The Arctic ocean is a major component of the world's atmospheric ocean system and within this ocean, sea ice is the key dominant environmental feature. This three to five metre thick perenial sea ice cover affects the magnitude of both heat and matter fluxes from the atmosphere and supports a tightly coupled biological community - the Arctic sea ice ecosystem. This work is dedicated to the study of the composition, structure and dynamics of the Arctic sea ice ecosystem. It considers the permanent Arctic sea ice cover as an integral steady-state ecological system. Detailed descriptions are given of time-scale characteristics, physical and chemical ice properties, and the species composition of sea-ice bio data. The ecological mechanisms which govern the ecosystem on both the vertical and lateral scales are discussed, including the function of microcommunities during sea ice evolution.