cryptophyte vs alga

cryptophyte and alga both are nouns.

Word	Noun	Adjective	Verb	Adverb
cryptophyte	Yes	No	No	No
alga	Yes	No	No	No

As nouns, alga is a hypernym of cryptophyte; that is, alga is a word with a broader meaning than cryptophyte:

cryptophyte: common in fresh and salt water appearing along the shore as algal blooms
alga: primitive chlorophyll-containing mainly aquatic eukaryotic organisms lacking true stems and roots and leaves

Other hypernyms of cryptophyte include algae.

cryptophyte (noun)	alga (noun)
common in fresh and salt water appearing along the shore as algal blooms	primitive chlorophyll-containing mainly aquatic eukaryotic organisms lacking true stems and roots and leaves