Vegetables from the sea
Seaweeds like nori, wakame, dulse and kelp, and microalgae like spirulina and chlorella, contain minerals that are rare in land plants.
Iodine — friend and foe
Seaweed is a natural source of iodine, which your thyroid needs. But the amount varies enormously: kelp (kombu) can contain so much that a single serving exceeds a safe daily limit. Enjoy nori and wakame in normal amounts, and go easy on kelp and seaweed supplements.
A note on B12
Seaweeds and spirulina are not reliable sources of vitamin B12 — they mostly contain inactive look-alikes. See Vitamin B12.