marine benthos vs benthos

marine benthos and benthos both are nouns.

Word	Noun	Adjective	Verb	Adverb
marine benthos	Yes	No	No	No
benthos	Yes	No	No	No

As nouns, benthos is a hypernym of marine benthos; that is, benthos is a word with a broader meaning than marine benthos:

marine benthos: organisms (plants and animals) that live specifically at or near the bottom of a sea.
benthos: organisms (plants and animals) that live at or near the bottom of a sea, lake, river or stream

marine benthos (noun)	benthos (noun)
organisms (plants and animals) that live specifically at or near the bottom of a sea.	organisms (plants and animals) that live at or near the bottom of a sea, lake, river or stream
	a region including the bottom of the sea and the littoral zones