The Arctic Ocean is undergoing major changes in many of its fundamental physical constituents, from a shift from
multi- to first-year ice, shorter ice-covered periods, increasing freshwater runoff and surface stratification, to
warming and alteration in the distribution of water masses. These changes have important impacts on the chemical
and biological processes that are at the root of marine food webs, influencing their structure, function and
biodiversity. Here we summarise current knowledge on the biodiversity of Arctic marine ecosystems and provide an
overview of fundamental factors that structure ecosystem biodiversity in the Arctic Ocean. We also discuss climateassociated
effects on the biodiversity of Arctic marine ecosystems and discuss implications for the functioning of
Arctic marine food webs. Based on the complexity and regional character of Arctic ecosystem reponses to
environmental changes, recommendations are made for the establishment of long-term observatories across the
Arctic, in support of sustainable management and conservation actions