Dinoflagellate cysts in the surface sediments of the White Sea

Abstract

-Dinoflagellate cysts were studied in 42 samples from the surface sediments of the White Sea. The total concentration of dinocysts varies from single cysts to 25000 cyst/g of dry sediments, which reflects the biological productivity in the White Sea waters and the regional particular features of the sedimentation processes. The highest concentrations are observed in silts; they are related to the regions of propagation of the highly productive Barents Sea waters in the White Sea. Generally, the spatial distribution of dinocysts species in the surface sediments corresponds to the distribution of the major types of water masses in the White Sea. The cysts of the relatively warm-water species ( Operculodinium centrocarpum, Spiniferites sp.) of North Atlantic origin that dominate in the sediments indicate an intensive intrusion of the Barents Sea water masses to the White Sea along with hydrological dwelling conditions in the White Sea favorable for the development of these species during their vegetation period. The cold-water dinocyst assemblage ( Islandinium minutum, Polykrikos sp.) is rather strictly confined to the inner parts of shallow-water bays, firstly, those adjacent to the Onega and Severnaya Dvina river mouths.

Hydrological changes in the White Sea during the historical period inferred from analysis of dinocysts

“…tribution of these species and their ecological tolerance [12] as well as with results of our previous studies in the White Sea (table, [9]). The autotrophic community consisting of five species is dominated by Operculodinium centrocarpum , which prevails also in Recent sediments of the White Sea [9].…”

“…The dinocyst assemblage in the examined cores numbers 12 species and their groups (table) characteristic also of surface waters in the present-day White Sea [3,9,15]. The sum concentrations of dinocysts range from 500 to 85 000 cysts/g varying usually from 2000 to 3000 cysts/g of sediment (Fig.…”

“…At least 100 cysts were identified in each sample. The defined correlations of the composition of dinocyst assemblages and their distribution in bottom sediments of the White Sea with the main hydrological parameters of the sea photic layer served as a methodological base for paleoreconstructions [9].…”

“…For determining concentrations of dinocysts, a tablet with a fixed quantity of Lycopodium clavatum spores was added into the preliminarily weighted sample at its initial treatment stage [9]. Microfossils were studied under the light microscope Zeiss Axiostar+ with magnification of 400.…”

“…The sediment samples taken with a step of 1-4 cm for the dinocyst analysis were treated in line with the procedure used at the A. Wegener Institute in Potsdam [9]. For determining concentrations of dinocysts, a tablet with a fixed quantity of Lycopodium clavatum spores was added into the preliminarily weighted sample at its initial treatment stage [9].…”