Synonyms for Bladderwrack (same or very similar meaning)
WordNet sense 1 (similar to and found with black rockweed):
Ascophyllum nodosumWordNet sense 2 (a common rockweed used in preparing kelp and as manure):
tang, tang, black rockweed, bladder fucus, Fucus vesiculosusFrom the ODE community, based on WordNetadd/edit