The role of depositional regime on carbon transport and preservation in Arctic Ocean sediments

A suite of organic biomarkers was examined in six sediment cores from two shelf-basin transects in the Chukchi and Beaufort Seas of the Arctic Ocean to compare the sources and preservation of organic carbon between the two differing depositional regimes. Profiles of polyunsaturated fatty acids (PUFAs) and several algal sterols reveal the dominance of marine carbon on the broad, shallow Chukchi Shelf and Slope, and suggest that episodic pulses of marine material may be incorporated relatively unaltered into sediments. Biomarker profiles show carbon from terrestrial sources is present throughout the Chukchi transect, but is of lesser importance and is degraded compared to that seen in the Beaufort Sea. In contrast, the narrow Beaufort Shelf system is greatly influenced by the Mackenzie River with terrestrial contributions to total organic carbon estimated as over 95% for the shelf area and approximately 65% farther offshore. An unexpected correlation between dinosterol and α-amyrin in shelf and slope sediments suggests that dinoflagellates may contribute significantly to phytoplankton abundance in areas of seasonal open water. At basin locations that are almost permanently covered with ice, sterol profiles reflect diatoms as the main source of marine carbon.