The sub-Antarctic Magellan region in southern Chile belongs to the most extensive fjord regions of the world and the coastal and marine environments are exposed to natural and anthropogenic perturbations. Research on the marine ecosystems have received some attention, however, research on the flow of energy is rather limited. To trace energy flow and resource distribution across communities are of considerable concern to current ecological studies, thus understanding how the marine benthic ecosystems are organized, on the base of which food sources they are built upon and how benthic organisms utilize resources. Heterogeneous environmental conditions along the Sub-Antarctic Magellan region, however, suggest the possibility of a great heterogeneity in community structure and population dynamics. Studies of the trophic structure and energy flow are essential in this context. The aim of this thesis is to increase the knowledge of the ecological role ofbenthic species to communities living in the sub-Antarctic Magellan region. The main objectives of this research include: (i) to investigate the trophic ecology of conspicuous species and their ecological role in the marine benthic communities of the Magellan region; (ii) to describe the trophic structure of two shallow-water benthic community types in the Strait of Magellan in order to establish baseline descriptions of trophic relationships for community structure and function, and (iii) to estimate benthic secondary production in this sub-Antarctic region as a proxy for energy flow along latitudinal gradients. The main results indicate that local/regional environmental conditions and biological features may originate clear differences on the trophic structure and energy flow patterns. This research gives valuable insight into ecological functioning of marine benthic communities present in the sub-Antarctic Magellan region and may offer useful information to build food web models.