2012年马卡诺夫海盆与楚科奇深海平原浮游动物夏季的垂直分布及地理差异

利用2012年9月1—6日采自马卡诺夫海盆3个站位和楚科奇深海平原1个站位的分层浮游动物样品，研究了浮游动物在0—1 000 m水层的垂直分布以及地理差异。结果表明，浮游动物在上层分布密集而在深层比较稀少。4个站位在0—50 m、50—100 m和100—200 m水层的平均丰度分别为265.0、360.7和231.2 ind·m^-3，而在200—500 m和500—1 000 m的丰度只有64.4和36.9 ind·m^-3。在数量上占优势的种类中，植食性为主的拟长腹剑水蚤(Oithona similis)、北极哲水蚤(Calanus glacialis)和极北哲水蚤(Calanus hyperboreus)集中在200 m以浅的水层。虽然在200m以下杂食性种类矮小微哲水蚤(Microcalanus pygmaeus)、隆剑水蚤(Oncaea spp.)和细长长腹水蚤(Metridia longa)的丰度明显降低，但是占浮游动物总丰度的比例却明显更高。两个调查海区浮游动物种类组成相似，但是楚科奇深海平原大型桡足类极北哲水蚤的丰度较高，而小型桡足类丰度较低?垂直分布上差异主要在于500—1 000 m水层，马卡诺夫海盆站位丰度为22.7—92.6 ind·m^-3，而楚科奇深海平原只有1.6 ind·m^-3。深海区浮游动物丰度的地理差异说明生物泵的作用存在空间异质性。类似地理差异产生的原因在于楚科奇深海平原存在数量较多的极北哲水蚤，它们在春季融冰前就上升到表层摄食冰藻，显著降低了有机物的垂直通量。

Vertical Distribution of Zooplankton in Makarov Basin and Chukchi Abyssal Plain in Summer 2012

Using samples collected in the Makarov Basin (MB) and Chukchi Abyssal Plain (CAP) in September 2012, the vertical distributions and geographical differences of zooplankton in the 0—1 000 m layer were analyzed. According to the species composition and abundance, both the diversity and the abundance of zooplankton changed with depth. On average, zooplankton abundance was 265.0, 360.7, and 231.2 ind·m^-3 at depths of 0—50 m, 50—100 m, and 100—200 m, respectively, while it was only 64.4 and 36.9 ind·m^-3 at depths of 200—500 m and 500—1 000 m, respectively. Herbivorous species such as Oithona similis, Calanus glacialis, and Calanus hyperboreus gathered in the 0—200 m layer and dominated in number. Although abundance of omnivorous species such as Microcalanus pygmaeus, Oncaea spp., and Metridia longa also decreased with depth, their percentages in the total abundance increased. Despite similar species assemblages recorded in each layer, epipelagic abundance of the large copepod C. hyperboreus was higher and that of small copepods was lower at the CAP station than at the MB stations, whereas in the 200—1 000 m layer, total abundance was much lower in CAP. Abundance of zooplankton in the 500—1 000 m layer varied between 22.7 and 92.6 ind·m^-3 in MB but it was only 1.6 ind·m^-3 in CAP. Geographical differences of zooplankton abundance in the mesopelagic layer were in accord with the heterogeneity in the function of the biological pump. It was suggested that low zooplankton abundance in the mesopelagic layer of CAP was induced by the high density of C. hyperboreus in the epipelagic layer, which starts feeding before ice melting in the spring, consequently reducing the downward flux of organic matter formed mainly by ice algae.