Linked from
The 6 pages that link to Seaweed, each with the reason it gives.
IodineRelated: Courtois encountered iodine while extracting compounds from seaweed ash.
SeafoodBroader topic: Seaweed is seafood despite being algae rather than an animal.
KelpNarrower topic: Kelp is a large, forest-forming subset of seaweed.
NoriNarrower topic: Nori is one edible, cultivated kind of seaweed.