Understanding of processes that shape and maintain functioning of the Arctic marine ecosystems necessitates quantitative and qualitative studies of organic matter (OM) and its variability in sea ice. Constantly changing ice cover is the most prominent spatial and temporal inconsistency in the Arctic basin, which affects formation of the marine ecosystem biological structure. Our work was aimed particularly at studies of OM, rates of its transformation in various ice structures, i.e. snow, ice, sub-ice water, and meltwater pools (puddles). Comparative data are presented on quantitative distribution as well as on elementary (Corg, Norg and Porg) and biochemical composition (proteins, carbohydrates and lipids) of dissolved and particulate organic matter (DOM and POM, respectively) in the multi-year (2 year) and 1 year ice cover in the Arctic basin and other elements of ice ecosystems (snow, ice, sub-ice water and puddles). Estimations of recycle rates of OM and the main nutrient salts in the production–destruction cycle of the ice ecosystems are made based on activities of redox enzymes of the electron transport system (ETS) and hydrolitic enzymes (protease and alkaline phosphatase). It is shown that the amount of total Corg, Norg and Porg in the ice ecosystem changes in broad ranges with the maximum concentrations at the lower part of the core of both the fresh and the old ice. The concentrations of particulate Corg also vary greatly with the maxima characterizing multi-year ice whose content of POM almost doubles that of the 1 year ice. The main biochemical component of DOM in all the elements of the ice ecosystem are lipids and carbohydrates, while in POM these are proteins with the maximum concentrations in the multi-year ice due to local accumulations of microogranisms. Microflora in the cores is marked by high intensity of redox and hydrolytic reactions. It is notable that in cores cut in the 2 year ice, rates of OM oxidation and hydrolitic splitting of phosphororganic compounds are 1.5–2.0 times higher than in the 1 year ice. Cryophytes have low energy of activation of these reactions (3–6 kcal m^–1); this allows them to support intensive metabolism under low temperatures.