Продукционные характеристики фитопланктона пролива Брансфилд в летний период

Abstract

Production characteristics of summer phytoplankton in the Bransfield Strait were studied in January 2020 during the 79th cruise of the R/V «Akademik Mstislav Keldysh» in the Atlantic sector of the Southern Ocean. The primary production, concentration of chlorophyll «a» and the relative content of pheophytin «a» in the sum of chlorophyll «a» and pheophytin «a» were determined. The concentration of chlorophyll «a» within the upper 125 m layer varied from 0.04 to 1.29 mg/m3 with an average value of 0.61 mg/m3. The maximal values were detected in the upper 20 m layer in the northwestern part of the section. The integral content of chlorophyll in the photic layer ranged from 16.67 to 62.43 mg/m2 with an average content of 36.66 mg/m2, decreasing from west to east. The relative content of pheophytin «a» in the euphotic layer varied from 20 % to 68 % with an average value of 42 %. The lowest values of pheophytin, indicating active photosynthetic processes, were observed in the northwestern part of the section at depths of up to 30 m, in the surface horizon in the central part of the strait, and at depths up to 80 m at the southeastern stations. The depth-integrated primary production was equal to 116–206 mg C/m2 per day, the most active synthesis of organic matter was revealed in the surface horizon. The assimilation number was 0.33–0.45 μg C/μg Chl/hour*L, reaching maximum values in the upper ten-meter layer of water. The northwestern part of the Bransfield Strait was the most productive.