Permalink : http://hdl.handle.net/2115/82343

JaLCDOI : 10.14943/bull.fish.71.1.39

KEYWORDS : Antarctic Ocean;Zooplankton community;Copepoda;Population structure

Various zooplankton studies have been conducted in the Indian sector of the Southern Ocean, but studies investigating spatial changes in both meso- and macro-zooplankton populations are limited. To reveal the north-south change of the mesoand macro-zooplankton community structure and the population structure of large copepods, we investigated zooplankton communities collected by the Ocean Research Institute (ORI) net along the 110°E transect in the Indian sector of the Southern Ocean during the austral summer. The zooplankton abundance and biomass were high at the stations north of 60°S and was dominated by large copepods, especially Calanoides acutus. A cluster analysis identified four zooplankton community groups. The distribution pattern of the community groups is likely to be related to the frontal system. The population structure of the dominant species of C. acutus, Calanus propinquus and Rhincalanus gigas had a similar tendency ; early copepodite stages were abundant in the northern region, while late copepodite stages dominated in the southern region. The meridional changes in the population structure are explained by different reproduction periods in each region related to sea-ice melt timing.