Bioluminescence Begins to Appear in the Mesopelagic Zone.

Because sunlight is very limited in the Mesopelagic Zone, some organisms living in this layer of the ocean exhibit bioluminescence. It is the uppermost oceanic layer where this phenomenon regularly occurs. The eyes of fish that live in the Mesopelagic Zone are also adapted to the scant light; they are generally larger and directed upward so that the fish can see the silhouettes of potential meals against the dim light.