MACROZOOPLANKTON DISTRIBUTION AROUND THE ANTARCTIC DIVERGENCE OFF WILKES LAND IN THE 1996 AUSTRAL SUMMER : WITH REFERENCE TO HIGH ABUNDANCE OF SALPA THOMPSONI (19th Symposium on Polar Biology)

• Main Authors: チバ サナエ, ホリモト ナホ, サトウ リキ, ヤマグチ ユクヤ, イシマル タカシ, Sanae CHIBA, Naho HORIMOTO, Riki SATOH, Yukuya YAMAGUCHI, Takashi ISHIMARU
• Format: Report
• Language: English
• Published: Proceeding 1998
• Subjects: macrozooplankton; distribution; Antarctic Divergence; Wilkes Land; Salpa thompsom; Antarctic; Austral; The Antarctic; Antarc*; Antarctic Krill; Antarctica; Euphausia superba; Polar Biology; Proceedings of the NIPR Symposium on Polar Biology
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=5362; http://id.nii.ac.jp/1291/00005362/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=5362&item_no=1&attribute_id=18&file_no=1

Distribution and abundance of macrozooplankton off Wilkes Land, Antarctica in austral summer were studied in relation to environmental features associated with the Antarctic Divergence (AD). A single species of salp, Salpa thompsom, dominated others both numerically and by biomass, occupying 44% of mean total abundance with the maximum density of 29873 inds./l000m^3 (44 mg C/m^3). Abundance of Antarctic krill, Euphausia superba, was low through the sampling area (max. 41 inds./1000m^3: 2.9mg C/m^3). Total length frequency and stage of maturity of E. superba suggested relatively late spawning and low recruitment ratio, respectively. Salps and major copepod species showed a spatially partitioned pattern across the AD, in which the former dominated in areas north and south of the AD while the latter was predominant near the AD. Active reproduction of salps seemed to be ongoing in the areas where mean chl a concentration within the euphotic zone was around 0.4-0.6 μg/l, but suppressed where that was higher than 0.6 μg/l. Clogging of mucous nets of salps was considered to be one of the causes of their low abundance at high chl a concentration as observed near the AD. The results suggest that the relatively limited phytoplankton growth, particularly in the eastern side of this research area, may have provided the food condition which was optimal for salp reproduction but unfavorable for other phytoplankton consumers, permitting an explosive population growth of salps.