Chondrus crispus vs red algae

Chondrus crispus and red algae both are nouns.

Word	Noun	Adjective	Verb	Adverb
Chondrus crispus	Yes	No	No	No
red algae	Yes	No	No	No

As nouns, red algae is a hypernym of Chondrus crispus; that is, red algae is a word with a broader meaning than Chondrus crispus:

Chondrus crispus: dark purple edible seaweed of the Atlantic coasts of Europe and North America
red algae: marine algae in which the chlorophyll is masked by a red or purplish pigment; source of agar and carrageenan

Chondrus crispus (noun)	red algae (noun)
dark purple edible seaweed of the Atlantic coasts of Europe and North America	marine algae in which the chlorophyll is masked by a red or purplish pigment; source of agar and carrageenan