Meeting Abstract
Warming induced coral bleaching is a major environmental stressor occurring on reefs. The coral holobiont, the coral host and its associated microorganisms, is a unique, complex system of symbiotic interactions that can be represented as a network. We have determined the global coral-Symbiodiniaceae network’s resistance to temperature stress by developing a model to simulate an environmental “attack” (warming) on the network. Interactions (links) between coral species and algal symbionts (nodes) are weighted by considering individual thermotolerances and creating a combined threshold for each association. As temperature increases, links are removed when their threshold is surpassed. A coral is considered bleached when it has no more links. Resistance to temperature stress was determined from the response of the network to the bleaching model. Warming caused network breakdown in ways that differed from randomized networks, supporting that network structure and specific thermotolerances affect temperature stress resistance. Ecological robustness, how much perturbation is needed to decrease a network’s nodes by half, was determined for multiple link and node removal models. Networks were more robust to link removals than to node removals. Of the link removals, removing links according to the bleaching model resulted in the lowest robustness. Natural networks will maintain a higher level of stability under environmental stressors compared to random networks, because of their interactions, unless those interactions are susceptible to a certain stressor, as is the case for coral reefs. The global network of coral-Symbiodiniaceae interactions and their associated thermal thresholds is non-random, and this architecture leads to a higher sensitivity to environmental perturbations.
