Meridional asymmetric distribution of the primary production in the Atlantic Sector of the Southern Ocean in the austral spring and summer

Abstract

The spatial distribution of the phytoplankton productivity was investigated in the Atlantic Sector of the Southern Ocean in the austral summer of 2009–2010 and the spring of 2010 on the basis of field measurements. In October–November, the average integrated primary production and the concentration of surface and integrated (photosynthetic layer) chlorophyll “a” in the Subantarctic waters of the Drake Passage exceeded the similar values along the Greenwich meridian by 3, 2, and 1.5 times, respectively. Similar primary production was observed in December–January for the water column in the eastern and western sectors of the studied area. The chlorophyll “a” concentration in the surface water layer was higher by 1.7 times for the Greenwich meridian area compared to the deep layers, but the concentrations of this pigment in the deeper layers did not differ. During the spring, the average primary production in the water column (the chlorophyll “a” concentration in the surface and in the photosynthetic layer) differed in the Drake Passage and along the Greenwich meridian by 2.3, 1.6, and 1.7 times, respectively. The opposite pattern was observed during the summer period, when the parameters listed above were higher for the Greenwich meridian area by 1.9, 2.5, and 1.7 times, respectively. Therefore, the western Antarctic areas in the spring are characterized by higher production than the eastern ones, and an opposite pattern is observed in the summer. The possible reasons for the meridional zonation of the chlorophyll “a” and the primary production are discussed in regard to different seasons.