Seagrass meadows are key components of coastal zones, but are rapidly declining with losses often characterized by sudden collapse. Mounting evidence suggests that this unpredictable non-linear behavior results from strong internal feedbacks. Yet, despite these recent insights, both protection and restoration of seagrass meadows remain extremely difficult, suggesting that certain fundamental mechanisms may be overlooked. Indeed, in two recent studies, we report on the discovery of an ancient mutualistic detoxification feedback between seagrass and sulfide-consuming lucinid bivalves, and show how breakdown of this facultative mutualism can amplify seagrass degradation. Although this work suggests that this mutualism could be vital in mediating seagrass productivity and ecosystem stability, its generality and importance, as well as how its role may change due the global change, remain to be investigated. Here, we propose a worldwide crowdsourcing survey to correlatively determine if and how strongly various seagrass and lucinid species are associated across climate and sediment conditions. Next, we will test interaction strength for the most important temperate to tropical seagrass-lucinid associations under various temperature and sediment conditions (the most important factors affecting the mutualism) in laboratory experiments. Finally, the resilience of the seagrass-lucinid mutualism will be tested in a worldwide crowdsourcing field experiment in which we manipulate sulfide production and mutualism strength. With this unique combination of worldwide surveys and experiments, and detailed laboratory experiments, we aim to answer whether the seagrass-lucinid mutualism should be more solidly integrated into seagrass conservation practices to significantly improve restoration success and resilience to global change.