Zostera marina vs eelgrass

Zostera marina and eelgrass both are nouns.

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

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

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

Other synonyms of Zostera marina include grass wrack, sea wrack.

Zostera marina (noun)	eelgrass (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