Differences of the protozoan biomass and grazing during spring and summer in the Indian sector of the Southern Ocean

• Main Authors: Becquevort, Sylvie, Menon, Patricia, Lancelot, Christiane
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2000
• Subjects: Océanographie biologique; Ecologie; protozoan; biomass; grazing; southern; ocean; feeding; activity; potential; prey; Antarctic; Indian; Southern Ocean; The Antarctic; Antarc*; Polar Biology; Sea ice
• Online Access: http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/56900; https://dipot.ulb.ac.be/dspace/bitstream/2013/56900/1/2000-PB-5-309-320.pdf

The dynamics of protozoa were investigated during two cruises in the Indian sector of the Southern Ocean: the early spring ANTARES 3 cruise (28 September to 8 November 1995) and the late summer ANTARES 2 cruise (6 February to 8 March 1994). Biomass and feeding activity of protozoa were measured as well as the biomass of their potential prey – bacteria and phototrophic flagellates – along the 62°E meridian. The sampling grid extended from the Polar Frontal region to the Coastal and Continental Shelf Zone in late summer and to the ice edge in spring, crossing the Antarctic Divergence. Protozoan biomass, although low in absolute terms, contributed 30% and 20% to the total microbial biomass (bacteria, phytoplankton and protozoa) in early spring and late summer, respectively. Nanoprotozoa dominated the total protozoan biomass. The geographical and seasonal distribution of protozoan biomass was correlated with that of phototrophic flagellates. However, bacterial and phototrophic flagellate biomass were inversely correlated. Phototrophic flagellates dominated in the Sea Ice Zone whereas bacteria were predominant at the end of summer in the Polar Frontal region and Coastal and Continental Shelf Zone. Furthermore, bacteria were the most important component of the microbial community (57% of the total microbial biomass) in late summer. Phototrophic flagellates were ingested by both nano-and microprotozoa. In contrast, bacteria were only ingested by nanoprotozoa. Protozoa controlled up to 90% of the daily bacterial production over the period examined. The spring daily protozoan ingestion controlled more than 100% of daily phototrophic flagellate production. This control was less strong at the end of summer when protozoan grazing controlled 42% of the daily phototrophic flagellate production. info:eu-repo/semantics/published