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.