Beyond corals: unveiling the ecological roles of macroalgae in the Red Sea - a review

Macroalgae are fundamental components of coastal and reef-associated marine ecosystems, where they function as dominant benthic primary producers and play a key role in maintaining ecosystem structure and functioning. Through photosynthesis, macroalgae support marine food webs directly via herbivory and indirectly through detrital and dissolved organic matter pathways. In addition to their trophic importance, macroalgae act as habitat formers and ecosystem engineers, increasing structural complexity and providing shelter and nursery grounds for a wide range of fishes and invertebrates. These attributes place macroalgae among the most important drivers of coastal productivity and biodiversity worldwide. The Red Sea offers a unique ecological context for examining macroalgal roles due to its extreme environmental conditions, including persistently high temperatures, elevated salinity, strong evaporation rates, and generally oligotrophic waters. Pronounced spatial gradients in temperature and nutrient availability further influence macroalgal distribution, diversity, and productivity across the basin. Despite the Red Sea’s global recognition as a biodiversity hotspot, particularly for coral reefs, macroalgal communities in this region remain comparatively understudied. This review synthesizes current knowledge on the ecological roles of macroalgae in the Red Sea, focusing on their contributions to primary production and carbon cycling, habitat formation and structural complexity, nutrient uptake and recycling, and trophic interactions within and across coastal habitats. The role of macroalgae as bioindicators of environmental change and coastal degradation is also highlighted, emphasizing their relevance for ecosystem monitoring and management. Key research gaps include limited long-term monitoring of macroalgal communities, insufficient understanding of physiological responses to extreme Red Sea conditions, and a lack of standardized methods to quantify biomass, carbon fluxes, and trophic linkages. Addressing these gaps is essential for improving ecosystem-based management and advancing understanding of macroalgal ecology in the Red Sea.