Material Legacies on Coral Reefs: Rubble Length and Bed Thickness Are Key Drivers of Rubble Bed Recovery

ABSTRACT Disturbances on coral reefs—which are increasing in intensity and frequency—generate material legacies. These are commonly in the form of rubble beds, which depend on rubble stability and/or binding to facilitate coral recruitment and recovery. Yet, our understanding of rubble stability and binding dynamics across environmental gradients is limited. Characterising and categorising rubble material legacies in context of their likely recovery trajectory is imperative to the effective deployment of active intervention strategies used to restore degraded reefs, such as rubble stabilisation, coral outplanting and larval seeding techniques. We quantified rubble characteristics across environmental gradients on the Great Barrier Reef. The likelihood of rubble stability and binding increased with rubble length and rubble bed thickness, and rubble length was a good predictor of bed thickness and rubble branchiness. Thin rubble bed profiles (