019)

В ноябре 2019 г. в Южно-Китайском море (исключительная экономическая зона СРВ) впервые за последние 30 лет была проведена крупная комплексная геолого-геофизическая совместная экспедиция ТОИ ДВО РАН и Вьетнамской академии наук и технологий (88-й рейс НИС «Академик М.А. Лаврентьев»). Области изучения – геофизика, геология, гидроакустика, газогеохимия, гидрооптика, геомикробиология, палеогеография и гидрология. В толще вод и донных отложениях впервые обнаружены газогеохимические аномалии, сравнимые с аномалиями над нефтегазоносным шельфом о-ва Сахалин. Впервые в районе исследований выявлены геомикробиологические индикаторы углеводородных скоплений. Уточнены рельеф, геофизические поля, гидрологическая структура, особенности седиментации, палеогеографии и минералогии континентального шельфа Вьетнама и прилегающих глубоководных бассейнов. Предложено выделить тонкодисперсные карбонатно-глинистые осадочные отложения в самостоятельный минеральный ресурс. Выявлены районы, перспективные для поисков новых залежей нефти и газа, газогидратов, скоплений железо-марганцевых образований и др. Более 70 % научного состава экспедиции составляли молодые ученые. In November 2019, for the first time in 30 years, an integrated geological and geophysical joint expedition of the POI FEB RAS and the Vietnamese Academy of Science and Technology was carried out in the South China Sea (EEZ Vietnam) (88 cruise of the R/V “Akademik M.A. Lavrent’yev”). The set of methods consisted of geophysics, geology, hydroacoustics, gasgeochemistry, hydrooptics, geomicrobiology, paleogeography and hydrology. Gasgeochemical anomalies were found in the water column and bottom sediments, comparable with the anomalies over the oil and gas deposits along the Sea of Okhotsk shelf of Sakhalin Island. For the first time in the study area, deep water geomicrobiological indicators of hydrocarbon accumulations have been identified. The relief, geophysical fields, hydrological structure, features of sedimentation, paleogeography and mineralogy of the continental shelf of Vietnam and the adjacent deep sea basins are refined. Finely dispersed carbonate-clay sediments were proposed as a new mineral resource. Areas that are promising for the search for new deposits of oil and gas, gashydrates, accumulations of iron-manganese formations, and others are identified. Young scientists occupied more than 60 % of the scientific expedition staff.

The Deployment of the Seismometer to Investigate Ice and Ocean Structure (SIIOS) on Gulkana Glacier, Alaska

The Seismometer to Investigate Ice and Ocean Structure (SIIOS) is a NASA-funded analog mission program to test flight-candidate instrumentation on icy-ocean world analog sites. In September 2017, an SIIOS experiment was deployed on Gulkana Glacier. The instrumentation included a Nanometrics Trillium 120 s Posthole seismometer, four Nanometrics Trillium Compact (TC) seismometers, four Mark Products L28 geophones, and five each of Silicon Audio (SiA) 203P-15 and 203P-60 seismometers. The SiA sensors served as our flight-candidate instruments. The instrumentation was arranged in a small (&lt;2 m) aperture array with most sensors deployed in the ice. We also placed five of the SiA seismometers on top of a mock lander to simulate placement on a lander deck. The instrumentation recorded an active-source experiment immediately after deployment and then passively for 13 days. We conducted an active-source experiment using a sledgehammer striking an aluminum plate at 13 locations, with 9–13 shots occurring at each location. During the passive observation, the experiment recorded one large Mw 7.1 event that occurred in Mexico and four other teleseismic events with Mw&gt;6.0. The active- and passive-source signals are being used to constrain the local glacial hydrological structure, environmental seismicity, to develop algorithms to detect and locate seismic sources, and to quantify the similarities and differences in science capabilities between sensors. Initial results indicate the flight-candidate instrumentation performs comparably to the Trillium Posthole up to periods of 3 s, after which the flight-candidate performs more comparably to the TCs.

The Anthropogenic and Natural Factors’ Impact on Water Quality in Cooling Pools (the Lake Gusinoye as a Study Case)

The materials of the expedition of the Faculty of Geography of Moscow State University on Lake Gusinoye in August 2019 made it possible to assess the hydrological structure of the lake, the distribution of the flow of the main tributaries and wastewater from the Gusinoozerskaya state district power station. An analysis of the distribution of the chemical components and nutrients showed that dynamic mixing plays a significant role in the lake regime. The increase in the content of nutrients and mineralization components is insignificant and is determined by the flow of municipal sewage from settlements, from former quarries and mines, and mineralized groundwater.

The Summer Circulation in the Gulf of Suez and Its Influence in the Red Sea Thermohaline Circulation

The Gulf of Suez is accepted as an important location for Red Sea Deep Water formation, but the circulation and exchange with the Red Sea around the year remains elusive. A summer cruise in the area gives the opportunity to investigate features of the summertime hydrological structure and exchange with the Red Sea. An inverse estuarine circulation and exchange with the Red Sea is evident. The topographic patterns of the gulf play an important role in the circulation. Two sills, one in midbasin and a second at the mouth of the gulf, inhibit the bottom flow, topographically trapping waters that were formed in the cold season. Although the water mass characteristics of the outflowing waters during the other seasons are not directly related to the deep waters, they can influence the water column structure of the northern Red Sea. A simple box model shows that their contribution can have a significant influence in the formation of the intermediate layer. A hypersaline (40.6 psu) but relatively warm (23°C) water mass, originating in the Gulf of Suez, is detected at intermediate depths (100–150 m), with a strong signal in the western part of the Red Sea.