How do plants grow under the sea without sun?

Sunlight can extend down into the ocean up to 660 feet. In murky waters it only extends 50 feet. This zone is called the sunlit zone but it is also called the euphotic zone or epipelagic zone. Plants grow in this zone where they can get sunlight. A plant that grows in the ocean like a seaweed or kelp does not need air.

The middle layer of the world's oceans receives only faint, filtered sunlight during the daytime. This is because the seawater absorbs the sunlight. This barely-lit ocean layer is called the twilight zone or the disphotic zone (disphotic means "poorly lit" in Greek) or the mesopelagic zone (mesopelagic means "middle sea").

In the disphotic zone, there is enough light to see during the day, but not enough light for photosynthesis to take place, so no plants live in this zone. The amout of light decreases with depth. Because of this, food is not abundant.

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 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.





Source(s):
http://www.enchantedlearning.com/biomes/...