Characterising ecosystem service provision by two morphologically distinct kelp species (Laminaria hyperborea and Saccharina latissima) and the biophysical drivers shaping these services: a systematic map protocol

Important ecosystem services (ES), defined by the Millennium Ecosystem Assessment as benefits people obtain from ecosystems, are provided by kelp forests (e.g. nutrient cycling, nursery sites for fisheries and habitat provision). However, kelp forest degradation is extensive and ongoing with 40–60% of kelp forests degraded over the past 50 years threatening ES provision. Management efforts often overlook species-specific biophysical drivers of service provision and the role of morphological diversity (e.g. stipitate or prostrate growth forms) in mediating ES. Effective marine spatial planning that incorporates ES provision requires understanding of these drivers, but current efforts are limited by poor spatial data on kelp distributions and ES provision. This systematic map aims (i) to catalogue and classify the ecosystem services that have been reported for Laminaria hyperborea and Saccharina latissima (two kelp species with contrasting growth forms), and (ii) to map what evidence exists on biophysical drivers associated with variation in these services. Following Collaboration for Environmental Evidence (CEE) guidelines, this systematic map will conduct a search of peer-reviewed literature from Web of Science, Scopus, and Google Scholar using terms for kelp species and ES, refined via the PO framework (Population, Outcome). Search string replicability will be validated using 10 benchmark articles. The screening process will utilize a three-stage process (remove duplicates, title and abstract screening and full text screening) which will prioritise studies quantifying ES provision (e.g. wave attenuation, biodiversity metrics, kelp farming) and/or biophysical drivers of ES provision for Laminaria hyperborea and Saccharina latissima. Data will be synthesized narratively and, where feasible, presented through tables, figures and geographic mapping that compares ES across growth form and biophysical drivers (e.g., light availability for primary productivity, turbidity for carbon sequestration). This systematic map aims to identify gaps in knowledge of kelp service provision, with the results highlighting kelp ES knowledge to guide future and current marine spatial planning.