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The article describes the design and operational principles of the MDS-II bottom multimodem station, located in the coastal zone (depth of location 25 m) of the northeastern Black Sea at the Gelendzhik test site of the Shirshov Institute of Oceanology, Russian Academy of Sciences. The station is connected to the coastal center by a bottom fiber optic cable, through which power is supplied to the station, and online transmission of measurement data takes place. The station is an underwater server to which one can connect a measuring device and get a real-time access to it, as well as remotely control on its operation. The design of an automatic stationary station for vertical sounding (SSVS) of the water column, which is also used at the Gelendzhik test site, is described as well. This station is moored close to the MDS-II multimodem station and is connected to one of its modems. The station consists of a bottom electric winch installed on the seabed and a floating module (probe) on a cable line wound around the winch drum. When the command "sounding" is given, the cable unwinds and the floating module, equipped with temperature and pressure sensors, floats and measures the water temperature profile from the bottom layer to the sea surface. Then the cable is wound on a drum, and the floating module returns to the bottom layer. A prototype of a new SSVS is being developed, which will allow sounding of the water layer with a thickness of up to 100 m. It will be equipped with a multiparameter probe that makes joint measurements of hydrophysical and biooptical parameters. [ABSTRACT FROM AUTHOR]

The use of towed underwater unmanned vehicles equipped with photo, video, and sonar systems has proven its effectiveness in studying the seafloor surface in integrated research of the World Ocean. This class of devices solves a wide range of tasks, including biological studies of benthic fauna and surveys of underwater technogenic objects. The towed vehicle "Videomodule" was developed at the Shirshov Institute of Oceanology, Russian Academy of Sciences, and has been successfully employed for such surveys for several years. The paper discusses the technical features and application issues of working with the "Videomodule." [ABSTRACT FROM AUTHOR]

The article presents brief results of expeditionary studies of the Southeastern Baltic Sea and eastern Gulf of Finland during cruise 53 of the R/V Akademik Boris Petrov (2023). The expedition was a continuation of longstanding oceanological research conducted by the Atlantic Branch of the Shirshov Institute of Oceanology, Russian Academy of Sciences. Integrated geological, geophysical, hydrological, hydrochemical, hydrobiological, and geoecological research was carried out. New data on the state and dynamic of natural systems of the Baltic Sea were obtained. [ABSTRACT FROM AUTHOR]

Based on the materials of 20 expeditions conducted by the Shirshov Institute of Oceanology (IO RAS) in various areas of the coastal zone of the Russian sector of the Black Sea from 1999 to 2021, empirical equations of the relationship between the relative transparency (Secchi depth, Zd) and mass concentrations of the total suspended particulate (SPM), suspended mineral (SMM), and suspended organic matter (SOM) fractions (Cspm, Csmm, and Csom, respectively) were obtained. The Zd values were recorded in the range from 0.1 to 21 m; SMM concentrations, from 0.11 to 104 mg/L; SOM, from 0.09 to 2.0 mg/L; and chlorophyll a (Ca), from 0.03 to 4.4 µm/L. The relative abundance of SOM in SPM ranged from 1.1 to 48.7%. The calculation error for these equations is estimated. The determination coefficients r2 = 0.85 (for logCspm and logCsmm) and 0.72 (for logCsom). The influence of the SOM concentration on the accuracy in calculating Ssmm and chlorophyll a concentration on the accuracy in calculating Csom was revealed. It is concluded the empirical formulas can be used with respect to the entire dataset to calculate the concentrations of these SPM fractions in the entire studied water area. It is proposed to consider the method for estimating the content of SPM fractions using the obtained empirical equations as a regional variant of passive sounding of the upper layer of the sea with a Secchi disk. [ABSTRACT FROM AUTHOR]

