Freshwater chlorophycean algae in recent marine sediments of the Beaufort,Laptev and Kara Seas (Arctic Ocean) as indicators of river runoff

Freshwater chlorophycean algae are characteristic organic-walled microfossi ls in recent coastal and shelf sediments from the Beaufort. Laptev and Kara seas (Arctic Ocean). The persistent occurrence of the chlorophycean algae Pediastrum spp. and Botryococcus cf. braunii in marine palynomorph assembla ges is related to the discharge of freshwater and suspended matter from the large Siberian and North American rivers into the Arctic shelf seas. The d istribution patterns of these algae in the marine environments reflect the predominant deposition of riverine sediments and organic matter along the s alinity gradient from the outer estuaries and prodeltas to the shelf break. Sedimentary processes overprint the primary distribution of these algae. R esuspension of sediments by waves and bottom currents may transport sedimen ts in the bottom nepheloid layer along the submarine channels to the shelf break. Bottom sediments and microfossils may be incorporated into sea ice d uring freeze-up in autumn and winter leading to an export from the shelves into the deep sea. The presence of these freshwater algae in sea-ice and bo ttom sediments in the central Arctic Ocean confirm that transport in sea ic e is an important process which leads to a redistribution of shallow water microfossils.