Recovery without resilience? Contrasting benthic recovery trajectories six years after a mass coral bleaching event

As coral reefs move further into the 21st century, their perturbation landscape is changing, raising serious concerns about their future. In particular, more frequent and intense marine heatwaves are considered major threats. Following these events, reefs can fail to recover, shifting away from live coral dominance toward other benthic organisms, with significant losses of ecosystem services. Addressing this challenge requires urgent efforts to safeguard and enhance coral reef resilience, as well as to restore reefs that fail to recover. Here, we investigated the recovery of 12 fringing reefs around Unguja Island, Zanzibar (Tanzania), six years after a mass coral bleaching event. Recovery trajectories varied across reef sites, with increases in live coral cover ranging from 5% to 42.5%. Four reefs indicated high live coral cover (≥58%) with no major increases in non-reef-building benthic organisms. In contrast, two reefs were algal-dominated, with live coral cover below 25% and algal cover up to 45%. Although the majority of remaining reefs showed recovery of live coral close to pre-disturbance levels, they also showed signs of increasing abundance in non-reef building organisms, including turf algae, macroalgae, corallimorpharia and soft corals. These patterns indicate growing vulnerability and reduced resilience in some reef systems. Reducing local stressors, such as nutrient pollution and overfishing of herbivorous fish, and incorporating resilience-based management strategies into existing coral reef management plans should be a priority to combat reef degradation and improve resilience in the face of rapid environmental changes.