Vertical distribution of wet mesozooplankton biomass in areas of three hydrothermal fields in the North Atlantic at night hours

New data on vertical distribution of plankton over hydrothermal fields of the Mid-Atlantic Ridge were obtained. Direct observations from the Mir deep-sea manned submersibles and samplings with use of BR plankton nets allowed to describe for the first time plankton distribution over the Menez Gwen vent field (37°50.5'N). No prominent near-bottom maximum of gelatinous animals was observed. Influence of the upper boundary of the water layer of Mediterranean origin on the vertical distribution of various plankton groups was shown. Distributions of euphausiids and copepods Calanus helgolandicus over the Lost City hydrothermal field (30°07.2'N) is assessed in detail; it is shown that south boreal interzonal species Calanus helgolandicus regularly penetrated up to 30° N.