—The paper discusses the spatial distribution of the main parameters of primary production in the Bransfield Strait in the austral summer. The integrated primary production in the strait varied from 435 to 741 mgC m –2 day –1 . The share of primary production in the total production of phyto- and bacterioplankton in the upper 10 m layer was 82–91%. Potential photosynthetic capacity (F v /F m ) was high within the euphotic layer (0.418–0.749) throughout the area. The production parameters in the two main water masses in the strait did not differ. Photosynthetic efficiency (the ratio of the assimilation number and the relative electron transport rate, AN/rETR) varied in different subregions of the study area by almost six times.