Drools over your Mom's vegan food. I miss the vegan shops in Taiwan and NYC.
The nori cultivating process is fascinating. Most are grown on indoor farms. I think what you are worried about is the zooplankton (animal plankton) eating off the photplankton (seaweed and algae) and getting processed. The other is fish feeding off the seaweed farms. They do set traps for fish. For the most part it's like worrying about eating insects and insects eggs off vegetables and grains.
I think it's fine. You shouldn't worry.
My parents are vegan but they are always telling me not to eat scallions, onions, and garlic because it's like eating meat. (some sort of religious references)
