The Lomonosov Ridge, crossing the Arctic Ocean from Greenland to the New Siberian Islands and separating the Eurasian and Amerasian basins, underlies an area with nearly permant ice cover. Satellite passive microwave ice concentration data show that the southern Lomonosov Ridge, close to the Eurasian continental margin, is generally covered by more than 95% ice during most of the season, and even during summer ice concentration remains above 90%. Sea-ice cover in the study area, however, shows a distinct interannual variability, and sometimes ice-free areas occur [1]. Because of the extensive sea-ice cover and light limitation, primary production is restricted to a period of about three months during summer.Data on biomarker composition and fluxes using long-term sediment traps are still very rare in the Northern High Latitudes and are restricted to the arctic marginal seas and sub-arctic regions. Here, data on the variability of biomarker composition (as proxy for marine and terrigenous organic-carbon input) and flux of IP25 (a highly-branched C25 isoprenoid, a new proxy for sea-ice coverage; cf., [2]) from the central Arctic Ocean are presented for a one-year period. The study was carried out on material obtained from a long-term mooring system equipped with two multi-sampling traps, at 150 and 1550 m depth, and deployed on the southern Lomonosov Ridge close to the Laptev Sea continental margin from September 1995 to August 1996 (see [3] and [4] for details). The biomarker data are interpreted in terms of seasonal variability of lateral organic-carbon input, primary production, and sea-ice coverage.