Аннотация:Brief results of comprehensive studies of the southeastern Baltic Sea on cruises 47–49 of the R/V Akademik Boris Petrov (2021–2022) are presented. Research methods included geophysics, geology, paleogeography, hydrology, hydro- and geochemistry, hydrobiology, and geoecology. New data on paleolandscapes and parameters of long-term monitoring of spatiotemporal changes in the abiotic and biotic components of the Baltic Sea ecosystem were obtained.