The preservation of the marine ecosystems and the sustainable use of the marine resources and socio-economic services they provide must be a priority objective for society. In this context, the objective of my research project is to understand the ecosystem response to anthropogenic stress, through empirical and theoretical tools. These responses often involve a nonlinear behavior that generates abrupt and unexpected transition from a non-stressed state of the ecosystem to an altered and impoverished state in which the ecosystem loses the ability generate ecosystem services. Therefore, it is essential to determine the stress tolerance thresholds from which this transition occurs. Studying Mediterranean marine macrophytes ecosystems, we aim to develop predictive and diagnostic elements that would help to predict the thresholds around these critical transitions. The understanding of these transition would help to explain the macrophyte communities sensitivity to other environmental conditions, such as global warming or eutrophication.