Polycystine radiolarians in surface sediments in the Arctic Ocean basins and marginal seas

Abstract

The polycystine radiolarian faunas in the Arctic Ocean, including the adjacent Arctic seas, have been studied in more than 377 surface samples. The deep basins in the Arctic Ocean have revealed 31 polycystine radiolarian species (11 spumellarians and 20 nassellarians). The polycystine radiolarian fauna in the southern Norwegian Sea was introduced from the north Atlantic Ocean ca. 13 400 yr BP. The shallow low Arctic marginal sea sediments (Iceland, Barents, and Chukchi Seas) have a strong dominance of Cannobotryidae (79%, 77% and 74%, respectively), while the deep Arctic Ocean basins (Nansen, Amundsen, and Makarov Basins) have a dominance of Actinommidae (90%, 70%, and 75%, respectively). The arctic polycystine radiolarian faunas have a strong affinity with the Norwegian Sea fauna, which supplies the Arctic Ocean with faunal elements that can live, thrive and reproduce there. In the Chukchi Sea the Pacific faunal influence is obvious (41 species), but none of the Pacific species are found in any abundance in the Amerasian Basin. No radiolarian species was found to be endemic to the Arctic Ocean except for a morphotype of Actinomma l. leptoderma, with a round inner sphere. This species is a possible endemic candidate for the Arctic Ocean. Eight species are to be found in all of the central Arctic basins, and can therefore be referred to as circumpolar species: Actinomma leptoderma leptoderma, A. l. leptoderma (with round middle sphere), A. l. longispina, A. boreale, Spongotrochus glacialis, Pseudodictyophimus platycephalus, Cycladophora davisiana, and Tholospyris(?) gephyristes, while Amphimelissa setosa probably is the only true arctic radiolarian species.