Responses of marine and insular ecosystems to climate change. Climate influences a variety of ecological processes. It acts through local environmental conditions such as temperature, winds, precipitations, oceanic currents, but also their interactions. Local environmental changes are often associated with large-scale phenomena. They drive exchanges of energy and biomass, and finally growth, recruitment and migration of species. The understanding of climate change impacts on marine ecosystems requires a better understanding of their effects on the apex of food webs. We here report results of recent studies showing the impact of large-scale environmental changes such as El Ni?o, North Atlantic Oscillation and Antarctic circumpolar waves on the functioning of marine and insular ecosystems. These phenomena act at relatively small scales in time and space compared to climate changes, but they have similar consequences as predictions of climate change models. They provide natural observatories of ecosystems responses to environmental conditions and global changes.