Biology and Oceanography. Of, relating to, or inhabiting the open sea beyond the edge of the continental shelf; (also) spec. denoting the parts…

Of, relating to, or designating the shallow region of the sea between the littoral zone and the edge of the continental shelf; inhabiting this region.

Designating the part of the sea or other body of water which is penetrated by sufficient sunlight for the growth of plants. Chiefly in photic zone.

Pertaining to or designating the upper layer of the photic zone in sea-water where sufficient light penetrates to permit photosynthesis.