Marine tidal race environments undergo extreme hydrodynamic regimes and are favoured locations for offshore marine renewable tidal energy developments. Few ecological studies have been conducted within these complex environments, and therefore, ecological impacts from tidal energy developments remain unknown. This thesis aimed to investigate the ecological aspects of marine tidal race environments in two themes, using a combination of field-based sampling techniques. I first examined the natural ecological variation of a marine tidal race environment at the spatial and temporal scale. These studies were based on the benthic and intertidal communities within the Alderney Race tidal environment, Alderney. My results suggest that both communities vary in species diversity and composition, at different spatial gradients and timescales. Species showed opportunistic or resilient life history characteristics, highlighting the overall influence of the strong hydrodynamic conditions present. I then explored the ecology of a marine tidal race environment within a renewable tidal energy development site. These studies were based within the European Marine Energy Centre’s tidal energy development site, Orkney. Here, I investigated ecological variation in terms of fish interaction and benthic assemblage structure with a deployed tidal energy device, and, the structure of intertidal communities within the overall development site. Interestingly, my results indicated species-specific interactions with the deployed tidal energy device, which was related to species’ refuge or feeding behaviour. These results also imply that different communities show varied spatial and temporal heterogeneity within a development site, associated with the complex interplay of abiotic and biotic processes. This work begins to reveal the ecological consequences of tidal energy development, with single devices acting as potential short-term artificial reef structures. Further research is recommended within these environments, with reference to how the hydrodynamic regimes directly influence these communities, and, the overall ecological consequences of future large-scale tidal energy development scenarios.