/ˈbenˌTHäs/
Noun
1. The community of organisms which live on, in, or near the seabed, also known as the benthic zone. This community lives in or near marine sedimentary environments, from tidal pools along the foreshore, out to the continental shelf, and then down to the abyssal depths. (wikipedia.org)
2. The flora and fauna at the bottom of the ocean or other body of water. (wiktionary.org)
3. Animals and plants living on or within the substrate of a water body (freshwater, estuarine or marine). A region including the bottom of the sea and the littoral zones.Organisms (plants and animals) that live at or near the bottom of a sea. Divided into the littoral benthos near the water surface and banks and the profundal benthos found at the bottom of a water body. Benthos pertains to organisms that occupy these areas. (biology-online.org)
4. Organisms that live on or in the bottom of a body of water. (merriam-webster.com)
5. The assemblage of organisms inhabiting the seafloor. Benthic epifauna live upon the seafloor or upon bottom objects; the so-called infauna live within the sediments of the seafloor. (global.britannica.com)
Word origin: Coined by Haeckel from Greek benthos “depth of the sea,” related to bathos “depth,” bathys “deep,” of unknown origin.