Journal Article Meso-zooplankton abundance and spatial distribution off Lützow-Holm Bay during austral summer 2007–2008

12pp.25 - 33 , 2017-06
To elucidate spatial differences in mesozooplankton community structure in local scale, vertical hauls using a 60-μm mesh closing net were carried out off Lützow-Holm Bay in January 2008. All of the zooplankton samples collected from three layers (0–100, 100–200, and 200–500 m) at seven stations were dominated by Oithona spp., Oncaea spp., Ctenocalanus citer, Microcalanus pygmaeus, and copepod nauplii. The cluster analysis of mesozooplankton abundances showed three distinct groups according to sampling depth, which appeared to be due to the preferential vertical distribution of dominant copepods. The other cluster analysis on integrated abundance upper 500 m revealed that mesozooplankton community structures at stations located on the western and eastern edges of the observation area (Cluster A) differed from those at the central stations (Cluster B). Abundance of copepod nauplii, Oithona spp., and C. citer differed between Clusters A and B, which was likely caused by differences in recruitment and early development in the dominant copepods, being associated with the timing and duration of ice edge blooms. This suggests that such heterogeneity in abundance and recruitment/development of dominant taxa was likely caused by local heterogeneity in sea ice dynamics. This may affect our understanding of zooplankton distribution.
動物プランクトン群集の微細分布特性を把握するため、リュツォ・ホルム湾沖の7定点において閉鎖式ネットによる定量観測を実施した。群集解析の結果から、植物食性の強いCtenoclanus citer などの発育段階組成とノープリウス幼生密度の違いによって同海域における群集構造が水平的に異なることが示された。この結果は海氷融解によって引き起こされる植物プランクトンブルームの時期とその持続性の違いが餌環境の違いを生じさせたためと分かった。海氷のダイナミクスとローカルな海底地形との関係は東南極の広い海域で報告されており、本研究が見出した優占カイアシ類の再生産と初期生育のローカルスケールにおける違いは、他の海域でも同様に起こると考えられる。

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