Journal Article Variability of the fauna within drifting sea ice floes in the seasonal ice zone of the Southern Ocean during the austral summer

12pp.19 - 24 , 2017-06
Sea ice covering the seasonal ice zone in the Southern Ocean contains micro-organisms (sea ice biota). Studies of sea ice biota have mostly been conducted on the land-fast ice and large ice floes, despite most sea ice in the Southern Ocean being seasonal and drifting ice types. We sampled 17 drifting sea ice floes in the marginal ice zone off Adélie Land, East Antarctica, in January 2013 and 2014. We found high densities of copepods such as Harpacticoida species (18,787 ± 50,647 inds.m−3), Paralabidocera antarctica (1773 ± 6370) and their nauplii (69,943 ± 149,607), as well as foraminiferans (193,869 ± 408,721) within ice. Variability in the animal assemblages among the different ice floes was observed. Cluster analysis of samples based on the assemblage of sea ice fauna revealed two major groups, which were divided by the year of the sampling, and were dominated by harpacticoid nauplii and foraminiferans, respectively. Sea ice trajectory and drifting duration estimated from satellite data were different for both years, although the origin of the sea ice was in the same bay. This study suggests that the variability of fauna among sea ice floes may reflect the continuance period of ice formation and the trajectory from where they originated.
本研究では、南大洋の流氷内でみられた微小動物群集の組成について解析した。東南極アデリーランド沖において2013、14年に採集した合計17塊の流氷を分析した結果、高密度でハルパクチコイダ科のカイアシ類(18,787±50,647 inds.m-3)、Paralabidocera antarctica(1,773±6,370 inds.m-3)およびそのノープリウス幼生(69,943±149,607 inds.m-3)、有孔虫類(193,869±408,721 inds.m-3)が出現した。クラスター解析では、流氷内の微小動物群集は採集した年の違いによってハルパクチコイダ科カイアシ類が優占するグループと有孔虫類が優占するグループの大きく2つに区分された。衛星より得た流氷の軌跡データを解析すると、2013年と14年では流氷の生成と軌跡に違いがみられた。本研究の結果は、流氷内の微小動物群集組成と流氷の生成、軌跡の関係性について示唆するものである。

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