An assessment of rhodolith bed ecosystem services

BACKGROUND: Rhodolith beds are formed by free-living coralline red algae some of which form maerl habitats. They are among the most widespread and longest lived benthic biogenic habitats in the photic zone, yet their contributions to ecosystem services are poorly known. SCOPE: Here, we review the global literature on rhodolith bed ecosystem services using the Common International Classification of Ecosystem Services (CICES), which distinguishes final ecosystem services from underlying ecological functions. KEY RESULTS: The documented ecosystem functions of rhodolith beds include carbon and nutrient cycling, calcification, sediment dynamics, oxygen production, and water filtration. These processes underpin key regulating and maintenance services and build habitats with high biodiversity. Rhodolith beds provide nursery, refuge and recruitment habitats for diverse microbes, macroalgae, invertebrates and fishes supporting fisheries and aquaculture. In some regions, rhodolith-derived carbonate is mined for agricultural, nutritional and industrial uses. Despite the ecological importance of these coralline algal habitats, significant knowledge gaps remain. Cultural ecosystem services are rarely quantified, and no studies have assessed their contributions to coastal protection, fisheries productivity, water quality or human well-being in socioeconomic terms. CONCLUSION: CICES is a framework for identifying and classifying services, yet data linking rhodolith habitat extent and condition to measurable human benefits are severely limited. Strengthening this evidence is essential for integrating rhodolith beds into ecosystem-service assessments and informing management decisions in a changing ocean.