benthos vs epipsammon

benthos and epipsammon both are nouns.

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

As nouns, epipsammon is a hyponym of benthos; that is, epipsammon 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
epipsammon: Microscopic flora and fauna found on the surface of and/or attached to sand grains.

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

benthos (noun)	epipsammon (noun)
organisms (plants and animals) that live at or near the bottom of a sea, lake, river or stream	Microscopic flora and fauna found on the surface of and/or attached to sand grains.
a region including the bottom of the sea and the littoral zones