Lobophora–coral interactions and phase shifts: summary of current knowledge and future directions

In studies on coral–algal interactions, particular attention has been devoted to corals. Focusing on the macroalgal genus Lobophora (Dictyotales, Phaeophyceae), common on coral reefs and extensively studied in coral–algal interactions, this review aims to summarize what is known and highlight the conditions necessary for Lobophora blooms, the contrasting effects on corals, and the taxonomic and functional diversity of the genus. Studies show that under normal conditions, Lobophora–coral interactions are natural and pose no specific threat to corals as long as the algal cover is controlled by coral defenses and herbivory. In contrast, disturbances freeing-up space for colonization and reducing herbivory permit Lobophora in association with other seaweeds to opportunistically take over reefs and by density-dependent negative feedbacks prevent corals from recovering. Lobophora is, however, a species-rich group and only certain Lobophora species thrive in degraded reefs, and the specificities of interactions and phase shifts will vary among species, thus stressing the importance of taxonomic identification in the study of coral–algal interactions. This review accentuates the complexity of coral–algal interactions and the importance to consider not only the taxonomy of corals and seaweeds but also their life history traits, ecology, microbiome, and the environmental settings.