Vertical distribution of mesoplankton at the northern margin of the North Atlantic gyre in June-August 2001

Vertical distribution of mesoplankton was studied over a single season in 2001 at two sites in the western and eastern parts of the northern margin of the North Atlantic gyre. Plankton was sampled both with use of BR 113/140 net and observed from the Mir deep-sea manned submersible. In near-slope waters southeast of Newfoundland (Titanic Polygon) there occurred intensive interaction between subtropical and sub-polar waters and plankton communities. The subtropical gyre community being more mature from the succession viewpoint created a ''net'' of carnivores and scavengers (shrimp and smaller animals) feeding plankton supplied from the north and thus increasing their own biomass. Due to features of hydrological conditions in 2001 in contrast to other years, the plankton supplied from the north was dominated by small copepods, while abundance of larger Calanus hyperboreus was small. Perhaps due to this fact, abundance of macroplanktonic shrimp decreased, while abundance of mesoplanktonic carnivores (Themisto, Sagitta, and Pareuchaeta) increased. In East Atlantic, within the Porcupine abyssal plain (Bismark Polygon) contrasts in frontal boundaries decreased and community interaction became less expressed. While vertical distribution of plankton at Titanic Polygon was characterized by a series of extraordinary features, distribution at Bismark Polygon was much more ordinary.

2001年单季期间，研究人员于北大西洋环流（North Atlantic gyre）北缘东西两侧的两个站位，开展了中型浮游动物（mesoplankton）的垂向分布调查。浮游生物样品通过BR 113/140型网具采集，并借助和平号（Mir）深海载人潜水器完成现场观测。在纽芬兰东南侧的近坡水域——泰坦多边形区（Titanic Polygon），亚热带与亚极地水团及浮游生物群落间存在强烈的相互作用。从群落演替的视角来看，亚热带环流群落更为成熟，构建了由食肉动物与食腐动物（虾类及小型动物）组成的‘捕食网络’，以摄食来自北部的浮游生物，进而提升自身群落生物量。受2001年特殊水文条件影响，与其他年份相比，北部输入的浮游生物以小型桡足类（copepods）为优势类群，而大型北极哲水蚤（Calanus hyperboreus）的丰度相对较低。或许正因如此，大型浮游虾类的丰度有所下降，而中型浮游食肉动物（钩虾属(Themisto)、箭虫属(Sagitta)及真哲水蚤属(Pareuchaeta)）的丰度则显著上升。在大西洋东侧的豪猪深渊平原（Porcupine abyssal plain）——俾斯麦多边形区（Bismark Polygon），锋面边界的差异有所减弱，群落间的相互作用也更趋平缓。尽管泰坦多边形区的浮游动物垂向分布呈现出一系列非同寻常的特征，俾斯麦多边形区的分布模式则更为常规。