The Aphotic Zone.docx

The aphotic zone (aphotic from Greek prefix ἀ- + φῶς "without light") 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 in this zone comes from dead organisms sinking to the bottom of the lake or ocean from overlying waters. 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 a lake or ocean directly affected by sunlight.