Distribution of Aquatic Palynomorphs in Surface Sediments from the Laptev Sea, Eastern Arctic Ocean

Abstract

Aquatic palynomorphs were studied in surface sediments from the Laptev Sea shelf and the adjacent continental slope. The Laptev Sea is characterized by a strong salinity gradient owing to an extreme freshwater influx from the Siberian rivers in summer. The assemblages are composed of various organic-walled microfossils, in particular dinoflagellate cysts, chlorococcalean algae, acritarchs and several groups of zoomorphs. The species composition and the distribution pattern of dinoflagellate cysts and chlorococcalean algae is related to the salinity gradient of the surface water from the coast to the continental slope. A distinct change in the dinoflagellate cyst assemblages occurs across the continental slope corresponding roughly to a salinity interval of 28 to 30. Assemblage I from the shelf is dominated by Brigantedinium spp., Algidasphaeridium? minutum and related morphotypes. Impagidiniuml pallidum, Nematosphaeropsis labyrinthus and Operculodinium centrocarpum characterize assemblage II from the continental slope. The chlorococcalean algae assemblages are composed of Pediastrum spp. and Botryococcus cf. braunii which usually live in freshwater. Therefore, their occurrence in the marine environment reflects the freshwater discharge into the Laptev Sea. The strong gradient in chlorococcalean algae concentrations suggests that the influence of freshwater is confined mainly to the shelf.