| Term: | aphotic zone |
| Definition: |
The aphotic zone is the portion of a lake or ocean where there is little or no sunlight. It is formally defined as the depths beyond which less than 1% of sunlight penetrates. Consequently, bioluminescence is essentially the only light found in this zone. Most food comes from dead organisms sinking to the bottom of the lake or ocean from other zones. The depth of the aphotic zone can be greatly affected by such things as turbidity and the season of the year. The aphotic zone underlies the photic zone, which is that portion of the ocean directly affected by sunlight. |