The project is intended to provide, within the problem of accurate assessment of global carbon cycling, a methodology and its application to produce time series of quantitatively assessed DOC fluxes brought into and spread over the Kara Sea during the time period of significant climate shifts in the northern high latitudes. Specific objectives: 1. Collect the spatial and temporal distributions of DOC concentration in the estuaries of the Ob and Yenisey Rivers and further out in the open sea. 2. Collect and analyze past and present field data on DOC for validation of the respective satellite data, 3. Assess the taxonomic composition, concentration and biomass of pelagic algae, the share of heterotrophic algae in the phytoplankton community, 4. Assess trophic- and bacterial decomposition chain-interactions in the estuaries of the Ob and Yenisey Rivers; 5. Establish vertical profiles of DOC in the river deltas and open Kara Sea depending on season and prevailing wind vector, 6. Develop a dedicated GIS for an efficiently organized storage of data, 7. Quantitatively assess the actual (net) fluxes of DOC into and across the Kara Sea during the ice-free-free period but also beyond this period with due consideration of DOC freezing in sea ice. The salient innovative feature of the proposed project is that, based on the new achievements in both methodology owned by the project team (advanced operational bio-optical algorithm, techniques based upon spatial and temporal averaging and interpolation that allow to degrade the inference of cloud screening) and improved MERIS software, we are going to quantify DOC content in the Kara Sea for ice-free period from spaceborne data at high spatial and temporal resolution and give an insight into DOC transport further into the Arctic Basin. So far no attempts have been ever undertaken to tackle this task, whose accomplishment will provide a basis for considering the role of extra-distant transport in the formation of DOC budget in the northern Atlantic. The project as a distinct multidisciplinary nature: hydrobiogeochemists and mathematical modellers will provide remote sensing experts with indispensable data on the Kara Sea hydrodynamics, pathways of water and matter transport from river deltas through the sea, water stratification/vertical and horizontal distribution of key ecological parameters, numerical assessments of the role of organic carbon transformations through trophic interactions and hydrochemical reactions. The major deliverables are expected as the outcome of the project implementation: Quantified (i) fluxes of DOC into the Kara Sea from the major estuaries, (ii) pool of DOC in the Kara Sea (iii) fluxes of DOC out of the Kara Sea into the open Arctic regions. The project is directly relevant to the scope of the 2006 INTAS Thematic Call on Earth Sciences and Environment: Global Climate Change Focusing on Carbon Stocks, and it is of top relevance to supporting the EU strategy for sustainable develop