Benthos: the flora and fauna found at the bottom of the sea or lake. Covers quite a wide range of uses, for instance, animals in rock pools are benthic, though only a few inches below the surface. In the ocean, used to contrast organisms in the sea depths (though not actually on the bottom), with plankton, living in the upper pelagic zone. The problem is addressed by extending the pelagic zone down below the light to the bathypelagic and abyssopelagic zones. These terms, however, are mostly not used.