The ISOLUME project addresses the impacts of changing marine lightscapes, particularly from coastal darkening and artificial light at night (ALAN). Led by Germany and involving partners from six European countries, the project investigates how marine lightscapes have changed over decades to centuries. Using historical data, remote sensing, and modelling, ISOLUME analyses changes in light intensity, location, timing, and spectra. It spans marine, estuarine, and freshwater systems, with case studies across Europe. Findings will support monitoring, management, and policy frameworks to mitigate the ecological effects of altered lightscapes.