Abstract:

Diatoms from surface sediment samples in Bering Sea and Chukchi Sea are analyzed to reveal the distribution pattern of the surface sediment diatoms and their relationship with the ocean environment. Absence of diatom is found in sediment samples in the north of Arctic Sea Ice Minimum, showing the growth and reproduction of diatoms are strongly inhibited by sea ice. In areas between Arctic Sea Ice Minimum and Sea Ice Maximum, i.e. areas influenced by seasonally changed sea ice, the sea ice diatom group (mainly Fragilariopsis oceanica and Fragilariopsis cylindrus) is found to be the dominant diatom species. Arctic sea ice is therefore confirmed to be an important influencing factor for the surface sediment diatoms in Bering Sea and Chukchi Sea. The Chaetoceros resting spores are more abundant in Chukchi Sea than Bering Sea, which is coincident with the modern phytoplankton composition in Chukchi Sea and Bering Sea, and possibly be attributed to stronger hydrodynamic condition in Bering Sea. The abundance of Chaetoceros resting spore are lowest on the northeast Bering shelf, possibly because of the lower water depth, stronger effect of the coastal current and river influx, relatively coarser sediment particles, or relatively strong wind and bottom current. The Arctic diatom group (dominated by Bacterosira bathyomphla, Thalassiosira antarctic v. borealis and Thalassiosira antarctic resting spore) is more abundant in Bering basin and the central and north of Chukchi Sea, while the coastal benthic diatom group (including Paralia sulcata and Delpheneis surirella) is mainly found on the northeast Bering Shelf and nearby the Cape Lisburne in Chukchi Sea. Thalassiosira nordenskioeldii is most plentiful around the Bering Strait, and Neodenticula saminae is only found in the Bering Sea, especially in the Bering basin, indicating close correlation with the Pacific waters.

Key words: Bering Sea, Chukchi Sea, Surface sediment, Diatom