eelgrass vs Zostera marina

eelgrass and Zostera marina both are nouns.

Word	Noun	Adjective	Verb	Adverb
eelgrass	Yes	No	No	No
Zostera marina	Yes	No	No	No

As nouns, eelgrass and Zostera marina are synonyms defined as:

eelgrass and Zostera marina: submerged marine plant with very long narrow leaves found in abundance along North Atlantic coasts

Other synonyms of eelgrass include grass wrack, sea wrack.

eelgrass (noun)	Zostera marina (noun)
submerged marine plant with very long narrow leaves found in abundance along North Atlantic coasts	submerged marine plant with very long narrow leaves found in abundance along North Atlantic coasts
submerged aquatic plant with ribbonlike leaves; Old World and Australia