The paper presents the results of microbiological study in the coastal waters of the northwestern Pacific Ocean and the Sea of Okhotsk, obtained during the expedition of cruise 23/4 of PV Professor Multanovsky (August-September 2023) within the Floating University Program. Quantitative characteristics and spatial distribution of bacteria transforming major classes of organic compounds, including petroleum hydrocarbons (diesel fuel), lipids, and phenols, in the surface and bottom layers of the water column were determined. The abundance of heterotrophic bacteria in the surface and bottom layers ranged from 10³ to 10⁵ cells/mL. The abundance of hydrocarbon-oxidizing bacteria ranged from 1 to 10² cells/mL in the surface layer and from 1 to 10 cells/mL in the bottom layer. The abundance of lipolytic bacteria varied from 10 to 10³ cells/mL in both layers. The phenol-oxidizing bacterial group ranged in abundance values from 1 to 10² cells/mL in both the surface and bottom layers. The investigated bacterial groups exhibited non-uniform distribution in the coastal waters of the Kamchatka Peninsula. Maximum values are associated with the anthropogenically loaded Avacha Bay, exploited bays, and sites of active river runoff. During the study period, the water temperature of the surface layer ranged from 11.0 to 16.1°C, and the bottom layer ranged from 1.3 to 11.3°C. The pH values in surface water varied from 8.38 to 8.49. The depth at the bottom water sampling stations was from 13.5 to 780 m in the Pacific Ocean and from 26 to 62 m in the Sea of Okhotsk. No significant correlation was found between the abundance of identified microbial groups and the recorded physical and chemical parameters.
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