In this dissertation, I investigate the role of light at night and its influence on animal behavior and ecology. In the first chapter, I review the role of light in marine systems and how aquatic environments and their inhabitants are adapted to specific sources, rhythms, and types of light at night. The marine realm’s biological organization through light availability creates a unique scenario in which light pollution can disturb marine systems across multiple scales of biological organization. In the second chapter, I investigate the influence of natural light at night on tree swallows, a common study species and a diurnal cavity nesting bird. I find that tree swallows tend to wake up later following brightly moonlit nights in temperate regions but wake up earlier after a bright night in high latitude locations. These findings reinforced the importance of light at night across organisms of diverse life histories and ecosystems. In my third chapter, I experimentally test the interactive effect of cool temperature and bright light at night on an aphid-lady beetle system. In cool conditions, aphids increased population levels, but in warm environments, lady beetles were able to control aphid populations well. This indicates that light pollution can interactively shift key trophic systems in conjunction with other stressors. Finally, for my fourth chapter, I investigate the compounding effects of light pollution, sound pollution and rising sea surface temperatures on Northern Caribbean coral reef systems. Although a limited number of these reefs were affected by light pollution in 2016, reefs experiencing artificially bright nights often, if not always, experienced other anthropogenic stressors, which made them at greater risk for bleaching. Over the course of this dissertation, I exhibit how light at night affects systems across the globe, from the depths of the ocean to the organisms intertwined with North American agriculture. However, light pollution does not occur in a vacuum, and the interactive impacts of its presence may drive further biodiversity loss.