serrated wrack vs brown algae

serrated wrack and brown algae both are nouns.

Word	Noun	Adjective	Verb	Adverb
serrated wrack	Yes	No	No	No
brown algae	Yes	No	No	No

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

serrated wrack: brown algae seaweed with serrated edges
brown algae: algae having the chlorophyll masked by brown and yellow pigments

serrated wrack (noun)	brown algae (noun)
brown algae seaweed with serrated edges	algae having the chlorophyll masked by brown and yellow pigments