Grazers of all shapes and sizes inhabit and feast on the vast meadows of seagrass in the tropics. However, in our current changing world, human-induced stressors can disrupt the delicate balance between marine plants and their herbivores. Using results from field experiments, this thesis describes the impact of global warming, changes in megafauna and invasive species on the functioning of Caribbean seagrass ecosystems. Sea turtles and fish were found to have opposing effects on the expansion success of invasive seagrass. Additionally, turtles in high-predator environments and turtles fed by tourists exhibited a deviating grazing pattern. Changes in native-invasive seagrass species composition as well as turtle grazing intensity directly affected the ecosystem services seagrass provides, such as the level of carbon storage. Therefore, conservation efforts should not focus on single species such as the sea turtle, but include other grazers, predators and their habitat, to ensure high-value and balanced ecosystems resilient to future change.