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., Alfiidasphaeridium? minutum and related morphotypes. Impagidinium? 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.

Dinoflagellate cysts in the surface sediments of the White Sea

“…(1) The concentrations of dinoflagellate cysts in the sediments of the White Sea are 20 times as low as those calculated previously for the Barents Sea [46] and are compatible with the values obtained for other Arctic seas, for example, for the Laptev Sea [30]. Their quantitative distribution over the White Sea is controlled by the grain-size composition of the sediments, which is responsible for the preservation and conditions of existence of cysts, and by the salinity of the surface waters, which governs the number of planktonic species of dinoflagellates.…”

“…3) is a widely spread cosmopolitan species; this is confirmed by the ecology of this cell during its mobile stage (biological taxon Protoceratium reticulatum). This dinoflagellate species is a neritic species widely spread in seas and oceans of the boreal zone [30,32,34]. Another dominating cyst species Pentapharsodinium dalei (Scrippsiella trochoidea), in contrast to those previously mentioned, refers to the Peridinium group and is also a cosmopolite that is mostly distributed in the Northern Hemisphere [9].…”

“…In the central part of the Basin, Nematosphaeropsis sp. was noted; with respect to the feeding type, it is an analog of Operculodinium centrocarpum, although it dwells at greater depths [30,32,34]. Dvina Bay is located in the eastern part of the White Sea and represents a wide stratified estuary with the maximal runoff of the Severnaya Dvina River.…”

“…Meanwhile, only one-fifth of them form cysts that can be conserved in the sediments [30,34]. In the recent years, the studies of the dinocysts of the Arctic seas have made great progress and allowed scientists to reveal the general regularities of their composition and distribution in the bottom sediments depending on the hydrological and ice conditions of the shelf [26,30,31,35,40,46]. Up to the present, for this group of microfossils with different degrees of detailing, the characteristics of the species and quantitative compositions of their assemblages in the sediments of almost all of the Arctic seas have been obtained except for in the East Siberian and White seas.…”

Spatial distribution of benthic foraminiferal stable isotopes and dinocyst assemblages in surface sediments of the Trondheimsfjord, central Norway

“…Matthiessen (1995) found high relative abundances at the Greenland and Iceland shelf with a random occurrence in the central Greenland Sea and the Norwegian Sea. Radiosperma corbiferum has been recorded in high concentrations from the Baltic Sea, the Barents Sea (Sorrel et al, 2006 and references therein) and the Laptev Sea (Matthiessen, 1995;Kunz-Pirrung, 1999, 1998Sorrel et al, 2006;Price and Pospelova, 2011). Hexasterias problematica is a Prasinophyceae species (Parke and Dixon, 1964;Price and Pospelova, 2011) and has been recorded from Baffin Bay fjords by Mudie (1992) and in the North Sea region by Cleve (1900).…”