the photic, upper layers of ocean water; the ____ zone is the warmest region of ocean water and has the highest levels of dissolved oxygen
the depths; ocean water that is too deep for sunlight to penetrate. Because this zone is aphotic (a place where light cannot reach), photosynthesizing plants and animals cannot live in this region
a layer in a large body of water, such as a lake, that sharply separates regions differing in temperature, so that the temperature gradient across the layer is abrupt