benthos vs microbenthos

benthos and microbenthos both are nouns.

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

As nouns, microbenthos is a hyponym of benthos; that is, microbenthos is a word with a more specific, narrower meaning than benthos:

benthos: organisms (plants and animals) that live at or near the bottom of a sea, lake, river or stream
microbenthos: microscopic benthic organisms that are less than 0.1 mm in size.

Other hyponyms of benthos include marine benthos, epipsammon, endopsammon, epixylon, merobenthos, epipelon.

benthos (noun)	microbenthos (noun)
organisms (plants and animals) that live at or near the bottom of a sea, lake, river or stream	microscopic benthic organisms that are less than 0.1 mm in size.
a region including the bottom of the sea and the littoral zones