Isotopic data of kelps and particulate organic matter (POM) from relevant studies and estimated contributions of kelps to local consumers

Kelp forests are highly productive coastal habitats that serve as biodiversity hotspots and provide valuable ecosystem services. Despite being one the largest marine biomes, kelp forests have been drastically understudied relative to other marine systems. Notably, while the role of kelp as habitat-forming, or ‘foundation species’, is well-documented, a comprehensive understanding of kelp forest food web structure is lacking, particularly regarding the importance of kelp-derived energy/nutrients to consumers. Here, we provide a biogeographic perspective on the energetic underpinning of kelp forests based on published literature. We targeted studies which used geochemical proxies – stable isotope analysis – to examine the transfer of carbon from kelp to local consumers. These studies (n=94) were geographically skewed, with >40% from Northern European Seas and Temperate Northeast Pacific. Quantitative estimates for the percentage of kelp energy (or kelp+macroalgae if sources were pooled...