DISTRIBUTION AND COMMUNITY STRUCTURE OF PICOPHYTOPLANKTON IN THE SOUTHERN OCEAN DURING THE LATE AUSTRAL SUMMER OF 1992 (16th Symposium on Polar Biology)

• Main Authors: オダテ ツネオ, フクチ ミツオ, Tsuneo ODATE, Mitsuo FUKUCHI
• Format: Report
• Language: English
• Published: Proceeding 1995
• Subjects: Antarctic; Austral; Southern Ocean; The Antarctic; Antarc*; Polar Biology; Proceedings of the NIPR Symposium on Polar Biology
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=5272; http://id.nii.ac.jp/1291/00005272/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=5272&item_no=1&attribute_id=18&file_no=1

Abundance and community structure of picophytoplankton populations were investigated in the Southern Ocean during the late austral summer of 1992. Three major oceanographic fronts, the Antarctic Polar Front, the Subantarctic Front, and the Subtropical Convergence, were recognized based on the degree of latitudinal gradients of surface water temperature and nutrient concentrations. These fronts divide the area into four distinct zones, the Antarctic Zone (ANZ), the Polar Frontal Zone (PFZ), the Subantarctic Zone (SAZ), and the Subtropical Zone (STZ). Chlorophyll a concentration retained on a glass fiber filter (bulk CHL) was the most abundant (0.93±0.24μg/l) in the SAZ. Although the bulk CHLs in the surface waters of the other water masses were almost the same, ca. 0.3μg/l, the percent contribution of the pico fraction (less than 2μm) was different, 74±5% (STZ), 43±11% (PFZ), and 23±11% (ANZ). The cell density of cyanobacteria (CY) was greater than that of other picophytoplankton (OP) north of the Subantarctic Front (SAF). The lowest cell densities of CY and OP were found in the surface water of the ANZ (0.041±0.035×10^3 and 3.5±1.8×10^3 cells/ml, respectively) while the highest ones were noted in the SAZ (49±12×10^3 and 15+1.6×10^3 cells/ml, respectively). Since these changes evidently occurred around the oceanographic fronts, the fronts are important boundaries for geographical variations of phytoplankton size composition and picophytoplankton community structure in the Southern Ocean.