## 1 Introduction  
This study helps establish the monitoring network based on the observation of the processes of formation, accumulation, emission, and deposit of primary greenhouse gases (GHGs) in various ecosystems over Russia [1]. The research activity at the carbon observational site in the Gelendzhik area (Figure 1), located at the northeastern coast of the Black Sea, focuses on the development of infrastructure and technology for measurements of GHG fluxes over marine and coastal areas. The sea shelf part of the carbon observational site adjacent to Blue Bay of the Black Sea extends a bit beyond the shelf edge (the isobath of \(\sim\)250 m), 4 to 5 nautical miles from the sea shore. The area near Blue Bay houses the Southern Branch of the Shirshov Institute of Oceanology of Russian Academy of Sciences (SIO RAS; [[https://ocean.ru/en/index.php/otdeleniya-i-filialy-io-ran/yuzhnoe-otdelenie](https://ocean.ru/en/index.php/otdeleniya-i-filialy-io-ran/yuzhnoe-otdelenie)]([https://ocean.ru/en/index.php/otdeleniya-i-filialy-io-ran/yuzhnoe-otdelenie](https://ocean.ru/en/index.php/otdeleniya-i-filialy-io-ran/yuzhnoe-otdelenie)), accessed on 22 November 2021), where several oceanographic instruments were designed and tested during 1950-1990. Our team has used this base while working on R&D projectsfor the moored automatic mobile profilers since 2005 [2; 3; 4; 5; 6]. For an overview of the Black Sea physical and biogeochemical characteristics, see References [7; 8]. An automated tethered profiler is required to frequently measure the hydrophysical control of the carbon system in the shelf water from the bottom part to the air-sea interface at a geographically fixed location. Although this study focuses on the research and development of the profiler, the organization of the carbon observational site in the Black Sea is beyond the scope of the study. While profiler mooring should provide information on time variations of water column properties with a sufficiently high temporal resolution, water sampling will be carried out one or two times per month over a wide area to provide a spatial perspective on the processes under investigation. Other activities include the chemical analysis of seawater samples for dissolved and particulate organic and inorganic carbon and organic and inorganic nitrogen and observations of GHG fluxes over the sea-land interface zone using the eddy covariance and chamber (mobile and stationary) methods based on the data obtained from surveys on the research vessel and the buoy mooring data. Available satellite observations are used for data interpretation. Hybrid process-oriented and statistical (machine learning) models have been developed to retrieve carbon stocks and fluxes from remote sensing data. This helps better understand the carbon cycle in the sea-atmosphere system, which is necessary to evaluate the GHG balance using numerical models. The development of technologies to increase the GHG uptake based on terrestrial and marine ecosystems is one of the key activities being conducted at the carbon experimental site. This research program should provide an opportunity for high-level training with regard to the observation and analysis of experimental data based on GHG fluxes. Figure 1: **Left—**The Black Sea coastline and location of the carbon observational site. **Right—**Bathymetry of the Northeastern Black Sea area near the carbon observational site. Bathymetry is based on the ETOPOI Global Relief Model (shading (m)); ([[https://www.ngdc.noaa.gov/mgg/global/](https://www.ngdc.noaa.gov/mgg/global/)]([https://www.ngdc.noaa.gov/mgg/global/](https://www.ngdc.noaa.gov/mgg/global/)), last access: 24 September 2021).