A distribution analysis of scleractinian coral species in the Pacific Ocean using the data of the Shirshov Institute of Oceanology and literature data was carried out with regards to the global ocean conveyor belt. The idea was to evaluate if the Conveyor acts as a natural barrier for hydranth larva. Series of maps of scleractinian coral distribution in depths intervals of 1000–2000, 2000–3000, 3000–4000, and 4000–5000 m were created in order to study the characteristics of their distribution in the Pacific Ocean. The majority of stations (up to 300) with corals were registered in the depth range of 1000–2000 m. A few stations are located in deeper regions. The second highest number of stations (more than 60) are located in abyss depths deeper than 4000 m. However, only three species are present in this depth range. The geographical distribution of scleractinian corals shows longitudinal asymmetry. The majority of the stations are located in the western part of the Pacific. We are suggesting that this distribution is associated with the global ocean conveyor belt and with the evolution of the ocean. The paleogeographic evaluation of the possible time period when the species first appeared shows that relatively shallow water (1000–2000 m) corral associations are older than the abyssal scleractinian fauna. This supplements the hypotheses that we made in [4] of the evolution of F. marenzelleri and L. discus [4]. [ABSTRACT FROM AUTHOR]

The main goal of the work is to study the spatiotemporal structure of sea currents in the shelf–slope zone of the northeastern part of the Black Sea. The studies were carried out by numerical simulation methods using the combined hydrodynamic and spectral wave models incorporated in the DHI MIKE computational complex. The model has been verified based on the data of field observations performed by means of the hydrophysical test site of the Institute of Oceanology, Russian Academy of Sciences (Gelendzhik test site). As a result of calculations with a discreteness of half an hour, the fields of velocities and directions of currents for the period from January 2016 to December 2020 were obtained. Despite the fact that the total length of the massif is insufficient for climatic generalizations, analysis of the data obtained from the numerical experiment makes it possible to judge some general features of the seasonal dynamics of waters. As a result of the work that was carried out, the features of current velocity fluctuations in the frequency domain were revealed, and, based on the averaged current fields, the main seasonal features of water circulation in the shelf zone of the northeastern Black Sea coast were estimated. [ABSTRACT FROM AUTHOR]

The study considers the formulation of the problem and performs a numerical experiment for a short-term forecast of hydrological parameters using the data of two thermohaline surveys on September 14 and 16, 2019, at the test site of the Southern Branch of the Shirshov Institute of Oceanology, Russian Academy of Sciences (IO RAS) at Gelendzhik. Due to the small spatial scale of the survey area (about 15 × 15 km), a forecast as a solution to the Cauchy problem is impossible due to the large time gap between surveys. Therefore, the authors attempted to solve the forecast problem using the technique of a priori nonadiabatic sources, reflecting the temporal variability of the sought characteristics contained in the field data of the first survey. Essentially, this technique assumes a persistent trend of temporal variability of hydrological processes during the transition to the second survey. In this case, the problem of forecasting with nonadiabatic sources is divided into two stages using a quasi-hyperbolic system of equations. At the first stage, the problem of analysis with assimilation of the first survey data is considered, in the solution of which the required nonadiabatic sources are found. At the second stage, the forecast problem is solved by calculating nonadiabatic a priori sources. Comparison of the forecast results with the data of the second survey in this case yields satisfactory results. [ABSTRACT FROM AUTHOR]

The article presents data indicating the relationship of the bathymetric distribution of solitary endemic scleractinian corals inhabiting the Antarctic continental shelf and upper continental slope with the vertical density of the Antarctic Circumpolar Current. The study is based on materials collected by expeditions of the Shirshov Institute of Oceanology (IO RAS) and the literature data. The results show that endemic species that appeared in the Late Neogene and Pleistocene were unable to propagate across other oceans due to the existing horizontal and vertical density of the Arctic Circumpolar Current during that period. [ABSTRACT FROM AUTHOR]

The article presents information on the current experiment of research on wind wave parameters in the Black Sea coastal zone. Two wave-meter devices are the part of the measuring equipment of the Black Sea testing site Gelendzhik of the Shirshov Institute of Oceanology (IO RAS). The integral characteristics of wind waves accumulated and obtained in real time may be in demand by experts in operational and satellite oceanography. [ABSTRACT FROM AUTHOR]

As a result of the work of the expedition of the Institute of Oceanology in May 2021, the absolute values of the main hydrophysical, hydrochemical, geochemical, and biological characteristics of the water area of the western part of the Volga River Delta and the adjacent shelf are obtained. The lowering of the Caspian Sea level is leading to an increase in the slow runoff, which appears to be leading to a decrease in the amount of nutrients entering the shelf and a restructuring of the functioning of the ecosystem of the seaward edge of the delta front. [ABSTRACT FROM AUTHOR]