Microplankton of the Barents Sea: current composition and structure on the eve of the winter

The results of microplankton (Protista) investigations in the Barents Sea (standard "Kola Meridian Transect", ~70-78° N, 33° 30′ E) in November / December have been presented. Samples for the determination of the taxonomical composition and abundance have been fixed with buffered formalin and examined with light microscopy using Nageotte counting chambers. A list of species recorded in the Barents Sea on transect, abundance and vertical distribution of microplankton has been given: a) the seasonal composition of species ( Ceratium fusus, Dicroerisma psilonereiella, Dinophysis rotundata, Lessardia elongata aff., Oxytoxum caudatum, Pronoctiluca pelagica, Protoperidinium brevipes, Prorocentrum balticum (Dinophyta), Corethron criophilum (Bacillariophyta), Coccolithus pelagicus (Haptophyta), Halosphaera viridis (Prasinophyta)); b) mean values of the total biomass of microplankton and its distribution in the water column (1.14 mkg/l in the layer of 50-0 m, 0.97 mkg/l - 100-50 m, 0.75 mkg/l - 200-100 m, 0.53 mkg/l - 300-200 m). Such parameter as dominant species in the structure of the total number is less constant (the ordinary dominant O. caudatum, subdominants - L. elongata aff., P. balticum, C. pelagicus, C. criophilum ); in some years, at selected sites of the Barents Sea most of the total number has been formed to unusual species ( Emiliania huxleyi, Mesoporos perforatus ). The less stable characteristics of microplancton are dominant species composition in the biomass structure, total number of cells and their distribution in the water column.