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Abstract Introduction Regime shifts from canopy‐forming to turf‐forming macroalgae are increasingly documented on rocky shores worldwide, often as indicators of ecological degradation due to eutrophication, sedimentation, overfishing and coastal urbanization. Such shifts have prompted to management strategies focusing on turf species removal to encourage the recovery of foundation macroalgae. However, most restoration actions have had limited success, potentially because they overlook the facilitation effects between turf‐forming and canopy‐forming species, particularly in harsh habitats. Objectives This study aims to investigate whether the turf‐forming red alga Gelidium microdon facilitates the persistence of the canopy‐forming fucoid Fucus spiralis in high intertidal zones, with a focus on its potential role in ameliorating physical stress in harsh environments. Methods An experimental field study was conducted on São Miguel Island (Azores) at two moderately exposed sites. The experiment involved removing Gelidium from natural patches and monitoring canopy performance indicators for 4 months, including Fucus cover, recruitment, frond morphology, herbivory by native fish and physiological stress (assessed through maximum quantum yield of Photosystem II (PSII), Fv/fm). Results Turf removal resulted in a consistent decline in Fucus cover relative to control patches, with no significant difference in recruitment or Fv/fm values between treatments. Notably, desiccation scores increased significantly in the absence of Gelidium , suggesting that facilitation occurred primarily through amelioration of abiotic stress. Conclusions The findings highlight the positive role of turf species in mitigating environmental stress for canopy‐forming algae. Turf species may play a context‐dependent facilitative role in harsh intertidal environments, challenging the common practice of competitor removal in restoration efforts.
Gustavo M. Martins (Mon,) studied this question.