Modularity limits the spatial propagation of disturbance in experimental seagrass networks.

Understanding how habitat structure affects disturbance dynamics among connected patches is a central issue in ecology. Network theory predicts that a modular arrangement of habitat patches can limit the spread of local perturbations, reducing the probability of large-scale impacts. We performed a field experiment to test whether modular networks were more resistant to the spread of algal turfs compared to random networks within meadows of the seagrass Posidonia oceanica (L.) Delile. Networks were created by manipulating the canopy of P. oceanica to promote the vegetative propagation of algal turfs among network nodes from initially disturbed patches. Algal turfs spread more widely among nodes in random networks, whereas they remained confined within the nodes of the perturbed module in modular networks. Our findings support the hypothesis that modularity is a key trait of ecological networks for mitigating the spread of perturbations and emphasize the importance of considering habitat structure for conservation efforts.