black rockweed vs bladderwrack

black rockweed and bladderwrack both are nouns.

Word	Noun	Adjective	Verb	Adverb
black rockweed	Yes	No	No	No
bladderwrack	Yes	No	No	No

As nouns, black rockweed and bladderwrack are synonyms defined as:

black rockweed and bladderwrack: a common rockweed used in preparing kelp and as manure

Other synonyms of black rockweed include bladder fucus, Fucus vesiculosus, tang.

black rockweed (noun)	bladderwrack (noun)
a common rockweed used in preparing kelp and as manure	a common rockweed used in preparing kelp and as manure
	similar to and found with black rockweed