Seagrass meadows belong to the most important ecosystems of our world. Through their photosynthetic activity they are not only producing large amounts of oxygen that they release into their surrounding water or sediment, but they also sequester great amounts of carbon dioxide. As seagrasses die or lose their leaves, they get covered with sediment and in this way the carbon is buried in the ground. This process makes seagrass ecosystems one of the most effective carbon sinks in the world. Unfortunately, they also belong to the most rapidly vanishing ecosystems and are predominantly destroyed by man-made influences. The identification of early warning signals before damages to seagrass ecosystems are beyond repair, is the main goal of the SEANARIOS project. Therefore, the project will investigate and compare the responses of the dominant seagrass species in the Mediterranean (Posidonia oceanica) and the Gulf of Aqaba (Halophila stipulacea) to thermal and nutrient stress. Field and mesocosm experiments will be performed to identify physiological and molecular traits that could serve as early warning indicators for stress in seagrasses. The results of the empirical studies will be used to develop and parameterise an ecological simulation model to analyse the impact of elevated temperatures and nutrient levels. The model will be able to extrapolate the development of various seagrass species exposed to future thermal and nutrient stress. The results of different scenarios will be made available to policy makers that can in turn enforce improved measures and regulations to protect seagrass meadows.