Sources and transport of organic carbon to shelf, slope, and basin surface sediments of the Arctic Ocean

Abstract

Lipids in surface sediment transects across the Arctic Ocean were identified to define the sources of organic carbon and the transport of material in the ocean basin. Sterols representing diatoms (24-methylcholesta-5,24(28)-dien-3 β-ol, 24-methylcholesta-5,22-dien-3 β-ol) and dinoflagellates (4 α,23,24-trimethylcholest-22-en-3 β-ol) together with algal polyunsaturated fatty acids (20:5, 22:6) demonstrated the importance of primary production to organic matter inputs on the Chukchi Shelf. The presence of terrestrial biomarkers including long-chain n-alkanes and mono- and dicarboxylic acids in shelf sediments indicated that while the fraction of terrestrial biomarkers was small compared to marine material, the transport of allochthonous material impacts carbon cycling on the shelf. Algal biomarkers were found in all surficial sediments from the central Arctic basins, demonstrating that some fraction of primary production reached bottom sediments despite ice cover and light limitation. Marine markers represented a small fraction of the total lipids in central basin sediments. This implies that the basins are less productive than shallow waters, significant degradation occurs before the organic matter reaches the sediment–water interface, and substantial amounts of vascular plant material are exported to the central Arctic. Circulation and topographical features, such as the Transpolar Drift and the Lomonosov Ridge, appear to have an important influence on the transport and focusing of terrestrial material in the Arctic Ocean basins.