東北日本太平洋沿海域における現生石灰質ナノプランクトン群集の分布

概要

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Living coccolithophore assemblages were investigated in 32 surface water samples taken from the western Pacific Ocean off the coast of the Northeast Japan, and a total of 51 coccolithophore species were identified. Three coccolithophore assemblages are recognized, corresponding to distinct water masses : the Cold Oyashio Current, Tsugaru Warm Current and Mixed Water. In the Oyashio Current regime, the standing crop of coccolithophore was very high and diversity was low. The floral assemblage was dominated by "cold-water type" of Emiliania huxleyi, and Coccolithus pelagicus was a common member of the flora. In the Tsugaru Warm Current regime, the standing crop of coccolithophore was low, and the flora was characterized by abundant occurrence of "transitional type" of E. huxleyi and Gephyrocapsa oceanica as well as by a relatively common occurrence of Braarudosphaera bigelowii. In the Mixed Water regime, "warm-water type" of E. huxleyi and Gephyrocapsa ericsonii were abundant and common components of the flora, respectively.
1997-12-20