Abstract <p>The inflow of Atlantic water has a strong impact on the Arctic Ocean. Various modifications of these waters enter the St. Anna Trough, where they interact and continue to flow along the continental slope towards the east. The paper presents the hydrochemical characteristics of Atlantic water masses in the St. Anna Trough based on field observations during an expedition in August 2021. Main differences between two branches of Atlantic water have been identified. It has been demonstrated that there is a correlation not only between temperature and oxygen saturation of water, but also between temperature and nutrient ratios and aragonite saturation state. The obtained characteristics of the two branches of Atlantic water reflect the differences in the regional conditions under which these water masses form and the specific features of transformation of their chemical composition. These parameters can serve as indicators of water mass transformations and changes in marine ecosystem conditions in the Arctic region.</p>