Production Characteristics of Phyto- and Bacterioplankton on the Transatlantic Transect (December 2019–January 2020)

The production characteristics of phyto- and bacterioplankton were obtained on the Transatlantic transect along the route of cruise 79 of the R/V Akademik Mstislav Keldysh in the Atlantic Ocean in December 2019–January 2020. These data were analyzed taking into account the biogeographic zoning of the study region, determined by various hydrometeorological conditions. Primary production (PP) was 0.8–34.2 mgC m–2 day–1 with an average value of 8.9 mgC m–2 day–1 in the euphotic zone. The daily assimilation number on the transect varied in surface samples from 7.2 to 260.1 mgC mgChl–1 day–1. Chlorophyll a concentrations ranged from 0.01 mg/m3 in the SASTG region to 0.59 mg/m3 in the NASTG province. Integrated primary production varied from 258 to 765 mgC/m2. The bacterial production (BP) in the surface horizons varied from 0.04 to 16.1 mgC m–3 day–1 with an average value of 3.7 mgC m–3 day–1; the maximum values were observed in the Lomonosov Current with a maximum at a depth of 160 m. Bacterial production in the water column varied from 23.2 mgC/m2 to 6182.7 mgC/m2. We suggest that the highest bacterial production observed in deep-sea horizons is associated with high concentrations of DOM.