sargassum vs gulfweed

sargassum and gulfweed both are nouns.

Word	Noun	Adjective	Verb	Adverb
sargassum	Yes	No	No	No
gulfweed	Yes	No	No	No

As nouns, sargassum and gulfweed are synonyms defined as:

sargassum and gulfweed: brown algae with rounded bladders forming dense floating masses in tropical Atlantic waters as in the Sargasso Sea

Other synonyms of sargassum include sargasso, Sargassum bacciferum.

sargassum (noun)	gulfweed (noun)
brown algae with rounded bladders forming dense floating masses in tropical Atlantic waters as in the Sargasso Sea	brown algae with rounded bladders forming dense floating masses in tropical Atlantic waters as in the Sargasso Sea