1. Makarov M. M.
   
   Limnological Institute, Siberian Branch of Russian Academy of Sciences, Irkutsk, Russian Federation (ru)
2. Kucher K. M.
   
   Limnological Institute, Siberian Branch of Russian Academy of Sciences, Irkutsk, Russian Federation (ru)
3. Budnikov A. A.
   
   Lomonosov Moscow State University, Moscow, Russian Federation (ru)
4. Помогаева Т. В. (Pomogaeva T. V.)
5. Малахова Т. В. (Malakhova T. V.)
   Доп. аффилиация: International Scientific Center for Ecology and Climate Change, Sirius University of Science and Technology, Sirius, Russian Federation (ru)

Purpose. The purpose of the study is to detect bubble gas emissions and to quantitatively assess bubble gas fluxes on the Black Sea shelf off the southeastern coast of Crimea, as well as to focus specifically on methodological approaches to investigating the spatial localization and comparative evaluation of the activity and intensity of seafloor bubble gas emissions.

Methods and Results. The hydroacoustic records, seafloor video records, and hydrological measurement data collected during the scientific expeditions of R/V Professor Vodyanitsky (125^th cruise, November 2022, 132^nd cruise, July–August 2024, and 135^th cruise, June 2025) were used in the study. The research consisted of three stages: 1) broad-scale shelf surveying at depths of 10–80 m, 2) boundary detailing of the sites with the identified seep clusters, and 3) monitoring of the activity of gas emissions at the selected sites. In total, more than 600 seeps were revealed over all the survey periods. Analysis of their distribution over depth showed that approximately 90% of all the recorded gas flares were located at depths of 35–45 m. To compare the temporal and spatial variability of gas emission activity, a specific indicator – the seep density (ratio of the seep number to the scanned bottom area) – was introduced. The maximum seep density reaching 6.3 seeps per hectare at the site near Cape Martyan was recorded in summer 2024. The hydroacoustic data made it possible to calculate the average values of gas emissions from individual seeps: 38 L/day (0.07 t/year) in 2022 and 10.7 L/day (0.011 t/year) in 2024.

Conclusions. The study results, including the data on spatial distribution, density dynamics, and flux magnitude, constitute the basis for monitoring gas emissions on the Crimean shelf. The pronounced interseasonal and interannual variability of seep density indicates the significant role of external factors in regulating gas emissions. The obtained data form a basis permitting assessment of the contribution of methane seeps to the regional carbon cycle.