gulfweed vs brown algae

gulfweed and brown algae both are nouns.

Word	Noun	Adjective	Verb	Adverb
gulfweed	Yes	No	No	No
brown algae	Yes	No	No	No

As nouns, brown algae is a hypernym of gulfweed; that is, brown algae is a word with a broader meaning than gulfweed:

gulfweed: brown algae with rounded bladders forming dense floating masses in tropical Atlantic waters as in the Sargasso Sea
brown algae: algae having the chlorophyll masked by brown and yellow pigments

gulfweed (noun)	brown algae (noun)
brown algae with rounded bladders forming dense floating masses in tropical Atlantic waters as in the Sargasso Sea	algae having the chlorophyll masked by brown and yellow pigments