Zooplankton community structure and its long-term variation in the western subarctic Pacific Ocean

利用20世纪80年代初至21世纪初的NORPAC网样（直径45 cm，网目0.33 mm，垂直拖距0 ~ 150 m），对西亚北极太平洋中型浮游动物生物量（湿重）、种类组成和丰度进行了季节性和年际测定。浮游动物群落中，桡足类在生物量和丰度上均占绝对优势，其峰值出现在初夏，其中大型桡足类、冠新哲水蚤（Neocalanus cristatus）、长刺哲水蚤（N.plumchrus）、弗氏哲水蚤（N.flemingeri）和真哲水蚤（Eucalanus bunchus）占很大比例。这种增加被解释为这些大型桡足类在早春移动到表层，在那里它们积极进食并迅速生长，直到初夏。其次是桡足类、毛颚类和磷虾类，季节性和局部性地有零星的盐滩和石砾类。夏季桡足类生物量的年际变化约为一个数量级，但与水文条件，特别是与表层温度的关系不明显。受黑潮影响的亚北极西部海域浮游动物群落的物种多样性高于亚北极东部海域（阿拉斯加湾）。

Mesozooplankton biomass (wet weight), species composition and abundance were determined seasonally and interannually in the western subarctic Pacific Ocean, using NORPAC net samples (45 cm diameter, 0.33 mm mesh, 0〜150 m vertical haul) from early 1980's to early 2000's. Zooplankton community was always predominated by copepods both in term of biomass and abundance, with their peak in early summer Large copepods, Neocalanus cristatus, N.plumchrus, N.flemingeri and Eucalanus bungii were accounted for a large part of the copepod peak. This increase is interpreted as that these large copepods move up to the surface layer by early spring, in which they actively feed and rapidly growth until early summer. Following with copepods, chaetognaths and euphausiids were abaundnt, with sporadic occurence of salpids and doliolids seasonally and locally. Summer copepod biomass showed interannual variation with about one order difference, but they showed no clear relationship with hydrographic conditions, especially with surface layer temperature. Species diversity of zooplankton community in the western subarctic Pacific, where are temporally affected by the Kuroshio Extention, was implied to be higher than in the eastern subarctic Pacific (Gulf of Alaska).